How long to charge battery?

sudzs

My poor little Fiesta had been neglectd and left sitting outside the house for 6 weeks. Went to start it and it was dead as a dodo. The battery was new last Spring so I think there could be some problem draining the power when the car is not in use.

But anyway, I got it jump started last night and left it ticking over for about an hour... hopefully it will start today but how long of a run would give it a full charge?

crosstownk

An hour might not be enough. You should disconnect the battery from the vehicle and charge it on a slow charge overnight to ensure it is full charged.

But see how it goes after the hour...................

peasant

You'd need to run it for several hours (and not just ticking over either), but in the current conditions with lights on and demisters, blowers, wipers, etc you still wouldn't get a full charge.

Try and get a loan of a battery charger (or buy one, they're not expensive) and plug it in over night. If you ever lay it up for long again, you could always use the charger agin to keep it topped up while you're not driving.

The worst you can do is empty your battery, charge it a little and then drain it completely by starting the engine (huge draw on power) ...a deep discharge like that kills any battery for good.

So today, get it jump started again instead of starting yourself.

saobh_ie

Is leaving a little Fiesta ticking over for an hour a good idea? I know I wouldn't leave any vechile ticking over for an hour.

unkel

I would not let it tick over, but rather drive it. Surely the battery would be fully charged after an hours driving, even if using lights / wipers / demisters, etc. all at the same time

JohnCleary

1) It's bad to leave an engine idling for so long
2) Drive the car, the battery will charge faster

sudzs

Thanks all!


Why is it bad to leave a car ticking over for so long??

galwaytt

JohnCleary wrote:

2) Drive the car, the battery will charge faster

No it won't, it charges at the same rate, or close as dammit the tolereances in the regulator.

You battery, if only slightly depleted, will recover by using/running the car, but only if it's slightly depleted. It's only getting a tiny charge off the alternator, as it's only a top-up device, say 1v at a low amperage.

No, you need a proper charger - cost you about Eur25, and put it on a slow charge overnight. As a guide, a good charge for a battery is about 10% of it's capacity, e.g. a 20Ah battery charging for 10hrs at 1.8-2A.

That's why, kiddies, don't be putting car chargers onto motorbike/lawnmower batteries etc - the too fast charge rate of a car charger wrecks the battery.

sudzs

Well, I went out this morning to try to start it up. And it started! No problem!!!

What a relief!

But will someone tell me why it isn't good to leave a car ticking over for an hour??

Gary ITR

When the car is being driven the rad is being cooled by the wind you are creating. But if the car is stationary it has to rely on the fan

sudzs

Thanks!

Thought it might have been something along those lines. Seems to have survived allright though... maybe time will tell!!!

crosstownk

Idling a car for long periods isn't really all that harmful as long as it's not done regularly. The radiator fan should be well able to control the engine temperature, but with more difficulty in warmer weather. It should not cause overheating - when the coolant temp gets to low the thermostat will close, when it gets too hot the fan will kick in. Long periods idling, especially from cold, can accelerate corrosion in the exhaust system as condensation is present. This condensation, when mixed with exhaust gasses can be corrosive. If you do idle the engine, for battery charging etc, be sure to rev the engine every now and then to clear excess condensation.

I've often left engines idling all day, in a garage, when checking for certain faults like small coolant leaks, oil leaks and other faults that only occur at normal operation temperature.