Amp Killing Battery?

[Jonthesharp]

The battery went dead in my wife's car right after I installed a sub and I am trying to prevent it from happening again.

I checked the remote wire with the car off and it had 0 volts

I checked the positive to ground on the amp with the car off and it had 12+ volts (as seems expected)

I disconnected the remote and the ground wire and tested the positive terminal with the ground terminal (not the wire) and it had 3-4v. This was also true with the positive disconnected. It would eventually go to zero over time. I assume this is the capacitors losing charge, but I am worried that its leaching power off the battery when the amp is off.

Can anyone confirm if this is normal or if there is an issue going on here?

Thanks

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[adulbrich 5,000+ posts]

It's not normal for an amp to kill a battery when not powered on.

It is normal for the amp's capacitors to store a bit of power after being disconnected.

Either something else killed the battery or there is an internal problem with the amp if the remote wire isn't keeping it on.

I'd say load test the battery, and then hook the amp up and see if it does it again.

 

[shredder1 10+ year member]

You didn't wire the amp turn on to a constant power source did you?.. I'm reaching here...

 

[Jonthesharp]

Yes? I have the amp going to the battery with the understanding that if the remote switch was properly turning it off (as it seems to be by the power light turning off with the car) then it shouldn't but pulling any power from battery while it and the car are off.

 

[shredder1 10+ year member]

Yes? I have the amp going to the battery with the understanding that if the remote switch was properly turning it off (as it seems to be by the power light turning off with the car) then it shouldn't but pulling any power from battery while it and the car are off.

.

I'm going to ask a specific question here... is the amp turn on lead wired to a constant source or do you have it wired somewhere else?... where, hopefully the head unit turn on lead.

 

[Jonthesharp]

I just put in a new battery after the last incident (it's a new car as seemed worth it to keep her from getting stranded with the kids). So Load testing it shouldn't be needed.

How can I test the amp to see if there is an issue causing it to leach power when it's off?

 

[Jonthesharp]

I'm going to ask a specific question here... is the amp turn on lead wired to a constant source or do you have it wired somewhere else?... where, hopefully the head unit turn on lead.

Oh sorry, I misread your first question. No it's going to an aux in the fuse box. I verified it's not getting power at the amp when the car is off, and the amp power lights turn off when the car is off.

 

[shredder1 10+ year member]

Oh sorry, I misread your first question. No it's going to an aux in the fuse box. I verified it's not getting power at the amp when the car is off, and the amp power lights turn off when the car is off.

Sorry I HAD to ask... the problem as described seemed eerily familiar...

 

[BOOMINGRANDPA 5,000+ posts]

amp shouldn't be doing it if wires are right as always my 1st thing is to check the ground, make sure no paint under it but even that shouldn't do this.. did u run speaker wire under anything or power wire check it to be sure non of the insulation rubbed off.. i had a dome light wouldn't turn off 2 days we had just installed alarm system so we replaced it (easy since i worked at a shop) but light was still on.. it was a speaker wire got under seat belt bracket and grounded it.. so as we always say check wires but in your case u need to check the whole length of the wires not just the connections

 

[hispls 5,000+ posts]

If you have a DMM you can always just measure current into the +12 terminal on the amp with the car off and see if there is a problem.

Of course if you deep cycle a standard car battery a couple times that will kill it super fast so if the batter has been drained to the point where you needed a jump start more than once or twice it's well worth having it load tested just to see if things are OK.

 

[JDay]

If you have a DMM you can always just measure current into the +12 terminal on the amp with the car off and see if there is a problem.
Of course if you deep cycle a standard car battery a couple times that will kill it super fast so if the batter has been drained to the point where you needed a jump start more than once or twice it's well worth having it load tested just to see if things are OK.

And if that's the case it's time for a high-output alternator.
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