My car is blowing up batteries! =/ 2003 VW Passat 1.9 litre

[mikeote]

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

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

[E-bmw]

mikeote said:

Can any thing else cause the instant death of a battery?

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

Yes, you connected it the wrong way round, either that or there is a full earth on the positive lead from the battery.

You may not have connected it "backwards", but was the battery the exact correct type as a slightly different one may have the terminals the other way round.

[mikeote]

Nope, I double checked and I definitely didn't connect it the wrong way round; the battery posts are the same way round as the original and are very clearly marked. It could also be the alternator right? Apart from checking for brakes in the insulation of the wires from the positive battery cable to for example the starter / alternator etc can you suggest another way for checking if that positive battery cable is shorted to ground?

If the multimeter (when it arrives) shows that there is no AC running from the alternator to the battery cables, then I could put some current through the negative battery cable (using a power probe) and see if it shows up on the positive battery cable.

Thanks
Mike

[Penelope Stopit]

Nothing could possibly drop a new good battery from fully charged to zero, not even a dead short through the main battery cables

The battery cables would start melting if there was a dead short

If there was a dead short on the cables the battery post would have started rapidly burning up as you connected the terminal to it

mikeote said:

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 above is incorrect

[paintman]

Check the positive lead from the battery.
Usually go to the starter motor & meet another wire on the same terminal which comes from the alternator.
Work your way along these wires looking for damage which could allow contact with metal.

Edited by paintman on Friday 10th April 18:03

[GreenV8S]

There's too much hyperbole and ambiguity in your post to take it all at face value.

A main power cable shorted to ground would explain some of the symptoms but not all of them.

mikeote said:

the battery which was previously 12 volts and now zero volts! =/

After being connected for how long? Even a dead short directly across the battery won't flatten it instantly. Where are you measuring the voltage? How have you confirmed that your meter works and you're using it correctly?

If you want to test for a short in the wiring, disconnect the battery and measure the resistance between the battery positive connection and vehicle ground. If you see less than 100 Ohms there's something going on that needs further investigation.

[stevieturbo]

So it didnt actually blow up the battery ? or batteries ?

check all main wiring from battery to chassis/alternator/starter etc prior to refitting any other battery

And/or disconnect the alternator before going any further.

[annodomini2]

You probably have a short and the most likely culprit is the alternator regulator failing.

Using a multimeter measure the resistance across the battery connections if it measures at or very close to zero.

If this is the case, disconnect the alternator output and measure the resistance between the output terminal of the alternator and it's housing, it should be the same value if the alternator is dead.

Otherwise you'll need to dig deeper.

[finlo]

I would expect much smoke billowing from the alternator if the short was that severe!

[mikeote]

Thanks for all of the replies guys, it's several times the number of replies I received on any other forum I've posted on.

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 as greenV8's mentioned; 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?

stevieturbo: Yes one battery did literally blow up, the lithium battery inside the jump starter. The other battery it insta-killed though it did not blow up.

annodomini2 said "If this is the case, disconnect the alternator output and measure the resistance between the output terminal of the alternator and it's housing, it should be the same value if the alternator is dead." Will do thanks!

Thanks again guys I'll keep you posted once the new multimeter arrives (weds or thurs).

[stevieturbo]

Cheap chinese crap like those jump pack things....could blow up anyway.


When you get a new battery or whatever, do not connect anything up directly. Place either a fuse or suitable breaker in the line, so if you are connecting into any sort of dead short the fuse will blow, rather than causing more harm.

[GreenV8S]

Bear in mind that if you do have a short on the main power cable, it may be intermittent and affected by you moving cables around.

[NMNeil]

Bit of a puzzler.
If you short out a new fully charged car battery the shorting wire will glow red hot and continue to do that until either the wire melts or the battery is completely discharged. It won't happen instantly. As you disconnected the battery before the smoking part the battery will still recover and give a voltage reading of over 9 volts.
If you have a bad diode in the rectifier it will allow some AC through and over time will damage the battery, but it won't do what you described. The PN junction in the diode will fail and give an open circuit, they can't have a short circuit even if the silicone substrate in the diode melts.
A shorted cell in the battery will still allow the battery to show about 10 volts, but may not have enough power to start the engine.
Even a cheap lithium charger will have a built in BMS to prevent overcharge and over discharge.
Just can't understand how the battery goes from 12 to 0 volts in a matter of moments.

