Psplendid Psions!!
If any of the failures are of rechargeable batteries, there is a 'fix' which restores life and battery. This applies particularly to the Revo but may be applicable to others. It requires the Revo to be recharged while being super-cooled ... in the freezer. ...... wrapped in freezer blocks worked for me. Don't know the technicalities but it may be that the charger cut-out operates on a thermostat reference. Might be worth a try