I have a self propelled walk behind. Toro increased the size of the replacement battery for this model. I don't know if that has anything to do with my problem. The original charger, which had some heft to it, died. I bought a new charger in August 2011. It is smaller and lighter. I plugged it into the mower and then the outlet and let it charge overnight. Next morning battery still dead. I finally got around to taking it back in October. Took it back and they tested it and it wasn't putting out a charge and gave me a replacement. At that time I took the battery out of the mower as I store it in the basement for the winter. Mower is in shed. I jury rigged the charger to the battery and charged it up.
Finally got around to putting the battery in the mower (was using the pull cord). Again, I plugged it into the mower and then the outlet and let it charge overnight. Next morning battery still as weak as it was before charging. At that point I jury rigged up a lower voltage cell phone charger and it charged the battery.
Bought another charger, samething but this time I heard it pop as soon as I plugged it into the outlet.
These new style chargers run about $26 a pop. What would cause them to short out if that's whats happening? You can't reverse the battery connections. Red to positive is a larger connection.