Please review my off-grid 24v setup to suggest best Lithium Battery upgrade

[DickTater]

Hello wise people.
First-time poster.

I foolishly never asked for help building the original, and decided I needed to ask for help before I drop $2k on new batteries.

Q: Can I keep my setup, primarily as-is, and swap in some 24V Lithium battery solution that will best use the system's potential...and do I have anything in my setup which would be harmful/reduce life of the Lithium batteries?

For 5 years this system charged (12) lead-acid 210aH golf cart batteries. 3 strings of 4batts x (6v) = 24V.
So I believe it was 3 serial strings in parallel - 24v @ 610aH.
It was mostly guess work on panel potential vs batt capacity.
I calculate the lead-acid battery pack had 15.1kW capacity. Maybe 8-9kW usable.

6 x 370w Silfab Panels (DC). 2 banks of 3 panels each. Each bank of 3 panels connected in parallel to one CC.

I use two EPEVER 40A Tracer 4210AN MPPT 100V charge controllers.
I have a WZRELB 3000watt Pure Sine Wave Inverter 24V DC to 120V AC 60HZ (1st one died at about 10 months, the replacement is still going for the last 4 years)

I primarily used this for charging my Chevy Volt with approx. 16kW battery capacity.
Depending on C. Wisconsin temps, the car would go 30-44 miles on a full charge. My battery bank on a sunny summer day could charge the car up to 21+ miles after I got home at night. On sunny weekends it could charge the car all day, too, while banking any overage.

I can replace the EPEVER charge controllers if it will make enough of an improvement to warrant it...but would rather not. I THINK they are doing fine...but perhaps they aren't the right tool for the job or I could configure things better.

Hopefully that is enough information to go on, any help would be appreciated.

I will see if I have some of my hand drawn schematics to illustrate.
I can't swear how I have the panels wired (serial or parallel) but I can go trace my wiring to know for sure. But each bank of 3 - 370 W panels is dedicated to one EPEVER 40A Tracer 4210AN MPPT 100V charge controller and I believe how they are attached to the CC is in parallel.


I initially had 8 batteries when launched in January, upgraded to 12 almost immed. Also I was wrong about the car's batt. capacity...likely it was closer to 15-16Kwh




Notes on primary uses:
For about 3 years this worked well, dumping as much as I could from my solar battery bank into the car with the 110v, 8a Level 1 charger (approx 1500w) coming from the WZRELB inverter. Using a 220v, Level 2 charger is more efficient but wasn't feasible. I would switch the car charger (manually) to wall-outlet (grid) power when my solar bank was empty. The batteries were starting to disappoint after about 3 years. I managed to water them fairly religiously but then got lazy a couple of times after the 3 year mark and didn't do the batteries any favors. Very rough calculations, for about 4 years I was able to provide about 60% of my hybrid electric car's electrical miles using sunpower...possibly 30k miles. At $3 a gallon, that would be $2150 in my case. No idea how much eff. I was losing between panels and batteries, or batteries to car. Prob. 15-20% overall at least. But this whole system is all localized, the panels are ground mounted outside against the garage, the controllers and batteries just inside that same wall and the car parked on that side of the garage. It has been reliable and effective, if not ideal or best efficiency.

 

[MisterSandals]

3 strings of 4batts x (6v) = 24V. It was mostly guess work on potential vs capacity.

Hopefully wired in a balanced manner. Cannot tell from your pic.

(12) lead-acid 210aH

I calculate the lead-acid battery pack had 15.1kW capacity.

12x 210Ah x 6.4V nominal? = 16128Wh (8064Wh usable, discharging 50% down to nominal voltage)

3x 370W / 28V charging = 46A max definitely running at or near max capacity (40A)

I could replace the EPEVER charge controllers if it will make enough of an improvement to warrant it.

Are they charging your batteries to full every day?

Your array is 6x 370W = 2220W
8064Wh battery / 2220W array = 3.63h of quality sun

 

[DickTater]

Hopefully wired in a balanced manner. Cannot tell from your pic.

