Concerning the BDI showing only one bar, the one gentleman mentioned all the connections for the voltage to go through and can drop because of one thing or the other. I was told a trick by one Crown technician that works easily for me. I hook up my car charger, which I can set for AGM batteries and connect it to 2 of the 6V batteries and it shows 12V on the charger. Then I use the fast charge for about 30 seconds and turn on the key switch. It's always reset the BDI for me.

I only have this problem on older batteries I have to deal with until our next fiscal year when we can order new ones. It doesn't happen that often with them, most always when the operators leave it charged overnight. Then it will complete the charging process and slowly lose a bit of voltage until morning when it's unplugged. I've asked the operators to try and avoid that, but they don't care, lol.