First off, the two batteries in your truck are in parallel, which gives you 12 volts at twice the capacity, essentially the same as having a battery twice as big. In order to get 24 volts, you'd need some sort of a switch arrangement to put the third battery in parallel with the first two for charging and then in series with the normal 12 volt wiring to make 24 volts. You can't have 24 volts and charge the extra battery at the same time without some relatively fancy electronics. Assuming the lift runs on 24 volts and therefore requires some significant current, the easiest way would be to add a 24 volt alternator to the engine and two 12 volt batteries in series. This second system would be completely independent of the vehicles normal electrical system. If you don't use the lift a lot and can stand a slow charge rate, a simple kluge approach might be to use one of these cheap 120 volt interters to run a 24 volt battery charger to keep a second set of batteries charged. You'd want some sort of a relay on the input to the inverter so you don't leave it running when the engine isn't on and run down your starting batteries. You might also do a search & see if you can find a 12 to 24 volt converter that could be used to charge the second set of batteries. I've never seen one, but that doesn't mean they don't exist. Keith
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