Ambient Temperature: The temperature of the surroundings with respect to a particular reference point. The ambient temperature for a charger is the air temperature in the vicinity of the charger.

Ammeter: An instrument used to measure current. The unit for the measurement of current is amperes.

Ampacity: Current carrying or current providing capability.

Ampere: SI unit for the amount of electrical charge traveling through a conductor per second.

Absorption Mode: The charging state during recharge where a lead acid battery accepts the final 15-25% of its capacity. The voltage for a 12V lead acid battery is regulated at approximately 14.6V during absorption while the battery acceptance current continually decreases.

Battery: Two or more electrochemical cells electrically connected in a desired series/parallel arrangement to achieve a particular voltage/current capability.

Breakdown Voltage: The voltage where the dielectric insulation fails or is severely degraded by excessive leakage current or arcing.

Brownout: A reduction of the AC voltage, either by the utility company to reduce power consumption or due to heavy loading on a power line that has a high source impedance.

Bulk Mode: The charging state during recharge where a lead acid battery accepts the 75-85% of its capacity. The charging current for a 12V lead acid battery is regulated at its maximum current output while the battery voltage continually increases until the absorption stage is reached.

Burn-In: Operating a battery charger or power supply, usually at or near rated load to verify the unit was manufactured correctly.

Capacity: The total number of ampere-hours (or watt-hours) that can be delivered by a battery under specified conditions of discharge, such as current draw and temperature.

Cell: The fundamental electrochemical unit generating or storing electrical energy. For instance, a lead acid 12V battery is obtained by placing in series six cells of 2V each.

Charging: The process of converting the current supplied to a battery from an external source into chemical energy stored by the battery for later use.

Closed Circuit Voltage: The instantaneous voltage of a battery when a load is applied, i.e.. current is being drawn from the battery.

Continuous Load: A load expected to continue for an extended period of time. Commonly electrical equipment is rated for peak load and continuous or average load.

Converter: An electrical circuit that transforms a DC input into a desired DC output.

Cross Regulation: The effect of load change on one output to the regulation of another output. This is particularly important in multi-output battery chargers.

Current Limiting: A protection circuit that limits the maximum output current in order to protect the load being driven and the battery charger or power supply providing the power.

Cut-Off Voltage: The battery voltage where further discharge is terminated to prevent deep discharge and subsequent damage to the battery.

Cycle: The discharging and charging of a rechargeable battery. Many manufacturers provide the number of charge/discharge cycles that a rechargeable battery can undergo before a measurable decrease in specification performance.