Elektrik: Flat Battery

[Beumers]

Hi all.
I found my car with a flat battery. After recharge again. Battery check was oké.
Amp test result 0,45 Amp current leak. I took out the fuses one by one and found the dash was faulty. Turned out the odometer kept on. Not all the time but when I tap the instruments cover in front of the odometer it flips on and stays on for a while. One time it stays on for days. The other time it goes black after a few minutes.
Did anyone experienced the same problem or semilar? It doesn't need to be a faulty odometer. There can be alot of causes.
Thanks Henk.

My car is a 735 1986.

[wian0011]

I'm familar with that issue and I know that there are so many reasons why this might happen.

I guess a good value (when everything is gone "to sleep") is significantly lower than 0.1 A.

However, it will take some time to bring everything in sleep mode. IHKA will be one of the last that is put to sleep (not sure... 5-10 minutes).

Well known items that have a problem get to sleep are:

1. IHKA
2. Central Door lock + power windows
3. Radio and amp
4. CD player
5. ...
6. many more

Take a look to:  http://bmw.e-wiesinger.de/#batterie (however, in German. Use google to translate).

[Beumers]

Thank's Wian.

So if I would wait for half an hour, there should be less then 0.1Amp. The lowest value I got was 0.2Amp. while the car was switched of for at least an hour. But than the door was open so I'm not sure. I try and pul all the fuses to see what the readings will be.
I should have mentioned that you can answer in German. I speak and read it without a problem. To write in German is an other matter.

So nex time feel free to answer in German.

Henk.

[Beumers]

Oké. I read the article in the link to Andreas' BMW site.
It's more clear now. I've had the key in the ignition and one of the doors was open for the whole time. Lights were off of course. So this value of 0,2=200mA. is not to bad. I'll try to switch off everything correctly and see what results I get.

Thanks again.

[wian0011]

My problem was located in the climate control unit (not the control panel). This is send "to sleep" by an "easy" transistor circuit. Some of the involved resistors are loosing there values by time so the transistors are not cutting off the voltage.

As a result the full climate control is consuming power. The next morning the car won't start anymore.

[Beumers]

So this means the problem could be anywhere. Suppose I replace the odometer with an other one the problem could still be there.
Still it makes perfect sense if I add up the figurs. The battery is drained in a week. To drain 85Amp houres from the battery in 7 day's you need 5-6 watt's. Gif or take because I don't know exactly how long it took to drain the battery. So it's a small light bulb or somthing like the odometer allthough I don't know how many Watt's the odometer takes. Probably less than 5 watt's if it's only the display.
In any case I have to figur out how I proceed.
I have to put my car in storage for the nex 3 month (government rules for oldtimers.) so I won't have time to work out the problem. Nex year I take it from here and if I find out what causes the current leak I'll post it on this forum.

Henk.

[wian0011]

Think about:
your 85 Ah battery is never fully charged. Let's assume batterie is charged about 60 Ah. Next: What power is required to start your engine? I guess when your battery falls below "somewhere" about 30 Ah (?) you can not start your engine.
Sure, all of them are just very rough estimations.

However, even when everything is going to sleep as expected and you're operating a well charged and maintained battery you will get in trouble after about 3 weeks. At least after 4 weeks you can not start your engine anymore.

Summary:
When you tell that your battery is drained within 1 week... I'm not sure if you have a problem.

[Beumers]

Let's hope your're right but I'm afraid something is wrong.
It's difficult to remember the time space between each individual moment I used the car. In my mind it's idle for a month sometimes and it's always been oké. Starts right up. No noticeable loss of power. Last time I've got this flat battery I used it a short while ago. That's why I thought I left the doom lights on. But after a full 24 houres charging the battery, something like a week later it was flat again. As flat as they can get. Unable to open the car. Absolutely no lights. All memory like time gone.
So after a new charge I got it checked at the garage to be sure it wasn't faulty because I bought it in march this year. It was completely full 14,3 volts and it had a starting voltage of 12 volts. So I'm fairly sure it's not the battery.
Well, I can only try and find the problem if there is one.
But I think it's not normal when your car is parked and locked and you can see only the odometer brightly light up in the dark. I tap the screen and it shuts down.
Not oké.
Very helpfull link by the way.

Thanks Henk.

[Beumers]

If I put the car on the OBD1 device, is it something that should show up in OBD1?

Henk.