Charging a battery

swingaloo

I'm prepared for the 'women drivers' remarks because this may be a silly question but here goes-

If a car has a flat battery and has been started using jump leads I know that you can help put some life into the battery by driving the vehicle round for a while (obviously without lights / heater running/ radio etc).

Does it have the same effect if you just leave the vehicle ticking over in the drive or is that just draining the battery again?

Its a diesel engine if that makes any difference.

sk240

Hi, whats caused the battery to go flat?
Once started it will take in the order of 30-60 mins of normal driving to fully recharge a battery that is in good condition.
You could just leave it idling for an hour, but that does seem very wastefull.
Also charging it using a 12v charger would be a good option

swingaloo

sk240 wrote: »

Hi, whats caused the battery to go flat?
Once started it will take in the order of 30-60 mins of normal driving to fully recharge a battery that is in good condition.
You could just leave it idling for an hour, but that does seem very wastefull.
Also charging it using a 12v charger would be a good option

Thanks for the reply.

Its a transit van and has had a problem with the battery for ages. Bought a brand new battery for it and after a few days it was flat again. Took it into a garage who tested it as we thought something must be draining the battery. Auto electrician looked at it and said nothing draining battery and fit new connectors to it.

Kept it at garage for 3 days and it started each day, got it home and it started the following day but the day after that it was flat again.

No idea what going on with it but its going back into garage next week.

Stoke

Personally, I recommend slow charging over alternator charging. I use a battery conditioner which charges over the space of about 12 hours.

The alternator dumps a lot of energy into the battery in a very short space of time, they can pretty much charge the entire battery in like half an hour or something? This tends to reduce the overall lifespan. Of course, if you have no other option (i.e. you need to get to work) then just jump and drive. Batteries are cheap disposable items, all things considered.

AdrianC

swingaloo wrote: »

I'm prepared for the 'women drivers' remarks

Given that we have no way of knowing your gender, I wouldn't be too worried...

If a car has a flat battery and has been started using jump leads I know that you can help put some life into the battery by driving the vehicle round for a while (obviously without lights / heater running/ radio etc).

Does it have the same effect if you just leave the vehicle ticking over in the drive or is that just draining the battery again?

The alternator in even vaguely modern cars generates some charge even at idle. Not as much as with the revs raised even a little bit, but enough to get some charge into the battery. Obviously, the more the charge generated is consumed (lights etc), the less is available to go into the battery.


But that assumes the alternator is working properly, and the battery is flattened because it's simply been depleted through lights etc being left on. If the battery is knackered, or the alternator's not playing, then all bets are off.



A lot of people's received wisdom seems to be stuck in the 1960s and before, when cars had dynamos that were much more borderline in capacity.

System

swingaloo wrote: »

If a car has a flat battery and has been started using jump leads I know that you can help put some life into the battery by driving the vehicle round for a while (obviously without lights / heater running/ radio etc).

Does it have the same effect if you just leave the vehicle ticking over in the drive or is that just draining the battery again?

It will put a little charge in the battery but almost nothing because the vehicle uses a lot of electricity to keep running as it has to run a fuel pump, electrically operated fuel injectors, the onboard computers.

A point of note though: Once a car battery voltage drops below 10.5V it is damaged. If you use the vehicle regularly you may not notice that damage but it will be there and most likely you may find that once the cold winter weather returns you park the car up OK but when you go out the following morning the battery is flat so be prepared for that eventuality.

Stoke

You can actually refurbish a car battery using Epsom salts. I've seen it done. The thing is, by the time you've invested time, money, and effort it just isn't worth it.

Robisere

After any "charging" journey, leave the engine running, have someone in the driver's seat. Turn on lights in 'dipped' beam, stand in front of the lights and have the person behind the wheel gradually rev the engine. The lights should brighten slightly. If they don't, some component (not necessarily the alternator, but usually) is not allowing the alternator to charge the battery.

I think your auto electrician made an incorrect or not thorough enough diagnosis, but that's just my view. Maybe a "short" somewhere, robbing current.

sevenhills

swingaloo wrote: »

Its a transit van and has had a problem with the battery for ages. Bought a brand new battery for it and after a few days it was flat again. Took it into a garage who tested it as we thought something must be draining the battery. Auto electrician looked at it and said nothing draining battery and fit new connectors to it.

Kept it at garage for 3 days and it started each day, got it home and it started the following day but the day after that it was flat again.

If your auto electrician is competent, maybe its nothing to do with the battery or charging, but the starter itself?
Or maybe the glowplug system?

sheslookinhot

Could it be related to a poor earth connection ?

Norman_Castle

Buy or borrow a battery charger. The alternator is designed to keep the battery topped up, not to fully recharge the battery.