No it was crudely wired with no balancing. That will certainly need to be done better if I spend money on Lithium.
There are no bus or terminal blocks - if that is the correct term - but instead were directly wired from the CC. I will be looking to improve upon that and realize it created uneven wear-tear on the batteries. I did shuffle the battery order at the 1.5 year mark. The first incarnation of this car-charging setup was more of a proof of concept.

Are they charging your batteries to full every day?

I don't really have any way to guage that or prove it. They seemed to charge up nicely and would dump non-stop for 5-6 hours until the inverter detected low voltage and cut out. Less in winter, more during summer.
(ETA) The EPEVER monitoring software's SoC reading was notoriously inaccurate, and from what I understand....even more so since I didn't have the battery connections balanced.

The batteries stopped being useful for car charging a year ago and were recently recycled.

Thanks!

 

[Rednecktek]

Yes, you can just drop in the LFP's and maybe change the settings on your SCC to play better with the LFP profile. No need to replace your other stuff.

 

[DickTater]

Thanks for the replies!
I am shopping around right now, basically to replace my old Lead Acid capacity of 15-16 kWh. (8kWh usable)
I am counting on LFPs to give more useable kWh, and last longer with no maintenance.

Based on my current setup, is 15-16 kWh of LFPs a good target capacity, or should I be shooting for a different number?
Let's assume my average thru the year is 6 hours of good sunlight.

I am brand new to shopping for LFPs and would appreciate any advice on best 24V LFP batteries and configurations. I assume it would be better to get fewer batteries at higher ampHours. I will be searching the forums for best rated/reviewed LFPs but if anyone KNOWS of a better forum and can point me in the right direction, or has direct information to impart, that would be most appreciated. At minimum, if anyone has definite DO's or DONT's to pass along, I really want to dodge any avoidable missteps.

 

[Rednecktek]

Yes, a single high capacity 24v battery is almost always better than multiple low capacity batteries if for no other reason that it's less wires involved and no balancing issues.

As for capacity, how well did 8kw last for you? If it was plenty for your needs then it's a good starting point. If it was coming up short then you can use 8kw as a starting point. 8kw is about 300ah of cells, or a pair of 200ah batteries which gets you a purchasable size and good amperage for your inverter.

DO make sure the batteries have series support. I don't know if low temp protection is a concern or not, it's a price premium for some reason.

 

[DickTater]

Hello Good Folks, I now have 2x LIPULS 24v 200ah
LiFePO4
I want them connected in Parallel to work with my 24v inverter.
The manufacturer has verified connecting in Parallel is fine.

You can see how I had my lead-acid battery bank connection setup before (upthread drawing).
It shows I had the CCs and Inverter hooked up to the diagonal opposite corners of the battery bank, directly. From what I understand, that was not ideal.

So I would like to do it properly this time.

1 - Can it be as simple as to buy two bus bars as I have shown below? With the CC and Batteries and Inverter sharing the same bar?
2 - Can the batteries be connected in Parallel by means of the bar, especially if their cables are identical gage and very short distance?

Edit: I ordered 5 post/600a bus bars but they won't be here for weeks. I ordered another 400a with 4 posts that gets here in 2 days....and just going to have to live with that for the short term...stacking some of the cables on one post.

I understand I want to be using heavy gage cabling and making the shortest, most identical runs possible.
This is in my garage and I can move anything I need to (not like a boat or RV where space is affecting layout).


24v @400ah

I know there are some good threads on this forum that cover much of this information but I haven't found exact hits yet for some of my questions.

After this step is decided I will need to ask about best practices for a fuse(s) and grounding. Both are things my initial setup never had.

 

[Raymond Enriquez]

Swapping to lithium batteries could be a game-changer, but you'll want to make sure your current setup won't mess with their lifespan. The way you've described your system, it seems like it should work fine with lithium, but it's always good to double-check with the battery manufacturer to be sure. If you're happy with the EPEVER controllers, no need to change them unless they're causing issues.