12v lifepo4 x 2 problem.

JulianG

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Joined
Oct 21, 2019
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29
I have 4 x 280ah 12v home built lifepo4 batteries.

I now want to combine 2 of the batteries to give me 24 v but don't have the room to make 1 battery easily.
Can I join to sets of 4 cells each with a long bus bar or better heavy cable 25cm long? Then use 1 new 8 cell BMS.

It's on a river boat so need 12v for general use bow thruster lights electric loo ect so I use 2 x 12v batteries in parallel. I then need 24v for kitchen induction hob and and 900w combi oven electric drive with a lynch motor.

If I flatten the batteries I do have a panda generator as back up as well as a 100a alternator.

My current BMS are 200a 12v and can't be used in series.

Or can Anybody recomend a BMS for series use?
 

JulianG

New Member
Joined
Oct 21, 2019
Messages
29
Thank you will take a look.
Having drilled down into my BMS it looks like I can attache them in series But the supplier stated "we don't recomend it" without clarification. Not sure what the down side is of having 2 x 12 in series v 1 x 24v.
 

FilterGuy

What, me worry?
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Nov 26, 2019
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Location
Los Gatos CA
Not sure what the down side is of having 2 x 12 in series v 1 x 24v.
The primary issue of having 2 x 12 is that there is nothing to keep the two in balance. However, if they are decent cells and properly set up, this should be a minor issue. The second thing is that with 2x12 there are two BMSs and therefore twice the possibility of a BMS failure.
 

JulianG

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Joined
Oct 21, 2019
Messages
29
So the benifit is when charging, if I de couple, using 300a relays, the two 12v batteries I can charge them from my generater or my alternator as 12 v batteries. When I need to use them the relays will join them back up.
 

JulianG

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Oct 21, 2019
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29
This is one of my 4 batteries. 2 of which I transport home and power my lawn mower then charge via solar and when not mowing use to them to power one ring main in the house.
 

Goboatingnow

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Jul 3, 2022
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828
I have 4 x 280ah 12v home built lifepo4 batteries.

I now want to combine 2 of the batteries to give me 24 v but don't have the room to make 1 battery easily.
Can I join to sets of 4 cells each with a long bus bar or better heavy cable 25cm long? Then use 1 new 8 cell BMS.

It's on a river boat so need 12v for general use bow thruster lights electric loo ect so I use 2 x 12v batteries in parallel. I then need 24v for kitchen induction hob and and 900w combi oven electric drive with a lynch motor.

If I flatten the batteries I do have a panda generator as back up as well as a 100a alternator.

My current BMS are 200a 12v and can't be used in series.

Or can Anybody recomend a BMS for series use?
the general answer is yes you can do as you say , whether you can one BMS or two is largely a personal choice issue
 

Mickrobb

New Member
Joined
Nov 25, 2020
Messages
5
Thank you will take a look.
Having drilled down into my BMS it looks like I can attache them in series But the supplier stated "we don't recomend it" without clarification. Not sure what the down side is of having 2 x 12 in series v 1 x 24v.
Don’t buy the jk bms, I brought 3, 12v bms and 2 failed
 
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