Like a broken record, the same scenario kept repeating, I'd make sure the start batteries were turned on, check for 24V everything would appear alright, engage the lazy sounding starter and she'd fire up with 28V showing on the gauge. We'd head down the road blissfully ignorant that come morning, when we're far from any jumper cables or, when we were smart enough to remember them it was the most embarrassing situation possible, hit the button and get the dreaded "REARRRR-click click click". Let's see, brand new batteries?, "yep", disconnect switches?, "ya", 24 V alternator functioning properly? "sure." What could it possibly ####### be? It wasn't until I was headed home after dark, the night of the airbag replacement that the problem showed it self. Electrical System 2 which runs the basic 12V driving accessories comes from a tap off just one of the two 12V batteries hooked in series to produce 24V. Since you're drawing power from the positive side of the last batt in the series, it creates an imbalance thereby overcharging the first batt and undercharging the last batt. The cure is an equalizer and while I'm sure that the previous owners of our coach pulled their hair out over this problem, It is a problem no more.
Finally, 13.7 volts to the headlights!
Older Vanner Model 60-50 scored on ebay for $80
Nice and simple hookups.
You gotta love when a device has the wiring diagram printed on the side. Here's some arrows with labels so you can wrap your mind around it. The newer models are said to be much more accurate but my readings showed both batts having identical voltage (13.7V DC) at idle and the newer models cost five times as much. I hope this helps someone out there struggling with battery imbalances. It can be frustrating to say the least.