CATL 302 Ah cells on their side?

[steven1955]

I have a 1975 FMC 2900r motorhome with cooked AGM house batteries, so it's time to upgrade to LiFePO4. The existing 12V nominal power converter would be retired and appropriate LiFePO4 chargers would be installed along with appropriate wiring, fusing, etc.



There are two unused awkwardly shaped spots in the motorhome I cannot fit any of the premade batteries I can find, but I can fit 4 CATL 302Ah 12V packs in a 2 x 2 stack (vs the most common 1 x 4 stack) in two different places. The catch is that in one spot the cells would be on their sides, and in the other spot the cells would be angled at about 45 degrees off horizontal. I have looked to see if CATL specifies acceptable operating positions, but have found nothing.

These home made battery packs would not be in a housing, but they would be installed so that they could not shift position, and all wiring would be protected against being crushed or short circuited.

If I don't build these packs and use commercially available batteries I have to sacrifice useful storage space, so the driver here is to save our storage space, not money. And I don't really need another project, but I'd really like to keep all of my storage space.

And if I end up building these packs, I'll need a suitable BMS. These cells have a rated maximum discharge current of 302A, but I don't need that much. I'd like to keep this at 150 to 200 amps, and don't know enough about BMS's to know if the BMS can be rated lower than the battery maximum discharge current.

Thanks in advance for any guidance.

 

[TorC]

Am I reading right you're looking at making two 12V batteries, totaling 8 CATL 302Ah LFP cells?

2x2 is just fine. Just run the busbar sequence correctly, and it'll work the same.

From what I read, compression, or at least maintaining form is very useful, but not critical. I think I'd still make up something to keep the cells together as a block, even if it's just two end plates on the broad sides of the cells and a couple lengths of allthread. Especially because they'll be in a high vibration environment, protecting the terminals from stress is prudent.

 

[steven1955]

Hi TorC,

I have two places I could put these battery assemblies. (I may only install one battery at this time.) Each assembly would be in a 2 x 2 block of cells clamped or banded together. The BMS, depending on what is chosen, might have to be mounted near the cells, but may not fit on the cells themselves due to the shape of the spot I have to put them.

The real question is whether the CATL cells will be OK operating on their sides and/or at a 45 degree angle. The absence of positioning information in the online literature does not mean that these CATL cells will be OK in a non vertical position. I can see that in some cell designs the vent might have to be on top.

And the nearly real question is what BMS to use.

 

[TorC]

Good, that's what I thought on cell count. Looks like there was a typo in your OP and I wanted to be sure everyone was picturing the same thing.

On which BMS, I'd go with either JBD or JK. Some people have good luck with Daly, but they seem to be more trouble. If possible, choose one with sufficient output so that one going offline won't take your system down - assuming you're keeping 12V. Going to 24V is possible, but it will require a little more finagling to get some of the wires routed. I hope both locations are fairly close together for either system.

BMS need only be near the cells. It's common for them to have a short wire coming out, but this can be extended. Given the choice, I'd connect the B- directly to the battery, and then extend the other side only, but you can extend both.

I don't know the answer on side mounting cells.

 

[steven1955]

I have continued looking for a definitive answer, and have not found it. The closest I've found to an answer is this thread where the OP had one cell that leaked some electrolyte out one cell's vent. And the cell apparently still worked.

Regardless, for now I am going to move forward with two 200Ah of pre made 12V batteries and give up some storage space.

 

[jimf909]

I'm also interested to know if LiFePo cells can be used on their sides. Does anyone have a definitive answer to this? Thanks.

 

[Browneye]

The general consensus is they can be, but the manufacturers recommend orienting them upright.
I had the same quandary, thought I only had space for cells on their end, but ended up being able to orient them upright after all.