"Did you ever wonder about the meaning of terms used in battery literature?"
By The Engineers at Die Hard Battery

Did you ever wonder about the meaning of terms used in battery literature? Here, courtesy of the customer-friendly engineers at DieHard marine batteries, is a short glossary of the most widely used marine battery terms:

AMP (Amp, A)-- Short for ampere. The unit of measure of electrical current through a circuit. A 10-AMP battery charger will recharge your battery twice as fast as a 5-AMP battery charger.

AMP HOURS (Ah) -- This is the unit of measure for a battery's electrical storage capacity. To determine a battery's ampere-hours, you multiply amperes by hours of discharge.

BATTERY GROUP SIZE -- Spec chart designation identifying battery sizes by the Battery Council International. Standard batteries for marine use are sizes 24 and 27.

COLD CRANKING AMPS (CCA) -- This is the discharge load in amperes which a new, fully charged 12-volt lead-acid battery at 0-degrees Fahrenheit (minus 18 Celsius) can continuously deliver for 30 seconds and maintain a terminal voltage of at least 7.20 volts.

MARINE CRANKING AMPS (MCA) or CRANKING AMPS (CA) -- The discharge load in amperes which a new, fully charged 12-volt lead-acid battery at 32 degrees Fahrenheit (0-degrees Celsius) can continuously deliver for 30 seconds and maintain a terminal voltage of at least 7.20 volts.

DEEP CYCLE -- A battery specifically designed to repeatedly run heavy loads and accessories in boating and marine applications.

ELECTROLYTE -- Another term for battery acid. This is the liquid or gelled solution of water and sulfuric acid in a lead-acid battery.   Electrolyte conducts and participates in the electrochemical reaction within the battery. In a fully charged lead-acid battery, the typical weight proportion of the electrolyte is 35 percent sulfuric acid and 65 percent water.

GASSING -- Gassing occurs when a 12-volt lead-acid battery is charged above 13.8 volts, causing the water to decompose into hydrogen and oxygen gasses. The amount of gassing depends on the portion of the charge current that is not absorbed by the battery and the on-charge potential of the battery.

GELLED ELECTROLYTE -- This is a jelly-like electrolyte mixture of sulfuric and phosphoric acids, fumed silica and pure water. Gelled electrolyte is used in some marine and wheelchair batteries because it won't spill. Factory sealed batteries with gelled electrolyte, called Gel-Cell batteries, can provide power even if fully submerged in water or turned upside down.

HYDROMETER. -- This is a device with a float used to measure specific gravity of the liquid electrolyte in a lead-acid battery.

OPEN CIRCUIT VOLTAGE -- This is the electrical potential of a battery at rest, when it is neither delivering nor receiving power. It is typically 12.67 volts for a fully charged lead-acid battery.

RATED (20-HOUR) CAPACITY (Ah) -- The conventional means for declaring the capacity of a lead-acid battery. It is the ampere-hours that should be delivered by a new, fully charged 12-volt lead-acid battery at 80 degrees Fahrenheit (27-degrees Celsius) during a continuous 20-hour discharge period and maintain a terminal voltage of at least 10.50 volts.

RESERVE CAPACITY (RC) -- The number of minutes which a new, fully charged 12-volt lead-acid battery at 0-degrees Fahrenheit (27-degrees Celsius) can be continuously discharged at 25 amperes and maintain a terminal voltage of at least 10.50 volts.

SPECIFIC GRAVITY -- This is the density of the electrolyte compared to water. Typically, the electrolyte in a fully-charged lead-acid battery is 1.265 times denser than water at 80-degrees Fahrenheit (27-degrees Celsius).

VOLTAGE -- The unit of measure for electrical potential.

WATER EVAPORATION -- This is the major cause of battery failure.   When water in battery acid evaporates, the lead plates are exposed and can corrode.

Marine Battery Care

Battery Tips from the Engineers at DieHard Battery Starting (or cranking) batteries are designed to deliver short bursts of high-current electricity to the starter motor of the boat engine and to handle shallow cyclingand light electrical loads. Starting batteries use many thin plates with low density active material and low antimony or calcium lead alloy grids to maximize starting power and minimize water consumption.

Deep cycle batteries are designed to repeatedly provide electrical power to low-to-medium loads such as trolling motors and pumps over longer periods of time. In contrast to starting batteries, deep cycle batteries use fewer plates but thicker plates with denser active material and higher antimony lead alloy grids.

Allowing any marine battery to sit in a discharged state for a long period of time will damage the battery's energy-storage capacity and shorten its useful life. The battery's grid metal corrodes much faster in weaker electrolyte, and sulfate build-up on the battery's plat surfaces inhibits recharging.

Maintain your battery's electrolyte level to within one-fourth of an inch below the bottom of the vent well splash ring. Use only distilled or de-ionized water, and give your battery an equalizing charge to mix the electrolyte after adding water.

A slight over-charge is OK for a deep-cycle battery but too much over-charging creates heat which causes the plates to shed their active material. This reduces its energy storage capacity. A 12-volt, fully automatic battery charger with a 10 or 20-amp rating is recommended for most overnight charging situations.

Before storing a battery, add electrolyte to the recommended level, recharge it and wipe the surface with a mixture of baking soda and water. Store it in a cool place. Today's plastic-cased batteries can be stored on a cement floor. Do not store a battery where temperatures are often below freezing.

Batteries self-discharge due to local action and temperature and may need an occasional charge boost during periods of inactivity.

The state-of-charge of a battery can be easily checked with a hydrometer or voltmeter. A new, fully charged marine battery will have a specific gravity range of 1.265 to 1.290 at 80 degrees Fahrenheit and an open circuit voltage range of 12.6 to 12.8 volts.