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JBD / Overkill BMS 120A 4S Lifepo4 in series / parallel

squowse

Solar Enthusiast
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Jan 4, 2021
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Who's tried using these in series / parallel?

Any definitive information?

It's this one I'm particularly looking at.
 
Has anyone tried to parallel (2) BMS on the same battery ( example one 4S1P battery) --curious if this would work
 
there’s another thread where someone claimed that they asked @OverkillSolar

response: it’s not recommended.

but there’s apparently not a clear reason why to not do so.

and the user did connect two parallel to same pack and apparently it’s been ok and all magic smoke inside.

it’s important to ensure the configurations are compatible with each other
 
I have two 4s batteries, each with its own BMS. Runs fine paralleled to the common bus bars. I've seen the two BMS on one battery thread and I think the guy is nuts (but not clinically nuts). The loss of accurate capacity numbers is one reason to not do this. The counter argument is that most of us are running a shunt to keep track of capacity.
 
there’s another thread where someone claimed that they asked @OverkillSolar

response: it’s not recommended.

but there’s apparently not a clear reason why to not do so.

and the user did connect two parallel to same pack and apparently it’s been ok and all magic smoke inside.

it’s important to ensure the configurations are compatible with each other
Yeah I think I saw that and it confused me.
 
@squowse Can you clarify your question. Are you asking about connecting two BMS to a single 12V (4S) pack OR connecting two 12V (4S) packs each with it's own BMS in parallel configuration? I'm confusing myself now o_O
 
@squowse Can you clarify your question. Are you asking about connecting two BMS to a single 12V (4S) pack OR connecting two 12V (4S) packs each with it's own BMS in parallel configuration? I'm confusing myself now o_O
The latter - 1 BMS per 4 cells.
I was asking for series or parallel. Or even both.
 
One of the few well done manuals you are going to find for a Chinese product. He did the manual himself and has a reputation for no nonsense good support.

I'd shoot him an email for further clarification .... or if there is a limit to how many you can put in a series configuration.
 
Oh thanks I didn't even know about that. I think their listing even used to say " we don't support the bms". Or was that a different company.
My mistake that was Battery Hookup that said they didn't support this BMS. They just sell it. Honest I suppose.
 
I tried 4p2s with 2 120a bms .. worked but the amp draw was never equal but not a big deal.. so I switched to a 2s4p and one BMS when I found it would start my onan 20210125_100732.jpg
 
I am new to this... this is what I am calling my 2 configuration maybe my 4p2s is just 2 x 1p4sScreenshot_20210304-201404_Whiteboard.jpg
 
Parallel works. Series works.

But... If you're going to create an 8s 24v battery, you might as well use a single 8s BMS instead of two 4s BMS.

Have you tried it (or anyone else on here)? I can't think of a reason it wouldn't work, I just find it odd overkill would say its not recommended. Other battery manufacturers (battle born) also don't seem to like putting their systems into series
 
Have you tried it (or anyone else on here)? I can't think of a reason it wouldn't work, I just find it odd overkill would say its not recommended. Other battery manufacturers (battle born) also don't seem to like putting their systems into series
Where did you see that they don't recommend it ..... did you see the manual like above that says it's OK?
 
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