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What do a battery’s different specs mean?

If you’re in the market for a new battery, you might be taking a look at the many great batteries available from Marshall. For beginners, or people who just don’t want to think about their cars that much, all the different specifications on a battery can become pretty overwhelming.

You want to be sure you’re getting the right battery for your car and the best performance in your budget, but how do you know what that looks like?

In this handy glossary, we’ll explain all the different specs you’ll find on a car battery listing from Marshall Batteries.

A glossary of car battery terms


In car batteries, acid refers to a chemical that can release hydrogen ions when mixed with water. For most lead-acid batteries, this is sulfuric acid.

AGM (Absorbent Glass Mat)

Some batteries use AGM technology. This refers to a special separator inside the battery that is made up of glass microfibers. These microfibers absorb and retain the electrolyte, meaning that if the battery becomes damaged the electrolyte will not spill. These batteries are maintenance free, as the electrolyte is suspended in a dry state rather and does not need watering.

Ampere (Amp, A)

Amps are the unit of measure for the rate at which electrons, or an electrical current, flows through a circuit.

Ampere-Hour (Amp-Hrs, Ah)
The amp hours of a battery indicate its capacity for electrical storage. So the higher the amp hours, the most power the battery can hold and therefore the longer it will last. This is obtained by multiplying the current’s amps by the time it takes to discharge the battery in hours. So, for a 5 amp battery that discharges after 20 hours, you’d get 100 amp-hrs or Ah.

Cold Cranking Amps (CCA)

Cold Cranking Amps is a rating used to define a battery’s ability to start an engine in cold temperatures. This is because a great amount of amps is required to start an engine in the cold, albeit only for a short burst. Simply put, the higher the CCA, the greater the starting power of the battery.


One battery cycle is a single discharge and a single recharge.

Deep Cycle battery

A deep cycle battery is designed to provide a steady, lower amount of electricity over a long period of time. It may provide larger surges, but is overall intended to give a sustained charge for appliances and security systems. The battery is intended to be deeply discharged many times.


Discharging is when a battery is in use, or delivering a current. Some batteries may be deeply discharged – which means a low current is being drawn from the battery. In a deep discharge, the actual voltage will fall below the final discharging voltage.


Electrolyte is a conductor that enables an electrochemical reaction, thereby generating electricity. In a lead-acid battery, the electrolyte is sulfuric acid diluted with water.


Gel batteries contain an electrolyte that has been immobilised using a chemical like fine silica. This is to prevent spillage, in lieu of an AGM.

Lead-acid battery

A lead-acid battery is what most people think of when they think of a car battery. It contains plates, lead and lead oxide with a solution of sulfuric acid and water.

Read more: What is a battery and how does it work?

Marine Cranking Amps (MCA)

MCA serves the same purpose for marine batteries as the CCA does for car batteries. While CCA is measured at 0°F, MCA is measured at 32°F. This is because marine batteries are typically never used at temperatures below freezing. Just like CCA, MCA is an indication of the starting power of a battery.


A maintenance-free battery generally requires no service watering during its lifetime.

Open-circuit voltage

Open circuit voltage is the voltage of a battery when it is neither delivering nor receiving power. Essentially, it is the “idle” voltage.

Reserve capacity rating (RC)

This rating represents the time a battery will continue to operate essential accessories if the alternator in your car fails. Your alternator will typically convert chemical energy into electric energy to replenish your car’s battery as your drive. However, if this fails, the battery will continue providing a current until its reserve capacity has run out. The RC is represented in minutes and is only indicative for a new, fully charged battery delivering 25 amps at 27°C.

Starting, Lighting, Ignition (SLI) Battery

Also called a starting battery, an SLI is your standard rechargeable battery for a passenger vehicle. It supplies electricity in a large short burst to power the motor, lights and ignition system of your car before the alternator kicks in to replenish what was discharged.


A volt is the unit of measure for electrical potential. If electricity were water in a pipe, imagine volts as the water pressure.


VRLA stands for valve-regulated lead-acid battery. These batteries don’t have free liquid electrolytes. They feature one-way burp valves that permit gas to vent from the cell as necessary while maintaining a slight pressure within the battery required to facilitate chemical reactions.


A watt is the unit for measuring electrical power, or the rate of doing work. Watts can be calculated by multiplying amps by volts.

Watt-Hour (Watt-Hrs, WH)

A watt-hour is a unit of measure for electrical energy, very simply expressed as watts multiplied by hours. While watts measure the amount of power provided at a moment in time, watt-hours are used to express the amount of energy used over a period of time.

Need help finding a new car battery?

If you’re not sure what to buy, don’t worry. We’re more than happy to help you find the best and most suitable battery for your budget and requirements. Holler for a Marshall on 1300 627 742 or contact us online for a new battery quote.

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