I currently have a 450 watt amp pushing one 12" sub. Just recently i had to get a new battery for my car because the amp was draining to much power from the battery. I was told i needed a capacitor to help with the loss of power, but i don't know what size capacitor i need. Anyone have any input?

 

you don't need a cap - it won't help you at all. whoever told you that shouldn't be consulted in the future.

what did you use for a remote turn on for the amp? verify the amp actually shuts off when the head unit is off.

batteries die from a few things:
failing alternator
age (5+ years)
current draw when car is off

i guarantee that amp/sub combo isn't too much for the car/battery unless you play it with the car off for extended periods of time. a cap won't fix an ailing electrical system. your battery has 100x more energy storage than a standard stiffening cap.

 

a capacitor won't really do anything? I tested my battery the other day while the sub was on, and when the bass wasn't going it was 14. when the bass was on it dropped to like 13. 6 or something. Is that bad? Is that what killed the other battery. Although i do use the radio a lot when the car is off. Plus it was the factory battery. and i have a 2005.

 

13.6V with the stereo on is actually pretty good. anything above 13.8V is great.

a battery will last about 5-8 years with normal use. with a stereo the life is shortened a bit.

playing with the car off will kill a single battery. for long listening sessions (more than 20min) you'd need an extra battery or two and a high output alternator to charge them + recharge them after your listening sessions at night.

you must ensure your battery are charged regularly - meaning you reach 14V while driving the car. Autozone will load test your battery for free.

caps are too small to do anything. if placed right next to an amplifier, with wire as short as possible (only a few inches), they can help with some transient voltage drop at the amplifier. they won't do a thing to help a battery or help you play with the car off.

 

I have the same sub and amp as you for almost a year and I've never had any battery problems. I got it installed by best buy so maybe they already put a capacitor on..

 

yeah, i did some research, and the capacitor won't help that much, a high power alternator would. But i don't really have the money for that right now, and i had mine for about a year too, and i never thought it was causing any problems.

 

i'm buying a 140A HO alternator online right now. I just got mine from McGowan Starter and Alternator, corresponded with Gene. The price was $150+shipping and it's new with an upgraded 140A stator, rectifier, and regulator. Then i'll have mine respun at a local shop for >180A. I'll match that up with the largest AGM battery I can fit (not deep cycle). You should always keep a voltmeter visible when you add a high power system. I'll have a back up alternator from here on out, one larger just incase i upgrade later on.

The only way you'll stay above 13.8V is if the alternator can put out enough current to keep up with the car and the stereo.

Irragi and Ohio Generator are two great manufacturers, but run $300-500. Granted, i'll have that much in the pair of alternators, but i'll have two. After talking to Ohio Gen today, they provide an output graph of the alternator, and they output more than rated. His example for my car was rated 160A nominal, 180A peak, but tested at 219A peak. It was also $525.

 

damn. When i get that kind of money ill consider upgrading my alternator. And just to make sure, a cap will do little to nothing with helping my voltage drop, correct?

 

correct, the cap won't do a thing to help your battery woes.

 

Good post with good information..good job...