Two months ago I started a thread on entitled "Does Bluetooth work in an aluminum camper? Victron vs. Renogy." I was thinking of upgrading my existing lead acid batteries to lithium ones, and was comparing two vendors.
This thread ultimately became a long and fruitful discussion about how to do a lithium battery upgrade. It had a lot of great input from #DavidM and #Merlin, with some additional input from #Pinstriper. It went way beyond Bluetooth! Had I known that the discussion would become so inclusive, I would have named it something like "How do I go about getting a Lithium treatment?"
My old lead acid battery (93Ah) could no longer hold a charge, and my AC power converter was making a making an annoying sound whenever it charged the batteries (ever wonder what tinnitus sounds like?... this is the same!). I had a PWM solar controller that I wanted to upgrade to MPPT, and I was never quite satisfied when charging of my lead acid batteries from my tow vehicle.
An upgrade to Lithium batteries would give me a number of benefits. Not only would I have more storage capacity, but I would also be able to charge the batteries more quickly. I decided to go with two 100Ah batteries so that we could make better use of campsites with "no hookups" when we stayed at our favorite parks or went on an extended trip. Although we could have kept the existing power converter (for lead-acid batteries), this would have never fully charged the batteries (because of lower voltages) and would have likely reduced the lifetime of the batteries (since the battery management would not have a high enough voltage to do cell balancing). My old PWM solar controller did not support Lithium, and I wanted to upgrade to MPPT anyway. Since Lithium batteries can recharge very quickly, they can draw a lot of charge... this made it wise to get a DC to DC controller that regulated the current from the TV and ensured that adequate voltage was being used to charge the batteries.
After a lot of discussion on the "Bluetooth" thread, I finally decided on particular components. A block diagram is shown below.
Lithium Block Diagram R1.jpg
I've purchased nearly all of the equipment. I still need to find a way to connect MC4 connectors through the side of the travel trailer, since I'm currently in the habit of moving solar panels around the trailer. Also, I haven't purchased any equipment associated with the inverter. Installing the components will require some work. Some of that has already been done. This thread will begin with what I've done so far. As I make progress, I'll add notes.
The "Bluetooth" thread includes a lot of information from forum members in response to my questions about different components and manufacturers. I ultimately purchased the following:
- Battle Born BB10012 batteries (100 Ah). There are other options for a lower price, but the Battle Born batteries appear to have consistently received good ratings. The battery management keeps the unit from being charged at freezing temperatures, which can ruin the battery. The batteries are "designed and fabricated" in the U.S... Although the cells probably came from someplace outside the country, customer support is more available and there appears to be a wider knowledge base.
- Progressive Dynamics PD9145AL (AC to DC) Power Converter. This is a deck-mount version that supports Lithium batteries only. Progressive Dynamics makes a Lithium compatible unit that could have been inserted directly into my existing PD4045 Power Control Center, but that unit only supports "single stage" charging. The PD9145AL supports "two stage" charging, which can help extend the life of Lithium batteries.
- Victron BlueSolar charge controller MPPT 100|50. A MPPT 100|30 would have probably done the job just fine (even if I added another couple of panels to the three 100W panels that I already have), but I ample room in case I decided to use even more panels.
- Victron Orion-Tr Smart Isolated DC-DC charger. It was this beast that initiated the "Bluetooth" discussion, because there is no other way to configure it other than with a Bluetooth connection.
- Blue Sea Bussmann Surface Mount 187 series DC circuit breaker (80A). I could have also used a panel mount circuit breaker, but I wanted to be able to see as many of the connections as possible, literally "above the board".
- Blue Sea MaxiBus BusBar (Pat No. 2126). I got two of these, one for positive and one for negative. Each bus bar has six 5/16" posts. This may be a little overkill, but it allows me to troubleshoot components without removing the cabling for other components.
Did I mention that I have a Livin' Lite Camplite 14DBS? Although this is great for my wife and two dogs, space is at a premium. I was reluctant to give up an entire cabinet, and my wife didn't want to give up space for the dog food. Nonetheless, I wanted to keep the batteries indoors... to keep them from freezing, and to keep honest folks honest! The other components mentioned above also take up more space than what was there before. Therefore, I decided to make a "circuit board" that would fit in the space that divides one of the cabinets under the sink with the "power/fuse/breaker" cabinet directly adjacent to it.
The "circuit board" is made out of sheet PVC. I used this because it is non-metallic and easy to work with. Also, you can glue pieces together (think plywood) in order to make it stronger. Since PVC contains chlorine, it can generate dioxin if it burns. However, it is my understanding that PVC has a much higher ignition temperature than wood, and does not stay lit unless something else (like wood) is burning it. CAVEAT: I'm not a expert on this, so you should investigate this yourself if you consider using sheet PVC for this purpose. Since I have an aluminum camper, I figure that I will have other things to worry about if the camper frame is hot enough to begin to burn.
Basic Cicuit Board.jpg
The circuit breaker is at the top left corner of the circuit board. The solar charge controller and the DC/DC converter are in the middle, and the bus bars are on either side. Holes below the charge controller and the DC/DC converter allow for cables from the AC/DC power converter, the DC distribution panel, the TV DC entrance, and the solar panel entrance. The notch in the lower right is for the wheel well of the 14DBS. The funny squiggle above that is to allow room for the hot/cold PEX tubing that goes to the galley sink.
This is the rear side of the circuit board. There are up to three layers of sheet PVC, each 3/8" thick. The sheets are held together with plumbing PVC cement (I didn't use the PVC primer, but I did clean the pieces with acetone). Components are held in place with tee-nuts (which were glued in place with cyanoacrylate). CA and PVC seem to love each other... I tested one tee-nut before using this approach, and the nut actually deformed rather than come away from the PVC.
The user manuals for the solar charge controller and the DC/DC converter recommend having more space than you see from the front of the board to allow for air flow across the heat fins on the back of the components. For this reason, I cut out the portions of the PVC immediately behind the components to allow for more air flow. I also chamfered the top/bottom edges of the second layer to facilitate air flow.
Cicuit Board Back.jpg
Since the components have a high profile, they partially blocked the opening of the cabinet in which they were being installed. I managed to offset them with "spacers" made out of layers of sheet PVC. The layers were held together with PVC glue and CA glue. The edges were filed away in some places to account for welds in the adjacent aluminum tubing.
Spacer bars.jpg
This is where the components will be installed. Due to the "spacers" mentioned above, the components will actually occupy space behind or above aluminum tubes.
Where circuit board will sit.jpg
This is what the circuit board looks like after install. The lithium batteries are sitting on the wheel well. Ultimately, they will need to be held in place with a battery tray (which I haven't made yet). The components are recessed enough that they did not stand out beyond the edges of the cabinet door, and there is enough space the slide the batteries in and out if I need to.
After install.jpg
This is from the inside of the cabinet. I installed the shunt (can I mount this directly to the bus bar?). I have not installed cables to the batteries yet. Holes below the charge controller and the DC/DC converter allow for cables from the AC/DC power converter, the DC distribution panel, the TV DC entrance, and the solar panel entrance. I'll be adding these cables after I install and connect to those components.
From Inside.jpg
Finally, this is from the top. The existing PD4145 (with DC distribution and fuse box) is at the bottom of the picture. The PD9145AL will be installed right where the flashlight is sitting. This is above the wheel well. I'll need to make a mount for this as well.
From the top.jpg
Many thanks to those that have provided help so far. Thanks also to those that made it possible to imbed pictures within the text of posts on this forum!
My next step will be making the battery tray and the mount for the PD9145AL AC/DC converter. I'm hoping to use some tips from #Pinstriper for this.
