205 Discharging Battery

[djinuk 2]

My 205 gti 8v battery keeps randomly at different times when the car is off discharging, ive been to a auto electrical guy who said there is a chance when the car is stopping the alternators is stopping in a certain position allowing the discharge. Im having the battery tested today but does anybody have any ideas, no lights sterio etc are being left on , and 70% of the time its fine, its just randomly I have a dead battery.

[Rom 0]

See if theres any drains. Take the negative terminal off, put one end of a multimeter on the battery negative, and the other end on the negative. Effectively bridging the cable and battery via the tester.

Swith it to amps and see what is being drawn, i think upto about 0.5 amps is ok, for clock, alarm etc. Much over would indicate something is drawing current, and draining the battery.

 

Im assuming you have tested the alternator is charging etc.

[M@tt 77]

do as Rom suggested and if you do have a higher reading than mentioned then pull the fuses out the fuseboard one by one to see which cause the reading to drop down. Then its a case of checking the wiring diagrams to see what runs off that particular fuse to find the culprit of your drain. (assuming it is a drain and not just a buggered cell or something in your battery)

[djinuk 2]

well ive been out and done as you said and my readings were 0.07 amps, hmm,, out of interest should my car continue to run if the battery terminal was removed whilst the engine is running, reason i ask is mine will not.

Edited January 7, 2009 by djinuk

[Rom 0]

I cant say ive ever tried that lol !

 

Wont with no power lead, but not sure with earth. As technically, the lead will still be earthed by the other cables, but the circuit to the battery will obviously be broken.

 

0.07 amps is fine. I wouldnt worry until youve had the battery tested, as thats the most likely culprit. No point making work for yourself until you have ruled it out.

[Redtop 14 2 Cars]

Check your connections at the black box that holds the plugs for the fans etc. I found a connection that was loose there that would cause a drain of 2.8 amps on mine but when wiggled stopped. Check all your common earths and easy to get to connections if your batt and alternator turns out to be 100%.

[djinuk 2]

Well folks, i tried my best with it here, i got the battery back, been told its fine no problems with that, so i decided to check my drain on the battery again.., so i set my multi meter to the 10A reading (forgive me if thats wrong wasnt to sure) but anyway when i put the meter in line my drain this time was 0.12, i did as described and removed fuse by fuse until the drain stopped. when the 7th fuse from the left (15amp) was removed the drain dropped to 0.03, i started the car with the fuse removed to work out exactly what it powered, and found that it was power to the cd player.. however i also found that with the fuse out back in however with the facia from the cd player removed the current drawn was 0.07 (the same as last night. Now its pretty safe to say the problem is the cd player, however i am unsure if its going to be the wiring due to the fact that with the facia removed the drawn current drops to a just about acceptable level ., hmm does anybody have any suggestions. For the moment i have removed the fuse.

 

Hope that makes sence, im giving it my best shot as usally electics scare me

 

just to sum it up

 

Drain on battery with fuse in and cd player facia on = 0.12

 

Drain on battery with fuse removed = 0.03

 

Drain when fuse is in however facia removed = 0.07

Edited January 8, 2009 by djinuk

[Rom 0]

That still shouldnt cause problems.

 

I 'think' this is how ratings work, but its been a while..

 

Lets say your battery is labelled 50AH , this is how many amps it will run for 1 hour. In this case 50 amps, for 1 hr, will discharge a fully charged battery. Your only pulling 0.12 amps. So it would take around 17 days to discharge your battery.

 

The radio will pull power, as thats how it saves your presets, settings etc. Any clock, alarm etc will do the same. But 0.12 amps is very low, that shouldnt cause any problems. Its only when the drain is high, like 1amp etc that it will drain a battery quickly. And even then, in this example would be 50 hours.

 

What kind of test did they do ? I never drop test batteries, i always use the newer types of testers. Based on what youve said though, if the battery is fine, 0.12 amps wont flatten your battery any time soon. So if there is an issue...it must be elsewhere....

[djinuk 2]

yea they said they drop tested it, means nothing to me though, , i think im going to carry a spare battery and just see what another battery does, if it fails to go flat within say a week im guessing it is the battery and even though they tested it tehre is still a problem.. would lose terminals cause a problem at all, as i know my posotive isnt greatly tight.

[Rom 0]

Loose terminals can cause problems yes

We get a few cars in at work where someone forgot to tighten the terminals on the PDI And they cut out, wont start, etc.

So sort those out. This could be messign with the charging / starting.

 

If you havent, its worth checking all the cables / connections to / from the alt / starter / battery. If there corroded, or the wire is in bad condition it could be messing things up. Can create a high resistance, making it harder to charge the battery, start the car etc, as above really

 

Drop testing places a load on the battery, and measures the power. It can show problems internally by readign the data it puts out. Im not a fan of them myself. There a big contraption you place on the terminals, like 2 big prings connected to each other. But they do work.

Just not as fancy as the newer testers, which can give more detailed information about any faults.

Edited January 8, 2009 by Rom

[mikeyd 13]

could be the altenator as i had one that you could start in the morning, drive 15 miles and leave all day and then struggle to start at night

finished up one night started fine and then flattened the battery in less than 4miles!!!apparently it had a short in the altenator which caused it to drain and not charge!!!

fitted new unit - problem solved

if your battery is ok have you got a spare altenator to try?

[djinuk 2]

possibly the only thing thats not really pointed to the alternator is that the car dosent seem to drain when driving , so i can finish any journey and the car will start straight away after, its usally when the car is left overnight. To rule it out can anybody explain how i go about testing the alternator.

[M@tt 77]

with the car running put your multimeter across the battery with it set to volts you should find it reads about 14.4v if charging correctly.

[djinuk 2]

ok ill do that tonight, out of interest wont that run a huge amount of power through the multi meter and super heat the wires.. sorry new to auto electrics

[ultimatepug 0]

ok ill do that tonight, out of interest wont that run a huge amount of power through the multi meter and super heat the wires.. sorry new to auto electrics

 

not at all fella, wack your meter on and run the car then test the battery with your meter and that will tell you if its charging or not. failing that test the power to the alternater with a good earth.

[Rom 0]

Thats what multimeters are for !!

 

Measuring volts is pretty simple. Its not getting any major current / amperage sent through it. This is what can nuke meters. But even so, they should have a failsafe. A trip switch, or fuse of some sort.