New Car Head Unit / Sub Woofer Causing Battery Drain/Battery Not Charging Issues

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AidanS

458 posts

Ultimate Geek

#140976 25-Feb-2014 21:07

So last week I installed a new head unit and sub woofer (and amp) in the boot of my 96' Toyota Caldina.

The install went well, and everything worked fine, until yesterday (about 6-7 days after install) the car failed to start.

After a jump start, the car ran fine. Then this morning (25th), the car failed to start again. After a jump start it got me to the place I needed, and then without turning the car off it got me home again. And (not) to my surprise it failed to start yet again this afternoon.

After doing some reading online I think I've narrowed down the issue to poor choice of grounds for either my head unit and/or the amp in the boot. Apparently a poor ground will cause the battery to not get charged properly which explains why it took nearly a week for the issue to actually become noticeable.

I've already checked all my wiring to ensure I've connected the constant 12v+ and the ignition operated 12v+ the correct way around as this can cause battery drainage. However a "drainage" issue wouldn't explain my situation as it took nearly a week for the battery to "die". And now it's "dead" it won't go back to 'full" again. I also tested the alternator to ensure it was giving a constant voltage of about 14.3-5 volts, which it is.

Tonight, I've disconnected both the head unit and amp's 12v+ and ground cables, and jumped the car and "charged" it for over half an hour. The battery now gives a steady 12.5 volts or so, when the car is off. And the car seems to start okay tonight.

My plan is, to see if it starts fine tomorrow, which if it does, concludes either one of my grounds is the issue in which case, my main question leads in:

How should I ground my after market equipment? I had the amp grounded to an existing ground bolt, that the boot's cigarette charger was connected to. It had a lead that went of behind the car panel's somewhere. I presume this is a factory installed "ground". And the head unit was attacked to some metal frame behind the dash, which was easily accessible. Is there any way I can easily find out which grounds are suitable or not?

I have an easily accessible alternative ground for the amp (the bolt's/frame under the boot's carpet holding the rear seats), if I need, but an alternative ground for the head unit would be more of an issue. I'm aware the point of ground connection needs to be free of paint, or any coating. Also the battery is only about two months old, so "shouldn't" be the issue.

Any help, comments or advice on this situation would be much appreciated!

Thanks,
-A.

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johnr

19282 posts

Uber Geek
Inactive user

#994444 25-Feb-2014 21:11

How did you charge the car battery for 30 minutes? Hope you don't think the car alternator is going to do this,

First off charge the car battery for 24 hours on a bench charger then get it load tested with a CCA meter

John

Mattmannz

471 posts

Ultimate Geek

#994668 26-Feb-2014 09:25

A good quality multi meter is always worth having around. Allows you to easily measure voltages, voltage drop/resistance, andcurrent draw so you can see what's going on.

To test your alternator you can't rely on voltage alone, you need to confirm the amperage as well by loading the system with lights, fans etc and using a clamp meter to test the output. It's possible that the rectifier has partially failed and the alternator can still output 14v but with load it dies.

Same with the battery, as John mentioned above a load tester should be used on the fully charged battery to see how long it can handle load.

Always check the battery connections, you need to have solid clean connections from the battery to the starter and alternator and vehicle body. Without load these connections might look okay and give okay values from your meter but once you load them they can drop away quickly. I always clean all connections with sand paper including body earths. If you are worried about corrosion you can paint over the finished earth once the cables are screwed/bolted to the earth point.

Matt.

Mattmannz

471 posts

Ultimate Geek

#994971 26-Feb-2014 17:11

If the battery won't hold charge anymore it's either because it's faulty or it's been continually run flat over a period of time and is now damaged.

Batteries don't like being run flat and partially charged but to kill a battery it usually takes quite a number of times of doing this, from your description it doesn't sound like you have been abusing your battery.

Either way if its under warranty you will probably get a replacement as it's difficult to tell that a battery has been abused and they usually just replace them.

Fingers crossed it's a faulty battery and away you go :-)

If you have a multi meter pull the positive lead off the battery and measure the amp draw without the stereo connected. Repeat once it's connected.

Matt.

AidanS

458 posts

Ultimate Geek

#996309 28-Feb-2014 12:43

For anyone interested, had the car battery charged on a bench charger and the car still wouldn't start.

Took to back to Marshall and they said that the 3 month old battery was in fact faulty, and replaced it.

Everything is now running smoothly :).

(Hopefully things won't go bad in another weeks time).

Cheers,
-A.