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

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AidanS

458 posts

Ultimate Geek

#994582 26-Feb-2014 07:14

gregmcc: First of all sort out any battery issues, beg, buy or borrow a car battery charger, fully charge the battery.

You will need to find a multimeter and test the amount of current draw by the amp and head unit while the keys are off, a typical standy by current drain should only be a few mA.

Next step to help with any grounding problems is check the voltage at the battery with the keys off, and again at the amp with the keys off, much difference, the greater the difference the poorer the connections, prefore the same test with the car running and the amp going cranking out a bit of power, you may need 2 meters at the same time, one at the battery, one at the amp, there will be dips in the voltage that correspond with the beat of the music, but if all is good both meters should read the same.

I suspect the standby current is the problem, maybe the remote turn on wire has been hooked up to +12V so the amp is always running even when the keys are off causing excess current drain, ideally this wire should be connected to the "remote turn on" from the head unit.

Greg

Thanks for that Greg. My remote wire and 12v+ wires are definitely wired correctly, as the amp turns off with the key ignition.

I'll do some more testing today to try to determine the overall issue.

Thanks to everyone for all the input!

-A.

blakamin:
They're just the factory BMW ones! Mind you, when you've got electric & heated seats, auto everything, and a 10 speaker stereo system from the factory, they probably decided they needed them! :D

Dayum, that's a lot haha.

-A.

AidanS

458 posts

Ultimate Geek

#994587 26-Feb-2014 07:26

Quick update, car started once this morning, and now won't start. Taking battery into Marshall's to get an overnight charge, and then we'll go from there.

-A.

Bung

6477 posts

Uber Geek

Subscriber

#994665 26-Feb-2014 09:20

How old is the battery? Newer "calcium" types don't like being flattened and need proper recharging. Just over 12 volts isn't very flash at terminals. If you have a meter did you ever measure discharge while off?

Edit 12.7 ok but as said before needs load test.

trig42

5809 posts

Uber Geek

ID Verified

#994667 26-Feb-2014 09:20

It does sound like you have a porked battery, and just putting that little bit extra load onto it stuffed it.

Grounding shouldn't be the issue (all the metal bits attached to the car should be grounded, it really doesn't matter a great deal where you connect things (obviously, bare metal is best).

How old is your battery? Is it the factory battery?

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.

AidanS

458 posts

Ultimate Geek

#994970 26-Feb-2014 17:05

The battery was put in December last year by Marshal Batteries, and it's one of their own branded ones too. So either it's a coincidence, or me doing the head unit / sub woofer has potentially porked the battery, as suggested.

-A

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.

Equinox IT

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AidanS

458 posts

Ultimate Geek

#995024 26-Feb-2014 18:53

Mattmannz: 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.

Thanks for that Matt.

The little "built in" meter on the Marshall battery is still on "green" implying that it's got 50-100% charge, but obviously that can only be so accurate.

I've given the battery to a friend tonight so he can charge it with his proper wall charger, and I'll see how it goes after that.

If I still have problems I'll go back to Marshall and see how it goes.

I ran a few tests (with a multimeter) with my after market equipment and their grounds, and have now concluded the grounds are definitely adequate, and combined with people's posts on here, the grounds are not at all the problem.

Thanks again, for all the help guys, hopefully all gets sorted over the next two days. Lucky we've got enough cars to still be able to get around lol.

Cheers,
-A.

Niel

3267 posts

Uber Geek

Trusted

#995068 26-Feb-2014 20:10

The green bubble tells you the state of the acid, dies not tell you anything about sulfation. My battery was dead but still green.

You can never have enough Volvos!

Aredwood

3885 posts

Uber Geek

#995894 27-Feb-2014 23:13

Are you sure the problem isn't just you driving round with the volume right up. Therefore too much load on the charging system. Battery therefore not getting enough charge.

Azzura

603 posts

Ultimate Geek

ID Verified

#995911 28-Feb-2014 00:14

It is possible the car stereo system (if it a a large enough system) is taking more power from the battery than the alternator can produce, which will lower the charge gradually until the battery has no juice.

Mattmannz

471 posts

Ultimate Geek

#995955 28-Feb-2014 06:51

A typical car alternator can output around 1000w of energy. You would have to be cranking the stereo continuously to outrun the alternator and flatten the battery.

Matt.

Batman

Mad Scientist
29760 posts

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Lifetime subscriber

#995971 28-Feb-2014 07:58

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

John

if anyone's thinking what I was thinking - don't. brings back memories of when I was about 10. did just that, plugged a battery directly into the wall socket. bad idea.

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.

Mattmannz

471 posts

Ultimate Geek

#996333 28-Feb-2014 12:58

Good to hear

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