Glossary of Terms

Ampere - Unit of electrical current abbreviated as amps or A. Amps = Watts/Volts or A = W/V.

Ampere Hour (Ah) - The capacity of a storage battery is measured in ampere hours. One ampere hour is defined as a current flow of one ampere for a period of one hour. Five ampere hours means a current flow of one ampere for five hours, a current flow of 2 1/2 ampere for 2 hours, or any multiple of current and time that will result in five. This relationship can be expressed as follows: Capacity (Ampere hours)= I*T, where I is the current (in amperes) and T is the time (in hours).
Unlike other storage batteries, a Corvus battery’s Ah rating does not change with discharge time.

Boost Charge - A charge applied to a battery which is already near a state of full charge, usually of short duration.

Capacity - The quantity of electricity delivered by a battery under specified conditions, usually expressed in ampere hours.

Capacity, Rated - A designation by the battery manufacturer which defines the performance of a new battery at a defined rate of discharge. For Corvus advanced Li-ion batteries this means one hour.

Capacity, Residual - Capacity remaining at particular point in time after any set of operating conditions, usually at a partial state of charge condition.

Cell Balancing - Cell balancing refers to processes which provide the ability to match one cell’s voltage to all other cell voltages in the pack. This is important to ensure maximum life cycles.

Cell Reversal - Reversing of polarity within a cell in a multi cell battery due to over discharge.

Charge - The conversion of electrical energy from an external source, into chemical energy within a cell or battery.

Charge Rate - The rate at which current is applied to a cell or battery to restore its capacity.

Charge Retention - The ability of a charged cell or battery to resist self discharge.

Charge, State of - Ratio of the amount of capacity remaining in a battery to the capacity when fully charged. A battery at 25% state of charge has 25% capacity remaining versus what it could give if fully charged.

Charger - Device capable of supplying electrical energy to a battery.

Charging - The process of converting electrical energy to stored chemical energy. Charging is the opposite of discharging.

Charging Efficiency - Ratio of the ampere hours delivered on discharge to the ampere hours needed to fully charge a battery.

Constant Current (CC) Charge - Charging technique where the output current of the charge source is held constant. Warning! This procedure may damage the battery if performed on a repetitive basis.

Constant Voltage (CV) Charge - Charging technique where the output voltage of the charge source is held constant and the current is limited only by the resistance of the battery and / or the capacity of the charge source. Also known as Constant Potential (CP) charge.

Current - The rate of flow of electricity. The movement of electrons along a conductor. It is comparable to the flow of a stream of water. The unit of measurement is an ampere.

Cut Off Voltage - Battery voltage reached at the termination of a discharge. Also known as end point voltage or EPV.

Cycle - One sequence of discharge and charge.

Cycle Life - The total number of charge/discharge cycles before the battery reaches end of life (generally 80% of rated capacity).

Deep Discharge - Withdrawal of more than 80% of the rated capacity.

Depth of Discharge - The portion of the capacity taken out during a discharge, expressed as a percent of rated capacity.

Discharge - The conversion of the chemical energy of a cell or battery into electrical energy and withdrawal of the electrical energy into a load.

End of Life - The stage at which the battery fails to deliver acceptable capacity (typically 80% of nameplate rating).

Float Charge - A method of maintaining a battery in a charged condition by continuous, long term, constant voltage charging, at a level sufficient to balance self-discharge.

Gassing – There is no gassing under normal operation with Corvus battery packs. They are a completely sealed battery.

Internal Impedance - Same as internal resistance.

Internal Resistance - The opposition or resistance to the flow of a direct electric current within a cell or battery; the sum of the ionic and electronic resistance of the cell components. Its value varies with current, state of charge, temperature, and age. With an extremely heavy load, such as an engine starter, the cell voltage may drop significantly. This voltage drop is due to the internal resistance of the cell. A cell that is partly discharged has a higher internal resistance than a fully charged cell, hence it will have a greater voltage drop under the same load. This change in internal resistance is due to the accumulation of lead sulfate in the plates.

Open Circuit Voltage - The voltage of a battery when it is not delivering or receiving power, and has been at rest long enough to reach a steady state (normally, at least 4 hours).

Overcharge - The forcing of current through a cell after all the active material has been converted to the charged state. In other words, charging continued after 100% state of charge is achieved. The result will be the decomposition of water in the electrolyte into hydrogen and oxygen gas, heat generation, and corrosion of the positive electrode.

Self Discharge - The decrease in the state of charge of a cell or a battery, over a period of time, due to internal electrochemical losses.

Series Connection - Voltage of the system is cumulative. Capacity stays the same.

Shelf Life - The period of time (measured from date of manufacture) at a specified storage temperature, after which the cell or battery needs to be boost charged so it does not suffer permanent capacity loss.

State of Charge (SOC) - The available ampere hours in a battery at any given time relative to its full charge capacity.

Temperature, Ambient - The average temperature of the battery's surroundings.

Temperature, Cell - The average temperature of the battery's internal components.

Trickle Charging - Method of charging in which the battery is either continuously or intermittently connected to a constant current charging source to maintain the battery in a fully charged condition.

Vent Valve - A normally closed check valve located in a cell which allows the controlled escape of gases when the internal pressure exceeds its rated value.

Venting - A release of gas to safely vent excessive gas build-up inside a cell. Excessive gas build-up is caused by operation outside of rated parameters.