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What can drain a car battery in 24 hours? need help
drago13666 
16/7/07 10:20:27 PM
Guru

I've had an awful lot of bad luck with my car lately

first the immobiliser suddenly decides to start working (its never worked in the past 2 years i've had the car, have to go home and find the key fob to turn it off.

Day later when i go back to my car to try and start it, the battery is flat, call the racv, they take an hour to arrive, the guy says the battery is dead an i need a new one, battery guy is called takes an hour to arrive an gives me a new battery, everything is sweet and i drive home.

Day later i go to drive my car to work and the battery is flat, brand new battery flat, that was saturday, sunday we took the battery out and had it on the charger all day to make sure the battery wasn't a dud, battery charged fine.

today we tried it in the car and it started agian but i'm worried its gonig to go flat again so i've disconnected it until i can work out whats going on.

I know that both times i did not leave the ligths or anythign else on in the car, my car beeps at me if i do and i'm very careful about things like that.

My guess is that something is shorting somewhere, we checked any fuses that we could find and nothing looked out of the ordinary.

When the car is off there is about 0.8A draining across the battery. (whats normal when a car is completly powered off?)

I dont' knwo wether the sudden working of the immmobiliser is related or not.
the day befor the immobiliser started working someone refersed into me, tiny bit of panal damage but nothing that would effect any of the electronics in my mind. My first gues was the jarring might have knocked a wire to start the immobaliser and short somethign but i can't find anythign loose, also cant find any obvious wireing that might be shorting or part of the immobilise.

Any help to stop my battery continually going flat would be a great help thanks.

Car 92 mazda 323 astina sports liftback model
only mods are a sports exhaust installed befor i had the car
new stereo system installed 1 year ago had no problems since

The car does desperatly need a service and i want to take it but i want to make sure ill be about to get it there and home again without the battery going flat, just thought i'd ask on here if anyone had any ideas befor i take it to the mechanics to see if they have any ideas when they fix the rest of the car.

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fabricator 
16/7/07 10:49:53 PM
Overlord

I'd check the alternator is actually working, if thats not working then your going to have virtually no change in your battery.

24hours x 0.8 amps is 19.2 amphours. I think car batteries are 100 amphours plus. 0.8 amps isn't much, it could just be a relay and some related electronics. I'd say the immobiliser is the most likely thing to be drawing the power though.

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drago13666 
16/7/07 10:59:21 PM
Guru

it might be somethign to look at but would 45min of driving flatten a brand new battery if the alternator wasn't working? becuase when i got the the new battery the only thing that happend to my car was a 30-40min drive home and then parked on the street for a day

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"while tibetan monks prey for two weeks befor their mandalas to transform them into 3-dimentional floating palaces of light, with virtual reality one only need to press a button..."

Truth suffers from too much analysis

aliali 
16/7/07 11:56:16 PM
SuperHero
Immortal


Got a multimeter drago?
If not grab a cheapy from DSE or somewhere, should be able to get one for under $20.00
Disconnect one battery terminal set the meter to read amps and hook up the multimeter between the battery terminal and the disconnected lead, See if there is much current draw. Should be around a few hundred milliamps at a guess.

If it is more than that then you have a problem. If there is little discharge (there will be some due to the immobiliser and assorted bits) then it is an alternator problem.
For the former you could try pulling fuses till the draw drops markedly or stops this will tell you approximately where the culprit is as most fuses are marked with what they protect.
Oh have you fitted a high power sound system? If the amp is not disconnected when you switch off the ignition it could be drawing enough to flatten the battery.
Also a warning do not try and start the car, or turn on any heavy loads (lights, stereo or the like)while the multimeter is hooked up this way, you will fry it and possibly cause an explosion or fire.
A quick check of the alternator can be performed by hooking the battery back up as normal and then setting the multimeter to dc volts (20v or 30v not 12v)hook the meter across the battery terminals and it should read approx 12.6v. Start the car and lift the engine revs to a couple of thousand rpm. Voltage should increase to about 13.5v to 14.5v. This indicates the alternator is putting out a least a bit of a charge. For a full check you need to take it to an autosparky.


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Rybags 
17/7/07 1:41:33 AM
Hero
Immortal


0.8 Amps seems a tad on the high side for a car doing nothing.

If the alternator's stuffed, you should get a good few hours driving (without lights) before it drains too much.

Checking that should be easy enough. Just test the voltage across the terminals stopped and with the engine at a moderate speed (about 2,000 RPM).


