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Message: [QUOTE="mikeeg02, post: 1371946, member: 24194"] The alternator will charge whatever you hook to it. Stock alternators are between 110-130 amps. Lets say you use 100 amp hours of capacity starting the truck. Your alternator should have that capacity charged in about one hour of drive time. Not idle, because their output is reduced. But running down the road at cruise rpm, you will be charging at ~100 amp rate. If you do in fact run the batteries down just enough to start, it will just take longer to fully charge your batteries at a ~100 amp rate. In short no, there's no problem with the alternator. As far as wiring goes. If you ran a 30' piece of #10 house (~.001 ohms per foot)wire between your rear battery, and starter, and tried to use the starter under load (lets say trying to draw 300 amps), the voltage measured at the starter would be ~3.5 volts(assuming the battery is at 12.5), the starter would not turn over, and it would sound like you had a dead battery and if left long enough the wire would melt the jacket and be on fire. Because your wire cannot deliver the amperage the starter motor needs, the voltage drops at the other end. Basically the starter is just dissipating heat at this point. (This is assuming the rear battery is providing all the current, which you should because you're planning for the worst case) Now with 30' of 00 wire, (~.000078 ohms per foot) and the starter trying to use 300 amps, the voltage measured at the starter would be 11.8 (assuming 12.5 at the battery) Double up the wire, and you are looking at 12.15 at the starter. Now you are getting almost all your voltage to the starter. 00 THHN wire with a jacket rated at 90*C (similar to most automotive wire) is only spec'd to deliver ~200 amps of current. Your starter will exceed that, which is why you will want to double that up. That and the less voltage drop = more power at the starter, for your coldest days of starting. Sorry for the long post, I just don't want to see you disappointed in your setup in the long run. And while the wire size is somewhat overkill because they should share the load between the front and rear battery, I would still run two pieces of #00 wire for the + and two for the -. Connecting the two batteries together. [/QUOTE]