I recently found a 900VA APC UPS in the thrift stream, unopened in its original box. The box was dusty, and looked 'old'. As expected, the battery was NFG. It's a 24V pack, open-circuit. I clipped an old consumer battery charger (leak generator) to it. This high-tech tool uses a diode in series with a 4W night light bulb to convert line voltage into charging current. The point is that it starts out with very high voltage into such a badly-sulfated battery, 80+V by my measure, and was able to force in a dribble. The lamp filament was barely glowing at first.
Once the voltage got down to about 25V I switched over to a 30VDC power supply in series with a Heathkit square wave generator, which was pumping in a very ringy 100kHz square wave according to the oscilloscope. After 2 weeks the square wave is 'flat', though the rings are still there. The battery has recovered enough that the UPS will now pass its self-test, though I have yet to actually try a load on it. -- Jim _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