Of course, there's someone who could probably resolve your problem much better than anyone else here, but it seems he's not allowed to logon here as of a couple of days ago.

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merlin13 
17/7/07 8:04:48 AM
Titan

Did the RACV bloke actually test the alternator output/battery charging voltage with a meter at any stage (eg, what aliali 'n Rybags said) , or just scratch himself and say "Yup, yer battery is rooted"?

Seems kinda odd that the immobiliser suddenly started working after a clout. Obviously points towards something loose and/or something now shorting out somewhere.

But I would have assumed normal bouncing around should have brought this symptom to the surface long before now. Unless you drive like a Little Old Lady on Valium, of course... :]

From what you've said so far, one thing I'd be suspicious of here would be the backup battery for the immobiliser. If it hasn't worked for a couple of years it might now be rooted from not being used and is constantly dragging hundreds of milliamps but not charging up, maybe.

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über-Bantumi 
18/7/07 2:20:20 PM
Titan

Sounds like the immobiliser may have an open and be draining it...

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smadge1 
18/7/07 2:54:56 PM
Titan

the only things drawing power in my car when it's turned off are the clock, the trip meter and the radio. (I know, three things that reset when I had to replace my battery 2 weeks ago)

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über-Bantumi 
18/7/07 4:55:51 PM
Titan

Quote by smadge1
the only things drawing power in my car when it's turned off are the clock, the trip meter and the radio. (I know, three things that reset when I had to replace my battery 2 weeks ago)

Are they on the one circuit?

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Green rooms = no

smadge1 
18/7/07 6:19:59 PM
Titan

i've no idea, sorry.

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Scouse Git 
18/7/07 8:36:31 PM
Banned

Quote by über-Bantumi
Sounds like the immobiliser may have an open and be draining it...


I think you mean a short.
Sounds like too much of a coincidence to me.

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Blueeyed Iceman 
18/7/07 8:48:59 PM
Guru

Too bad our resident auto elec is banned at the moment. Could have asked him to give a few pointers.

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ADO 
19/7/07 10:36:02 AM
Titan

Quote by Blueeyed Iceman
Too bad our resident auto elec is banned at the moment. Could have asked him to give a few pointers.



+infinity

But yeah, alternator fo' sho'. Your immobiliser could have gone into "lock down" mode when it though someone was tampering with it - but it was actually just the battery going flat.

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ADO 
19/7/07 10:37:34 AM
Titan

My immobiliser does this when my battery goes flat, also.

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Quote by Mi Goreng
I am powerful, yet delicious.



Builty 
19/7/07 12:34:45 PM
Champion

I've read some info that suggests that the average capacity of a car battery is around 30 to 60 amp hours (continuous, not cranking.)
800 mA drain on a battery of that rating would make it flat in 38 to 75 hours or so. Not that far from 24 hours.
I'd suggest that 800 mA is too high for static current draw and that something is drawing too much.

Perhaps meaasure it and remove one fuse at a time to try to isolate which circuit/device.

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Rybags 
19/7/07 1:59:00 PM
Hero
Immortal


You might want to try putting the battery in charged, then pulling some fuses, and leaving it overnight.

Also, check that something stupid like the interior boot or glovebox light isn't staying on and draining it (fold-down rear seats come in handy for this).

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drago13666 
26/7/07 10:38:36 PM
Guru

sorry i didnt' get back to this soon, been a pretty hectic time, incase anyone is interested it turned out that it was the immobiliser that was causing a random parisidic drain on the battery, (the service guy said it was randomly coming on and off and variable drain.) ended up just disconnecting the whole thing, cheaper than trying to fix the problem and since i hadn't used it since i had the car i wasn't missing much.

got new tires and fixed the airconditioning at the same time so it was quite an expencive service

-----
"while tibetan monks prey for two weeks befor their mandalas to transform them into 3-dimentional floating palaces of light, with virtual reality one only need to press a button..."

Truth suffers from too much analysis

Scouse Git 
27/7/07 12:05:28 AM
Banned

I'm surprised you can afford the internet after that lot!

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MEC 
3/8/07 12:17:28 AM
Overlord

Nice fix.


Edited by MEC: 3/8/2007 12:22:53 AM

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PurpleWinter 
5/8/07 3:58:09 PM
Guru

...Immobiliser huh... I'll need to remember that one...


Edited by PurpleWinter: 5/8/2007 03:58:43 PM

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