How to Check your Car Battery

AutoTrader NZ
Published 9 September 2020

Below is a step by step guide on how to check your car battery and some warning signs as well as other issues relating to your car battery. Checking your car battery at least once a year is vital to make sure you don’t get caught out with a car that won’t start.

All car batteries are different and some can last 6 years while some can last just 2. Batteries also do not like the cold, so you may find if you end up in a cold environment that your battery isn’t working 100%. 

Batteries are specific to each vehicle. It is best to talk to a professional about which fits your vehicle so you can get the right size and specifications for your vehicle. When replacing your battery always make sure you have the correct CCA rating (cold cranking amp rating), the (Ah) or ampere hour and the size. Some vehicles, especially modern vehicles, need the battery calibrated to the ecu to work properly. 

Visual inspection

Some batteries have a diode on top that will be green if the battery is good and black if it is not. 

Multimeter Steps

  1. Find a multimeter or battery tester and make sure it can test and is set to dc voltage.
  2. Have your engine off and locate the battery under your bonnet (or boot in some cases) and find the negative and positive terminals (lift up the plastic cover of the terminals if they have them).
  3. Put the positive and negative prongs on the battery terminals and make sure your prongs positive (red) and negative (black) are on the corresponding terminals. You should have a reading around 12.5 volts or higher. Make sure you do the test in the morning before driving the car with the engine fof as you will get a more accurate reading. 

Underlying issues that are not because of a bad battery 

  1. Parasitic loss, this happens while your vehicle is off and has to do with electronic components in the car drawing electricity when the car is not being driven.
  2. Your alternator charges your battery and if this is not working properly your battery will not charge properly, this can often be misdiagnosed as just a bad battery so it is best to test your alternator as well as your battery.