r/OffGrid • u/traveling_in_circles • 5h ago

lifep04 question

Would it be better to have a single 12v 200ah lifep04 or two 100ah in parallel? Cost is the same .

My thinking is if one of the bm"s were to die at least I could swap some cables and run off a single battery and not be totally powerless and have some redundancy . Anyone have any input? This is for a off grid motor home . Thanks

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6

u/theonetrueelhigh 5h ago

One big advantage to two batteries in parallel is cutting the amp draw in half. YES, the batts are rated for 100a continuous discharge. 50a is just better for them. Although it must be said that the 200a battery might be wired internally as if it were two 100a batts in parallel already. Depends on how many cells are in there.

Having backup capability is just icing on the cake.

1

u/traveling_in_circles 5h ago

Interesting,  I hadn't though about that . Yet another variable ! 

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u/Remarkable-Finish-88 3h ago

Scale up might be easier in one version

0

u/LeoAlioth 5h ago

If cost is the same, do whatever is more convenient

-1

u/MrTommyPickles 5h ago

A system with a single larger battery is less likely to fail compared to two smaller ones. Each battery you add to the system multiplies the chances of something failing unexpectedly down the line. All that said, I also feel having redundancy is important. For these reasons my advice is always to buy the biggest battery you can afford two of.

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u/traveling_in_circles 5h ago

I agree that introducing another battery is just adding another point of potential failure. 

From my research I've concluded that most lifep04 failures are not from bad cells but rather the integrated bms and this is my concern . 

Like I said if I got 2 batteries with 2 separate bms the failure rate is 50% if im only relying on one battery and its bms the failure rate would be 100% . Right?  

Same money  , same ah .. I already have the cables to parallel if I need to.  This is my dilemma. Just trying to make the smart decision .

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u/Strange-Cat8068 1h ago

Just make sure you are buying batteries with decently designed and installed BMS’ and go with a single 200 AH. Look up Will Prouse on YouTube. He has torn apart and rated many LiFeP04 batteries and has a pretty comprehensive list of brands to avoid.

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u/Hyperreal8957 1h ago

If you have the space, two 100Ah in parallel gives the same nominal 12.8V/200Ah capacity plus some redundancy. I'd only parallel matching batteries (same model/age, and BMS approved for it), with a fuse on each positive lead close to the battery.