Always On Power - How to get it?

[Bravotwofive]

2007 EXL

Several dead batteries after working on the interior of the car have prompted me to look at alternatives. This can occur after 40 minutes or so if the interior lights are on. This battery was replaced under warranty from the dealer, and still has not solved the problem. According to the dealer, if any cabin lights are on the computer is also on. It is only a drain of 600 milliamps with only one interior light on. Therefore if I assume a 1amp draw with everything on, I would still expect more than 40 minutes of battery until the vehicle is unable to start.

The end goal is to have enough power to run a laptop on a power inverter with occasional always on 12 volt. My current solution is either to purchase an Optima battery with 800 CCA, and hope that gives me more time. This would be the easiest solution.
Or to remove the extra head rest in the back, and put in a bank of sealed 12v 14.0 AmpHr batteries, an isolator, and an alternate power run to the front console area. These options I like better, although don't care for all the extra work.

Even if I do the battery bank method I still have the short battery power problem if the interior lights or radio are left on. So after all of this I am looking to you folks for informed suggestions. I am not really looking for the option of carrying around a starter supply battery.

There are 3 basic questions I need to find an answer to.
1. Can I install an isolator switch from the alternator lead to the main fuse box?
2. Is there a straight forward approach to separating starting function from all other electronics operations?
3. Is it worth trying a $170.00 battery first?

Thanks for any suggestions.

[rocky]

Look for the LED thread by Cmasten and replace all the interior lights with LEDs

[N_Jay]

What are your typical trips like?

I think you want deeper discharge, not more CCA.

Putting a set of batteries on an isolator will give then relatively short life due to low charging voltage.

Just start the car.

[youbetcha]

Something isn't right. A typical car battery is 40-60 amp hours, not 40 amp-minutes. If you are starting a car you need hundreds of amps for a brief period of time. If you draw a low current then your battery will likely last longer than rated. You should be able to run a 12 watt (1 amp) light for days before a complete drain, although you reach a threshold of not being able to start your car before fully draining the battery.