Battery Checking & Charging

Vehicles demand a lot from batteries, they power starter motors, run the car stereo, air conditioning, heaters. headlights and other accessories.  It is essential that batteries are maintained well and are taken just as seriously as any other car maintenance.

We classified batteries into two main types, maintenance free and Lead-acid batteries. 

Before working on car batteries, it is worth making a visual inspection.  Make sure that terminals are free of any corrosion, dirt and rust.  Terminals must be bolted tight for a good connection. Lose connections can affect the alternator's charging system as well as the battery's performance.   Make sure cables are healthy and not worn out.  Before working on the battery, it is recommended to disconnect the negative terminal.

Load testing:

If the battery is a lead-acid battery (non maintenance-free), the fluid level and density of the fluid must be checked first.

Hook up the load tester in parallel circuit (negative to negative, positive to positive) and check the voltage level of the battery.  Check the Cold Cranking Amps (CCA) of the battery. It will usually be around 250-350 CCA.  Turn up the load tester to 50% of the battery's CCA. (300CCA = 150A) this function simulates the battery's voltage level during the cars starting up process. If the voltage meter drops down to the red zone, the battery may need a full charge, or replacement.

To check if the charging system is running healthy,  start the car and let it idle. keep a multi-meter on the battery (hooked up in parallel) or the load tester, to keep an eye on the voltage level of the battery. Switch as many electronic components in the car as you can, including the headlights, stereo, heater, air conditioner etc.  If the voltage of the battery drops too low, or 11V or under, the alternator is not charging at full potential.  Causes of this may be loose or uneven alternator belt, bad terminal connections or cables, corrosion or rust.


States of charge:
100% = 12.6V-12.7V
75%   = 12.45V-12.5V
50%  = 12.3V-12.4V
25%  = 12.15V-12.2V


Assuming there are 6 cells in each 12V battery, each  cell should have at least 2.1V. If state of charge is less than 12.6V, check the fluid level and density of each cell.