what is the best way to wire dual batteries. I have a kilby dual bat set-up ordered but was wondering about how to hook them up. I have to tell you it's all greek to me when it comes to wiring so any help please be specific.
It depends on how you want to manage your batteries. Do you want one to be a backup of the other or do you want them to work in tandem? There are several differnt wiring options but you need to know how you want to run them.
A lot of people I know connect the winch (and other heavy accessories) to the second battery (usually a deep cycle) and use a solenoid to disconnect the starting battery during heavy draw periods. Others just wire the two together and be done with it. There are advantages and disadvantages to both. The first option can send voltage spikes to your electrical system if it isn't done right. This is usually caused when there is a large voltage dicrepancy between the two batteries. However, you will never be left in a situation where you don't have enough juice to restart.
The parallel battery system is good because it is really simple to wire and provides you with lots of current without draining too quickly. In this situation I would probably use 2 deep cycle batteries. The disadvantage is obviously that you can drain them both and be stuck in the middle of nowhere.
What I have been planning on doing (when I finally have enough cash to get a winch) is replace the little stock battery with a HUGE heavy truck battery. They are about the same size as 2 batteries next to each other but many are designed for high vibration and high current draw. Besides, they are usually quite cheap from farm supply stores.
If you decide to run a parallel configuration, I would suggest taking some hints from the RV and Maritime industries. Read about the set-ups they have been using for years.
I would use a make-before-break dual battery switch to allow battery 1, 2, both, or none to be connected when needed. The make-before-break contact feature ensures there will never be an immediate open circuit to the output of the alternator when the engine is running - this condition will almost certainly cause a failure.
The other thing I would do is add a high power isolation diode in series with each of the batteries (+) terminal. The isolation diode ensures the batteries will not discharge each other when sitting dormant or when there is a weakening or failure of one of the batteries should they be left connected in parallel.
The last thing I would do is ensure I had a circuit breaker connected very close to each battery that would protect the battery, charging system, and wiring in case there was an inadvertant short which could cause the batteries to explode, melt wires, damage electronics, melt metal, etc...
The last thing is to ensure your wire guage can handle the ampacity when under maximum charge and discharge cycles.
When disconnecting your battery, always disconnect the (-) terminal first and then the (+). When connecting the batteries back up, connect the (+) terminal first and then the (-) terminal. This will ensure you don't cause a (+) to ground short with your wrench when connecting and disconnecting.