Okay, I've been searching through for long enough now, and I've just run out of knowledge so hope someone can help.

My car mostly lives in the garage, and recently hasn't been being driven much. I had the dash all out to replace the heater matrix, came to start it up and battery was dead. Fair enough, I've had the car a year and I have no idea how long the battery's been in before that.

Replace battery, starts up fine. Run it for a bit, stop it. Start again, all's well. Start it up today (four days later) and it reluctantly starts. Bit weird, but still. However, go to start it again this afternoon and it's completely dead again.

Here's my conclusions so far:

1. The alternator is working. When jump started, there's 14v across the battery terminal *themselves* - not the cables going to them, but the actual terminals. Therefore the alternator must be working and giving 14v to the battery.

2. The voltage in the centre console is 12v with the engine off, and 14v with it on. Again, alternator must be working.

3. The could be something draining current. However I don't have an alarm, and I'm pretty sure the lights flash if the alarm is going off anyway? I also have barely anything else in the car any more.

4. After a 20-minute drive (having jump-started), I got back and turned off the engine. Immediately tried to restart it, and nothing - completely dead. Therefore anything draining current would have to be drawing hundreds of amps to immediately flatten the battery, and if that was happening then it'd pull it from the alternator when running and the car would idle really high.

The only conclusion I can come to is that I've maybe bought a dud battery that won't charge, but does that even happen anymore? That would imply however that it was coincidental that the old one died then the new one was dud? Seems unlikely.

If anyone can help, please do. I'm all out of ideas...

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How do I know if it's working? What's it meant to do?

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Hmm, that sounds like exactly the thing that could've happened - in fact the left hand side of my dials weren't lit up and I had to give them a comedy whack to get them lit up.

In saying that, that was at the start of the drive.

I'll have a check tomorrow, cheers matey

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But surely if I have 14v to the battery then that's that, it should be charging?

Or have I misunderstood somewhere? Is it possible that the alternator can be knackered and still be giving 14v?

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Well this is what I don't get, 14v is being delivered to the battery, and yet it just doesn't seem to be being charged.

Is there anything that could be wrong which would mean that the voltage is being delivered but nowhere near enough current?

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Check the battery voltage, if it's a dud it will hold a voltage for a few seconds then drop off to nothing.

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Bye bye Sundance Kid

Chris - yesterday I had a meter on the voltage having turned the engine off (this was earlier in the day) and the voltage dropped from 12.8v down slowly, and I got bored and did something else at about 12.5v - however as it's a 12v battery I wouldn't be surprised to see it drop *to* 12v. I'll check it this evening having left it a day, see what the voltage is at.

I've also got one of those clamp-type ammeters at work, I'll nick that to see where current's going.

How to I know (short of jacking it all up) which wire goes to the alternator? Presumably just a large wire running to the positive terminal of the battery? I seem to remember there are two or three, I assume the largest positive cable will be going to the starter motor.

Stan - yes, the car running by itself has 14v across the terminals, this is what I don't understand. Don't know about the battery light yet, I'll check that tonight also.

I think I've got a trickle charger at my parents, I'll grab that. Once it's charged, what's the best way to load test it?

Cheers people, much appreciated.

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Fair point, but the car goes from not starting to starting perfectly with a booster attached.

Good thought though, cheers.

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True, but again I wouldn't get 14v across the battery terminals if that were the case.

I've invested in a decent battery tester which can apply up to 500A of load to the battery, so I can add that to my list of things to test. I'm thinking:

1. jump the car, take it for a 20-minute drive, then check the voltage. If it's 14v, it should've charged.

2. Remove battery terminals with the engine running to stop anything discharging the battery when the engine stops

3. Give the battery a load test. If it fails, it's a dead battery for sure. If not, at least I'll know to look elsewhere.

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Good points mate, I'll add them to the list of things to check for

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