Changed Shunt from 100 amp to 300 amp

[Skinny76]

So I upgraded my house battery to 4x100 ah batteries in a 2s2p configuration from a 200ah 12 volt. I had a battery monitor system, which worked well with a 100 amp shunt. I rewired the monitors to the new setup. Old monitors max at 100 amps in settings. New shunt is 300 amps. Voltage is accurate, but watt draw is showing close to 1/3 of what my growatt, multimeter and knowing my microwave draws "x" amount.

Should I upgrade the monitors? Need more info? Thanks for any help you can give.

 

[snoobler]

Shunts work by measuring a voltage drop. That number is typically 50, 75 or 100mV when the shunt is at maximum rated current regardless of shunt size.

Since you're showing exactly 1/3 the current, then the 300A shunt likely uses the same 50, 75 or 100mV scale as your old 100A shunt, so it's only showing 1/3 the voltage drop it used to. The monitor needs to be configured for a 300A shunt. Some can't. If it can't be configured for it, it needs to be replaced.

 

[Skinny76]

Shunts work by measuring a voltage drop. That number is typically 50, 75 or 100mV when the shunt is at maximum rated current regardless of shunt size.

Since you're showing exactly 1/3 the current, then the 300A shunt likely uses the same 50, 75 or 100mV scale as your old 100A shunt, so it's only showing 1/3 the voltage drop it used to. The monitor needs to be configured for a 300A shunt. Some can't. If it can't be configured for it, it needs to be replaced.

Thanks. Yep. Max setting is 100 amp for sure. Going to look to replace.

 

[Bob B]

Is there a calibration procedure? As long as you aren't over 100A draw, you might be able to calibrate to that shunt anyway.

 

[Skinny76]

Is there a calibration procedure? As long as you aren't over 100A draw, you might be able to calibrate to that shunt anyway.

I'm not sure. I do know there is only two options on the meter, 50 amp or 100 amp. I think I have found a pair of meters that are 300 amp and shouldn't take too much cutting to my existing mounting board, so minimal work to replace.