Battery completly drained in hours

[metale]

Hi guys, any tips or clues are appreciated:

I was out in the city in the morning, and the car ran normally all day. Topped the tank, went here and there, everything normal, started fine everytime.

Came home, had lunch, and some 3 hours after leaving the car, I get to it and the central locking wouldn't open. Hum... strange :confused I open in with the key, put the key in the ignition, and no lights whatsoever. Nothing in the cluster, nor the lights on the headliner, nothing.

Grabed a multimeter and the battery poles read 0.60 volts :eek:

What could have happened in so little time to cause this? What would you do to diagnose? No garage at the moment.

The car has been driving fine, no warnings, no lights, no hard starts, nothing.

(1995 E36)

Thanks

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Update:

I went to remove the battery from the car. It is winter here, nowhere near snow but not warm either. Car engine is completly cold (it's been 6 hours since I parked it) but battery is hot.

Removed it and brought it inside, out of the rain. I must have taken a bad reading first time (did I?) because it now reads 6.90V. Hum, after some 15min it reads 7.30V. Still hot.

What the ... is going on here? Internaly shorted battery?

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7.70V, still hot. This is with the battery disconnected, on the floor of my house. I'm putting it outside NOW before it explodes on me.

[E36328Coupe]

The terminal voltage drops under load.
Batteries do recover somewhat when left.
Shame you hadn't got a reading as soon as disconnected.

Have you changed anything recently? Quite often it is something people have done themselves.
Or a chaffed wire, for example boot lid wiring
Or even a failed diode in alternator
Or maybe an overloaded battery warped a plate and shorted internally.


If the battery is good tracking a parasitic drain down can be as simple as putting an ammeter in line and then pulling fuses until the drain drops off. The fuse that makes the big drop is the affected circuit(s). If that does not show a drop then the drain is either unfused or in some other accessory wiring, for example a BIG amplifier that is not set to shut off with the stereo.

Or other stuff :)

[metale]

No changes, no new parts or out of the ordinary use. Also, no subwoofers, xenon or something like that.

Maybe a short somewhere on the car, but would have to be catastrofic as to drain everything in a couple of hours, no?

I just went and got another reading: 7.90V and still hot. Battery has been out of the car for 1h30m, and outside in the rain (under a plastic bag) for 40 minutes.

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Update:
Car is running with new battery. We'll find out tomorrow if it was just the battery or something worse.

The haunted battery was left at the place where I bought the new one...

[jmo69]

I think you're right about the battery shorting out. Out of the car and not connected to anything, it shouldn't be building heat. A load test would have told you something about the condition. I'd check the voltage of the new one periodically to make sure the car isn't causing the drain.

[E36328Coupe]

If it was mine I would guess........................

If the battery was the route cause it is unlikely to be held at 0V when on the car and then have a higher terminal voltage off the car because any internal short would still be in effect.

A short in the car could cause damage to the battery.

I certainly would not leave the car unattended with a new battery connected until it is checked out.

I would probably check resistance between +ve battery lead and earth if it was mine.
A guestimate of the current drain could them be worked out with OHMS law.
However what is the effective resistance for a tiny current flow (such as a multimeter testing resistance) can be quite different for a big current flow.
Of course there may be different readings after disconnecting the car that there would be with it running which an ammeter would be able to deal with (not cranking)
And no idea if the tiny current of an OHM meter could count as a brown out lol


....................however, it is not mine and I recommend nothing

[metale]

So just better to take it to a car electrician? Because I did not understand any of that :)

I still haven't tried the car today (just woke up). If a short/drain on the car is present, it has to be a drastic enough one that it drained the older battery in hours. If so, I'll have a non-starting car again today, after 12+ hours with the new battery connected.

Or a burnt out car.

I tried to track the buy receipt for the old battery. Could not find it, but my guess is it's at least 3 years old, maybe 4. So the old battery may have just died, since in almost 14 years of having my E36 I never had a battery living much more that that.

[xlDooM]

It's very unlikely that the battery has died in such a fashion that earlier in the day it started fine and then it was at zero point something volts. The only way I see that happening involves smoke at the very least. The fact that the battery is recovering somewhat when you leave it disconnected is extra evidence for the short.

Have you checked all the electrics? Opened the sunroof, adjusted the seats if they're electric, opened all the windows, interior lights, radio, heater, AC, rear window demister? Something like a short in the seat heater could draw a lot of current without tripping a fuse.

[metale]

I'll check it as soon as possible.

Seats are manual and non-heated. No A/C. Sunroof is disconnected at the button due to a physical problem in the mechanism.

Radio and interior lights all worked fine last night with the new battery (engine running).

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Update

So... car started fine, after being left for some 15+ hours. Left it running a bit, toke it around the neigbourhood, seems normal.

Let's see.

[xlDooM]

Good luck. If it's a wire where the insulation has worn through from rubbing against something earthed, you have more dead batteries in your future, and a bitch of a diagnostic job... I hope for you it was just a dud battery but I'd be scared anytime I leave it :(

[metale]

You bet, so am I... Especially if I have to park it somewhere else than at my doorstep.