Tom:
The most commonly used connection to go through the trailer wall for portable solar hookup is the SAE connector, sometimes called the Zamp connector. Here is a page of SAE sockets and male connectors on Amazon: https://www.amazon.com/s?k=sae+connector&ref=nb_sb_noss. You have to be careful about the polarity with these connectors.
Use MC4 cables from your solar panel to the connector as MC4 cables are available in various lengths and up to #8 gauge and then splice to the SAE connector to go through the trailer wall.
David
Two steps forward, one step back...
First step forward....
I finally assembled and installed trays for the lithium batteries and the AC/DC charger. I've posted comments and pictures in a separate thread (started some time ago) at Can I put batteries indoors on wheel wells? (https://aluminumcamperforum.com/index.php?topic=1576.0)?
I now have all of the major components installed for the lithium upgrade. I've added cabling to connect the batteries, AC/DC charger, DC/DC converter and solar controller. For those that are wondering, YES... I do have both lithium batteries connected together without switches between them. Once I fully charged them individually, I cabled them together in a "till death do us part" configuration so that they will be charged/discharged as a single unit in wedded bliss.
I've bypassed the old lead-acid battery, and connected the DC system to the distribution panel that was part of the AC/DC converter. Although I have the solar controller installed, I still need to install an entrance for cabling from the solar panels. Although the shunt is installed, I need to connect the sensor wires and reprogram the device. However, the AC/DC charger and DC/DC converter are fully connected.
I've since been able to charge the batteries from shore power. Since the batteries are connected to the DC distribution panel (through a breaker), I can actually use my trailer. In fact, if I were to fully charge the batteries, I'd be able to take it out for a long weekend (or more) without worrying about recharging.
Second step forward...
This past weekend, I rerouted the cabling that originally went from the AC/DC charger (in the trailer) to the lead-acid battery (on the tongue of the trailer). This cabling now connects the input of the new DC/DC converter (in the trailer) to the junction box for the 7-way trailer connector (on the tongue of the trailer). At first, I was thinking of replacing the existing #10 cable with #8 cable, but noticed that things were VERY TIGHT in the junction box for the 7-way trailer connector. Instead of 5/16 bolts, connections were made with #10/32 screws. I would never be able to fit #8 lugs inside the box. Sooo, I stuck with the #10 cable.
Once everything was in place, I conducted my first test. I connected the 7-way cable connector to my truck, and started the ignition. Inside the trailer, I had disconnected the batteries by turning the breaker off. I checked the voltage from the DC/DC converter, which was 14.2V (appropriate for the lithium battery preset). Appliances like the fan and lights seemed to be working properly. I used a clamp ammeter to measure the current coming into and out of the DC/DC converter, and everything seemed as it should be. I was able to monitor input/output voltages using a Bluetooth connected cellphone.
One step back!...(hopefully only one)
I then turned the breaker on, so that the lithium batteries would be connected. The batteries were nearly fully charged, so I did not expect any large current draw. However, I noticed right off the bat that something was wrong. The ammeter showing that the output of the DC/DC converter would go from 20A to 0A every several seconds. The input of the DC/DC converter would go from 30A to 0A. The voltage into the DC/DC converter would go from 14V to 9.8V. At that point, the cellphone app would say that the charger was "disabled" due to undervoltage. At times, it appeared that not only was the charger disabled, but that the unit had actually turned itself off entirely so that it did not appear in the cellphone app! All this was happening every several seconds.
Therefore, I repeated the test. This time, I did not turn the circuit breaker on. Instead, I turned on individual appliances (fans, lights, etc.) while recording voltages and currents into and out of the DC/DC converter. By steadily increasing the number of appliances, I was able to change to draw on the output side of the converter from 0.6A (phantom load) to 10.3A. As I did this, the current going into the converter changed from 0.6A to 15A. The input voltage changed from 13.2V to 10.8V.
While doing the test, I had to disable two features on the DC/DC converter. The first was "Auto Engine Off Detection", which assumes that the ignition is off if the input voltage falls below a certain value (around 13V). At this point, the charger would normally be disabled, so I had to turn off the feature to keep the charger working. The second feature was "Input Voltage Lockout", which turns the whole system off if the input voltage falls below a certain value (around 12V). I had to turn off the feature to keep the charger working. I would think that if everything was hunky-dory, I would not have had to disable either of these features. The current that I was drawing was only half of what the DC/DC converter documentation said that it could provide.
It appeared that I was drawing a lot more current from the tow vehicle that I had ever expected, and was bringing the voltage down as well! I wasn't sure if this was a problem with the DC/DC converter, or if it was a problem with the cabling. I came up with a quadratic equation for the required input current and resulting voltage drop from the tow vehicle, using the efficiency factor (87%) from the converter manual and the resistance for #10 cable (from David's WireSizer program). Even if I assume a 50' round trip for the length of the truck and the camper, the current draw should only be around 11.2A (instead of 15A) and that even with a ensuing voltage drop, the voltage should higher than 10.8V. I played around with the numbers a bit, and noticed that the calculations seemed to line up with the actual values if the resistance was 3 to 5 times greater than what I thought it should be.
I know that my cable harness is a mess... I dragged it for around a mile a couple of years ago, and wore away a good amount of plastic... but the conductors seem to be intact, albeit a little rusty and maybe not as tight as they once were. I was surprised to see the small terminal screws in the junction box for the 7-way trailer connector... they are nothing compared to what I used to connect the batteries and other components. I wonder if these connections could be contributing to resistance, and if there is some way to "clean up" the connectors... particularly the 7-way connector.
At this point, I'm also wondering what size cable is used between the alternator and the 7-way connector on the truck, and if it would be appropriate to increase it to something greater (#8 AWG? Maybe #4 AWG as Dave mentioned in a previous post). I also wonder if I should bypass the 7-way connector entirely and use an "Anderson" type connector, or something like what Dave mentioned above for the solar setup.
Today I cleaned the pins on the 7-way connectors... both on the tow vehicle and on the trailer. I first sprayed them with "tuner control cleaner and lubricant"... I bought this a long time ago when radios had something called "knobs". I then gently rubbed emery cloth against the surface of the connectors. Afterwards, I used a small flat screwdriver to bend the connector blades so that the connections would be a little tighter.
The change was significant. The DC/DC converter was able to function with the lithium batteries connected, without cycling the charger on and off. Things seem better, but I'm still not out of the woods.
Admittedly, the batteries might have had more charge on them today then yesterday, and therefore might have drawn less current. So I reran the tests that I had done yesterday, while turning on appliances and measuring voltages and currents. Yesterday, it seemed as if the cables/connectors were providing 3 to 5 times the resistance of 50' of #10 cable. Today, the same setup (with a cleaner connector) was only providing around 2 times the resistance. Much better. Yesterday, when I had the maximum number of appliances on, the output current from the DC/DC converter was around 10.3A, the input to the DC/DC converter was around 15.0A and the input voltage was around 10.9V. Today, the output current was the same (10.3A), but the input current was reduced to 13.0A, and the input voltage increased to 12.4V. This suggests that there was less loss in the cable run, so the DC/DC converter did not need to draw as much current, which helped to reduce the voltage drop.
When I switched the batteries in place, The DC/DC converter provided 18.9A to charge the batteries. However, it drew 27A from the tow vehicle (dangerously close to the 30A fuse limit). The input voltage to the converter was 11V, and the output voltage was 13.7V (since the battery was charged enough to be in float mode).
When I re-enabled "Auto Engine Off Detection", the charger shut itself off due to the low voltage input to the DC/DC converter. At this point, the DC/DC converter seemed to act as a piece of wire... instead of providing 27A, it drew 4A to 7A (it bounced around a lot), and only provided 4A to 5.5A to the batteries. The input voltage was around 12.9V to 13.2V... if it got any higher than this, the charger would get enabled, draw more current, which would reduce the input voltage and turn the charger off again!
