I have a 500a smart shunt attached to 2 300ah lithium batteries connected through parallel wiring to my RV. I connected the shunt correctly with the negative from the battery going to the side that say battery and the other to the rv. I am connected through onshore power yet the shunt shows 4.4amp draw. This continued until it showed 0 SOC but the voltage was still 13.3 and shore power was still powering the coach. Any thoughts on what could be wrong?