Power Surge - Voltage above 110% of rated RMS voltage for one or more cycles.
Dry Cell - A cell with immobilized electrolyte. The term "dry cell" is often used to describe the Leclanche cell.
Capacity Retention (or Charge Retention) - The fraction of the full capacity available from a battery under specified conditions of discharge after it has been stored for a period of time.
Filter (phase-shift) - Filter used to reduce, if necessary, the overall distortion due to the current harmonics injected into the mains upstream of a UPS by its rectifier-charger. Filtering is superior to that of a traditional filter of the L or C type.
Distortion (total) - Ratio between the rms value of all harmonics of a non-sinusoidal alternating periodic value and that of the fundamental. This value may also be expressed as a function of the individual distortion of each harmonic Hn= Yn /Y1.
Load power - Apparent power Pu that the UPS inverter supplies under given load conditions. It is less than or equal to the rated output Pn. The ratio Pu/Pn defines the % load of the inverter.
Cutoff Voltage (also see End Voltage) - The battery voltage at which the discharge is terminated. The cutoff voltage is specified by the battery manufacturer and is generally a function of discharge rate.