Sooo... I need to figure out a way to reduce the resistance more. Things work now, but I'm drawing 27A which is scary close to the 30A fuse limit. And I have to disable the "Auto Engine Off Detection" to do this. And things may get worse with depleted batteries. I plan to deplete the batteries more and rerun the test.
Any suggestions for how to reduce the resistance more would be appreciated (recabling with thicker gauge, better connectors, etc). I know that some recommendations were made in the initial thread... I'll go back and reread these (again!).
Here is how to find bad connectors that may be causing your voltage drop:
Hook a digital voltmeter to a good ground, using a long cable that will let you reach the entire circuit. Then put your load on and starting with the source, the TV's battery presumably, check each connection, in and out. Any measurable drop, other than long wire losses should be investigated.
You obviously need to get to near the predicted wire voltage drop.
BTW, you are using the round trip length for Wiresizer, right?
David
From your detailed description so far, I suspect you need more work on the 7 pin connector and it's terminal block. It's hard to clean up rust to make a good connection. Have you considered replacing the 7 pin harness with new? How is the 7 pin connector in your tow vehicle? Anything bent or corroded?
I'm bothered by the 27A draw even when the batteries are fully charged. More to think about there.........
David,
Yes... I am using the round trip. I'm estimating that the combined cable run through the truck and the trailer is around 25' in one direction, or 50' in both directions. Right now, the return in the trailer is via a (white) cable back to the terminal block for the 7-way connector. I suppose that I could ground the return to the chassis, near to the DC/DC converter, and that this might reduce the resistance for the return current. However, using a cable to the terminal block seemed more straightforward.
I like the idea of using a voltmeter and looking at voltage drops. I suppose that I could do this at the truck battery, the fuse box in the truck (maybe), the terminal block for the 7-way connector on the trailer, and then at the DC/DC converter in the trailer. However, it would be great to be able to do this just before the 7-way connector on the truck. It's hard to get to the connectors when the cable is connected though. I was hoping to do this today, but spent too much time matching wits with a groundhog. I lost. I did manage to get the shunt connected and the ammeter calibrated. Let's see the groundhog do that!
Merlin,
I did clean the 7-way connector on the truck. It didn't look corroded or bent. I've thought about replacing the 7-way connector on the trailer since I did drag it a bit. Even though I finagled the blades back into position with a screwdriver, I'm wondering if they don't fit as tightly as they should. However the replacement parts that I've seen at the RV store (where you just replace the connector, not the cable) seem like they are cheap plastic. The wiring harnesses available online seem a little better, but the power and return seem to be at most #10AWG, which is what I already have, and the terminal screws accept small crimps (not like the lugs that I'm using in the camper), and the 7-way connectors are copper but not tin plated. Should I be looking for something that has at least #8 for power/return, larger terminal screws, and tin-plated connectors? Does something like this exist?
It does look kinda silly to have #8 cable coming out of the DC/DC converter, with only #10 going in. The cables going into the DC/DC converter are much longer and carry more current. However, I'm concerned that I will not be able to get a #8 lug to fit inside the terminal block. The screws inside the block are 10/32, and it is not easy to find a #8 lug for that size screw. I found a 60 piece kit (https://www.amazon.com/haisstronica-Battery-Terminals-Eyelets-Tubular/dp/B09G9D5R9B/ref=sr_1_8?crid=1YHW9C1KORQ9E&keywords=wire+lugs&qid=1649644434&s=industrial&sprefix=wire+lugs%2Cindustrial%2C66&sr=1-8) that has five such connectors... it seems strange to buy a whole kit for 5 connectors. I guess that I have to keep on looking. Presumably crimps are smaller than lugs, but I've not seen #8 crimps for a #10 terminal screw.
I plan to do David's test, but I wonder if I'll need to resort to using a separate connector (like Anderson (https://www.amazon.com/Anderson-Power-Products-Connector-Housing/dp/B07CHD4JCK/ref=sr_1_4?crid=3YSD2CC6VM4I&keywords=anderson+connector&qid=1657246522&sprefix=anderson+connector%2Caps%2C78&sr=8-4)) to carry the power.
I don't think there are any 7 pin connectors that take more than 10 gauge wire for power. You could replace the entire thing all the way back to the junction box and then use dielectric grease on the connections. A molded connector would be your best bet. From your descriptions of mechanical damage and corrosion, I bet the 7 pin you have is a high resistance.
https://www.etrailer.com/Trailer-Wiring/Bargman/54006-059.html
Despite the steady rain, I was pretty enthusiastic about doing David's "voltage drop" test. I got everything set up, only to notice that the DC/DC Converter would not stay engaged due to a "low voltage lockout". I could have disabled this, but I noticed a really low voltage on the dashboard of the TV. It was around 12.6V. Normally the voltage from the alternator is around 14.4V when I first start the engine, and then drops down to 13.2V to 13.6V a couple of minutes afterwards. There are times though (I noticed this a couple of days ago) when the voltage is only 12.6V at the alternator. Why does this happen? Does the truck reduce idle? Does the alternator go into a different mode? I had "tow mode" on.
Merlin,
Thanks for the link for 7-pin cable, as well as the tip for dielectric grease. I notice that there are some 7-pin connectors labeled "RV style"... does this mean that they have a special pinout for RV's? Or is there some other benefit? I measured my cable length, and think that I may be able to get away with a 6' cable (https://www.etrailer.com/Trailer-Wiring/Bargman/54006-009.html), which appears to be significantly cheaper, while still being a Bargman. Is Bargman better than Hopkins?
I did notice that the is one wire that extends from the 7-pin connector, through the junction box (without stopping there), and into the trailer breakway battery. I'm thinking that this is a 12V line... If I replace the 7-pin connector, can I daisy-chain this breakaway battery wire to the 12V line in the junction box?
Let's talk about the breakaway battery. There is an old thread that also discusses this. The breakaway battery supplies DC to the brakes when the cable pulls the switch on the tongue closed in an emergency breakaway. It is independent of the TTs house battery. This is a problem, particularly for those like me who don't camp for the winterish 6 months. The small 5-10 Ah AGM battery runs down and it is toast.
The solution is to get rid of the breakaway battery. Inside the junction box on the tongue, you can get to the wires to the battery. Disconnect them from the battery and wire the positive from the switch to the pin #4 circuit- the one that keeps your house batteries charged and which goes to your DC to DC charger once it is all finished and working.
This change eliminates the breakaway battery and uses the more robust house batteries for that purpose.
David
David,
I could do that, but that would mean that I would have to run a separate set of cables from the house batteries to the breakaway battery. When I installed the DC/DC charger, I used the cables that originally connected the battery (outside the trailer) to the AC/DC charger (inside the trailer) so that they now connect the junction box (from the 7-pin connector) to the DC/DC charger (inside the trailer).
I did replace the breakaway battery last year, and was wondering how to keep from having to do it again, so this info may come in handy. I was wondering if it would be necessary to replace the #10AWG going from the junction box to the DC/DC charger with something like #8. If I did, then I could use the #10 for the breakaway battery. However, as your test indicates, and as Merlin suggests, I may have other fish to fry.
The rain let up, so I managed to get outside and do the "voltage drop" test. I did two tests, one with a bunch of appliances turned on, but the lithium batteries disconnected, and the second test with both the appliances AND the lithium batteries connected. Here are the results:
Appliances only:
Current into DC/DC charger: 12.0A
Current out of DC/DC charger: 8.7A
Voltage at TV battery: 12.59V
Voltage at junction box: 11.65V (drop of 0.94V... 78% of total drop)
Voltage into DC/DC charger: 11.39V (drop of 0.26V... 22% of total drop)
Voltage out of DC/DC charger: 14.17V (absorption mode?)
