Volumetric Energy Density - The ratio of the energy output of a cell or battery to its volume (Wh/L).
Cathode - The electrode in an electrochemical cell where reduction takes place. During discharge, the positive electrode of the cell is the cathode. During charge in a rechargeable battery, the negative electrode is the cathode.
Cubicle (parallel UPS unit) - Cubicle containing a rectifier/charger and an inverter. It is connected to one or several other identical cubicles and a bypass cubicle to make up a parallel UPS.
Backup time - Time during which the UPS can supply the rated load with nominal-quality power while the mains are down. This time depends on the battery and the efficiency of the UPS. Typical backup ranges from five minutes to several hours.
Current (float) - DC current that maintains the battery at nominal charge, corresponding the float voltage. This current compensates open circuit losses.
Brownout - A steady state RMS voltage under nominal by relatively constant percentage.
Thermistor - A temperature sensitive resistor, usually made from specially processed oxides.