Our Solar Terms Glossary is meant to be as easy to understand, yet technically correct, as possible. We hope you find it helpful.

**AC** – alternating current; electric current that reverses direction at regular intervals

**AGM** – absorbent glass mat; a type of battery in which the battery acid is absorbed by fiberglass mat material and then packed between the plates of the battery.

**amp** – short for ampere; one amp is equivalent to one coulomb per second; measures the rate of flow of electric charge

**amp-hour** – a unit of electric charge; one amp-hour is equivalent to a current of one ampere flowing for one hour

**battery monitor** – a device that displays the electrical state of a battery or battery bank

**charge controller** – a device that regulates the charge going from an array of solar panels to a battery bank

**circuit breaker** – a safety device that cuts off transmission of current if the current passing through it exceeds a certain level

**combiner box** – a box that houses the combination of two or more strings of photovoltaic panels into fewer wires

**converter** – a device used to convert direct current (DC) voltage to another direct current voltage, or from alternating current (AC) to direct current

**current** – a flow of electric charge

**DC** – direct current; electrical current that flows in one direction

**deep cycle battery** – a type of battery that is designed to be discharged by as much as 80%

**depth of discharge** – term indicating how deeply a battery has been discharged; a battery that has a 25% depth of discharge means that 25% of its capacity has been used up

**equalization** – a process performed on lead-acid batteries to reverse a buildup of chemical effects and remove sulfate crystals that have built up on the lead plates inside the battery

**fuse** – a safety device in which a strip of wire breaks and cuts off the transmission of current if the current passing through it exceeds a certain level

**Isc** – short circuit current; the maximum amperage a solar panel can product with a shorted output

**Imp** – amperage at maximum output; the maximum amperage a solar panel will produce under normal conditions

**Inverter** – a device that converts direct current (DC) power to alternating current (AC) power; often also steps up voltage

**kW** – kilowatt; one kilowatt is equivalent to 1000 watts

**lead-acid battery** – a type of battery that consists of lead (or lead oxide) plates and sulphuric acid

**modified sine wave inverter** – a type of inverter in which the voltage produced has a step-like form and rises and falls abruptly

**monocrystalline** – a type of solar panel in which each solar cell is made of a single crystal ingot

**MPPT** – maximum power point tracking; a feature included in some charge controllers that maximizes the power output of a photovoltaic system

**parallel** – a circuit in which current follows two or more paths; wiring batteries in parallel increases effective capacity

**photovoltaic** – solar energy technology that converts solar radiation into energy

**polycrystalline** – a type of solar panel in which each solar cell is made of multiple crystal structures

**power** – the rate at which energy is transferred by an electric circuit

**pure sine wave inverter** – a type of inverter that provides electrical power similar to that which is provided by a utility company; the voltage produced has a sine wave-like form

**series** – a circuit in which current follows a single path; wiring batteries in series increases the effective voltage of the batteries

**shallow-cycle** – a condition in which a low percentage (10-15%) of overall battery capacity is discharged

**shunt** – a low resistance resistor; a necessary device to measure amps and amp-hours with a battery monitor

**solar panel** – a group of photovoltaic cells organized into the form of a panel

**string** – a number of solar panels connected in series to produce a specified voltage

**Vmp** – voltage at maximum power; the voltage at which maximum power is produced by a solar panel

**Voc** – open circuit voltage; the maximum voltage that can be produced by a solar panel

**volt** – a unit of electrical potential; in an electrical circuit, voltage is a measure of “push”

**voltage drop** – the voltage lost between two points in a circuit

**watt** – a unit of power; one watt is equivalent to one joule per second

**watt-hour** – a unit of energy; one watt-hour is equivalent one watt of power expended for one hour