Appliances plus lithium batteries:
Current into DC/DC charger: 30.8A (scary)
Current out of DC/DC charger: 19.3A
Voltage at TV battery: 12.55V
Voltage at junction box: 10.56V (drop of 1.99V... 74% of total drop)
Voltage into DC/DC charger: 9.86V (drop of 0.7V... 26% of total drop)
Voltage out of DC/DC charger: 13.52V (float mode?)
Both tests suggest that around 75% of the voltage drop occurred between the alternator and the junction box. I had hoped that replacing the #10 cable in the trailer would help things significantly, but am now realizing that it would reduce the voltage drop at most 25%... and probably much less than that.
Sooo... it seems that my options are to purchase a new 7-pin connector and see if that helps, or to put in an "auxiliary cable" that would be accessible through a second connector, with a separate fuse. The second approach could be another can of worms though. I was trying to determine what size cable is used in the truck... if the cables were small, then the "auxiliary cable" might make sense. However, much of it is wrapped in loam and tape, and I'd rather not disturb it.
Hmm! So lets look at in and out of the DC charger in the second case where the current is higher. The input to the DC to DC chargeris 9.86V at 30.8A or 304 watts. Output from the DC to DC charger is 13.52V and 19.3 amps (it is doing its job and limiting to 20A or is it 18?) or 260 watts. So it is only about 260/304 = 85% efficient. I would have thought it would do better.
Looking at the long 10 gauge wire from the TV battery to the junction box, about 25' one way, and 30.8 amps should result in a voltage drop of 1.6V. You are getting about 2 volts of drop. Maybe the length is more than 25' or the gauge is not #10 (doubtful) or Wiresizer is wrong, or there are connector losses- that I can believe. So check the connectors.
Finally 30.8 amps may blow the TV's fuse before too long but probably not. I would like to see it down to 25 amps though.
The DC to DC charger is doing its job- boosting voltage to where it needs to be, while using the available input voltage and limiting output current to 20 amps. But the input voltage is so low it pulls 30.8 amps to make that work. When the batteries are almost full the DC to DC charger should supply about 14.4 volts at the end of the charge cycle. That may really be a problem for the fuse.
David
Actually, the data sheet for the DC charger says that the efficiency is 87%... so 85% is not far off.
In my initial estimates, I was assuming 50' round trip for the entire cable run (including the trailer, since it is relatively short), but now that I've gone out there with a tape measure, I'd say that the round-trip run from the truck battery to the junction box is at least 50', with an additional 20' round trip for the camper. As you mentioned, WireSizer says 1.6V drop to get to the junction box, and I measured around 2V. For the 20' round trip for the camper, WireSizer says that the drop would be .64V, and I measured .7V. Together, the observed voltage drops are a little bigger than the calculated values (by a little less than half a volt), but I can imagine that this could be attributed to loss in the connectors, and the cable length in the truck could be greater than 50' round trip.
I was hoping that a new 7-pin harness might fix the problem, but now I am beginning to wonder if I (also) have to increase the size of the cable.
Well, you've been doing interesting and methodical work so far, so I'd say continue with one step at a time and hope it's a forward one and not a backward one. Do the connector and see where things are.
Quote from: Merlin on July 09, 2022, 10:24:37 PMWell, you've been doing interesting and methodical work so far, so I'd say continue with one step at a time and hope it's a forward one and not a backward one. Do the connector and see where things are.
I agree. Methodical solutions are usually the best.
David
Before I made any more "permanent" changes, I was hoping to see how the DC/DC converter performed if I bypassed the 7-pin connector and the #10 AWG cables entirely. I ran #8 AWG red and black cables under the trailer (just laying on the driveway) and connected it to the input of the DC/DC converter. I used a jumper cable to connect the other end to my truck battery, and reran the tests that I did a couple of days ago. Since I bypassed the 7-pin connector, I didn't take readings at the junction box.
Appliances plus lithium batteries (12.55V TV voltage):
Current into DC/DC charger: 26.9A
Current out of DC/DC charger: ??? See note below
Voltage at TV battery: 12.55V
Voltage into DC/DC charger: 11.1V
Voltage out of DC/DC charger: 13.5V
The good news is that, for the test that included the batteries, the current into the DC/DC converter was reduced by almost 4A. It's still high though. I wasn't able to measure to current out, because as I was about to do so I noticed a change in the voltage and current. This was probably because the alternator started charging as a higher voltage. So I recorded these new values as well.
Appliances plus lithium batteries (13.87V TV voltage):
Current into DC/DC charger: 23.0A
Current out of DC/DC charger: 19.0A
Voltage at TV battery: 13.87V
Voltage into DC/DC charger: 12.7V
Voltage out of DC/DC charger: 13.6V
Since the TV voltage went up, the current draw dropped from 26.9A to 23.0A. I wonder why the alternator decided to provide a higher voltage output today, but didn't do so a couple of days ago. I've since read that the alternator will reduce voltage in order to avoid overcharging the TV battery, or if there are heavy current draws, but I'm not sure how that would play into what I'm seeing here.
I bypassed three things in the test that I did above... the wiring between the alternator and the 7-pin connector in my TV, the 7-pin connector itself, and the wiring from the 7-pin connector to the DC/DC converter in the trailer. As Merlin suggests, I will replace the 7-pin connector, and see how much of a difference that makes.
The link that Merlin has above is for an "RV style" connector. I assume that "RV style" refers to pinout and wire colors, as suggested here (https://www.etrailer.com/faq-wiring-7-way.aspx). I plan to get a 6' cable, because that is the length of my current cable. Anyone have an opinion on which is better... Bargman or Hopkins?
I went to etrailer.com, and noticed that the Hopkins 8' cable was comparable in price to the Bargman 6' cable. However, the Bargman seemed to be a little better due to the double-bladed "pinch" connectors (assuming that this makes a difference) and silicone cable, so I ordered that. I made sure to get the "RV style" connector.
I recently got the Bargman 8' (https://www.etrailer.com/Trailer-Wiring/Bargman/54006-058.html) when rewiring my HD tilt trailer this spring. You can argue whether it its worth $75, but it is a very nice pigtail; super flexible and high quality wire. You won't be disappointed.
I recently discovered how NOT to clean the 7-way connector on the back of your tow vehicle. Yesterday, I tried to do this using steel wool. The moment I tried to do this, the 12V got shorted to ground through the steel wool. It started to glow a very pretty color. Good thing that I did not have any volatile solvent on it... otherwise I'd be writing this post from the intensive care unit.
I installed the Bargman 7-way connector today. I'm happy to report that it was not as exciting as yesterday. I was surprised, however, to see that insulation for the cable as well as the individual wires were all silicone. This did make the cable pretty flexible as Keeena had noted. The light blue color of the cable does clash a little with my "blue granite" Silverado, but I'm willing to make that sacrifice if the silicon protects the cable better. I hope that I'll never be camping if -67F temperatures, but if I am, I'll be glad to note that the insulation is rated for use at that temperature!
I also cleaned the connectors using CRC QD Electronic Cleaner (https://www.crcindustries.com/products/qd-174-electronic-cleaner-11-wt-oz.html) and then applied CRC Dielectric Grease (https://www.crcindustries.com/products/technician-grade-dielectric-grease-3-3-wt-oz.html) just as it began to rain.
After installing the 7-way connector, I repeated the test that I did a couple of days ago. Since it was raining pretty hard by now, I did not go out to measure the voltage at the truck battery. I think that it was probably around 12.6V. I'm wishing now that I had verified this.
