On 24/02/2013 08:06, Mike Cook wrote:
A friend has a battery powered Ryobi lawn trimmer ("weed whacker")
which doesn't work. The 12vdc wall wart puts out only ~ 12.4v.

I charged the lead-acid gel cell using a car charger. The charge
rate (selectable) was 0.5A. Afterward the trimmer seemed to work as
new.

For how long?

Can the car charger be used to charge this battery? He can install a
timer to limit charge time if that's something required.

Lead acid batteries are fickle things but last a long time if looked after.

I would prefer to use a charger that could detect end point and either
turn off or supply a constant voltage. There are some car battery
chargers that do this.

A final thing is to check battery terminal voltage. During a fast
charge you might accept a voltage of 14.5V, but under long term (float
charge) I wouldn't want the charger to push out more that 13.8V.

--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk