re charging battery

[jolly geoff]

battery has gone almost flat with trying to start in cold weather but once engine started have left it running to recharge but a friend told me i should turn lights on to improve charging, i thought all electrics should be switched off so as not to drain power who's right and why?.does this also apply to mobile phones as well should they be off or on when charging.

[R1Geezer]

Well its stands to reason that It will charge quicker with all unnecessary electrics off. Not sure what your mate is gettig at! Same principle with mobile phone.

[logic]

I agree with R1Geezer on this one, as much as it pains me to do so, :-)

[jolly geoff]

he says he's been told that turning the lights on engages the alternator and that speeds up charging

[nightmare]

so, if you run the engine with no lights on and the alternator is NOT "engaged", as you put it, exactly how do you think the battery is being charged ?

[R1Geezer]

your mate sounds like a bit of a plonker if ou ask me, as nightmar points out, the alternator is running whenever the engine is running so it stands to reason that lights on are draining power while the alternator is charging. It's like filling up a sink with a small hole in it. It will fill quicker if the hole is blocked.

[Nkakamasembe]

Nearly all car charging systems are now designed to perform at their pick with most electrical equipment on and at low engine rpm.This being an acknowledgement of the long time most cars have to spend in slow traffic with a/cs ,and other essential electric on.
In short the charging system will rise to the needs of any load put on the system.
I regulary use a diagnostic tool that I connect to the battery to get a pulse for RPM reading. with the headlights off it will struggle to get this pulse,with headings on the RPM read is instant.So your friend is right .

[dothawkes31]

well that has stunned me because everyone has always advised me to run the car but swithc all none essentail eletrics off to make sure the battery charges properly. Is that operhaps on new cars you mean then?

[tim01]

take the battery out of the car and put it on charge ,if the battery is running flat when you put it back in the car it is not holding the charge, so it could be the alternator or the battery ,so get that checked first i think halfords will be able to help you,you need a good battery in this weather, with the heater,going the lights,wippers, heated rear window.and also the radio, its a lot of power to use ,and if the battrey is old it will be to much .you will never charge the battery by running the car if the battery is knackerd

[odinslay]

Go with Tims idea, Everyone thinks that a car battery will fully charge while driving the car around, but that is not actually true. it only creates a surface charge which will not last very long. you'll need to charge the battery for at least 8 hours. Also check the water levels in it. the water should be covering the fins. if not get some FILTERED water and top it up