Appliances plus lithium batteries:
Current into DC/DC charger: 25.2A
Current out of DC/DC charger: 19.2A
Voltage into DC/DC charger: 11.8V (a drop of .8V from assumed truck battery voltage of 12.6V)
Voltage out of DC/DC charger: 13.6V
The current into the DC/DC charger was around 1.7A less than the test that I did a couple of days ago, when I bypassed the old 7-pin connector using a jumper cable and #8AWG cable. The voltage drop was smaller too, 0.8V instead of 1.5V. Current and voltage out of the DC/DC charger was about the same.
The current into the DC/DC charger was around 5.6A less than the test that I did last week, when I was using the old 7-pin connector. The voltage drop at that time as 2.74V!
So, as Merlin suggested, the new connector really helped. Thanks Merlin! Thanks also to David for his insight.
I still wish that the current as a little lower though... 25.2A is still cutting it close to 30A. And this is with the output voltage being 13.6V, not the 14.2V that might occur once the batteries are discharged significantly.
I still have the #8AWG cable hooked up underneath the trailer. Sometime I may run another test using #8AWG cable for the trailer, instead of the #10AWG cable that is hardwired right now. I may also re-run David's voltage drop test and see what values I get at the junction box for the 7-way connector... this might suggest how much of the loss is occurring through the length of the truck and the connector.
Thanks for the cleaning tip! I suppose that also might apply to wire brushes that could lose a bristle in the wrong place.
Good work on the V/A testing and results. I suspect (but don't know) that you'll be ok with the 25.2A current on a 30A fused circuit, even if the voltage rises. Carry a spare!
Good job! I think you have squeezed all you are going to get out of that Pin #4 circuit. I agree with Merlin that 25 amps is marginal for a 10 amp circuit on a 30 amp fuse. But I also think that as the batteries get more fully charged and the charging voltage from the DC to DC charger rises to 14+ volts, the battery's acceptance amperage will drop giving you more leeway.
As noted above keep a few 30A fuses on hand. If they do blow with some frequency then your only choice is to run a parallel circuit with the existing one to keep the amps down below 30. If you keep the original one active you don't need 8 gauge. 10 gauge will do fine with a 30A fuse so that both share the load and the amperage in each will be below 20A.
You might even try tying in the new circuit into the existing 30A fuse in parallel with the old. I suspect the lower voltage drop with a parallel circuit will result in a higher voltage into the DC to DC charger which should drop the current below 25.3A.
David
Remember when I said that I didn't measure the voltage at the truck battery because it was raining? Well, I should have! The next day I reran the test. I thought that the TV battery voltage was 12.6V, but it was really 14.05V. That means that if the TV battery voltage really did drop down to 12.6V, I could be consuming up to 4A more current. I bypassed the 10AWG cable in the trailer with 8AWG and reran the tests, but the results were negligible.
I have a trip coming up at the end of the month, so I plan to use the existing cable in the tow vehicle. However, I will plan to use the voltage lockout feature of the DC/DC converter to disable the charger if the input voltage drops below a certain point. I'll also be sure to carry extra fuses.
FYI, I contacted Victron and asked if there was some way to limit the current output of the DC/DC charger. They said "no". I was hoping to keep the unit working with half of the current, rather than try to provide max current and then turn itself off because of a voltage drop! Their recommendation was to bypass the OEM equipment in the TV with parallel cable, fuses, and connectors. My recommendation was that they include this little tidbit in their marketing material.
Sometime in the future I may try to add parallel cabling. I was hoping to add additional (or thicker gauge) cabling after the 30A fuse in the TV, as David mentions above. I looked under the hood of my 2014 Silverado, and noticed that there was not convenient access to 12V posts as there was in earlier model Silverados. There isn't much room around the fuse box, and the cabling looks like it would take a lot of guesswork to figure out, and a lot of work to reassemble. A lot of tape and loom! Medusa would have approved, though.
I guess that I would add a parallel line before the fuse, with a fuse of its own... and maybe even a separate cable/connection to the trailer (via something like Anderson connectors). This makes my head hurt a little bit though. I wonder if I may somehow be undermining the function of the original fuse. Is anyone aware of other threads where folks might have done something like this for other applications?
The only problem with running a parallel line from a different spot on your TV is that it probably won't be switched by the ignition like the OEM circuit is. This is important to keep from running down your TV's battery.
David
Good point... although I think that pin-4 may always be energized on my Silverado anyway. I didn't have the keys in the ignition when I managed to ignite the steel wool while cleaning the connector!
In addition to the shutdown voltage that I mentioned above, the Victron DC/DC converter has a "startup" threshold that it uses to determine when the engine is on. This may be helpful. However, the voltages change so much when I connect the house batteries that it may be necessary to start the truck, then run into the trailer to switch in the house batteries, and then get back into the truck to start driving. This could be a problem if I had to do this every time I stopped for a break, but it beats having a dead battery.
Last Thursday I finished installing the Anderson connector on the underside of the trailer, so that I could easily plug in a long cable to the solar panels. I was eager to get the Anderson connector installed, because that meant that I could finish all of the work on the trailer for the Lithium battery upgrade. All of the connections inside the trailer for the Victron equipment were now complete, and I could put everything under my kitchen counter back together... including the cables that came from underneath the trailer into the AC/DC conversion area underneath the cooking range.
I managed to do this just in time so that I could take the trailer to a family reunion in the Alleghenies in PA. The surroundings weren't too exciting... I was parked in an in-law's driveway... but it gave me a chance to check out the DC-DC converter and exercise the battery capacity. Although we didn't spend much time in the camper, our aging dogs did, and we made sure that every fan was available to be put to use if it got too warm. We refrained from connecting to 120V, and used the lithium batteries for normal functions as well as popping out the slide-outs, water pump for showers, and recharging our iPhones.
Since the batteries were fully charged before we left on the trip, I did not expect any charging to occur via the DC/DC charger. However, I was hoping to connect to the DC/DC charger while we were on the road. Unfortunately, I was not able to use Bluetooth to connect to the Victron DC/DC charger... I don't think that the signal could make its way out of the steel cab on the Silverado and into the aluminum trailer. Therefore, I couldn't tell what was really going on with the DC/DC charger. During the 43 hour period that we were parked, we consumed around 70AH. This is around 1.6A per hour. When we got back home after a 5 hour trip (including a .5 hour break to eat lunch), the available capacity had increased by 27AH. This means that the DC/DC charger charged the batteries 6A per hour on average. The nominal output of the charger is 18A per hour, but I suspect that there were times that the charger turned itself off due to under-voltages. While the charger was actually charging, the current was probably much greater than 6A, but if it got too high then the voltage drop from the cabling might have been enough to turn the charger off. I really wish that I could have connected via Bluetooth so that I could have seen what was going on. At least I didn't blow the 30A fuse!
For the solar connection to the trailer, I used Anderson connectors because they are easier to attach/detach that MC4 connectors, and should be able to carry more current than MC4 or SAE connectors (which seem to be available with thinner wire gauges, but not thicker ones). The ones that I purchased (https://www.amazon.com/gp/product/B07CHB5LCB/ref=ox_sc_act_image_2?smid=AL9QLWRAVC5ML&psc=1) can carry up to 50A. I mounted the connector on the underside of the trailer using a Trailer Vision (https://www.amazon.com/gp/product/B07ZX27CPZ/ref=ox_sc_act_title_4?smid=A6MN7KNR7CLV1&psc=1) mount. It has a spring-loaded cap that hopefully will keep some of the road crud from splashing onto the connectors. I tried to put it someplace that would be easy to reach from the side of the trailer, but not someplace that would get excessive spray from the tow vehicle or the wheels of the trailer. I've attached a picture. I used 8AWG wire with protective loom, which was fed through the same opening on the underside of the trailer that was used for shore power and the 12V from the 7-way connector. Since the Victron solar controller was in the same area, cable lengths were pretty short.
