I have dual alternators on my Duramax and ordered the truck with that option. Dual 145 amp. A single standard alternator would have a hard job keeping up with and fast recharging of the 2 truck chassis batteries and the 7 Group 31 deep cycle batteries for the 5th wheel with it's 2500 watt inverter. Works fabulously! Very short recharging time even when recharging with the diesel engine idling. Will have the same exact setup if we were to buy a new Duramax truck too!