# Friend recently installed sub/amp now battery keeps dying



## Rbtrucking (Jan 24, 2011)

I have a friend that installed a sub, amp in his car and now the battery keeps going dead after a couple of days. The battery and alternator were recently replaced. He did hook up the remote wire to the headunit so the amp does shut off when the headunit is turned off. Ground wire and power wire all look good. We are confused as to what could be causing the problem. Any ideas would be greatly appreciated.


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## FAUEE (Jul 22, 2010)

How far do you normally drive, and what size amp and what kind of car is it?

The most likely thing outside of the amp not turning off is that you're draining the battery while using the amp due to a small alternator and a large current draw, taking lots of short trips can also cause this.


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## Rbtrucking (Jan 24, 2011)

Im not sure on the size of the amp i know its a small one. The car is a 89 toyota camry. What you said about taking small trips and drawing too much power sounds like it very well could be it though because that is what he does alot.


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## FAUEE (Jul 22, 2010)

That's probably it. I can't imagine that car has an alternator that does much more than 60A, maybe even less. So if he's taking a lot of short trips he's likely never getting the battery charged back up to full anyways, then add the extra drain from an amp and you'll go through a battery a week.

His solution is to drive longer trips and/or not use the amp and/or upgrade to a high output alternator that will charge his battery back up from starting faster.


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## sqshoestring (Jun 19, 2007)

Get a $5-10 DMM with the 10A amperage plug on it, run the amp power through that, check for the amp drawing current while off. You could use a tester with a 12v bulb in it too. If no power there with amp off then the above is the issue unless he changed the wiring for something else in the car that is drawing current. A small amp (<600rms?) should not draw it down unless its on max loud 100% the time the car is running. Using the headlights while driving also takes more power as does the AC if it runs the cooling fan often. A class D takes less power with a tiny alt one should use class D or H on subs. Something like the 500rms class D kenwood you can get for ~$100 would have a hard time killing the battery in most cars. That is something like 40A draw if you play sine waves at clipping and don't eventually blow it up abusing it like that lol. An amp will only draw max very close or at max output, draw is far less than half at half volume.


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