I have a Pro-Nautic 40 amp 3 bank marine charger that I use to charge my 4Runner (dual AGM Batteries). This has worked well for years (my Diehard Platinum Group 31 Is on its way out after 8 years). My question is since its a 3 bank charger, I'd like to use it to charge batteries on other cars at the same time. I have one car that is driven rarely, and I'd like to top off my wife's suv battery periodically. Would there be an issue creating a common ground (splice 2 additional ground wires into the existing single ground the charger) and connect that common ground to 2 or three batteries in different vehicles, and run the remaining 2 positive leads on the charger to the other batteries? Basically have 3 positive leads and one common ground to 3 batteries on three vehicles. I have agm batteries on the other cars, so the battery type is the same, different brands. Would that work without frying something?