Shunt before or after BMS?

[kjemmo]

I have the following:

• 280AH 12V LiFePO4 battery pack
• A Daly 100A smart BMS
• A tr16 coulomb meter with a 350A shunt.

Do I place the shunt before or after the BMS?

Thanks.

 

[ereams65]

After

 

[Supervstech]

I guess it depends on if you want to include the loss from the BMS in the meter display or not...

 

[wholybee]

I don't know what "before" or "after" means, but option 1 is best. Current will be the same anywhere in the circuit, so the shunt will work fine in either location.

 

[John Frum]

Option #2 is useful the following scenario.
You can bypass the bms for high amperage loads(like an inverter) and still get current accounting.
Use an solid state relay or Victron battery protect for low voltage disconnect.
Don't put the battery protect in the high current path either though.

 

[Bob B]

I don't know what "before" or "after" means, but option 1 is best. Current will be the same anywhere in the circuit, so the shunt will work fine in either location.

Actually there is a path for current thru the BMS and back to the battery that won't go thru the shunt if it is placed as in option 1.
That may be a small amount of current since it will only power the BMS and the small balance current the Daly BMS has.

 

[wholybee]

Actually there is a path for current thru the BMS and back to the battery that won't go thru the shunt if it is placed as in option 1.
That may be a small amount of current since it will only power the BMS and the small balance current the Daly BMS has.

I would need to see the actual drawings, this may or may not be the case. I believe the BMS to be powered by the sense leads, but I could be wrong.

 

[Bob B]

I would need to see the actual drawings, this may or may not be the case. I believe the BMS to be powered by the sense leads, but I could be wrong.

..... in any case, the power from the BMS would not flow thru the shunt .... maybe not with the shunt in either position unless the BMS is powered via an external port as my Chargery BMS is.

 

[wholybee]

..... in any case, the power from the BMS would not flow thru the shunt .... maybe not with the shunt in either position unless the BMS is powered via an external port as my Chargery BMS is.

Quite true.

 

[Lord-Obsidian]

Wouldnt it be smart to put the shunt behind the BMS so its Monitor can't draw the battery empty when BMS cuts the load because of low voltage?

 

[upnorthandpersonal]

Personally I consider the BMS a part of the battery - everything else like a shunt comes after that.