Re: Dual battery -- why bother?
My take on dual batteries:
Not worth it unless a single 2150 battery wont be enough for your reserve capacity needs (IE your running electronics for a long time with the engine off). Most peoples dual battery setups amount to putting a 140hp 4 banger (stock battery) and a 300hp V8 (one bigger then stock aftermarket battery in one car to get 440hp, when they could have just put a single 440hp motor (big battery) for less money and less complexity.
A single 2150 battery can run a winch (with the truck running) for a very long time, I have never gone below 50% charge and I have had some tough stuck in mud pulls with my 12,500 superwinch. I have used my winch over 17 times now (4 times in a single night recently) and my 2150 battery and stock alt is enough to handle a 12.5 winch (but I don't have enough lighting put on the truck to absolutely need a bigger alt).
The only real 2 benefits to a dual battery setup is 1) if the primary battery has a failure, you can still start your truck without having to get a jump, replace the battery, or get out of your truck. If I was going to be out in the middle of nowhere by myself, miles from anything, a second battery would be a good thing to have. So would 2 spare tires, a spare CV axel, a ham radio, a full tool kit, and all sorts of other things similar if you want that "prepared" setup. The second benefit is increased reserve capacity, however like I said previous your not going to gain much throwing another stock like battery in the mix.
Does it make sense to spend 300$ (plus another battery) to have a fully setup dual battery kit? Well for most people I would say no. If you want to run things for days on end like fridges, it would make sense. Just remember Murphy's law, anything that can go wrong will go wrong. A single big battery has a lot lower chance of failure then two batteries and a bunch of wiring that most people will likely install incorrectly. Also runing duals with most setups will reduce the lifespan of each battery (mostly if they are different batteries and depending on how they are wired). Keep that in mind too.