A battery is an electrochemical device that stores and delivers energy.

Energy is chemically stored in the battery and when the terminals of the battery
are connected through a resistive load, electrical energy passes through the circuit.

Automotive lead-acid batteries are commonly referred to as starting batteries, which are generally 12 volts (12V) and are rechargeable.

These batteries supply power to the starter and ignition system to start the engine and to power additional auxiliary items such as clocks, computers, navigation systems and any other device that requires constant power.

Lead-acid batteries also supply extra power needed when the vehicle’s electrical load exceeds the supply from the charging system (alternator) and acts as a voltage stabilizer in the electrical system, evening out voltage spikes and preventing them from damaging other components in the electrical system.

A 12V lead-acid battery contains six separate cells at two volts each and a 6 volt with 3 seperate cells at two volts each.

The cells are connected in series by connections through the cell partitions. Each cell contains an element that consists of positive and negative plates.

The battery is then filled with liquid electrolyte (a solution of sulfuric acid and water) or as it is commonly called, battery acid.

Batteries are made of five basic components:
Positive plates
Negative plates
Separators – usually a micro-porous polyethylene synthetic material
Polypropylene container
Liquid electrolyte

Plates are comprised of two parts – the grid and the paste, both made of lead. The paste is soft and is the active material that chemically stores the energy. The grid provides a skeletal framework for paste adherence. Grids are made of lead alloys that resist corrosion and conduct electricity to and from the plate.

Positive and negative plates are stacked in an alternating fashion, with separators between the plates to prevent electrical shorting and to enable battery acid to flow back and forth. Both the positive and negative plates are connected at the top by a cast-on-strap that is welded to the plates.

Battery Council Industry (BCI) specifies standard battery sizes and configurations by group size. This includes standard overall size – length, width and height of the battery – and standard terminal type and position.

This industry rating measures the power a battery has available to start a vehicle’s engine at -17.8 degrees celcius or zero degrees Fahrenheit.

For a 12V SLI (Starting, lighting, ignition) battery, BCI defines CCA as the amount of current (number of amperes) a lead-acid battery at -17.8 degrees celcius or 0 degrees Fahrenheit can deliver for 30 seconds while maintaining at least 7.2 volts.

A battery’s RC represents the length of time a battery can maintain a vehicle’s electrical needs in the event of a charging system failure (alternator failure). BCI (Battery Council Industry) defines RC for a 12V SLI (Starting, lighting, ignition) battery as the amount of time (in minutes) that a battery can deliver 25 amps at 27 degrees celcius or 80 degrees farenheit while maintaining terminal voltage of at least 10.5 volts.

Batteries can easily be divided in two ways, by application and construction. The major applications are starting, dual purpose, and deep cycle.

The major construction types are WET (flooded), GEL (gelled), and AGM (Absorbed Glass Mat).

Sealed batteries are commonly known as maintenance free batteries. They are made with vents that (usually) cannot be removed.

A standard auto or marine maintenance free battery is sealed, but not fully leak proof. Sealed batteries have a valve allowing gas to vent during charging.

AGM (absorbed glass mat) batteries contain a glass mat separator that absorbs the electrolyte solution between the battery plates. The material’s design enables the fiberglass to be saturated with electrolyte – and to store the electrolyte in a “dry” or suspended state rather than in free liquid form.

Gel batteries are non-spillable, a silica gel is added to the electrolyte to reduce movement inside the battery case. To reduce gassing many gel batteries also use one-way valves in place of open vents, this helps the normal internal gasses to recombine back into water. Gel cells must be charged at a lower voltage than flooded or AGM to prevent excess gas from damaging the cells. Fast charging them on a conventional charger without using the appropriate Gel setting may permanently damage the battery.

Wet Maintenance free batteries are designed with Lead and Calcium alloy in the positive and negative plate chemistry or formulation.

A more functional and effective design than traditional batteries with removable vent caps.

Sealed batteries of this design have longer water retention and are a far more robust battery for today’s climates and conditions.

Other benefits are:
Less preventive maintenance due to less water loss
More forgiving when accidentally overcharged
Reduced terminal corrosion and ventilation
Lower discharge rate
Less risk to users due to it’s maintenance-free construction

Marine/RV batteries are available in three different versions–starting, dual purpose, and deep cycle.

The starting marine/RV battery is designed similar to that of a wet car/starting battery with carrying handles and is designed for high current and shallow discharges. The wet dual purpose marine/RV battery is a hybrid between a starting and deep cycle battery that is specifically designed for high vibration in marine/RV applications.

The deep cycle marine/RV battery is designed for deep discharge applications such as a trolling motor, golf cart, AWP and floor care equipment.

A marine/RV deep cycle or dual purpose battery will work as a starting battery if it can produce enough current to start the engine.

Good ventilation is required for all wet (or “flooded”) batteries to dissipate the gasses produced during charging.

For saltwater applications use only a sealed AGM or Gel Cell battery to prevent the formation of deadly chlorine gas that can occur if battery electrolyte is mixed with saltwater.

Absorbed Glass Mat (AGM) batteries have a glass mat between the plates. They have all of the advantages of the “Maintenance Free” batteries plus:

Much safer then wet batteries (due to hydrogen gas recombination during charging)

Do not require water

Lower self-discharge rate

In the perfect conditions AGM batteries can offer longer service life

Better vibration resistance & endurance

Can be used in saltwater applications

Spill proof and offers flexibility in mounting directions (follow manufacturers
guide lines)

Can be used inside a semi-enclosed area, like the passenger compartment or trunk

No sulfation from electrolyte stratification or water loss

Voltage/Electromotive Force (Volt,V,E): The electrical pressure driving electrons through a conductor.

Open Circuit Voltage (OCV): The voltage of a battery in the absence of a charge or discharge current.

Voltage Under Load (VUL): The voltage of a battery in the presence of a discharge current.

End of Discharge Voltage (EODV): The voltage of a battery at the end of discharge while under load.

End of Charge Voltage (EOCV): The voltage of a battery at the end of charge while still on charge.

Specific Gravity (SG): The density (mass/volume) of the liquid (electrolyte) relative to water, at the same temperature.

Ampere (A): The rate of flow of electrons. Electrical current.

Ampere-Hour (AH): A measure of current over time. Battery capacity (Ampere-Hour = Amps x Hours).

Watts (W): The rate of using energy to do work.      (Watts = Volts x Amps).

Watt-Hour (WH): The measure of power over time. Energy (Watt-hours = Volts x Amps x Hours).

Batteries must be appropriately charged to ensure proper mixing of electrolyte avoiding stratification.
Batteries should be charged after every use to ensure they are never stored in a discharged condition.
If batteries are stored for extended periods of time they should be charged frequently and should be connected to a smart battery maintainer.
Lead-acid batteries DO NOT have a memory affect (they do not need to be fully discharged prior to charging)

Always wear protective clothing, gloves and goggles when handling batteries

Do not smoke near batteries

Neutralize acid spills with baking soda immediately

Charge with vent caps securely in place

Provide proper ventilation during charging to prevent gas build up.

Keep flames, sparks or metal objects away from batteries (use insulated tools)

Keep batteries clean and dry

Check that all vent caps are tight

Check that all connections are tight (see recommended torque values)

Use a solution of baking soda and water to clean
if there is acid residue on batteries or corrosion on the terminals

Terminal protectors or protectant spray can be applied to terminals to reduce corrosion
Batteries should be fully charged prior to and during storage
Never store discharged batteries
Store batteries in a cool, dry place 
Recharge batteries prior to putting them back into service, ensuring they are fully charged