Ready to jump to Lithium... any advice appreciated!

tbrady · June 04, 2018, 06:55:36 PM

Ok, officially "done" now. I added a thermal controlled cabinet fan (comes on at 88 degrees and cuts off at 82) and added a 5" vent to exhaust into the bathroom. I ran through the test again and this time the temperature in that compartment never got above 89!

If you decide to do something like this let me know and I can give the specific details of how everything is wired up and the exact parts used. I probably spent 40hrs researching and couldn't find anyone that had changed their power center how I did (most people that did this were able to swap in a new converter to their power center (not possible with the WFCO 8735) but it is quite easy to unhook the converter in the 8735 and use a different one with minimal wiring. The total time to do the wiring and everything else is probably under 10hrs, less if you are not anal-retentive like I am!

Gary M · June 26, 2018, 12:04:06 PM

How did I miss this thread? I think I was busy doing my own battery upgrade at the same time. I ran into the same dilemma with the stupid WFCO 8735. I ended up just leaving it as is, and installed an additional 50a Cotek charger. They both play nice together. I still get the DC passthru function of the converter when I'm hooked up to AC power, and the WFCO basically disables its charging function when the Cotek is charging.

Love how clean and lightweight your install came out. I went the AGM route out of freezing temp concerns, but now i have 150 lbs of batteries under my bunk which I'm not all that happy about... So i still might switch to your setup at some point. I'm just curious how your setup will work in freezing temps. Like will you have to keep your coach heated all day and night while in freezing temps?

Also.. do you have a link to the fan stuff, and the HDPE plastic board you got? My temps have only got up to 91 degrees when charging at max 50a, but its been really cool where I'm at, and I'm thinking it will get a lot hotter under there come August.
For mounting i just used plywood, but the HDPE plastic board sounds like a better lightweight solution!

That's also cool that those batteries came with a bluetooth monitor. I had to install the Victron monitor with shunt to get bluetooth, but isn't it awesome to be able to check your SOC from outside at the camp fire?! That's probably my favorite part of my entire install.. lol

I probably showed you a pic of my setup already, but if not, here it is..

tbrady · June 28, 2018, 12:29:14 AM

Hey Gary,

In hindsight I probably should have started this thread under travel trailer mods! Regarding the freezing temps... that was definitely a concern and one of the reasons I put the battery in the compartment with hot water heater. I figure during the coldest of days if we keep the hot water heater on it will keep that compartment above freezing. Also, the BMS on the battery will protect it from charging if the battery is below 32 (which is really the only concern). The app on my phone shows me the battery temp as well.

Here is the HDPE I got-
https://www.amazon.com/Seaboard-Density-Polyethylene-Finish-Length/dp/B00K2QT4P4/ref=sr_1_3?ie=UTF8&qid=1530156250&sr=8-3&keywords=hdpe+sheet+1%2F4

Here is the cabinet fan etc-
https://www.amazon.com/gp/product/B001BEX52Y/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I only ended up using one of the fans as an exhaust to the bathroom. I was thinking that if it was still getting too hot I would use the 2nd fan to blow air in to the compartment. I just cut the black dual shroud thing in half.

Also, seeing how we are so close if you ever get serious about doing this I can show you exactly what I did in person.

tbrady · August 11, 2019, 11:05:37 AM

Just wanted to give a long term update on this mod... This has been the best thing we have done to the trailer by far. 99% of our camping is without hookups and with the new battery my wife can run all the lights, radio, stove fan etc pretty much all she wants. We usually can go about 3 days before I need to fire the generator up. If I wait until the battery is below 50% SOC the voltage drops enough that it will charge in bulk mode which is right at 30 amps an hour. So basically I only need to run the genny around 2hrs every 3 days which is great.

The one issue I need to address is how to charge this battery with the tow vehicle. Currently it will only charge the battery at about 1 amp/hr (at best).

DavidM · August 11, 2019, 11:30:58 AM

Well, congratulations on your new Li battery bank. I think I can answer one question and I have another question for you:

If you had FLA batteries, they would charge at about 3-5 amps from the TV at 90% SOC and maybe 10 amps at 50% SOC. This is due to the low voltage from the alternator and the voltage drop in the wiring. The battery is probably seeing at best 13.0 volts particularly at the higher charging current. You can probably improve this by running heavy jumper cables directly from the TV's battery to the LL battery to minimize the voltage drop but that won't work while towing.

Li batteries and their charge management system probably require a higher voltage to charge. That is why your TV won't charge them much. There are a couple of devices you could try to improve this. One would be a simple voltage to voltage converter which could boost the incoming voltage to your batteries up to say 15 volts.

Another way would be with an integrated V to V converter and a three step charger like Sterling makes. But I don't know if these work with Li batteries.

Now to my question: What is your estimated amphour usage in 24 hours? Mine is about 10 AHs but we are very conservative with power use. That lets me easily go three days with my single Group 24 battery and stay at 50% SOC or above.

David

tbrady · August 11, 2019, 01:20:12 PM

Thanks for the info David! We typically use anywhere from 15-25 amps in a day. We usually run the radio all night to play ocean wave sounds (kids and wife need the white noise) and sometimes we'll run one of the fans all night as well.

I don't pay near as much attention to usage as I used to. The best part is my wife can basically do what she wants without trying to be conservative. We even turn on the awning lights all the time which we never used to do.

