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Best Option for 12V 200A BMS?

tmckenna

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Jul 8, 2020
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Hi guys,

I'm fairly new here, but doing my best to pick up info as fast as possible. Planning on building a fairly large battery bank for my tow behind camper. I'm thinking I'm going to DIY build 2 of the 280Ah setups from a Moderator here that goes by the username Craig.

My question is regarding the BMS. I've seen the terms 4S and 8S thrown around and I'm not sure what they refer too. I'd also like a BMS capable of 200A discharge, I probably won't ever use all that power but I'd like to have it if for some reason I need to.

Any advice is much appreciated.
 
s = serial
4s means 4 cells connected in serial for a nominal voltage of 12.8 volts
8s means 8 cells connected in serial for a nominal voltage of 25.6 volts
16s means 16 cells connected in serial for a nominal voltage of 51.2 volts
 
s = serial
4s means 4 cells connected in serial for a nominal voltage of 12.8 volts
8s means 8 cells connected in serial for a nominal voltage of 25.6 volts
16s means 16 cells connected in serial for a nominal voltage of 51.2 volts

Ah understood, so in my application I would use a 4s?
 
Ah understood, so in my application I would use a 4s?

If you want a system voltage of 12.8 volts I would suggest you make 2x 4s batteries each with its own bms.
Then combine those in parallel to get 200 amps aggregate.
 
If you want a system voltage of 12.8 volts I would suggest you make 2x 4s batteries each with its own bms.
Then combine those in parallel to get 200 amps aggregate.

Thats what i was planning on, but i wanted each bank to be capable of 200a
 
Thats what i was planning on, but i wanted each bank to be capable of 200a
Thats going to be difficult with a commodity fet based BMS.
Thats probably why nobody has answered you before.
 
Thats going to be difficult with a commodity fet based BMS.
Thats probably why nobody has answered you before.

Whats wrong with something like this?

I could do 150A also. I really just want the system to be capable of 300A for a short period of time.
 
2x of the bms that @Zil speced running in parralel will handle short 300 amp bursts.
 
the bms zil specced is better than the victron? Also what is a commodity bms?

I'm glad you asked.
I don't know much about that Victron but I suspect its "better" because its made by Victron.
Also because its a Victron product I suspect its a vendor lockin vector.
As a market segment matures the feature sets of the competing products homogenise from the bottom up and the players increasingly compete on price.
https://en.wikipedia.org/wiki/Commoditization

In most things I stay away from the Apples, Teslas and Victrons.
 
I'm glad you asked.
I don't know much about that Victron but I suspect its "better" because its made by Victron.
Also because its a Victron product I suspect its a vendor lockin vector.
As a market segment matures the feature sets of the competing products homogenise from the bottom up and the players increasingly compete on price.
https://en.wikipedia.org/wiki/Commoditization

In most things I stay away from the Apples, Teslas and Victrons.

Alright it looks like ill go with the one Zil originally posted
 
If you want a system voltage of 12.8 volts I would suggest you make 2x 4s batteries each with its own bms.
Then combine those in parallel to get 200 amps aggregate.
Question on this: I have 8 cells wanting to make what you're talking about. But how would I actually parallel them? Are you paralleling the BMSs too? Or are you just creating the 4S packs, both with individual BMSs and then connecting Pack #1 pos terminal to Pack #2 pos terminal (and same with the negs?)
 
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