Battery monitor anyone?

[MitchB]

To finish up the project

[Merlin]

Very classy!

[DavidM]

I am thinking through how to install the $30 Drok battery monitor on my camper. I received the Drok unit and even though the installation instructions are in Chenglish I think I have it figured out. I also bought a 30 amp surface mount waterproof circuit breaker to correct a glaring electrical problem on almost all trailers- no over current protection for the wire near the battery. It will also give me an easy way to disconnect the battery when not in use.

The Drok shunt/measuring board has sensitive electronics inside so it must be protected from the weather. Ideally I would mount it inside the battery box but there is no room. So having saved the break away battery box that I removed and rewired, I plan to use that. I will mount the shunt inside and the surface mount breaker outside of the box. The breaker will trip the hot lead directly from the battery and then it will connect to the shunt.

The shunt/measuring board connects to the display with a USB cable. But the end that connects to the display is not a standard mini USB plug. It is wider and thicker than a USB connector and I don't know what it is. But I will run a standard USB cable from the shunt/measuring board which is a standard USB connector underneath the trailer and then up through the floor inside the cabinet where I will mount the display. Then I will use the supplied 3' ?/USB cable to make the final connection. Why they didn't use the same connector on both ends is a Chinese mystery.

The attached pic shows the breakaway battery box. the shunt and display and the two but different ends to the supplied USB cable.

So that is the plan. Any comments?

David

[tinkeringtechie]

The breaker will trip the hot lead directly from the battery and then it will connect to the shunt.

The shunt gets connected to the negative lead for this unit. It actually powers from it as well, so you just need to hook up the shunt and one positive lead on the terminal block.

The shunt/measuring board connects to the display with a USB cable. But the end that connects to the display is not a standard mini USB plug. It is wider and thicker than a USB connector and I don't know what it is.

It's just a female USB connector. The cable is a USB extension cord. No need to run a standard USB cable all the way to the cabinet... just splice any decent 4 conductor wire between the two ends and you'll be good to go. It uses RS485, not USB for communication so distance/noise are much less of an issue. If you don't want to mess with splicing then just get a longer USB extension cord like this:

https://www.amazon.com/Monoprice-15-Feet-Female-Extension-105435/dp/B003L137Y6/ref=sr_1_1?s=electronics&ie=UTF8&qid=1497454407&sr=1-1&keywords=usb+extension+cable+15

[DavidM]

Thanks for your thoughts and pointing out that the shunt goes in the negative circuit which is consistent with those I have installed in the past. The Chenglish and lack of any polarity symbols confused me.

I presume I wire it as per the two wire diagram, Figure 1 with the battery negative connected to the left hand big terminal of the shunt and the negative side of the load connected to the right hand lug. The positive side of the battery goes directly to the load (or in my case, through the breaker).

A separate power wire runs from the battery positive to the upper screw terminal on the shunt.

The supplied cable has male/female USB connectors as you say. Should have tried plugging one into the other, duh!! But I will probably run a long USB cable which I do have on hand rather than use 4 conductor cable which I don't have.

I will hook this up the next time we go camping, maybe in a few weeks. Then I will have more definitive data on amp hour (or watt hour) usage with no AC power available.

David

[MitchB]

What you're describing is the way I've wired mine (less the breaker part) and I have yet to blow up so I'm going with it.  I didn't run any cable to the inside for the display portion of the unit, rather I'm using the wireless feature.  In my case I have the bunk over the bed and not cabinets over the bed and if the display unit is on the bunk the wireless signal is strong enough but I can see how running a wire would be pretty straightforward also. 

Mitch

[DavidM]

Well, I got the Drok battery monitor mostly installed today, and damn if it doesn't work good. Some squirrely isses to work out, but all seems to work. This is how I installed it:

I used the small battery box that the breakaway battery came in to install the Drok shunt inside to have a drip proof place. I also mounted a 30 am breaker on the back side of the box. I ran the DC negative from the battery to one pole of the shunt and the negative load (the original wires that were connected to the neg terminal of the battery) to the other pole. I ran a 10 gauge wire from the battery's positive terminal to the bat side of the breaker and hooked up the pos loads to the load side.

I then ran a 14 gauge wire from the load side of the breaker to the top of the terminal strip on the shunt. This powers the shunt electronics. I hooked up the USB cable from the shunt to the display. I flipped the breaker on and violla the display came on.

It first showed zero amps so I turned on a few overhead lights and it showed 0.5 amp, 12.8 volts and 6.4 watts, all as expected. Then I hooked up my TV and started the engine. It first showed 13.5 volts and  a negative 4 amps that dropped to a negative 2 after a few minutes. The engine was idling and the battery was near full, so that was as expected as well.

