Smart BMS max current.

[PScott]

Is it possible to have max current customized on a BMS? I'm building a 14S6P pack with LG HG2 cells and considering this "smart bms" from lithiumbatterypcb.com. They only have 40A and 60A models but I want about 50A max.

https://www.lithiumbatterypcb.com/product/13s-48v-li-ion-battery-pcb-board-54-6v-lithium-bms-with-60a-discharge-current-for-electric-motorcycle-and-e-scooter-protection-2-2-3-2-2-2-2-2/?attribute_specification-selection=14S+li-ion+60A

 

[eee291]

You can go with the 60A BMS since you'll only be drawing a max of 50A.

 

[john61ct]

Yes, do not expect a normal BMS to actually do current throttling.

Like sizing a fuse, you buy a BMS that can handle a current higher than the bank will see.

It is your job as system designer to predict and control what that rate will be.

Personally I would use fuses rated lower than the BMS spec to make sure.

 

[PScott]

Yes, do not expect a normal BMS to actually do current throttling.

Like sizing a fuse, you buy a BMS that can handle a current higher than the bank will see.

It is your job as system designer to predict and control what that rate will be.

Personally I would use fuses rated lower than the BMS spec to make sure.

Are you saying i can configured the BMS to limit the current?

 

[flangefrog]

If you want the current to be limited, that is a job for your controller. The BMS can not limit the current but it can cut out if the current is abnormally high.

 

[john61ct]

Yes, do not expect a normal BMS to actually do current throttling.

Like sizing a fuse, you buy a BMS that can handle a current higher than the bank will see.

It is your job as system designer to predict and control what that rate will be.

Personally I would use fuses rated lower than the BMS spec to make sure.

Are you saying i can configured the BMS to limit the current?

No I am saying the opposite, I haven't come across one that does, and if such exists would be hundreds of dollars.

 

[PScott]

john61ct, Ok i understand what you're saying..limiting the current is the job of the controller..but why are BMS advertised by current rating? Im looking at this BMS and they have 14S in 30A, 40A, and 60A models....just different mosfets? Im going to send them a message and find out.


Paul

 

[eee291]

Yes, it is to save money obviously if you only need a 50A BMS you aren't going to get the 100A BMS for double the price are you?

 

[john61ct]

Like buying a connector, or a length of wire or as I said a fuse.

That is the rated maximum it will (in theory) handle without burning.

So with quality gear overspec by 20%, cheap Chinese sometimes need to search for the real number in fine print, then add a big heat sink, and then still need to 3x oversize for longevity