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Discussion Starter #1 (Edited)
Hi,
I have a 2001 Peugeot 307. Recently it developed a problem - battery drains. A fully charged battery gets almost flat (11.x V) within 5 days (no driving). I hooked up my multimeter and it read 0.8A for about 30 seconds when i locked the car, then some systems shut down and it dropped down to 30mA. There is no way that 30mA drains the battery so quickly. I left the multimeter running for an hour and it still showed 30mA-40mA. :/

At first I suspected that the battery was old (it was quite old tho), and I bought a new one, but the problem remains.

So what else can drain the battery?
 

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Discussion Starter #5 (Edited)
What about bad earth points ?

I don't know if I did it right but...

I connected my multimeter's positive to bat+ and multimeter's negative to various points around my car (engine block, chassis, bolts, even wheels) and it read the same voltage as the battery had (12.39V).

E: It appears that the battery drain only occurs if doors are locked / car on alarm, although multimeter still shows 0.05A, which should be totally acceptable.
 

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How are you measuring Amps ? IIRC, you have to interrupt the circuit, and have ALL current pass through the multimeter (in DC current i mean).

You can't just touch the positive and negative for Amps, the reading will be the multimeter load.
 

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Discussion Starter #7
Yes i know i have to put my multimeter in series if i want to measure amps, thats what i did and got 0.05amps. For bad ground tho i had no idea how to check, so i just measured a voltage between + and car parts. Just in case, i put my multimeter on series the other way around (started from bat- and onto to car negative wire, but it still showed about 0.05A.
 

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If there is a bad earth connection there will be a resistance between the earth cable and the part of the car the cable is bolted to causing voltage drop across the connection probably due to corrosion or dirt.

Edit

Just reread the post and I realised I'd written garbage.

Get a multimeter set to a low resistance range and put one meter probe on the earth lead and the other probe to the chassis. Any reading above 0 indicates that it isn't a good electrical connection. A readin of .1 - .3 ohms could be accounted for by a poor probe connection to the measured point.
 

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Discussion Starter #9 (Edited)
Get a multimeter set to a low resistance range and put one meter probe on the earth lead and the other probe to the chassis. Any reading above 0 indicates that it isn't a good electrical connection. A readin of .1 - .3 ohms could be accounted for by a poor probe connection to the measured point.
Thank you for reply.

I measured ~40+Ohms using engine block and 100+ Ohms using bolts, sometimes even 150+.

E: Well this is weird, I went to clean ground leads but first tried measuring again and it showed 0.5 Ohms from BAT- to engine block, and test leads together show 0.5 Ohms, so it's only lead's resistance. I tried with my land rover (has been sitting in a garage for 3+ months, but still starts in a snap), and it showed about 1.5 Ohms. Corroded/rusty bolts still show 100+Ohms but that's because of their ... corrosion I think. Tried measuring with leads on battery and +lead disconnected, all still the same.

Another thing I measured (no reason) was car+ lead and car- lead's resistance, it was 500 Ohms.
 

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Discussion Starter #10
Okay, summer is gone and battery problem came back with cold weathers. I checked each cell of my battery:
1 - 0.35V :eek:
2 - 2.5V (2.5-0.35 = 2.15V)
3 - 4.56V (4.56-2.5 = 2.06V)
4 - 6.6V (6.6-4.56 = 2.04V)
5 - 8.7V (8.7-6.6 = 2.1V)
6 - 10.7V (10.7-8.7 = 2.0V)

Now, when measuring voltage across battery terminals, it gives 12.58V.
Last night (-5C at least) I disconnected B+ cable, the voltage was 12.59V and then I checked it in the morning, it was still 12.58V. So I guess the cold weather doesn't to much to my battery.But if it was connected the voltage would have been 11.7-12.0V in the morning.

So, is there something on my car that triggers when the weather gets cold and starts draining from the battery? :D
 

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Okay, summer is gone and battery problem came back with cold weathers. I checked each cell of my battery:
1 - 0.35V :eek:
2 - 2.5V (2.5-0.35 = 2.15V)
3 - 4.56V (4.56-2.5 = 2.06V)
4 - 6.6V (6.6-4.56 = 2.04V)
5 - 8.7V (8.7-6.6 = 2.1V)
6 - 10.7V (10.7-8.7 = 2.0V)

Now, when measuring voltage across battery terminals, it gives 12.58V.
Last night (-5C at least) I disconnected B+ cable, the voltage was 12.59V and then I checked it in the morning, it was still 12.58V. So I guess the cold weather doesn't to much to my battery.But if it was connected the voltage would have been 11.7-12.0V in the morning.

So, is there something on my car that triggers when the weather gets cold and starts draining from the battery? :D
looks like you have a bad cell, if thats the case then even a small load will discharge the battery quicker than normal as the other cells have to work harder
 

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Discussion Starter #14
I guess so. This battery is old, it came with the car 14 years ago :D, still works in the summer tho. The new one is sealed so I can not check individual cells.
I started charging the old one, it peaked at 14.55V after 5 minutes and charger said it's full and lowered voltage to 13.6V @ 0.6A, the first cell is still 0.5V, too bad. Started charging the new one too, will see if that does any better.

But there is no such thing in my pug that starts "self-warming" when the weather gets too cold? :D
I have no more theories, one of the batteries is new, tested in the warranty, drain 30mA, resistance 0.X Ohms.
I do have many LEDs in my interior lighting, but they are all off and I suppose drain would show, if any of them used some current
 

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The interior lighting is not on-off, it's not relay controlled, they dim. You probably noticed that sometimes a few have faint light on them.

But this should be pointless, i have WAY more leds than you (led stripe on footwell, and under driver and passenger door, 5050leds, and i never have battery problems.)

Although you have a good voltage, your max amps and CCA rating will drop because you lost one cell. When you get -5ºC, the glowplugs engage, that added to the fuel heater and the starter, is probably putting to much on your battery.
 

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The duff cell will self discharge more so in cold weather and lower battery voltage enough to cause bsi and engine ecu to throw a wobbly and stop starting and shut down of various ancillary systems
 

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Discussion Starter #18 (Edited)
The new battery has been charging more than 18 hours and its still not full. I hope it's full by morning.

E:

Well that was fun, it was still charging but I had to use the car so I put it in and as I turned the ignition, my onboard voltmeter displayed 10.9V and well, the starter of course didn't do anything. So I'm running the old battery again...
 
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