Jamie wrote:

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.

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

Thanks.


THe OEM charger most likely is unfiltered. Put a cap on the output but
do not connect it to the battery and then do a voltage check.

More bad bad advice from Maynard Philbrook, as usual. Does the
voltage across the battery go up when the charger is connected?


If you see a jump in voltage then this means the battery is on its
last leg and you really shouldn't push it.


Bull****, as always. The connector for the charger may be bad,
especially if it disconnects the battery from the tool while on charge.
I've seen connects melted, or the solder overheat 7 the wires fall off
poor designs.


A good test for this condition is to fully charge it with your auto
charger and disconnect it and test the voltage a day later or few hours
later to note the discharge.

It is possible the charger is bad but I am going with a
bad battery. You can always get a weak battery to appear good with an
extra current source but the charge will dwindle.


You're long overdue for replacement.