712 connections at shunt are ok, the unit keep showing 0ah .
What is wrong , no reverse shunt connection
The most common problem I've seen when customers report their BMV not accurately displaying Ah is that they have connections which are bypassing the shunt. Are there any negatives connected to your battery other than the one going to the shunt? ALL negatives of your system need to come off the "load" side of the shunt, including chargers, chassis grounds, etc. (A common way of doing this is to just attach a negative bus to the "load" side of the shunt and then run all your negatives from there).
The only thing connected to your battery negative should be a cable going directly to the "battery" side of the shunt; all other negatives for your system need to run to the "load" side, no exceptions. The shunt can't measure any draw or charge that bypasses it - ie, that's connected directly to the battery - and I suspect that this is the cause of your inaccurate readings on the BMV.
I occasionally see an actually defective unit responsible for inaccurate Ah readings, but 98% of the calls I take about this are the direct result of device wiring that bypasses the shunt.
Confirmed the wiring all correct but amp hours used remains zero. Is there a way to confirm if the unit is defective before I tear the aft cabin apart again to remove it and return it to the store?
9 People are following this question.