I still have MC4 breakout connectors and an MC4 fuse (https://www.amazon.com/gp/product/B00YG2ESN8/ref=ox_sc_act_title_3?smid=ATVPDKIKX0DER&th=1) just before the solar panels. I still need to make a cable that would have an Anderson connector on one end and MC4 connectors on one end, to connect to the solar panels. Ideally, this would be a 30-40 foot UV resistant zip-cord cable at least 8AWG thick. BatteryCablesUSA (https://www.batterycablesusa.com/6-gauge-battery-jumper-cable-copper-by-the-foot) advertises 6AWG (no 8AWG), but it is currently out of stock and may not be UV resistant. If anyone has any recommendations that aren't copper clad aluminum (CCA), I'd love to hear it. A lot of stuff on Amazon is only 10AWG and/or CCA.
Interesting that you only recharged your batteries at about 6 amps while driving home. That is about what I used to get without a DC to DC charger from pin 4 of the 7 pin connector.
Since you seem to like fiddling with this stuff (like me) how about setting up a static test for an hour or so. First run the batteries down to about half, then start the TV's engine with the TV hooked up to the trailer. Also if possible put something on the throttle to raise the rpms up to 1,000+ rpm so the alternator is fully powered.
Then watch all of the voltages/currents for a half hour to an hour to see what is really going on.
Have fun!!!
David
Actually, I was glad to get that much. I really do think that the DC/DC charger is turning on and off, and your test would be a good way to confirm this.
In the past, I wasn't really able to rely on DC charging at all. During one of the first trips out with the Camplite, I made the mistake of leaving the refrigerator on DC while we drove. When we arrived at out destination, the house battery had gone down from 93AH down to 25AH! The refrigerator had been consuming the battery power, and the tow vehicle was doing little (if anything) to replace it. Since we were at a non-electric site, I had to use the tow-vehicle to recharge the battery without the refrigerator running. Even that seemed spotty... probably because the truck alternator was switching between 14V and 12.6V. I've read that the alternator will reduce voltage if it thinks that it may be overcharging the truck battery, but I'm not sure where the "logic" is to implement this. I tried little tricks to keep the alternator running at 14V (turning on tow mode and turning on the high beams), but I'm not sure if this made a difference.
I read your post yesterday, and have since disconnected shore power. Once the batteries get depleted halfway, I'll try the test that you suggest. This may be a good time to try out the refrigerator on DC power, now that I've replaced the broken relay that kept it from working in the past. That will be sure to consume a good amount of power from the batteries. I've been reluctant to "waste" the energy, but this might kill two birds with one stone.
When you do the test, keep an eye on the TV's battery voltage. Newish vehicles have "smart alternators" that do as you describe and cut the alternator output voltage under certain circumstances.
With the TV alternator voltage at 12.6 and a voltage drop of maybe a volt, yes the Victron may be shutting down and that would explain the low average amperage you noticed.
Something similar happened to me when I was trying to jump start a friend's car using our 2017 Mini as the charging source. The current through the battery cables would suddenly drop to near zero and wasn't doing anything to put a quick charge into my friend's battery. The Mini's alternator was cutting the voltage.
FWIW that car is too smart for its own good. You can't even change the battery yourself. As the battery ages the smart alternator compensates and if you replace the battery it stays the same unless you know how to reset it for a new battery by using an OBD2 device. I gave up and took it to my nearby independent shop and they reset it for me (or so they said).
Technology is getting too smart for us!
David
Last night I had left the refrigerator on in AC mode with four quarts of ice to to help bring down the temperature. This morning I ran the refrigerator on DC mode. It consumed around 15A, but the new relay worked and I was confident that I could use my refrigerator in DC mode... even if it were to consume a lot of current. Since it was hot, I also had the fans on... this added another 5A of current. So the refrigerator and fans were consuming around 20A. It took around 5 hours to get the lithium batteries to 100AH. By early afternoon I was ready to start the test!
I turned on the ignition in the truck, and monitored the voltages and current. The voltage into the Dc/DC charger was around 13.1V, and the output voltage was around 13.2V. The output current varied a lot, but seemed to be around 6A. This confirmed what I saw during my recent trip. Even though the maximum current was 18A, the charger would turn itself off because once the current became too high, it would cause the voltage to drop below 13.1V (the default threshold for engine shutdown detection). I thought that this cycle might occur every two or three minutes... but it was actually happening much faster than that.
Rather than wait to collect more data (like an adult would), I decided to stop the test and lower the threshold to a lower value to see if this would let me get more than 6A! I got nothing. By that time, the alternator decided to sit at 12.6V. I turned on tow mode, high beams, and sat there with my foot on the gas pedal, but the alternator still sat at 12.6V. At that voltage, the DC/DC converter declared that "engine shutdown" was detected, and kept the charger at a disabled state. It seemed that the alternator reduced the output voltage to keep from overcharging the TV battery.
So... I did my best to run down the truck battery. With the 7-way connector connected and the engine off, I turned on my high beams, running lights, and even recharged my iphone from the cigarette lighter.
After 45 minutes or so, I reran the test. As soon as the truck started up, the TV voltage would be around 14V. The DC/DC charger would produce around 10A at 13.3V. A couple of minutes later, the TV voltage would drop to 13.1 volts,, and the DC/DC charger produced around 6A... but this would decrease to around 4A a minute later. A minute after that, and the TV voltage would drop to 12.6V, which would ultimately turn the DC/DC charger off due to "engine shutdown detected". I am now wondering how I got an average of 6A of recharging on my recent trip.
For grins, I disabled the "engine shutdown" and "low voltage" thresholds. The DC/DC charger drew 29.7A. The input voltage was 9.6V. It provided 17.9A at 13.5V. It didn't blow my fuse, but came pretty close!
"For grins, I disabled the "engine shutdown" and "low voltage" thresholds. The DC/DC charger drew 29.7A. The input voltage was 9.6V. It provided 17.9A at 13.5V. It didn't blow my fuse, but came pretty close!"
Was the alternator voltage still at 12.6 while this was going on? If so that means a 3V voltage drop which is about double what you earlier reported. Could there be a new bad connection in the circuit.
If you could get the voltage drop back to a volt and a half or so, then the current would drop to about 25A. The other way is to run a separate larger gauge circuit, maybe even #6 gauge to keep the voltage drop down to a half a volt. That would probably drop the current even further, maybe into the low 20s even if the alternator is only putting out 12.6 volts.
But.... when the Li batteries get more charged they are going to want more voltage to maintain the 18 amps charging rate which will drive the alternator current back up.
But at the end of the day, it looks like you are fighting a losing battle with your smart alternator. An alternator voltage of 12.6 just isn't going to work well with a battery that requires as much as 14.4 V for a full charge.
David
I've not been following this thread closely but I have been thinking about the Victron DC/DC charger. I have a 2013 Toyota Tacoma TV which may or may not have a "smart"alternator. It does seem to stay at 13.6V then the TV battery is charged, which limits the TT charging even when connected with HD jumper cables. My question is, given the TV has a relay to prevent total TV discharge, what is the problem with disabling the Victron low input sensor and just letting it run with whatever it sees? Let one piece of smart technology defeat another piece of "smart" technology.
I don't think that there is a relay that prevents total TV battery discharge, at least while the TV engine is running. There is a relay that disconnects the Pin 4 circuit when the ignition is off but I don't think it has anything to do with the SOC of the TV's battery. That may be what you are thinking of.
So, here is another test suggestion (I am full of them, aren't I?): Draw down the TV battery to about 50% SOC. Then repeat the test that was just done. Hopefully the smart alternator will kick up the voltage to recharge the battery and at the same time provide a higher input voltage to the DC to DC charger.
