Charging A Battery With The Alternator

[Wallis22]

Just a quick question... I've just jump started my car as the battery was almost completly dead. If i leave the car running at idle will the alternator charge the battery to it's full power or do i have to drive the car or raise and hold the revs up?

Also, if leave it at idle, how long do you think i should leave it before turning it off and trying to start it again?

Thanks.

 

[Cupra Kid]

it my experience you need a very good run to charge a battery back up.

 

[myseatcupra]

it will charge but you wont get a full charge. like cupra kid said you'd have to have a good drive to put any charge in

 

[Wallis22]

Well, i let the car idle for about an hour then took it for a quick 5/10 minute drive (not taxed), thrashing it! God i missed that power! Lol.

Got home and turned it off. Left it a couple of minutes and started it again and it's fine.

 

[m0rk]

I've got a charger if you need a lend overnight. just to be sure.

COld weather deteriorates them quickly

 

[Wallis22]

I'll leave it over night and try it again tomorrow to make sure it still starts. Thanks for the offer.

 

[chris27]

it will charge but you wont get a full charge. like cupra kid said you'd have to have a good drive to put any charge in

i thought the alternator charged at the same rate wheter its idling or being thrased down the motorway

 

[myseatcupra]

your best bet is to borrow morks charger dude. then you know its fully charged. i dont think that altanator is at its best at idle.

 

[Wallis22]

Just to update, it's been left overnight in the freezing cold, and it's still charged enough to start the car with no problems at all.

Thanks for all the help guys.

 

[AlpineWhite]

i thought the alternator charged at the same rate wheter its idling or being thrased down the motorway

No, the current output of the alternator varies as a function of engine speed.

Also, the charging effect it has on the battery depends on the current draw from the vehicle electrical systems.

So if you want to charge a car quickly using the alternator, you need mid engine speed or greater, with everything switched off (radio, heater, fan, defroster, lights).