How long will a charged car battery last for?

knightstyle

Many years ago I stored a car for six months whilst working abroad, disconnected the battery and on return, having reconnected it I thought it would be flat but it managed to turn the engine over several times before it went completely flat. So I think batteries have got better now, the problem is that even when switched off cars still use some electricity so batteries go flat sooner.
Current battery is original in a nearly seven year old car and still fine.

scragend

Lincoln_Imp wrote: »

Not sure what you mean by that ?

It means that more often that not Halfords will tell you that your battery is knackered (even if it isn't), in the hope that you will promptly buy a new one from them.

Lincoln_Imp

scragend wrote: »

It means that more often that not Halfords will tell you that your battery is knackered (even if it isn't), in the hope that you will promptly buy a new one from them.

Right ,thanks for that
The battery was knackered though as had let him down twice within a couple of weeks

Strider590

knightstyle wrote: »

Many years ago I stored a car for six months whilst working abroad, disconnected the battery and on return, having reconnected it I thought it would be flat but it managed to turn the engine over several times before it went completely flat. So I think batteries have got better now, the problem is that even when switched off cars still use some electricity so batteries go flat sooner.
Current battery is original in a nearly seven year old car and still fine.

There's a limit to the current a car can take from the battery when off/parked/locked (a quiescent current). This maximum limit is around 200mA (which is actually quite high) and this is what most manufacturers work to at the design level.

So a 50aH battery should last AT LEAST 250 hours if kept connected to the vehicle.... If your battery is draining over night, you have either a serious fault OR a battery beyond it's useful service life.

reeac

forgotmyname wrote: »

Park it up for a month or two and come back and post the results.

I have a leisure battery outside. Not been charged for 3 months. Still charged. But stick a small load on that and it would have been dead. Even a flashing LED will eventually draw enough to kill a battery.

Not quite the same but my boat which spends each winter ashore has 2 leisure batteries totalling 170 Ah.which get a 24h. charge in December and again in April. As best as I can judge the batteries [both 7 years old] lose about 5% of their charge per month and as the master switch is off that's mostly internal loss.