Car battery is flat

Hi all,
Not to sure where to put this but I'm sure the mods will!

The battery in my Smart car is flat - interior light left on over night. I've just had a jump start from a taxi and was wondering how long I should keep it running before the battery has enough of a charge to start the car again in the morning?

Thanks

Bert

ideally drive it around a bit rather than just leave it idling. 10-20 mins prob fine

I'd say take it for a 20 minute drive around, with the engine at reasonably high revs. I'm not sure that just ticking over in neutral pushes much charge into the battery.

Yeah that should do it, but don't drive with the lights, radio, heated rear window etc. on, or you'll never get it charged!

Driving 12 to 15 K should be enough, if the interior light killed it it sounds a bit weak for the current temperatures though.

You may need a new one. How old is it?

That wasn't very smart of ya!

you could just throw it away and buy a new one (a new car that is)

I'd trickle charge it for 16 hours or so (this assumes you have a trickle charger) but it might be the case that you need a new battery, or if you're unlucky a new alternator. Was last night unusually cold? The cold weather is what ususally causes batteries to fail at this time of year.

Wow! thanks for the fast replies!

The battery was flat on Monday. I got a start and drove about for about 20 mins. On Tuesday morning though, it would not start. Although not totally flat (like Monday when I had to enter the car through the boot as the RC wouldn't work), it didn't have enough juice to get it going.

Jimbo - yep it's been bloody cold all week.

I'll head off up the A9 for an hour or so, The battery is only about a year old so hopefully I've not damaged it.

Thanks again

Bert

You won't damage a car battery just by running it down. In fact some people claim it's actually good for them. If it's only a year old and a long drive doesn't work take it back to where you got it, batteries usually have quite long guarantees. Unless of course the alternater isn't charging, but then you should get a warning light to tell you that.