It all depends on what type of converter you have. Rather than use the Magnetek converter which the PO replaced the Univolt with, I use a 5 watt PulseTech Solargizer solar charger/maintainer and/or a 1 watt BatteryMinder 3 stage charger. This will be the 4th winter I've used this setup and the batteries are in great shape. I just don't worry about losing water because of the type of charger.
'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system