just a little Boom

Enthuzed1 · 11-03-2005, 10:42 PM

hey guys, real quick...
i'm gonna put a pair of 8" subs in my car and i plan on using a separate battery placed in the rear....
i'm only gonna have the positive terminal powering the amp, and the amp grounded to the car chassis, right? or, will i be using the negative terminal instead of having the amp ground to the chassis?
also, any specific type of battery recommendations?

legion · 11-04-2005, 04:34 AM

You were right the first time. If you do it the second way, you won't have any power. Let me know how you mount your battery. I'd like to move mine to the rear to move it out of the elements.

sasquatch · 11-04-2005, 04:36 AM

With only a pair of 8s, there is no need to put another battery in. Just go and get an amp install kit and run the 0 ga. wire from your front bat to the amp. Make sure you place the included fuse as close to the bat as you can. If you are concerned about power draw, which will not be an issue with 8's, put a cap in next to the amp.

CJFusco · CJFusco's Garage

WHY DO YOU WANT TO ADD WEIGHT TO YOUR CAR?!?

Zero10 · 11-04-2005, 07:14 AM

If you're adding a pair of 8's, you probably won't be using more than a 400W amp (real 400W, not a pyramid piece of s*** 400W that's really only 20W), so just run some #4 wire from your battery back to the amp. A 400W amp will only draw ~35A at full power, and #4 wire is rated for ~80A. It will be just fine. Adding a second battery is just asking for things to go wrong.

Enthuzed1 · 11-04-2005, 07:33 PM

Quote:

Adding a second battery is just asking for things to go wrong.

hey don't scare me like that!!! what kind of things'll go wrong?

hey CJ, i figured on taking the rear seats out anyway, and i have no rear carpet or spare tire, so MAYBE i might break even......maybe.....

seaboltman · 11-05-2005, 02:39 AM

Zero is right, dont bother adding a new battery. With 2 8s, things will be fine running it off just he stock batery. Add a capacitor if anything and you will be fine.

Zero10 · 11-05-2005, 08:36 AM

Okay, what kind of things can go wrong?
One battery goes bad. One cell in it messes up, your electrolyte level gets low, whatever. The open-circuit voltage of that battery will drop below the other one, causing it to start drawing current from the other one, however the battery that is drawing current isn't charging, it's just being a parasite. Eventually it will kill both batteries, and you'll have to get a boost. This is why a lot of people use isolators when installing 2 batteries. Next thing that can go wrong. If you leave your lights on, or something, and run both batteries down a reasonable amount. Your car may still start, but you will be working the heck out of the alternator trying to charge up 2 batteries at the same time. In the long term this is very bad for your alternator. Next, the long wiring in-between the batteries can get damaged, the insulation can rot, crack, get crushed, whatever. It's a lot easier to short out that wiring than the short-length battery cables that are already on the car.

Some of those are a little bit far-fetched, but I think you get the point. I am in a little bit of a hurry, so perhaps my explanations are not as good as they could be.
The moral of the story is, 2 batteries works if the wiring is in good condition, large enough, and both batteries are kept in good conidition. However, as soon as any one part of this system begins to fail, you're in big trouble. Not to mention, the failure rate on 1 of 2 batteries is twice as high as the failure rate on one battery, and since if either goes bad you're stranded, you have twice the chance of being stuck.

For your installation, you will be fine with some #4 wiring to your amp in the back, and a decent amp driving your 2 8" subs. Hell, I even ran my 950W Alpine amp and 2 15" subs in the back of my 86 off of one battery, but I had to add a capacitor to keep the lights from dimming on big bass hits. That car had the world's smallest battery too, lol.

Besides, be happy, you just saved $100-$150 from not having to install a second battery. Use that to buy a sweet amp, or 2 10" subs instead of 2 8" subs. (Can you tell I'm a bass freak?

)

I'm not trying to come down hard on you with this or anything, but I am trying to keep things real, and come up with the best solution that I know of to this problem.
Best of luck!

AA_Ezra · 11-05-2005, 12:55 PM

8's no problem Depending on the amp You will need Certain gauge wire. 350 wats about 10-8 guage. 500wats i'de go with 4 guage especialy if you're going to go with bigger sub setup later. Wiring is pretty simple. Run Positive wire lead ( red cable ) all the way back, make sure you're fuse isent more then 1 foot way from yer battery post, Then Run the amp turn on cable ( blue ) from radio to the Amp. Don't jump it on the amp. Clean the pain off the chasis to get a good ground. Make sure you connect ground the very last. If you need any more help or ideas what you can do Check out my homepage of Just drop me a line ( still new to this but i'll try to reply my best)