I have installed a new BMV-712 on my camper that has 2 x 12v 115AHr AGM's in parallel. I also have a separate Volt/Amp meter installed. The BMV reads current lower than what it actually is. 3-5 Amps on Charge and Discharge. 10mm cable used to connect the shunt?
I have no idea if the BMV is just not a very accurate device or how to investigate the problem