geekIT:

 

Thanks guys.

 

OK, I've just checked my recently charged battery and it was, indeed, sitting at around 11v. 

 

This was the result of a 5-6 hour charge and a three km drive.

 

The charger, as predicted, is outputting just over 14v.

 

So I'll do a 24 hour charge. What battery voltage would you expect to see after that?

Grain of salt recommended, because I've done much worse to my batteries and still use them - but I've heard that if a car battery ever reports voltage below 12v for a sustained period of time, it's suffered permanent damage. Yours sitting at 11v AFTER a 6 hour charge suggests that it's probably a shadow of its former self in capacity terms and a new battery should probably be on your short to medium term shopping list.

Nominal voltage is 12.6v. A healthy battery should sit at that level not only when it's fresh off the charger, but after starting the car (and then immediately turning the engine off).

cadman:

 

allio:

 

I have a seldom-used car with a tiny battery that’s prone to going flat (Honda Jazz) so frequently have to deal with this.

 

 

Should just get a small, cheap charge-and-maintain charger and leave it connected to that battery when it's parked up. Lead-acid starting batteries don't like being slow discharged or kept at low voltages.

 

I do (the Ctek MXS 5.0 I mentioned in my post is a smart charger which reverts to a maintenance trickle once the battery is charged). Unfortunately I usually park on the road, so my usage isn't perfect and the battery still takes a bit of a beating.