Brief introduce of some Battery Terms

Ohm: A unit for measuring electrical resistance or impedance within an electrical circuit.

Ohm`s Law: Expresses the relationship between volts (V) and amperes (A) in an electrical circuit with resistance (R). It can be expressed as follows: V=IR. Volts (V) = amperes (I) x ohms (R). If any two of the three values are known, the third value can be calculated using the above equation.

Open-Circuit Voltage: The voltage of a Sealed Maintenance Free Battery when it is not delivering or receiving power.

Positive: Designating, or pertaining to, a kind of electrical potential; opposite of negative. A point or terminal on a Maintenance Free Battery having higher relative electrical potential. The positive battery terminal is the point to which electrons flow during discharge.

Primary Battery: A battery that can store and deliver electrical energy but cannot be recharged. A lead-acid battery is NOT a primary Maintenance Free Lead Acid Battery.

Reserve Capacity Rating: The time in minutes that a new, fully charged battery will deliver 25 amperes at 27°C (80°F) and maintain a terminal voltage equal to, or higher than, 1.75 volts per cell. This rating represents the time the battery will continue to operate essential accessories if the alternator or generator of a vehicle fails.

Resistance: The opposition to the free flow of current in a circuit or battery. It is commonly measured in ohms.

Sealed Battery: See VRLA.

Secondary Battery: A Maintenance Free Car Battery that can store and deliver electrical energy and can be recharged by passing direct current through it in a direction opposite to that of discharge. A lead-acid battery is a secondary battery.

Short Circuit: An unintended current-bypass in an electric device or wiring. Outside the battery, a short circuit is established when a conductive path is established between the two terminals of a battery. Inside a battery, a cell short circuit is the result of contact between the positive and negative plates and will cause a cell to discharge and render the battery useless.

Specific Gravity (Sp. Gr. or SG): Specific gravity is a measure of the electrolyte concentration in a battery. This measurement is based on the density of the electrolyte compared to the density of water and is typically determined by the use of a hydrometer (see Hydrometer). By definition, the specific gravity of water is 1.00 and the specific gravity of the sulfuric acid electrolyte in a typical fully charged battery is 1.265-1.285. Specific gravity measurements are typically used to determine if the battery is fully charged or if the battery has a bad cell.

Splash Barrel: A splash barrel is part of the battery's vent system. Its purpose is to keep acid out of the vents when the battery is upright as acid is splashed around in the cell from motion and vibration.

Starting, Lighting, Ignition (SLI) Battery: Rechargeable battery that supplies electric energy to an automobile to power the starter motor, the lights and the ignition system of a vehicle`s engine.

State of Charge (or State of Health): The amount of deliverable low-rate electrical energy stored in a battery at a given time expressed as a percentage of the energy when fully charged and measured under the same discharge conditions. If the battery is fully charged, the state of charge is said to be 100 percent.

Stratification: The unequal concentration of electrolyte due to density gradients from the bottom to the top of a cell. This condition is encountered most often in batteries recharged from a deep discharge at constant voltage without a great deal of gassing. Continued deep cycling of a stratified battery will soften the bottoms of the positive plates. Equalization charging is a way to avoid acid stratification.

Sulfation: The generation or conversion of the lead sulfate discharge in the plates to a state that resists normal recharge. Sulfation often develops when a battery is stored or cycled in a partially discharged state at warm temperatures.