I'm in the process of adding a second alternator to my Chevy express. The factory 145A alternator will be used solely to power vehicle systems, and secondary 240A alternator will be used to power a 3000W inverter. I'm not sure how to incorporate a charger or a regulator to properly charge my 105AH quasi-deep-cycle AGM battery.

I want to be able to recharge the battery as quickly as possible from a 50% state of discharge and follow the appropriate charging cycle while limiting charging current to 30A. Can anyone share a configuration that would work for me?

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1 Answer 1


What you're doing is very similar to a marine electrical system. Since you're only planning on pulling 30 A from the alternator for charging the battery, I'm assuming that all or most of the time the engine will be running when you're using the inverter.

In general, the battery will "take care of itself" as the battery discharges its internal resistance will drop and it will admit a higher charging current, and as it reaches a full charge the internal resistance will be rising which will cause the charging current to taper off.

The regulator's job is to maintain a stable output voltage as the engine speed changes by modulating the alternator field current. If you'll be using the inverter/alternator "underway" you'll be fine, but if you're using while you're parked, then make sure that you pick your alternator and pulley system carefully - you'll need to have the alternator running fast enough at idle to produce the output you need, while preventing it from overspeeding when on the road.

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