VictronConnect Shunt disagrees with BMS?!

[Rwinike]

Hi All,

f this has been posted before, I couldn’t find it and apologize.

I’m finally done top balancing my 280ah bank. I’ve connected in series, and am running a very rudementary capacity test. My small xantrex inverter, 300w, has two 53 watt bulbs plugged in, totally 106 watts.

My BMS shows a 8.1 amp draw which jives with the wattage. However, the VictronConnect shunt shows 229W?!??
What gives???
Is it possible to have that much inefficiency? Any why doesn’t the BMS reflect that?

thank you in advance for your help!

 

[rmaddy]

Probably unrelated to your issue but I notice some battery monitor settings in VictronConnect that you should change. The Peukert exponent should be 1.05 and the Charge efficiency factor should be 99% for LiFePO4.

 

[Rwinike]

Probably unrelated to your issue but I notice some battery monitor settings in VictronConnect that you should change. The Peukert exponent should be 1.05 and the Charge efficiency factor should be 99% for LiFePO4.

My apologies, the 4 cells are now in series

 

[rmaddy]

The SOC values are completely different too. Did you fully charge the batteries with the battery monitor in place such that both the BMS and the battery monitor showed 100% SOC when fully charged?

How is the shunt and BMS wired to the batteries? How is everything else wired to the battery and shunt? Post a clear picture or a wiring diagram so we can verify that everything is connected correctly.

 

[JeepDaddy]

Did you zero current calibrate the Victron shunt per the factory manual?

 

[Rwinike]

I thought I calibrated it correctly, but the SOC on the BMS and the shunt have been different from the start. The Daly BMS never showed 100% even when it was completely top balanced.

 

[Baughb]

Late to the party. After installing the Smart Shunt according to the manual, I manually synchronized the shunt to 100% once the BMS showed 100% according to the battery’s values (14.2v at 96.14ah). I then put the shunt in its auto synchronize mode (battery settings window) and it has been accurate but occasionally hits 100% before the BMS. The BMS’s bluetooth app does not seem to be as accurate (Xiaojang). That’s why I got the shunt. When I hit 100%, I sometimes (a week ago) reset it as I did from the commissioning/first start but I’m a geek for accurate readings.

The Shunt is not an absolute value because you tell it when it is 100%. It will always be relative to that synchronizing. So resetting the synchronization when I know it is 100% full has become a maintenance item for me.