Flat Battery

Did you connect the charger with or without the battery connected to the car?

The first time I connected the charger then put the clips onto the terminals, I remember that because the fuse popped as I connected the - ve terminal. The second time I did it the other way round, I connected the battery and then plugged in the charger. Same result.

Try disconnecting the battery from the car & leaving it to settle for 30 minutes & the battery voltage should rise back up to between 10 & 12V, then try charging it.

Yes, OK I can try that. Why would this have an effect on the voltage though; what will have been happening to reduce the voltage to such a low level; and how does disconnecting it alter the situation?

I have an idea that this is one of the problems with automatic chargers. They don't charge if the battery voltage is too low. A cheap basic trickle charger would probably be better.

Having said that, I'd suggest you replace the battery. Sounds like it's probably knackered anyway. Mike.

There's probably still a light stuck on you've not found, unless you've been unlucky the battery should recover. Once it's recharged you can see the light (so to speak) :-).

Put charger on 6v to get it started charging. Once it has a bit of charge it will take 12v. If charger doesn't have a 6v switch put a bulb in the circuit to limit current. One deep discharge event shouldn't take too much off batteries remaining life.

Any other things on? If tailgate switch is part of an alarm circuit it may have helped.

Hes thinking that the reason for the extremely flat battery is becuase the car is putting a load across the battery and has flattened it. If you take a load off any battery i.e. disconnect it from the cars electrics then it will recover somewhat.

Hopefully it hasn't been discharged so far that it won't recover otherwise you'll be looking at replacing the battery before trying to work out what caused the discharge in the first place.

-- Chris

Modern cars have some discharge even with everything switched off. If the battery is completely flat, this small load will pull the battery voltage right down. Removing the load allows some recovery.

I don't actually think this is going to help you however!

Does the charger have a 6 volt setting? If so, try it for an hour on the 6 volt setting, then change to the 12 volt one.

Batteries can fail in a number of ways; one of those is cell debris shorting out a cell. The battery's internal resistance is then low enough to raise the charger current substantially. This is a possibility in your case. I would have thought an "automatic" charger should have coped with that situation though.

Chris

Yes, I see what you're getting at. I've removed the battery (lost an

11mm socket in the process) and I'll wait and see what happens to it, probably overnight. Otherwise it's a new one, at =A392.00 - ouch!

Yes, I have an auto charger which is great but won't charge below 7v. I used a very old basic 4amp charger to put in just enough power to allow the auto charger to continue - although best to use a trickle charger as I did blow the bridge rectifier in the old 4amp as it tried to feed more current into the battery than the charger could handle.

Thanks one and all for the advice. I disconnected the battery last night and left it until this morning, by which time it had recovered to 10.2v. I reckoned this would be enough emf not to blow the fuse on the auto charger and in fact, that was the case. It charged for six hours and then started the vehicle first time!

That's 92 squid this thread has saved me. Drinks on me!

Mustafa

Nah, you'll still need a new battery in Autumn but at least you've got another 6m out of this one. Call it a tenner saved....

my old Accord limped on with an ancient knacked battery for years, until I left a door open overnight, after which it would not charge at all. I put this down to the fact that the Honda engine fired up instantly every time !