Probably the battery pack is worn out or has a "memory" problem. A worn out pack will have one or more cells shorted internally (one or more cells read 0 Volts, and an ohmmeter reads less than 1 Ohm when connected to the 0 Volt cell). If it is a memory problem, it is possible to recondition it, but not simple. You have to remove the pack, then connect a 150 Ohm resistor across each cell and let the battery sit until the cells are completely discharged. You can't just connect a resistor across the entire battery pack because the stronger cells will reverse-charge the weaker ones, which will cause them to short out.
Running the battery too far down will cause the reverse-charge problem, but not running it down at least occasionally will cause the memory problem. (Memory problem explained: the cadmium crystals grow when the battery is charged and shrink as it is discharged. However, the larger ones tend to remain intact on discharge and grow faster than the smaller ones. Eventually they block the ion flow through the battery, so the battery loses capacity. It's called a memory effect because the battery only "remembers" it has the capacity to go down as far as it is habitually used. Running the cell all the way down dissolves the over-sized crystals.)
It is possible you have a problem with the charger. Check for voltage on the charger plug. It should be about the rated output voltage printed on the charger box before messing with the battery.
Apr 23, 2011 |
Dirt Devil BD20035 Bagless Stick Vacuum