4S 48V/200A BMS for 12 x 4 battery bank

[Thingol]

Hello folks,

In my battery bank setup, I have got four identical 12V LiFePo batteries connected in series into a 48V bank. Each battery here has got its own BMS i.e., the BMS's do not talk, each does it's own thing. As you might guess, the first battery to charge up goes open circuit and so the rest of the bank is not charged up properly. I also have imbalance issues during discharge, between the batteries and I suspect within each battery too.

I would like to have a "parent" BMS over all these four batteries. I suppose this would be a 4S 48V BMS if I am getting the type designation right. It would manage the charging/discharging properly and keep the bank in balance.

Where can I find this? I searched a lot and but all I can find are BMSs designed to work with cell packs e.g., 16S 48V, 8S24V and so on. Does anyone have any links or leads to such a product? Daly on Aliex does not seem to have such.

 

[sunshine_eggo]

Your imagined solution does not exist.

Prior to installing 4X 12V LFP in series, they must be fully charged individually and then in parallel if possible. Even after doing this, you must periodically break the bank down and charge them individually/in parallel - even Battleborn requires this.

As an alternative, you can use a 48V balancer to keep the 4X 12V at the same voltage:

KiloVault Battery Balancers

KiloVault Battery Balancers help extend the life of a battery bank in your solar power system. 24V and 48V versions are used to maintain battery voltages across a series connection of batteries.

www.altestore.com

IMHO, you should limit your absorption voltage to 56.8 - 57.6V to minimize the potential for individual BMS cut-out and still permit some balancing during charge.

 

[Thingol]

"Your imagined solution does not exist."- this is what I really needed to hear.- I thought I was not searching properly. I was holding on getting Victron balancers thinking I might come across some magic solution in the form of a 4s, 48V balancer. I am familiar with the other workarounds of the issue. Victron balancers and lower absorption it is. A BMS would have been awesome though

 

[Rocketman]

I believe it could be done with a Batrium bms w/ blockmon’s or longmon’s, but that’s an expensive way.

Maybe put a 12v digital gauge on each battery, then manually add or reduce some amps.

 

[Thingol]

Your imagined solution does not exist.

Prior to installing 4X 12V LFP in series, they must be fully charged individually and then in parallel if possible. Even after doing this, you must periodically break the bank down and charge them individually/in parallel - even Battleborn requires this.

As an alternative, you can use a 48V balancer to keep the 4X 12V at the same voltage:

KiloVault Battery Balancers

KiloVault Battery Balancers help extend the life of a battery bank in your solar power system. 24V and 48V versions are used to maintain battery voltages across a series connection of batteries.

www.altestore.com

IMHO, you should limit your absorption voltage to 56.8 - 57.6V to minimize the potential for individual BMS cut-out and still permit some balancing during charge.

I see the Kilovault balancer you linked will draw up to 10Amps from the higher voltage battery. Victron balancers on the other hand will draw a maximum of 0.7Amps. I am guessing the Kilovault and other such balancers will correct imbalances quicker. The difference is huge though, why is that?

 

[sunshine_eggo]

I see the Kilovault balancer you linked will draw up to 10Amps from the higher voltage battery. Victron balancers on the other hand will draw a maximum of 0.7Amps. I am guessing the Kilovault and other such balancers will correct imbalances quicker. The difference is huge though, why is that?

IMHO, Victron assumes they're attached to their batteries that they believe will never need much balancing...

Kilovault and other higher current solutions assume schmucks like me will be putting them on their slapped-together used battery banks cobbled from whatever they had laying around.

 

[Thingol]

I believe it could be done with a Batrium bms w/ blockmon’s or longmon’s, but that’s an expensive way.

Maybe put a 12v digital gauge on each battery, then manually add or reduce some amps.

How sir? I cannot find this use case in Batrium docs and how-to's..