i need to know what i can run to keep a steady voltage without a real big voltage drop without a bigger alternator
Here's how to solve your problem.
1. Complete your install using the proper wire and do the wiring upgrade
already suggested.
2. Use your stock ALT and battery.
3. Buy a cheap voltmeter, a voltmeter with a needle, or a digital voltmeter
a peak-hold voltage feature. I don't know if cheap DMM has this feature, so
maybe just look for a needle voltmeter. {something like the one on the left},
they sell small cheap needle meters.
http://www.newsandtech.com/issues/2005/07-05/nt/images/22bourlon01.jpg
4. Connect the voltmeter to your battery with car engine running and note
the voltage without the amps turned on.
5. Now turn on the audio system and crank the tunes loud. If you have needle voltmeter, watch the
needle bounce as the voltage fluctuates, make note of the lowest needle bounce and note that voltage drop.
If you have a DMM with peak-hold, set it to capture the dips in voltage and it will capture the lowest reading and
hold the reading so you can see it.
If your voltage was 14V, then with music it dips down under 12V, then
you have some real data to work with. You can probably get away with
using your audio system if the voltage only dips down to 12V. You can
add an extra 'cheap' battery to augment.
If your voltage dipped very low, lets say 9V, then you have issues. Your
install is punishing your alternator and battery too much. You should buy a HO ALT
and have someone make custom brackets and make it fit in your car.
That is life in the world of high wattage audio.
You can cheat and use a battery array, more is better and you don't
need to use $300 batteries. If you bought a single $300 battery in those
conditions, it will get abused over time and go bad. You should
spend the extra bucks on a custom HO ALT install and then
redo the test with your stock battery. Spending $300 on a battery
without analyzing your electrical is funny.