Flat Battery.

[zabado]

Is there any problems with re-charging a flat battery while it's still connected to the car ?.

[bhg481]

No. Connect the charger and then switch it on.

[douglas9401]

There may be, depending on the car.

Disconnect the negative terminal and make sure it can't fall back onto the terminal while charging.

[bhg481]

I cannot see the difference between attaching jump leads from another car and attaching a battery charger. Why disconnect the negative terminal?

[EDDIE51]

I am with bhg on this, just charge it. No different from having a good a battery and it charges from the alternator as normal. Or from using jump leads.

[douglas9401]

http://www.telegraph.co.uk/motoring/caradvice/honestjohn/11276448/Should-I-disconnect-my-battery-to-charge-it.html

[zabado]

Thanks guys.

[Arrods]

In the 'old days' didn't they (with batteries you could top up with distilled water) tell you to remove the battery from the vehicle as the build up of gases could cause the battery to explode? (I have always charged modern batteries though without disconnecting terminals.)

[TWR]

If your battery has JUST LET YOU down all of a sudden Zab, it want's replacing, this weather will test any fault in a car battery.

[bhg481]

TWR is absolutely right - you need to know why your battery was flat. If you've been doing lots of short trips with all the electrics on then a recharge is OK. If you, say, left the lights on for an extended period you could well have wrecked the battery and a new one is the best option. If the car has been left outside in the cold and not used for several days be aware tha the battery might be reaching the end of its useful life.

[ToraToraTora]

no problems in fact it will save problems so connect it up and off you go.

[Ryzen]

If the battery is flat,the charge rate and applied voltage could rise and damage sensitive components.That said if a good quality charger is being used problems may be avoided.