Author Topic: ARGH! Why does my ****ing battery keep going flat? (Read 6246 times)

molgrips · « **on:** October 30, 2008, 08:10:14 am »

It seems to go flat over a few days. Fine, except that it's the second new battery I've had that did the same thing, and I've had the multimeter on the battery terminals and found that there's no current being drawn when everything's off. So wtf?

Could there be some kind of hidden drain I don't know about, that only comes in occasionally?

shegel · « **Reply #1 on:** October 30, 2008, 12:57:15 pm »

have you checked the alternator.....its possible that it could be getting 14 volts but not charging amperage. or the diodes could be bad causing the light to come on and it not charging. or you've got a gremlin somwhere like your suggesting.

shegel · « **Reply #2 on:** October 30, 2008, 12:58:33 pm »

Quote from: "molgrips"

Could there be some kind of hidden drain I don't know about, that only comes in occasionally?

possibly an exposed wire that is dangleing that grounds when it sways. i dunno

the caveman · « **Reply #3 on:** October 30, 2008, 01:00:40 pm »

If you have oem or an aftermarket alarm, you won't be able to check for battery drains by disconnecting the battery terminals because you are then disabling the system. If you do have an alarm or remote starter ,the only way will be to use a clamp on inductive ammeter to see if anything is pulling current while the battery is connected, doors locked and hood switch disconnected or enabled. If you can't do all that, then first try it with the radio disconnected for a day or 2, then any other accessories you may have. Before you test, also make sure ,while the engine is running, to engage all and any electricals, A/C radio etc, ABS etc, etc

molgrips · « **Reply #4 on:** October 30, 2008, 02:05:04 pm »

Quote

clamp on inductive ammeter

Ah yes, good idea... I did wonder if by disconnecting the supply briefly I reset whatevdr it was...

I still suspect the radio - it used to be always on, but I wired it into the supply for the heater fan so it works only when the heater fan can ie when ignition is on.

No alarm btw, but central locking.

jtanguay · « **Reply #5 on:** October 30, 2008, 02:40:21 pm »

if you have CAA you can get your system checked... they have pretty good tools to do that. they test the battery, alternator charging system, and for any drains when the car is off. pretty sophisticated IMO, and saves a lot of guess work!

the caveman · « **Reply #6 on:** October 30, 2008, 09:30:51 pm »

hey mr tanguay, look where he is :wink: I think over there it's the RCFDECAA

molgrips · « **Reply #7 on:** October 31, 2008, 03:38:49 am »

Just the plain old AA in fact

I'll get it tested as a last resort. This morning, after fully charging the battery overnight I put it back in the car and I saw a little spark as I reconnected the terminals. I swear, it's that damn radio, even though I wired it up to be off when the ignitions's off... grr..

the caveman · « **Reply #8 on:** October 31, 2008, 07:09:21 am »

If you see a spark when reconnecting ,then that is a fairly large drain , at least 1 amp. the most you can have without draining a battery is 30 mA.

jimfoo · « **Reply #9 on:** October 31, 2008, 11:08:56 am »

I had a bad diode on an alt once. It would charge the battery, but would discharge through the alt when the car was off.

shegel · « **Reply #10 on:** October 31, 2008, 11:19:23 am »

Quote from: "jimfoo"

I had a bad diode on an alt once. It would charge the battery, but would discharge through the alt when the car was off.

my golf had a bad diode for as long as i have owned it .....about 2 years. and i never had the battery drain on me. i dont think its the diodes

the caveman · « **Reply #11 on:** October 31, 2008, 02:17:17 pm »

I've seen both starters and alternators drain batteries, althought the starter one was weird.

jtanguay · « **Reply #12 on:** October 31, 2008, 04:41:53 pm »

Quote from: "the caveman"

hey mr tanguay, look where he is :wink: I think over there it's the RCFDECAA

hmmmm didn't see that... but they must still have as good of technology over there in the UK :lol: :wink:

and diodes just control the flow of electrons... can a diode fail and allow bi-directional flow??? that can't be good

molgrips · « **Reply #13 on:** October 31, 2008, 05:03:16 pm »

Ok, so I went out to try another test just now and guess what - no sparks.

:?

I carefully took the battery conection off whilst keeping contact via the multimeter, and no current. Great. So it only happens when I least want it to..... :evil:

burn_your_money · « **Reply #14 on:** October 31, 2008, 07:32:00 pm »

What setting are you using on the multimeter?

Have you verified that the alternator is charing?

How big is your stereo? If it's drawing more power then the alternator can provide, the battery will go dead.