With a winch, front light bar or fog lights, rear spot lights, onboard air, fancy sound system, large inverter, electric fans, or towing a trailer that needs power from your CJ, you may find that you need more power that won't leave you unable to crank the engine later. A dual battery is simple and easy and provides for those needs, and fits easily into your CJ with off-the-shelf parts. My main uses are camp sites with the front and rear spot lights, the inverter, sound system, and occasional winch use. I may have the lights and inverter and sound system going for hours in the evening, and I still need to crank the engine the next morning. So two batteries, kept isolated from each other, is the perfect solution. Simply hooking two batteries together can give you more power, but if one drains down or fails, it will take the other with it also, leaving you needing a jump to get started back up later. With them isolated, you can drain one and the other is still fully charged and ready...