2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/

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Fri 10 Apr 2020 16:20
2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/ - earthy mike

Hey guys, have you seen this before? I was driving down the road and my car just died, no warning, no nothing every thing just turned off. Luckily I was able to pull over to a parking space. I checked the battery which had zero voltage so I thought the battery had an internal short. To verify I plugged in a small cheap car just starter which instantly exploded!

I thought that this was just because it was a cheapo jump starter which couldn't handle being plugged into a shorted battery. I took the bus to my local auto place and bought a new battery. As soon as I connected the battery cables to the battery there was a fizzing sound, so I disconnected the cables and checked the voltage on the battery which was previously 12 volts and now zero volts! =/

So I'm thinking that it's not a battery problem... After doing a little research I found that if a diode has failed inside the alternator, the alternator can flood the cars electrical system with alternating current; which is my best guess so far. The alternator was on it's way out any way (I got it from a scrap yard), when I revved hard a warning showed up on the dash "alternator workshop". I checked the alternator a few times when it was running, and when at idle it was fine; so I thought it was just losing a bit of power generating capacity when the car was revved hard so kept using it.

Can any thing else cause the instant death of a battery? Could it be a short in the system? I've ordered a multimeter (lost my last one) to check for AC in the system. If there is AC coming from the alternator how can I get rid of this to make it safe to remove the alternator?

PS. I definitely did not put the battery in backwards.

Thanks!
Mike

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Fri 10 Apr 2020 18:16
2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/ - elekie&a/c doctor
Sounds like you have an alternator problem or an issue with the wiring to it . You need a multimeter to carry out some basic charging and volt drop tests.
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Fri 10 Apr 2020 19:40
2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/ - Railroad.

Disconnect the battery and use a multimeter to check continuity between the positive battery lead and earth. The reading should be O/L (or whatever your meter's symbol is for open circuit) or very high resistance ie, several megaohms. If you are reading zero ohms or even just a few then you have a battery short circuit to earth. The next thing to do is disconnect the alternator and see if the reading changes. If it does you've found your problem. If not then disconnect the starter motor main terminal and check again. Also check for any part of the main battery to starter motor/alternator cable that's chafed to earth.

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Sat 11 Apr 2020 22:06
2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/ - earthy mike

Thanks for your reply guys!

The big take away from your replies is that it's most likely a short, and that once my new multimeter arrives I can check the resistance across the battery cables, if it's less than 100 ohms there a problem. I will check it, then disconnect alternator and check again, then disconnect starter and check again etc etc


I forgot to mention in my original post that the cables did get hot. Also I stated that the voltage went to zero, what I meant was the battery didn't show any thing on the volt meter; so maybe some kind of fuse inside the battery for safety?

I'll keep you informed

Cheers!

Mike

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Sat 11 Apr 2020 09:37
2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/ - Big John

I took the bus to my local auto place and bought a new battery. As soon as I connected the battery cables to the battery there was a fizzing sound, so I disconnected the cables and checked the voltage on the battery which was previously 12 volts and now zero volts!

This sound wierd - whatever maybe wrong with your car - even if it presenting a dead short - shouldn't take a battery from 12v to zero volts instantly. If it did there would be something burning/heating up/fireworks as a healthy and charged battery can deliver hundreds of amps.

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Sat 11 Apr 2020 10:59
2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/ - Peter.N.

Its very unlikely that you could discharge a full battery instantly without smoke or flames somewhere, you are dissipating about 1kw of energy. The heaviest dischargers would be the alternator as mentioned or the glow plugs, both have a lot of thermal storage.

You didn't connect the battery up the wrong way round initially did you?

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Sun 12 Apr 2020 07:46
2003 VW Passat 1.9 litre TDI, 140,000 miles. - My car is blowing up batteries! =/ - Oli rag

Is it possible that you had your meter sent to shunt mode (measuring current) and have blown an internal fuse, by having the black lead plugged into the wrong hole when measuring across the battery terminals?

If the meter has fixed leads or only 2 holes then that couldn't happen.

Edited by Oli rag on 12/04/2020 at 07:48

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