[puddleglum]

I agree, that was another reason I thought the diode would be a good idea. The battery is now only seeing 13.3 volts. I haven't put an ammeter on it, but I think the draw to hold it at that voltage should be very little and 12v battery is no longer trying to keep the dc/dc's charged when the supply battery is turned off. I have a switch on the 24v pack to turn it off when I'm not driving the car so the only time it is trying to charge the 12v battery is when I'm driving, or when I forget to turn it off