A friend's Rolls has a separate battery for marker lights; they can be turned on when parking in questionable locations without fear of depleting the main battery.
However, automobile batteries are not suitable for this application, as they provide power for only a very short time; a Marine battery would be more appropriate (but either will require replacement every few years just as the starting battery does). I don't know about your planned mounting location; a passenger-compartment mounting of a hydrogen-emitting lead-acid battery sounds like a bad idea. I have no idea why you would recharge with solar when the alternator could do that, unless you are trying to accomplish something specific by using a standalone charger.
A more reasonable question might be "why?". Perhaps a timer would address whatever problem you are trying to solve. My car turns off all accessories after a short (annoyingly short, actually) period of time if the engine is not running.
I must say, though, unless you posted your question while drunk or English is not your native language, you should avoid working with electricity. or sharp objects. or crossword puzzles.
I used two 27DC-6 deep cycle batteries from Wal-Mart. Hooked them up in parallel (neg to net, pos to pos) and keep them charged with a 15w solar panel with charge controller. Plan to upgrade to a 120w panel soon. Hook an over-the-counter inverter to the battery and then plug in your accessories. Or just pick up a 12V accessory plug that clamps to the battery and provides 12v outlets to your accessories. Pretty simple and the solar panel keeps them topped off. And you can use a regular battery charger to recharge them after a particularly deep discharge. Deep cycle batteries are made to be consistently discharged and charged. Regular car batteries are not. In my case, the alternator in my 1979 Ford E-350 ambulance went out and nobody knows how to fix it without tearing out all my existing wiring. So I am using the solar panel to keep the two deep cycle batteries charged. I can run just fine off that with no alternator. And my ambulance has PLENTY of roof space for more panels. I've also toyed with the idea of using a Tripp Lite PV2000FC PV 2000W 12V DC to AC Inverter Plus with Charge/Load LED's hooked up to the deep cycle batteries and charged by both the solar panel(s) and/or a shoreline (extension cord from the house to charge the battery). This is an inverter/charger. It draws from the batteries and then charges them back when alternate power is available.