So I didn't have time to play with it, but here are some issues:

The monitor shows pos amps when it is discharging, ie no TV hooked up and lights on in the trailer. It goes negative when the TV is charging. This is backwards from other boat battery monitors I have installed and the opposite to logic. Maybe I got the shunt wires backwards and I will check. I assume all I have to do is switch the heavy shunt wires to make it display the way i want.

The other issue is a bit more serious. The watthour reading seems to be in absolute numbers, ie it increases while charging as well as while discharging. Again I need to look at it more as I may have been reading it wrong.

And finally, I wish it showed amp hours used and not watt hours. Batteries are rated in amp hours not watt hours.

But in any case it does work and I will sort out some of these issue over time. Here are the pics of the installation: The first is an overall shot of the breakaway box. The second is the Drok display sitting on top of the box. The third is the backside showing the breaker. The final shot is looking into the box at the shunt.

David

[MitchB]

Nice, did you install the breaker for any particular reason other than there is no fuse or breaker near the battery on the OEM install?

[DavidM]

The fact that there was no fuse protecting the wire from the battery was the primary reason. Also I always disconnect my battery when we get home after camping and the switch on the breaker makes that easy.

David

[tbrady]

David, did you figure out a way to see remaining amp/hrs vs watt/hrs?  I was reading reviews on Amazon and it looks like you should be able to see remaining amp/hrs??  I think I will probably get one of these to install over the winter...

[DavidM]

The camper is at a storage lot remote from our house. I will try to resolve all of those issues when we go camping next time, maybe next week.

But i don't think that the display has an amp hour option. When I scrolled through the menu, I just got watt hours. No biggie, I can mentally divide watt hours by 12.

Of more concern is the way it calculates amp hours as it seems to total the absolute value of the amperage even though it reports positive and negative amps. But like I said, I haven't spent much time working through the options. The day I installed it, the sun was beating down on me and I just wanted to finish up and go home.

David

[bryan.a.white]

I love this thread keeping track of where things are in the electrical system is tremendously helpful while boondocking. I added a 200W solar system and wanted to have a meter for both charging and discharging status of the system to make sure I don't use more than I bank in the batteries.

The gauge on the left measures the charging status and the gauge on the right measures discharging status. The current and power shows a charge when there is a net charging situation. When the power consumption exceeds the charging power the gauge on the right shows the amps and watts of draw. This is especially useful when the panels are not charging. This also reads shore power charging.

I especially like the watt hour feature. I can reset both to zero at anytime to keep track of things.

[Merlin]

I love this thread keeping track of where things are in the electrical system is tremendously helpful while boondocking. I added a 200W solar system and wanted to have a meter for both charging and discharging status of the system to make sure I don't use more than I bank in the batteries.

The gauge on the left measures the charging status and the gauge on the right measures discharging status. The current and power shows a charge when there is a net charging situation. When the power consumption exceeds the charging power the gauge on the right shows the amps and watts of draw. This is especially useful when the panels are not charging. This also reads shore power charging.

I especially like the watt hour feature. I can reset both to zero at anytime to keep track of things.

Awesome; another person like me! Can't have enough read-outs or data! (Though you do need the SeeLevel tank monitoring system  )

[DavidM]

I just got back from a short overnight camping trip and tested the new Drok installation. After i set up the camper i hooked up the display and zeroed all readouts. There is an amp hour display in addition to watt hours. I don't know how I missed it earlier. But the two work differently and don't seem to be in sync.

After it was zeroed the amps showed zero (no loads of any consequence in the camper), the voltage was 12.8, and both the amp hours and watt hours were zero.

So the next morning I checked power usage. Watt hours were 44 and amp hours were about 3.0. The voltage was about 12.5 which was probably pretty steady overnight. 44/12.5 = 3.5 AH which is not consistent with the voltage and watt hours.

Then I hooked up the TV and started the engine. Amps were a negative 5. Watt hours continued to go up and amp hours down. Really strange. I didn't try reversing the connections to the shunt which might have made charging positive, but that will have to wait for later.

BTW, I wasn't surprised at all at the low amp hour usage overnight. The fridge was off so there were no continuing loads, we used the lights for about an hour, the water pump for maybe 5 minutes total and ran the water heater for 20 minutes.

When we do the Maine meetup I will get a chance to do a longer term test with the refrigerator running. I still expect to stay under 10 AH each day.

David

[MitchB]

Near as I can tell the ah display at the bottom is used by setting the battery amp hours when fully charged and the estimated current battery amp hours. The device will then show the required amp hours until fully charged and it will go up or down depending on whether the battery is being charged or discharged. I haven't played with that yet but that's what the manual explains. I assume if you don't enter values for the battery state it will start at zero and go up or down accordingly from zero.