[naustin]

I swapped to four 12V Dakota Lithium LiFePO4 batteries in my Yamaha Drive and added a Victron Energy BMV 712 Smart Battery monitor (that uses a shunt). I also swapped from using one battery for the 12V circuit to having a step down voltage regulator supplying 12V to a marine fuse block for the existing 12V with plans to add more 12V accessories later.
It charged up and ran great until today when I left it sitting off for several hours and it seems like some kids played with switches because it was in reverse (which usually makes a loud tone) but the lights won't come on or anything once I turned the key.
I checked voltage overall and it is reading 2.873V... But when I check 3 batteries they are 12.8V to 13.4V each and the last battery shows -34.7V! I double checked everything again and am stumped.
I have 4 - 12V batteries in series with + charger connection, + voltage regulator, and + of motor controller on the + of the battery series, then the negative of the battery series connected to one side of the shunt for the battery monitor and on the other side of the shunt there is - of charger connection, - of voltage regulator, - of motor controller.
When I have the lights off and the key off, the battery monitor shows no amp draw and stays on continuously. When I found it tonight the battery monitor is not lit up.
Has anyone seen anything like this before?