I bought the 6A charger because a pair of deep cycle AGMs I keep for emergency purposes were apparently giving my frustrating loud Schumacher charger issues. I've tested the voltage across the battery terminals both during maintenance and without the charger attached and I'm still sitting pretty after a few months.I didn't realize the 10A version would allow you to run the terminals in parallel to the same connection, so if I was going to buy this again I'd probably get the next model up.This wouldn't be your best bet if you wanted to quickly charge batteries (like if you were in a hurry to get a car started or if you were trying to top off a battery bank from a generator) but for day-to-day maintenance it's quiet, it doesn't run hot, and it's dead simple to use.