Langley (L) - Unit of solar irradiance. One gram calorie per square centimeter. 1 L = 85.93 kwh/m2.

Lattice - The regular periodic arrangement of atoms or molecules in a crystal of semiconductor material.

Lead-Acid Battery - A general category that includes batteries with plates made of pure lead, lead-antimony, or lead-calcium immersed in an acid electrolyte.

Life - The period during which a system is capable of operating above a specified performance level.

Life-Cycle Cost - The estimated cost of owning and operating a photovoltaic system for the period of its useful life.

Light-Induced Defects - Defects, such as dangling bonds, induced in an amorphous silicon semiconductor upon initial exposure to light.

Light Trapping - The trapping of light inside a semiconductor material by refracting and reflecting the light at critical angles; trapped light will travel further in the material, greatly increasing the probability of absorption and hence of producing charge carriers.

Line-Commutated Inverter - An inverter that is tied to a power grid or line. The commutation of power (conversion from direct current to alternating current) is controlled by the power line, so that, if there is a failure in the power grid, the photovoltaic system cannot feed power into the line.

Liquid Electrolyte Battery - A battery containing a liquid solution of acid and water. Distilled water may be added to these batteries to replenish the electrolyte as necessary. Also called a flooded battery because the plates are covered with the electrolyte.

Load - The demand on an energy producing system; the energy consumption or requirement of a piece or group of equipment. Usually expressed in terms of amperes or watts in reference to electricity.

Load Circuit - The wire, switches, fuses, etc. that connect the load to the power source.

Load Current (A) - The current required by the electrical device.

Load Resistance - The resistance presented by the load. See resistance.

Low Voltage Cutoff (LVC) - The voltage level at which a charge controller will disconnect the load from the battery.

Low Voltage Disconnect - The voltage at which a charge controller will disconnect the load from the batteries to prevent over-discharging.

Low Voltage Disconnect Hysteresis - The voltage difference between the low voltage disconnect set point and the voltage at which the load will be reconnected.

Multi-Stage Controller - A charging controller unit that allows different charging currents as the battery nears full state_of_charge.

Low Voltage Warning - A warning buzzer or light that indicates the low battery voltage set point has been reached.