420mV Voltage Drop across JK BMS - SOLVED

[BipedalPrimate]

Putting final configuration parameters in a new system and noticed a difference in voltage measurements between a Victron SmartShunt and a JK B2A24S15P.

Battery measures 53.33v between cells 1-16. (Using two different multimeters.)

BMS measures 53.33v.

SmartShunt measures 52.89v and manual measurement confirms that.

Measurement across the B- & P- of BMS shows 420mv. (Using two different multimeters.)

The math between 53.33v & 52.89v is 440mv (not 420mv) but I can accept a 20mv measurement error, connection and cable losses.

Is that sort of voltage drop in a JK BMS to be expected?

What do other forum members experience wrt BMS voltage drop?

Note that the SmartShunt is connected to the P- side of the BMS.

 

[Quattrohead]

Is that voltage drop with or without a load? Is the BMS getting warm?
If there is no load on the battery and the BMS is turned off that could be a valid reading.

 

[BipedalPrimate]

Is that voltage drop with or without a load? Is the BMS getting warm?

There is no load - not yet connected to Inverter/Charger.

BMS is cool (about 24C).

BMS is turned on. When turned off, I wouldn't expect to get any readings across the BMS.

 

[Quattrohead]

There will be slight leakage through the mosfets even if they are turned off. Digital multimeters are extremely sensitive so I'm not surprised you're getting a reading.

 

[BipedalPrimate]

This has been resolved.

The BMS had Charge set to Off - once Charge was set to On, the voltage drop disappeared.

Not sure about the internal workings of JK BMS, but I suspect the voltage drop was associated with either diodes or Mosfets being engaged when Charge is Off.