separate battery in trunk

i was wondering if i could use a totally separate car battery in the trunk to power my neon lights and such that i would use whenever i have my trunk open.  would it be possible to use it with my amp and subs too? would it be on the whole time? thanx

I dont see why not. Thats usually what people do. They set up one battery to run the car itself, and the other battery to run all the goods. 1990 Honda Civic HB:

Clarion DXZ545MP H.U.

2- 6.5" Power Acoustik interiors

Diamond Audio 600.1 amp

Diamond Audio 15" M6MKII

Pyramid PB881X 4 CH. Amp

Wrong. In fact, it will cut the work the alternator needs to do almost in 1/2. Alternators are voltage regulated, not current regulated. Too many batteries can be a detriment, but 2 batteries on an 80-100 amp alt will be just fine. Be sure to use a proper isolator (not a constant duty solenoid) for extended battery and alternator life. Here is my car, the correct isolator, and the second battery in the trunk (AC Delco Platinum Professional AGM battery):

remember you must fuse the battery in both directions so that if any thing happens to the cable from front to rear your car will be protected.

There are too many variables he does not take into account. A few quick thoughts... The car will always need current to stay running, after a start the car will drag 30 amps to simply recharge the battery to it's desired voltage, as it is voltage regulated. Now let's add the additional load of running all our stereo on that drained starter battery. Not only are we replenishing the starter drained battery, but now we have additional reduced voltage that the alt needs to overcome, and what it delivers is being robbed by the stereo again. Keep the following in mind as you ponder the above statement... In order to produce current, the alternator needs input voltage. If the input voltage drops, the alternator needs to work harder to produce the same current, generating additional heat in the alt case (hence, premature failure). By doubleing our reserve capacity, we essencially cut the voltage drop in half to the alt reducing it's work load. Now, that is a constant duty solenoid install. Let's ponder a true isolator. A true isolator pulls it's input voltage off the main battery. The main battery sees minimal loads as we drive down the road. The requirements are typically small loads, rarely affecting total voltage of the main battery, and therefore not affecting the input voltage of the alt. By maintaining a steady solid input voltage, the alt needs to do less work to maintain the proper current to maintain system voltage. Keep in mind, the iso will detect which battery is lowest and send the proper charge to the batteries as they are needed, of course, biasing to the main alt as it is the input feed. So we have proper input voltage being maintained that reduces the work the alt needs to do, we have double the reserve capacity for those big bumps that will suck a single battery silly, and we still have the same load on the system overall!!! While I am a firm believer in most of the info on BCAE, this is outside his realm of expertise. Being that I am AC Delco and ASE master certified including L1, with my specialty being computer, electrical, driveability and emissions diagnosis and repair I would say I can safely suggest this is within my realm of expertise.