BMS set up for parallel batteries???

Hello all,

This is my first posting outside of the 'new comers' wading pool into the deep end so, hopefully some kind soul or two will toss me a life line and help me with a solution to my problem.

I'm trying to find info on how to use/set up/purchase a BMS system. I want to use 2, lifepo4 4 cell, 12volt batteries, connected in parallel and can not find what I am looking for.

I seem to remember something about what I need as being 4s 1p.....or maybe 4s 2p but, I'm not sure since my 73 year old brain tends to leak out more than it takes in.

Why connect in parallel, you ask? To incease the watt hour capacity and to make my under budget project more viable.

Thanks for reading this and many more thanks in advance for any and all assistance. Be safe.

MostlyBlind said:

Why connect in parallel, you ask? To incease the watt hour capacity and to make my under budget project more viable.

Click to expand...

Connecting the cells differently does NOT change the watt hour capacity.
volts x amp hours = watt hours

<assuming 100ah cells/batteries>
12v x 100ah = 1200wh x 2 batteries = 2400wh
vs
24v x 100ah = 2400wh

Check out the diagrams here (download the doc):

You will need a BMS on each battery. Probably a common port BMS as if you have separate port and one BMS turns of charging or discharging. The second battery will back-feed the first battery unless you have some blocking diodes which create their own problems.

Craig beat me to the answer to the question you asked.

I will add that if you choose to use 8 cells for a 12v solution, a common solution is the 2p4s cell configuration which yields 12v and can be managed with a single BMS.

See the doc i referenced in post #2

OK......you guys have convinced me that my attempt to come in under budget ($1,500.00) by using 2, 12v 60ah lifepo4 battery packs comes with way too many head aches so, can you suggest to me any reasonably priced 4s BMSs that will connect to a laptop and are available in the USA? Preferably under $100.00 but I am a bit flexible. Thanks.

I guess you came right in the end @MostlyBlind, but Smart ANT BMS is quite good for 75 USD and there are other Bluetooth Smart BMS out there for about 50 USD that Will Prowse has recommended (check his youtube channel).