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I've been having this issue recently where my battery would go flat after turning the car off after driving for short periods like 15 minutes or so. The car doesn't even click over and you could see the clock on the cluster fading in and out. After jumping the car everything else is fine. Could it be a sub or an amp causing the battery to drain?any help would be appreciated.

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Yes.

It could be anything

Including your battery might be too old.

Your alternator might not be charging correctly.

I've taken the sub out , I'll see how it goes . I'll even put some distiller water in the battery as well

I'd say the altenator must be working or the thing wouldnt have any power to drive (seen as its completely dead after key off)

I'd look at battery first but you can also check altenator as well

If you dont already have one, go buy a cheap multimeter from Jaycar or Supercheap etc. Get the car running and check the Voltage with the car running. Check either by putting the meter probes on each of the battery terminals, or you can also put one on the positive out of the altenator and the other on a good ground in the engine bay. Between 14.0V and 14.5V means the altenator is working properly.

Get a second person and keep the meter somewhere as above, checking voltage when the car is turned off. The BEST a battery can get when off is 12.6V, but usually anything around 12V is fine. If you have less than this, and judging by your description you may have alot less, you have a problem on the battery or cables. Check that the cables/terminals are clean and have a good earth and good connection on the positive end as well. If that all looks good then I'd say its battery.

Another way to check the altenator as well is to check the R terminal. Best done with a test light, putting it to positive on one end and probing the R terminal should make the test light light up while the car is off. when the car is running, putting the clamp on ground and probing the R terminal should make the test light light up

Should be plenty of info to help you out, and multimeters arent expensive, and can be very handy

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