Completely flat battery

[The Aardvark]

Afternoon All

Admittedly the car hasnt seen much use over the last few weeks due to snow and salt etc, but put an approx 8 hour charge in the battery last w/e - started fine.
Just been out to take it for a drive, and completely flat - not even enough to unlock the doors. Very faint flash from the alarm light.
Gained access manually, and nothing.

Battery was new this time last year. Sound like a flat battery or should I be looking elsewhere?

Cheers

[Alexdaredevilz]

Check 100amp fuse and alternator

[Tyre Tread]

After you put the battery on charge for 8 hours a week ago did you then take the car for a drive?

An 8 hour charge is unlikely to have fully charged the battery and if you then started it without taking it for a decent run you have taken a chunk out of its charge by starting it. Couple that with another week left standing and the cold weather effect on the battery and it's likely almost flat again.

If possible leave it on a trickle charge for at least 24 hours or enough to start and then a good run of at least 20 miles.

[The Aardvark]

Thanks for comments. No didnt head out for a drive so that could well be it. Have had a few flat batteries over the last few years but never so flat that i couldnt unlock the car. Will try for a decent charge in the next few days.

[Dr Mike Oxgreen]

The Aardvark said:

Have had a few flat batteries over the last few years but never so flat that i couldnt unlock the car. Will try for a decent charge in the next few days.

If you mean that this battery has gone flat several times, then that also won't be helping. Car batteries hate being deeply discharged, and each time it happens it'll never fully recover. They are the exact opposite of lithium rechargeables, which benefit from an occasional deep discharge.

[The Aardvark]

Dr Mike Oxgreen said:

If you mean that this battery has gone flat several times, then that also won't be helping. Car batteries hate being deeply discharged, and each time it happens it'll never fully recover. They are the exact opposite of lithium rechargeables, which benefit from an occasional deep discharge.

This was a brand new battery 12 months ago, and was absolutely fine all year. This is the first time that it has struggled, and hence the part charge last weekend. Agree that I should have really gone out and done a few miles, but unfortunately time and other restrictions got in the way.
So as this is the first time this one has gone flat, hopefully a good 24hr charge will help - as mentioned, just strange that there wasnt enough juice to even open the doors....

[tonys]

It could well be the battery, but without stating the obvious, are you happy that the connections are tight?

[Pothole]

Get an Oximiser or similar and leave it plugged in all the time.

[The Aardvark]

Connections are fine (The AA fitted the battery this time last year), and unfortunately the car is kept a little way away from the house. I do however have a large solar panel that is plugged in all year round, and it definitely makes a difference as to how quickly it runs down compared to when its unplugged.

Battery had a 3yr warranty so if it fails to hold a charge its back onto the The AA.....

[taylormj4]

Put a voltmeter across it. More than 11V is recoverable in my experience.
Anything less than 10.5V means you've lost a cell and unlikely to get that back even with a charge.
In fact charging a battery with a cell out is likely to gas it and wreck it further.