Merlin · August 11, 2019, 03:13:33 PM

Tbrady, Does your Sequoia have a 120V AC outlet?

DavidM · August 11, 2019, 03:50:00 PM

Quote from: Merlin on August 11, 2019, 03:13:33 PM
Tbrady, Does your Sequoia have a 120V AC outlet?

I think I know where you are going with this question: Use the 120V outlet to power your battery charger for faster charging, right? But most of these are limited to 150W AC which isn't enough to power the LL's converter and will only charge to 10A with a separate low power charger. Hooking up the two batteries with jumper cables will probably charge that fast, with the engine running which is the only way to do it.

David

tbrady · August 11, 2019, 04:40:49 PM

Quote from: Merlin on August 11, 2019, 03:13:33 PM
Tbrady, Does your Sequoia have a 120V AC outlet?

It doesn't have one...

Merlin · August 11, 2019, 06:10:45 PM

Ok. Just thought I'd see if what I do was possible (Davidm was correct!). I have a 120V AC outlet in my TV that can power this lithium battery charger to charge my 50Ah Born Free battery at 7.2A all the time I'm going down the road. Over a few hours, that provides more than enough juice to top off the battery, which I use for my electric cooler for travels when not towing. Nifty setup, but it would under-kill for your needs anyway.

https://www.amazon.com/NOCO-G26000-UltraSafe-Battery-Charger/dp/B004LWTHP2/ref=sr_1_4?crid=9RTLSV8NLISR&keywords=genius%2Blithium%2Bbattery%2Bcharger&qid=1565557190&s=gateway&sprefix=genius%2Blithium%2Bba%2Caps%2C147&sr=8-4&th=1

DavidM · August 11, 2019, 08:54:41 PM

Ok, I see where Merlin was going with this, using a small charger powered from the TV's 120V outlet to charge the batteries underway.

Like I said above you can do the same thing without a 120V outlet using Sterling's battery to battery charger. See https://sterling-power.com/collections/battery-to-battery-chargers/products/battery-to-battery-chargers-waterproof

The B to B charger seems to do what you want: take a low voltage source and boost it and regulate it to charge another battery. The Sterling product info says it works with Li batteries.

You would hook the input to your TV's charging lead then hook the output to your Li batteries. I think that the 20A version is the smallest that they offer. That may work ok, but it will be putting a lot of load on your TV's battery charging circuit which is limited to 30A. If you do this make sure that the TV's battery charging lead only goes to the B to B and not also to the converter where it is distributed to other 12V loads. Those loads may overload the 30A TV circuit when combined with the 20+A load of the B to B.

David

Merlin · August 12, 2019, 07:41:10 PM

Davidm, Thanks for posting info about the B-B charger. That's got very interesting applications and something I never thought about. It's especially useful for charging 2 different battery types from the same power source.

ADR · August 13, 2019, 02:07:37 PM

Quote from: DavidM on August 11, 2019, 08:54:41 PM
Ok, I see where Merlin was going with this, using a small charger powered from the TV's 120V outlet to charge the batteries underway.

Like I said above you can do the same thing without a 120V outlet using Sterling's battery to battery charger. See https://sterling-power.com/collections/battery-to-battery-chargers/products/battery-to-battery-chargers-waterproof

The B to B charger seems to do what you want: take a low voltage source and boost it and regulate it to charge another battery. The Sterling product info says it works with Li batteries.

You would hook the input to your TV's charging lead then hook the output to your Li batteries. I think that the 20A version is the smallest that they offer. That may work ok, but it will be putting a lot of load on your TV's battery charging circuit which is limited to 30A. If you do this make sure that the TV's battery charging lead only goes to the B to B and not also to the converter where it is distributed to other 12V loads. Those loads may overload the 30A TV circuit when combined with the 20+A load of the B to B.

David

I put the 30A Sterling unit in my Transit van to charge an onboard 105AH AGM from the vehicle- it has a couple of AGM profiles to select from- not all specify the same profile. Does a great job.
It can be wired to come on whenever the vehicle is running or it can do a voltage detect on the vehicle battery- when it is above a set point the Sterling comes on to charge whatever it is hooked to. IOW it won't run your power source dead while it charges whatever it is hooked to. It disconnects if the source battery gets too low.
When I originally installed the Sterling my van had a single flooded lead acid battery. I just finished modifying it to 2 ea AGM batteries and need to get into the vehicle PCM to reset it to AGM.
Once that is done I may remove the Sterling but it does have some nice features- such as a remote temp sensor you put on the battery you are charging so it can adjust the profile according to battery temp.

tbrady · August 14, 2019, 02:13:35 PM

Attached is a diagram that LifeBlue sent me for how to improve the charging but I don't quite understand it. Maybe one of you more smarter folks can dumb it down for me.

To me it looks like just adding a simple solenoid and running bigger wire? Is it really that simple?

Lifeblue also mentioned using a sterling unit in an email they sent me. Can you send me a link to what exactly you are using ADR?

Merlin · August 14, 2019, 03:11:39 PM

What the diagram looks like to me is just a way to hook up a house battery along with a starting battery. That's a long-solved need and many manufacturers make a solution for that. What's missing is a way to care for the lithium house battery with a charging profile (correct voltages for bulk and absorption stages and no float stage) to maintain it properly.