Originally Posted by alex_hunter
I've read minimum of 10% of total battery ah should be the charger amp output. I have 420ah total, so can I get away with a 40a charger or should I grab a 50??
You also have to factor in usage and how deeply you are cycling the batteries. If your charger is mostly working in a maintenance capacity then you have more than enough with a 40 amp charger or perhaps even less. If you are routinely discharging to 11.8 volts for example you could go as high as a 50 amp charger but certainly no higher. Also, factor in how much of that A/H capacity is your starting battery, if that is sometimes paralleled with the stereo bank and partially depleted.