Hello. I expect to convert my RV to Lithium soon. My battery box has room for six 3.2V cells. Is it possible to arrange them as 4 in series for 12V, then add a cell at each end in parallel? (1P4S1P?) Would that increase the total capacity while keeping it a 12 V system? Would it upset the balance, etc.? Thanks!
possible RV battery build
- Thread starter pearcedl
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John Frum
Tell me your problems
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- Nov 30, 2019
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Its possible but it would likely hurt more than it helps.
The total capacity for a battery is determined by its weakest cell.
If you identify the weakest cell and put it in parallel with another cell your next weakest cell gets promoted to the weakest and so on.
In your configuration you will now have two cells with ~approximately 2x the capacity of the other 2 so balancing almost certainly be a problem.
Makes sense - thanks for the help!
What size cells? Maybe smaller cells would fit 8 and increase capacity.
Picture with a tape measure to show the dimensions might help.
My 304 Ah cells are 3" thick. I have 21" to use, so I would need the smaller cells to be 2.5" thick. I don't know of any that are that thin....
160 Ah is 2.2 inches could be pared with the 304 or build a separate battery in parallel.
https://www.alibaba.com/product-detail/Docan-Grade-A-EV-160Ah-3_1600561477058.html
Not necessarily endorsing this specific link. Just my first example in the size range.
https://www.alibaba.com/product-detail/Docan-Grade-A-EV-160Ah-3_1600561477058.html
Not necessarily endorsing this specific link. Just my first example in the size range.
Very good - so it IS possible. Thanks - good lead. As I said, I'm new - so two batteries (or a paired/series single battery) would give me 320 Ah. Would a 120A BMS work for that? What is the 120A measuring?
304 + 160 = 464
Need 4x 304 cells and 4x 160 cells
Two batteries or one? If building a single battery the 120a is fine as long as maximum draw is maybe 100 amps. If driving a 2000 watt inverter to run a microwave it may come up short.... better to have a 200 amp for this. If building two batteries then will have two BMS at 120a = 240 amp and plenty of headroom.
Need 4x 304 cells and 4x 160 cells
Two batteries or one? If building a single battery the 120a is fine as long as maximum draw is maybe 100 amps. If driving a 2000 watt inverter to run a microwave it may come up short.... better to have a 200 amp for this. If building two batteries then will have two BMS at 120a = 240 amp and plenty of headroom.
I was going with 8 160s (for size/width).... So, two batteries it is, unless I can find a >200a BMS (haven't seen one yet). THANKS!
200 amp is not hard to find. Get some opinions on a good brand and good seller.
https://www.alibaba.com/product-detail/JBD-Lifepo4-BMS-100A-150A-200A_1600493735380.html
https://www.alibaba.com/product-detail/JBD-Lifepo4-BMS-100A-150A-200A_1600493735380.html
Thank you very much for your help!
