I run a clay shooting ground with around 45 traps which means I have around 60 batteries to keep topped up. I just keep it simple - 4 standard chargers - suitable for heavy duty charging (diesel engine size - I think they are 8 or 12 amp hour jobs)- connector strip to give me 8 sets of charging leads per charger and I just connect them up in parallel. I use all the same sized batteries i.e. 85ah sealed leisure type and an overnight charge tops them back up after a couple of shoots. Batteries normally last 3 - 4 years so it must b working OK. Obviously don't leave on too long and overcharge. Complicated charge protection circuitry doesn't work too well as it gets confused with the multiple batteries. 8 batteries per charger works well as it doesn't seem to overload anything or blow the protection fuse. Hope this helps.
John
