Battery Terminology

Active Material
Chemically active compounds in a cell or battery that convert from one composition to another while producing current (electrical energy) or accepting current from an external circuit.

Battery Polarity
A battery has two poles or posts. The positive battery post is usually marked POS, P, or + and is larger than the negative post which is usually marked NEG, N, or -. The polarity of the charger and the battery must always match to avoid damage to the battery and charger.

Cell
The basic electrochemical current-producing unit in a battery consisting of a set of positive plates, negative plates, electrolyte, separators and casing. There are six cells in a 12-volt lead-acid battery.

Cold Cranking Amps
Cold Cranking Amps is a rating used in the battery industry to define a battery's ability to start an engine in cold temperatures. The rating is the number of amps a new, fully charged battery can deliver at 0° Fahrenheit for 30 seconds, while maintaining a voltage of at least 7.2 volts, for a 12 volt battery. The higher the CCA rating, the greater the starting power of the battery.

Container
The polypropylene or hard rubber case which holds the plates, straps and electrolyte.

Cover
The lid for the case/container.

Electrolyte
A solution of sulfuric acid and water which conducts current through the movement of ions (charged particles in the electrolyte solution) between positive and negative plates. It supplies sulfate ions for reaction with the active material of both positive and negative plates.

Grids
A lead alloy framework that supports the active material of a battery plate and conducts current

Ground
The reference potential of a circuit. In automotive use, the result of attaching one battery cable to the body or frame which is used as a path for completing a circuit in lieu of a direct wire from a component. Today, over 99% of autos use the negative terminal of the battery as the ground.

Inter cell connections
Connections between the straps of two cells, positive of one cell to the negative of the next.

Open Circuit Voltage (O.C.V.)
The voltage of a battery when it is not delivering or receiving power. It is 2.11 volts for a fully charged battery cell.

Plates
Flat, typically rectangular components that contain the active material and a mechanical support structure called a grid, which also has an electrical function, carrying electrons to and from the active material. Plates are either positive or negative, depending on the active material they hold.

Reserve Capacity (RC)
Reserve Capacity, (RC) is a battery industry rating, defining a battery's ability to power a vehicle with an inoperative alternator or fan belt. The rating is the number of minutes a battery at 80 degrees F can be discharged at 25 amps and maintain a voltage of 10.5 volts for a 12 volt battery. The higher the reserve rating, the longer your vehicle can operate should your alternator or fan belt fail.

Separators
Porous plastic, electrically insulating sheets which allow transfer of ions between plates, but prevent physical contact between plates and resulting electronic conduction

Straps
Lead alloy castings that connect a number of same polarity plates together in a cell and carry current

Terminals
The electrical connection from the battery to the external circuit. Each terminal is connected to either the first (positive) or last strap (negative) in the series connection of cells in a battery.

Vents
Components that allow gasses to exit the battery while retaining the electrolyte within the case. Can be permanently fixed to the cover or removable, depending on battery design.
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