28-03-2024, 12:49 PM
John, this is how I was taught to test a battery, and I have tested thousands using this method.
Charge the battery with a fair bit of charge. Use your charger for a few hours or drive the car for at least half an hour.
Disconnect the charger and with battery disconnected put a voltmeter across the battery. It should read about 6.4 volts. If it's down at 6.1 then charge it for longer.
Re-connect the battery to the car and put voltmeter across the battery. Pull the starter for maybe 6 seconds and what does the voltmeter read? If starter motor is cranking the engine it might read around 5.0 volts for 6 or even then seconds. If it reads less, then the battery has failed the test.
If it does not crank the engine what voltage do you get? Less than 5 volts means battery has failed. No cranking and a voltage of 6 or more volts indicates there is a problem with connections somewhere or the starter motor itself. If you are at this stage, you simply do not know about the battery.
Charge the battery with a fair bit of charge. Use your charger for a few hours or drive the car for at least half an hour.
Disconnect the charger and with battery disconnected put a voltmeter across the battery. It should read about 6.4 volts. If it's down at 6.1 then charge it for longer.
Re-connect the battery to the car and put voltmeter across the battery. Pull the starter for maybe 6 seconds and what does the voltmeter read? If starter motor is cranking the engine it might read around 5.0 volts for 6 or even then seconds. If it reads less, then the battery has failed the test.
If it does not crank the engine what voltage do you get? Less than 5 volts means battery has failed. No cranking and a voltage of 6 or more volts indicates there is a problem with connections somewhere or the starter motor itself. If you are at this stage, you simply do not know about the battery.