What size wire do i need to hook up a car battery in the trunk for my amp?

what do you mean it cuts out? you mean it stops playing? If so, your amp is overheating. For your wire needs, use this chart: http://74.50.20.110/wiringdiagram.jpg As you run more wire, there is more resistance so you will need to use a larger wire.

Yep..just use a 4 gauge power wire like the one u have now....u need a battery isolator. mount it under the hood close to the main battery.. u run both ur power wires on the big terminals on the isolator to each battery, and one small terminal to ground, and the other terminal to acc, or remote with your amp remote to the back of your deck. then ground the trunk battery and run the long power wire coming from your main battery to that trunk battery. Make sure u put another fuse on the power wire at the second battery also...and yea you will eventually need to upgrade to 200 alternator.....just hooked up second battery this past weekend in mine...email if you need any more help with it...it's not that hard to do

For just a simple set up would go with up grading your factory alternator to a hi amp like a 200 amp (because if you thing about it you will be putting a lot more wear and tear on your oem charging system with having two batteries) then add one or two farad cap(s). That is how my system is running with no light dimming either. As for your amp shutting off I would say it is going into thermal shut down I would look at the gain control it my be too high or even how you wired the subs if they are wired in a 2 ohm load and the amp is rated stable at 4 ohm that could be the problem too. Good luck!

lol i just answered this, you need a constant duty solenoidmeaning when power is to it, it powers the stereo amp/s.it needs a charge wire from the regular system run to it,to maintain charge.you could use a very big relay or group of relays to omit solenoid, but with key on, it will run charge the spare battery, and during acc it will power your amp, and if you wanna get fancy, you could run your radio as well off the aux battery.you obviously know how a circuit works, im not gonna do it for you, just told you what you need how to hook it up, you design the circuit.also you do need a ground wire from aux battery to chassis. ok so if you run a small guage hot from your battery to a constant duty solenoid,then out to your aux battery,and hook a key on engine running hot tap to the constant duty solenoid trigger, it will charge when running, but also keep the cars primary system from running dead when the radio is overplayed. its not really neccessary to put radio on the circuit.