Brian, My understanding is that the Vanner equalizer draws from both batteries to keep them equal, hence the name "equalizer". Just make sure you do not exceed the rated capacity of the equalizer. Maybe somone with more electrical knowledge will join in. Another option would be a DC to DC converter which reduces 24 volts to 12 volts. Hope this helps, Jack
At the risk of prattling too much, if you are using a Vanner, there is a particular method of disconnecting the units. Someone may know, but check the manual or material printed on the unit. I believe the ground is disconnected first. It's printed on mine but I forget. Wouldn't want t damage a good Vanner, these things are typically expensive. ...JR