GolfGTIforum.co.uk
Model specific boards => Golf mk3 => Topic started by: patch900 on 24 March 2007, 16:13
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My neighbours car had a flat battery the other day and I gave him a jump start. Couldnt really say no.
Not drove the car for a day or 2 and got in and the battery was totally flat ! Is this a coincidence or have I done something ? The battery has always been OK before this.
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nah thats happened to me mate. It sucks but a dead battery can drain the life out of a good one. Your alternator or battery maybe are past it as well.
Deposits build on the plates and reduce the capacity over time. Try BAT-AID tablets £4 from an accesory shop, 2 tabs each cell then recharge wi a charger and should be good if the battery isnt knacked. Charging voltage from a good alternator is about 14v and when cranking the engine, the battery musnt drop below 10v. Less shows a weak battery.
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Cheers evil, it started today but not easily.
Think the battery has had it, will have the alternator checked out as well. Do you know much an alternator is ?
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depends if its from a scrappy or not, can usually get them reconditioned anyway, but new, ouch!
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cheers tom, will have it checked first. Fingers crossed its just the battery
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new high power alternator from euro car parts is bout 120 quid
not as much as people think
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You can get them rebuilt for about £30 though :D
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get a reconned exchange one, its quite cheap. As said, around £30 to £40 with your old one returned.
If you go to a breakers, a passat one will do as well if its exactly the same engine.
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Cheers mate, will change the battery first and see how I go. If it still acts up get the alternator changed.
Wished I had said no to the jump start but if someone asks you cant really say no.
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well at least its shown up a weakness in the car before you got stranded somewhere.
Kwiksh!t will do an electronic battery and starting / charging current test for free by the way if you just roll up and ask.
If you give a jump start you should always have the donor car running so the alternator gives charge to both batteries then start the other car after 5 mins of running so its easy on the donor battery.
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Cheers Evil, I think that is part of the problem. I didnt do as you said when I did it. Probably sh***ed my battery in the process.
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A brand new battery can be had for £30 believe it or not, just shop around a wee bit. Get one at 44Ah minimum, the ecu will detect an excessive voltage drop during starting if you get a smaller one, and you will get immobiliser problems / engine start lockouts.
For those who dont know this, the Ah rating means battery capacity (supply current versus time):
100Ah = 100A for 1 Hour to 1A for 100 Hours.
44Ah = 22A for 2 Hours, 44A for 1 hours etc etc
A golf starter which isnt the planetary reduction type like on new cars, will draw 300 to 400 amps during a cold start, the colder weather, the thicker the oil etc so a 44Ah battery even fully charged can only supply 400A for 6 minutes then its dead. A 100Ah one can do the same for 15 minutes.
If however you use a smaller one - say 30Ah, the voltage will dip when the current drawn exceeds 75% of its capacity, and can drop to 8v or less, which confuses the ecu - remember its still got to get sufficient power as well as all the other systems on the car, while the cranking engine is sucking it up like a vacuum cleaner.