If that works then you may be able to solve your problem by defeating the Victron's cut out.
David
David,
I was referring to the ignition operated relay to isolate TV and TT. My real question was about defeating the low input setting on the Victron. Seems like that setting would only be useful in the absence of electrical TV/TT isolation. I'm thinking of using the Victron only when set up at a campsite and with the TV running and connected to the Victron with heavy wire. I'm concerned that, even with heavy wiring, the TV alternator would limit the voltage seen at the Victron to something lower than the low input setting. What's the problem with disabling the low input setting?
"What's the problem with disabling the low input setting?"
None at all as long as the TV's alternator can be made (well fooled probably) to put out more than 12.6 volts.
David
In response to David's earlier question about alternator voltage... Yes, the alternator voltage was 12.6V when I did my last test with the low voltage lockouts disabled. It's possible that the part of the 3V drop is because the DC/DC charger is drawing extra current to compensate for the lower voltage of 12.6V... and that extra current means even more voltage drop! My math suggests that in an ideal case with #10AWG, the current draw should have been 25.6A (instead of 29.7A), and the voltage at the DC/DC charger should have been 10.8V (instead of 9.6V). It's like I'm seeing one and a half times the resistance that I expected to be seeing. Even though the 7-way connector is new, it probably is adding some extra resistance, as well as the hitch's junction box, and other connectors.
During my previous tests, I tried to "fool" the alternator into operating at a higher voltage by discharging the TV battery before running the tests. However, that didn't seem to work. Perhaps I didn't discharge it enough, but I'd be a bit leery about discharging my TV battery a lot in order to charge my trailer battery. This might be good for a test, but I wouldn't want to do it regularly.
In a pinch, I would like to think that CharlieM's solution might be workable in a campground setting, where I can monitor things via Bluetooth on my cellphone, and had extra fuses. With the current wiring and connectors, I'd have to expect a current draw of nearly 30A, if the alternator voltage was 12.6V. If there is another way to get the voltage above 12.6V without draining the TV battery, that might be even better.
I agree that it's tough to get lithium batteries to charge with an alternator voltage of 12.6V. In retrospect, it would have been good to have a DC/DC charger that would allow one to control the output current, so that one wouldn't have the larger voltage drops. Without this, the only option (it seems at the moment) is to put in heavier gauge lines and better connectors. I may wait awhile to do this. Until then, I'll be glad to get 6A (IF I can get it) and carry extra fuses. In a pinch, I would hope that I could disable the low voltage lockouts as CharlieM suggests. Is there a risk of harming the alternator if I do this, particularly if the engine was idling at a campsite?
Quote from: RV Squirrel on August 04, 2022, 10:45:56 PMIn response to David's earlier question about alternator voltage... Yes, the alternator voltage was 12.6V when I did my last test with the low voltage lockouts disabled. It's possible that the part of the 3V drop is because the DC/DC charger is drawing extra current to compensate for the lower voltage of 12.6V... and that extra current means even more voltage drop! My math suggests that in an ideal case with #10AWG, the current draw should have been 25.6A (instead of 29.7A), and the voltage at the DC/DC charger should have been 10.8V (instead of 9.6V). It's like I'm seeing one and a half times the resistance that I expected to be seeing. Even though the 7-way connector is new, it probably is adding some extra resistance, as well as the hitch's junction box, and other connectors.
During my previous tests, I tried to "fool" the alternator into operating at a higher voltage by discharging the TV battery before running the tests. However, that didn't seem to work. Perhaps I didn't discharge it enough, but I'd be a bit leery about discharging my TV battery a lot in order to charge my trailer battery. This might be good for a test, but I wouldn't want to do it regularly.
In a pinch, I would like to think that CharlieM's solution might be workable in a campground setting, where I can monitor things via Bluetooth on my cellphone, and had extra fuses. With the current wiring and connectors, I'd have to expect a current draw of nearly 30A, if the alternator voltage was 12.6V. If there is another way to get the voltage above 12.6V without draining the TV battery, that might be even better.
I agree that it's tough to get lithium batteries to charge with an alternator voltage of 12.6V. In retrospect, it would have been good to have a DC/DC charger that would allow one to control the output current, so that one wouldn't have the larger voltage drops. Without this, the only option (it seems at the moment) is to put in heavier gauge lines and better connectors. I may wait awhile to do this. Until then, I'll be glad to get 6A (IF I can get it) and carry extra fuses. In a pinch, I would hope that I could disable the low voltage lockouts as CharlieM suggests. Is there a risk of harming the alternator if I do this, particularly if the engine was idling at a campsite?
I've been struggling to figure out why you seem to be a special case, since charging an auxiliary battery (either in a trailer or for other purposes) using the vehicle alternator going through a DC-DC converter is very common and successful in the overlanding world. I think it comes down to having too high an expectation of the existing wiring and the 7 pin connector system. Those I've known to be successful use much large gauge wire, at least to the back cargo area of the vehicle, and in the trailer if feasible. Separate, heavy connectors are used too. As we all know, this 12VDC stuff is painfully affected by wire gauge due to the amps and resistances involved. I think you're fine running things as they are now, but I bet someday you'll get some bigass wire and find a way to get it all the way from the alternator to the camper battery, through all the appropriate safety and alternator preservation systems. Thanks for the continued interesting posts on this and to David for following all this so closely. If we had such a thing, you two would get the Tech Posts of the Year Award (TPOTYA)
Thanks Merlin. As you know RV Squirrel and I are collaborating on an article which discusses the issues involved with doing this. I had no idea it would get so interesting (at least to us Geeks) with smart alternators involved.
RV Squirrel- When you have everything installed send me an overall pic and I will incorporate it into the article as well as some of the issues you are facing.
David
Squirrel, I've started to collect examples of others who have used the same DC-DC converter you have and most are using a minimum of 4AWG wire all the way from the TV battery. I can't seem to insert diagrams from the Pages program into ACF, but as I get good ones, I'll send them to your email, which I have.
Merlin, thanks. If folks are using 4AWG wire, then it's understandable why I am having problems using 10AWG! I think that you are right... I'll end up upgrading to a beefier cable and connector, but probably not any time soon. Until then, I'll probably use the voltage limits while driving (and expect low charging rates), and in a pinch disable the voltage limits if parked at a campsite.
David, I only have one more thing to do, and that is to finish the cable for the solar panels. However, the installation in the trailer is essentially finished. I've attached pictures of the Victron equipment. Pictures for the racks used to hold the AC/DC converter and the batteries are in this thread (https://aluminumcamperforum.com/index.php?topic=1576.0). Like an idiot, I failed to take a picture of the AC/DC converter after I installed it in the tray and then put everything back together... but I can get one if you like.
Here is a picture of the Victron components, as seen from the inside of the cabinet where we keep dog kibble. The wiring is routed from the other side, where the deck-mounted AC/DC charger and DC distribution box is installed.
Without Positive Bus Bar Cover.jpg
As you may notice, the positive bus bar is exposed, so I made covers out of sheet PVC. They are held in place by "knobs" that I tapped so that they could be screwed on. I also covered the aluminum tubing near the positive bus bar with Gorilla tape (to act a bit as an insulator). This may not be the best thing, but its better than nothing!
]With Positive Bus Bar Cover.jpg.
This is what the equipment looks like from outside the cabinet.
