how to wire dual bms lifepo4 packs in parallel

Tres

New Member
Joined
Jul 25, 2020
Messages
12
I have a DIY build question. Building a solar generator with 2-280ah lifepo4 packs. Each has its own BMS. I want these to be in parallel. I understand that you hook pack 1 positive to pack 2 then use the positive of pack 1.
You do the same for the negative, but the BMSs are my question. Do you connect pack 1 BMS negative to pack 2 battery neg or bms neg? I would assume bms to bms, but for some reason it doesn't look right.
 

Dynoman

Solar Enthusiast
Joined
Dec 17, 2020
Messages
33
Location
Michigan
Take a look at the attached PDF for battery configs from FilterGuy. It and alot of other info is available by clicking Resources at the top of the web page in this forum. I would suggest you do your research on this forum before using the battery pack.
 

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emerge411

New Member
Joined
Jul 28, 2021
Messages
10
New member so take this with a grain of salt. I am setting up a similar battery config. You should treat the BMS as "internal" to each 12v battery config. When looking at diagrams with factory built batteries the negative end after the BMS is treated like the negative terminal.

To answer your question, the negative end of one BMS would NOT go to the negative cell terminal on the next battery but the end of that next battery's negative BMS connection.

It does seem a little odd at first. Remember that although your battery leads should be the same length the positive and negative leads do not need to be the same length. So all positive are the same and all negatives are the same but the negative and positives dont have to be the same length. My plan is to run both negative BMS leads to a stud then a single wire to the shunt/negative bus bar.
 
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