I've never heard of a modern gas truck with a factory dual battery setup. That's crazy. Dual alternators too? If not, that's gotta be one helluv'an alternator. Was it maybe a police/fire/fleet special order or something? Our mobile maint trucks in the AF had them and were gas, but they also had external throttle controls for jump starting other vehicles on the flightline.
I'd look at how it's wired if it only has one alternator and just run it on one battery. If it's just a regular duty truck, two batteries aren't needed. If they are wired in parallel, it's real simple. If they are in a series, that's a different story, but doable.
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