Does anyone know why a 2007.5 silverado 2500 with the 6.0 would have dual batteries, or if this was a factory option? Gotten a couple weird electrical problems with it in the past and was just curious.

 

My 97 Sierra 1500 has 2 battery trays, but only 1 battery installed. Usually 2 batteries are used for snow plow trucks, diesels have them a lot too.

 

It doesn't have the prep package for a plow. Does anyone happen to know how they wire them in together? It appears to be done professionally, but that doesn't always mean much.

 

There's two ways to wire batteries: series or parallel. In series, one battery's negative termal is connected to the other's positive. This effectively doubles working voltage (electrical "pressure") while maintaining capacity, allowing you to perform tasks requiring greater instantaneous work loads. In parallel, the positive and negative terminals are connected together. This orientation maintains the same voltage (in the case of automotives, ~12 volts), but doubles the electrical capacity.

The dual battery orientation is of the parallel sort and allows the vehicle to run more electronic equipment (coils for diesels, serious lighting setups, etc), as these items can draw significant amperage from batteries. Drawing too many would deplete a single battery quickly, which can damage them or diminish their lifespan.

In short, doubling the number of batteries is the electrical equivalent of having a second fuel tank.