[StescoG66]

My apologies for hijacking the OP's thread a bit here. My head is in a bit of a spin and perhaps am not seeing the wood for the trees.

I have been chasing a suspected short in the electrical system of my 1988 Alfa Sprint 1.7 project. I took the advice from a few posts above, dusted down the multimeter and did a resistance test across the two battery cables (no battery in car obviously). I set the multimeter to the 20kohm resistance setting and got a reading of 7.60. What does this translate as - I am using the 100 ohm minimum from above as my benchmark here, Would I be correct in saying that is 150Ohms? Alternatively if that translates as 76 Ohms is that an issue in a car with no fancy electronics in it?

Also, went to the alternator (which I suspect I have fried despite changing the regulator) Did resistance test from the alternator output to the alterator casing and got 0, so goosed I suspect.

Am I correct in the above assumptions?

Thanks in advance and apologies to the OP for the hijack - posted in this thread as I thought it may be useful to him too.

[Penelope Stopit]

StescoG66 said:

My apologies for hijacking the OP's thread a bit here. My head is in a bit of a spin and perhaps am not seeing the wood for the trees.

I have been chasing a suspected short in the electrical system of my 1988 Alfa Sprint 1.7 project. I took the advice from a few posts above, dusted down the multimeter and did a resistance test across the two battery cables (no battery in car obviously). I set the multimeter to the 20kohm resistance setting and got a reading of 7.60. What does this translate as - I am using the 100 ohm minimum from above as my benchmark here, Would I be correct in saying that is 150Ohms? Alternatively if that translates as 76 Ohms is that an issue in a car with no fancy electronics in it?

Also, went to the alternator (which I suspect I have fried despite changing the regulator) Did resistance test from the alternator output to the alterator casing and got 0, so goosed I suspect.

Am I correct in the above assumptions?

Thanks in advance and apologies to the OP for the hijack - posted in this thread as I thought it may be useful to him too.

Don't know why anyone would suggest to measure resistance to find a current drain when most multimeters have an ammeter to measure current

Make a fresh start

With a known good battery fitted and connected, disconnect the earth cable from the battery, set multimeter to Maximum Amps (likely to be 10 Amps but could be 20 Amps)

Connect multimeter between battery terminal you removed the earth lead from and the earth lead terminal

Current draw will then be shown

Post back here what the current draw is if you can't find the cause

Ooops Got That Completely Wrong. Post Back Here If I Owe You A New Fuse For Your Multimeter

The best method for finding a dead short or good short from battery positive to earth is to connect a 21 Watt bulb between the disconnected battery earth cable and the battery post it was disconnected from

The 21 Watt bulb will glow brightly if there is a big short present and you can wiggle, woggle or waggle all the cables and if that removes the short the 21 watt bulb will dim or go out, you will then have an idea of the area the short is at

Good luck

Keep well

I'm sorry

Edited by Penelope Stopit on Tuesday 14th April 16:44

[E-bmw]

StescoG66 said:

did a resistance test across the two battery cables (no battery in car obviously). I set the multimeter to the 20kohm resistance setting and got a reading of 7.60. What does this translate as -

Would I be correct in saying that is 150Ohms? Alternatively if that translates as 76 Ohms is that an issue in a car with no fancy electronics in it?

Am I correct in the above assumptions?

Er…..No!

I have no idea why you would think a reading of 7.6 on a 0 - 20K Ohm scale would equate to 1.5 k ohms or 76 ohms.

If it is an analogue meter it could mean 7.6 k ohms (but only if the needle range is 0 - 20).

If it is a digital meter it will mean 7.6 ohms.

[StescoG66]

Told you my head was fried.

[GreenV8S]

Penelope Stopit said:

Don't know why anyone would suggest to measure resistance to find a current drain when most multimeters have an ammeter to measure current

Re-read the thread. The OP is looking for a suspected short circuit or similar high current.drain.

[Penelope Stopit]

GreenV8S said:

Penelope Stopit said:

Don't know why anyone would suggest to measure resistance to find a current drain when most multimeters have an ammeter to measure current

Re-read the thread. The OP is looking for a suspected short circuit or similar high current.drain.

Thank you for pointing this out, now corrected

Hoping that StescoG66 hasn't blown the multimeter fuse and that the above edited post is spotted

Keep well

[annodomini2]

E-bmw said:

...
If it is a digital meter it will mean 7.6 ohms.

Depends if it's autoscaling.

7.60 at 0-20k, is 7.6k, which would not be a short.