With batteries.jpg
For the solar cable, I'm currently looking for 8AWG "jumper cord" to connect to the MC4 connectors on the solar panels, but I've not been able to find it. So I'll probably settle for two separate 8AWG positive and negative cables like these (https://www.amazon.com/WindyNation-Extension-Connector-Variety-Available/dp/B01L6OU74M/ref=sr_1_3_mod_primary_new?crid=WIOT5R6VH7PP&keywords=8%2Bawg%2Bmc4&qid=1659900452&sbo=RZvfv%2F%2FHxDF%2BO5021pAnSA%3D%3D&sprefix=8awg%2Bmc4%2Caps%2C197&sr=8-3&th=1). I'll probably make a short 8AWG "Y" cable to allow me to connect the MC4 cables into the Anderson connector on the trailer.
I'm debating whether it is better to have one pair of long cables (say 40' one-way), or multiple pairs of short cables (for example, three 20' cables). Having multiple pairs would allow me to configure the cables in series or parallel. This would give me the following configurations, assuming that the MC4 connectors had no loss (probably not a good assumption). All of these cable configurations assume that the solar panels are configured in parallel. The cable losses are determined using David's WireSizer program.
- Three parallel 20' cables (one for each solar panel). 5.3A per cable, 20' one-way. 1.2% percent loss.
- One 20' cable (for all three solar panels configured in parallel). 16A total, 20' one-way. 3.5% loss.
- Two 20' cables (for all three solar panels configured in parallel). 16A total, 40' one-way. 7.0% loss.
- Three 20' cables (for all three solar panels configured in parallel). 16A total. 60' one-way. 10.5% loss.
I'm assuming that any drop in voltage on the input side will ultimately translate to the same drop in current on the output side, given that the output voltage remains the same (either 14.4V or 13.6V). And if the parallel solar panel configuration resulted in too great a loss, I could play around with the solar panels in serial.
Really nice wiring job! It's fun to look at stuff done well. 8)
Thanks! After looking at the picture, I noticed that the cable to the circuit breaker is hanging down a bit. I pulled this down so that I could put the clamp ammeter around it. It's a handy spot for measuring current, but I need to stuff it back and/or attach another cable clamp to keep it in place.
Regarding the "one long solar cable" vs "multiple short solar cables"... I've found out that the contact resistance of an MC4 connection and a Anderson SB50 connection are both comparable to about half a foot of cable (plus or minus... the Anderson is actually a bit better than the MC4). So I'm thinking that it may make sense to buy multiple short cables and attach them as needed, and have the flexibility to put them in parallel if my solar panels are in parallel.
It would be interesting to know if you could downsize the cables by running higher voltage from end to end, and converting it at either end to 12v
I suppose that running at 24V could have been an option. Presumably, when running at twice the voltage you would have half the current, and therefore half the voltage drop. I could have put my two batteries in series to get 24V (Battleborn supports series configurations up to 48V). I'm pretty sure that the Victron solar controller supports this. However, the Progressive Dynamics AC/DC converter and the Victron DC/DC converter that I have do not support 24V. Anyways, the biggest problem is with the connection to the TV's alternator... so I'd need some kind of converter near the alternator.
I'm comfortable making changes to the trailer, but making changes to the truck is another matter. I'll probably end up making some kind of change, but I'll need to do some research first. I'll probably be bugging you folks with questions, but it may not be until next year. Thanks for the thought though.
I ran into a slight issue when crimping connectors for the solar panels. Most of the MC4 connectors are only good for #10... I was not able to find one for #8 AWG. I was intent on using #8 AWG wire, so that I could place the solar panels further from the camper. However, I discovered that the crimp tool that I used for #8 lugs (going between components) did not produce as good a crimp on the #8 MC4 connectors for the solar panels. The metal in the MC4 connectors is a thinner than that in lugs, and the resultant connection was wiggly-jiggly (technical term... don't feel bad if you haven't heard it before). I actually had to insert a piece of solid copper wire into the crimp tool to create more of an indent into the crimp when using my "lug" crimper. This wire was only there to help with the crimp and was removed afterwards.
The bad thing about MC4 connectors is that if you aren't quite happy with something, you can't disassemble it after you've installed the backshell. My only option with the first "wiggly-jiggly" MC4 connector was to cut it off entirely and replace it with another one.
MC4 connectors do tend to be a little safer than other connector types, because the metal surfaces are less exposed. Disconnecting them can be a bit of a hassle... even if you do have a tool, because not all MC4 connectors are alike. The tool works better for some MC4 manufacturers than others.
I found the same thing when installing MC4 connectors to run cables from my solar panels to my controller- thin material that doesn't form a good crimp. So I soldered them. Not the best solution as soldered wires have a hard connection that with long term vibration, can break.
David
Been a long time since i have been here. Spent last 4 years fighting knee replacement surgeries. Anyway my lead acid battery on my 2016 21BHS is shot and i am looking to go lithium. We do not boondock and generally use full hook-ups. Any thoughts on a drop in battery and/or the need for a converter?
Why go through the aggravation and expense of switching to Li If you never boondock? Replace the bad battery with a similar one, or for no maintenance switch to an AGM. Much cheaper and easier and works fine with your existing converter.
DAVID
Quote from: DavidM on February 06, 2023, 02:57:23 PMWhy go through the aggravation and expense of switching to Li If you never boondock? Replace the bad battery with a similar one, or for no maintenance switch to an AGM. Much cheaper and easier and works fine with your existing converter.
DAVID
thanks David. Suspected i might be told to go that way. Any thoughts on a good AGM battery or brand?
[/quote]thanks David. Suspected i might be told to go that way. Any thoughts on a good AGM battery or brand?
[/quote]
I have a pair of 100 Ah AGMs in my current RV supplied by WindyNation from Amazon at $200 ea. At G31 size they are probably too big for your battery box. WN, Renogy and Weize are all good, low cost AGM brands and should have a suitable G27 size that shlould fit. All are available through Amazon.
David
Thanks David! I appreciate the advice.
Quote from: ammobob on February 06, 2023, 02:33:37 PMBeen a long time since i have been here. Spent last 4 years fighting knee replacement surgeries. Anyway my lead acid battery on my 2016 21BHS is shot and i am looking to go lithium. We do not boondock and generally use full hook-ups. Any thoughts on a drop in battery and/or the need for a converter?
Good to see a post from you again! Welcome back. David's advice is right on. I would only add that I see Reno has both Costco and Sams Club. Costco sells Interstate and Sams Club sells Duracell. Both are good brands and both have excellent return policies. I've used group 27 AGM marine/deep cycle Duracell batteries from Sams Club and they've lasted since 2014. The cores are getting valuable, so be sure to take the old one in for recycling.
Quote from: Merlin on February 07, 2023, 11:09:36 AMQuote from: ammobob on February 06, 2023, 02:33:37 PMBeen a long time since i have been here. Spent last 4 years fighting knee replacement surgeries. Anyway my lead acid battery on my 2016 21BHS is shot and i am looking to go lithium. We do not boondock and generally use full hook-ups. Any thoughts on a drop in battery and/or the need for a converter?
Good to see a post from you again! Welcome back. David's advice is right on. I would only add that I see Reno has both Costco and Sams Club. Costco sells Interstate and Sams Club sells Duracell. Both are good brands and both have excellent return policies. I've used group 27 AGM marine/deep cycle Duracell batteries from Sams Club and they've lasted since 2014. The cores are getting valuable, so be sure to take the old one in for recycling.
So had an Interstate from Costco but only got 4 years out of it. Pulled it from the camper when not in use and kept it on a tricke charger. Checked the fluid levels regularly. So that being said how did you get one to last from 2014?
Some trickle chargers provide a constant high voltage that keep a battery charged, but can shorten the overall life. During the off season, I plug the camper into shore power once a month and let the converter charge the batteries for a few hours. If you do use a trickle charger, use a smart one with periodic staged charging like those made by Noco and Ctek. I do like the Duracell AGM batteries, but our Sams Club closed, so I'll probably go Interstate this time?