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[jereboam]

A few weeks ago, on a hot day, I opened all the windows and the sunroof in the morning, as we were going out in the afternoon.  I stupidly left the key in and the ignition on.  So, at going out time, the battery was absolutely flat.

I've got one of those fancy Halford's chargers which has lights which show how the charge is progressing.  When I connected up (left the battery in place - know I shouldn't), it showed a red light against  "20% - Charging essential".  

20 minutes later, it showed 3 amber lights, and indicated "100% Fully Charged".  And it was - it started the car immediately.

How can the battery go from 20% to 100% in just 20 minutes?

[Taxi_Driver]

It may suggest your car battery is nearing the end of its life......car batteries tend to appear to charge faster when they are dying.....as they increase in resistance and battery chargers think as they are taking less current they must be fully charged

[Plomien]

depends on the trickle charge rate

[Kevin Wood]

I wouldn't be too trusting of the lights on the charger either.

Kevin

[Bandit127]

It may suggest your car battery is nearing the end of its life......car batteries tend to appear to charge faster when they are dying.....as they increase in resistance and battery chargers think as they are taking less current they must be fully charged

This explanation gets my vote.

Charge required to start a car is, say, 200 amps. Cranking for 5 seconds is equivalent to...
83 amp minutes
1.4 amp hours
2% of the charge of a 70 amp hour battery.

So you could have just put enough in the battery to get the car started.. the alternator will do the rest on a resonable run.

Or you have a 200 amp charger!

Seriusly. could be time to get the battery checked. Higher internal resistance means less available current and this can quickly be checked with a load tester.

[jereboam]

Yeah, the battery is probably on the way out - it's the one that was in the car when I got it about two and a half years ago.  The car's going in on Thursday to have the bumper straightened out and 4 new Pirellis fitted, so I'll get the garage to check it out.  

More expense

[zirk]

Might wonna get a hair cut, while their changing those Tyres

[Vamps]

Yeah, the battery is probably on the way out - it's the one that was in the car when I got it about two and a half years ago.  The car's going in on Thursday to have the bumper straightened out and 4 new Pirellis fitted, so I'll get the garage to check it out.  


I have just changed the battery on my car, the original was still fitted to the car, 10 years old. Only went cos I left if flat for a few months

[Richie London]

It may suggest your car battery is nearing the end of its life......car batteries tend to appear to charge faster when they are dying.....as they increase in resistance and battery chargers think as they are taking less current they must be fully charged

i had 2 de walt batteries that charge in 10 mins, flat again in 5,only one place for them to be, in the bin  

[ians]

It may suggest your car battery is nearing the end of its life......car batteries tend to appear to charge faster when they are dying.....as they increase in resistance and battery chargers think as they are taking less current they must be fully charged

i had 2 de walt batteries that charge in 10 mins, flat again in 5,only one place for them to be, in the bin  

ouch - those babies are expensive.  My 18V ones have died too.

but please don't just bin them - they have nasty stuff inside which needs handling propoerly - the council recycling centre (aka tip) will have a separate bin for them.

[Kevin Wood]

but please don't just bin them - they have nasty stuff inside which needs handling propoerly - the council recycling centre (aka tip) will have a separate bin for them.

.. or cut the packs open, replace the cells and glue them back together.  

Kevin