Battery Basics

What are the functions of a battery?

The primary purpose of a standard automotive battery is to provide power to a vehicle's starter. To start the engine, electricity from the battery is used to operate the starter motor and to provide current for the ignition system during engine cranking.

When the engine is running, electricity from the battery may be needed to supplement the charging system when the vehicle's electrical load requirements exceed the charging system's ability to produce electricity. The battery also serves to ensure that should the car's alternator malfunction, there would still be some power left to get the car running for a limited time - hopefully enough to get to the intended destination.

When the engine is off, electricity from the battery is used to operate lighting, accessories, or other electrical systems.

Moreover, the battery acts as an electrical shock absorber, protecting vital electrical components from burning out during high voltage/current output. Developments in automotive technology have resulted in more sophisticated pieces of equipment becoming regular fixtures in today's vehicles. Since these gadgets continue to draw power even when the key is turned off, batteries have to deliver more power to serve the car's requirements.

What does RC and CA stand for?

"RC" stands for Reserve Capacity and is a very useful industry rating (for consumers) that refers to a battery's ability to maintain low amperage load for the automobile's ignition, lights and other vital electrical equipment should the alternator fail. RC is defined as the number of minutes that a battery can be discharged at 25 amperes until the voltage drops to 1.75 volts per cell or 10.5 terminal volts for a 12-volt battery.

"CA" stands for Cranking Amperes. This is the load discharged in amperes by which a new fully-charged battery at 0 degrees Celsius (32 degrees Fahrenheit) can continuously deliver for 30 seconds and maintain a terminal voltage equal to or higher than 1.20 volts per cell.

What does AH stand for?

"AH" stands for Ampere Hour and is a unit of electrical capacity. This tells you how much electrical energy the battery will store.

  • The total energy, expressed in ampere hours , that a battery can deliver continuously for a specified period of time ,when discharging continuously at a specified rate, to a specified cut-off voltage
  • Ah @ 20 ; AH @ 10  

Some say that "bigger is better" as far as batteries are concerned. How true is this?

Since today's vehicles are equipped with numerous advanced electrical gadgets, choosing the right battery can be a tough task. Original Equipment batteries are rated at the minimum required rating, since they are designed for cars with all the Original Electrical Equipment in place. But once you start putting additional accessories like high-powered stereos, amplifiers and so on, it will certainly have an effect on the electrical system/battery requirements of your car.

As suggested earlier, it is best to install a battery of HIGHER CAPACITY (AH, CCA or CA, RC) if you have installed additional electrical accessories. This is to ensure a margin of safety and better battery performance. Should you decide to install a bigger and more powerful battery, please note the following tips when carrying out the installation:

  1. Fit the battery first. Does the battery have a height clearance or fitting problem? If yes, do not proceed with the installation. Does the acid tray fit? If not, purchase a tray that will fit the battery. This is to protect your undertray from acid corrosion Does the battery hold down fit? If not, purchase a hold-down that will fasten the battery to the vehicle.
  2. Check if the new battery's gas exhaust vents directly face your car's electronic module. Some designs have their exhaust gas vents located on different sides of the cover (for MF-sealed batteries). Vents with direct exhaust may damage your vehicle's electronic control module.
  3. Always consult a battery expert or technician first before attempting to install a battery.

How do I determine the correct battery and power requirements for my automobile?

The best way is to consult your vehicle owner's manual. Your car dealer may also assist you in your car's minimum battery/power requirement. The OMMC's outlets and dealers are furnished with battery replacement manuals that specify the vehicle make, model and year along with the recommended OMMC battery size and capacity rating.

Note: Never use a battery with a capacity rating LOWER than what the vehicle manufacturer/Original Equipment recommends.

It is important to select a battery type that is consistent with your vehicle, its application, and your driving requirements or patterns. OMMC distributors will gladly help you make the right choice.

What is the average service life of a battery?

A battery lasts for 2 to 3 years depending on the weather and road conditions, electrical load of the car and the specifications of the battery.