Dead car battery symptoms — how to test your car battery
How can you tell if you have a dead car battery?
Dash lights mean nothing
If you turn the key and your dash lights come on, that does not mean the car battery is good. Why? Because it takes very little power to light up your dash lights. In many cases, it only uses a few amps. But starting your engine requires a minimum of 100 amps.
Rapid clicking when you turn the key is a sign of a dead car battery or corroded battery terminals
If you turn the key and hear rapid clicking, that means the starter motor is getting power, just not enough to fully engage the starter drive and crank the engine. Start diagnosing this by removing the battery terminals and cleaning the terminals and posts with a wire brush. Then reconnect and try starting the engine. If it start, then the corrosion was the problem.
You car battery is dead after it’s been sitting for a while
A shorted cell in a car battery can deplete its charge in a matter of a few hours.
Check battery state of charge and battery condition with a battery tester
Use a voltmeter to check your car battery voltage. A fully charged battery should read 12.6 volts and 12.2 volts represents a battery that’s 75% discharged. If your battery reads 12.6, that’s not the end of testing. Battery voltage only tells you the battery’s State of Charge (SOC). It does not tell you the battery’s State of Health (SOH).
To determine SOH, you’ll need a modern battery tester that performs a simulated load test along with a conductance/resistance test. These tests determine the condition of the lead plates and bus connections inside the battery. A battery can pass the SOC test but fail the SOH test. You should replace a battery that fails the SOH test because its an indication on impending failure.
Use a digital battery tester to test your car battery
To conduct a proper test, the battery tester need to know what type of battery it’s testing. If your tester doesn’t have settings for the different types of batteries, it’s obsolete.
For example, a car battery tester uses a different testing protocol for each type like, starting-lighting-ignition (SLI-also called a flooded lead acid battery), Absorbed Glass Mat (AGM), Spiral wound glass mat (Spiral), or Lithium (LiFePO4, LFP).
The Solar BA9 battery testing is an affordable tester that tests all the batteries above except lithium.
The “toaster” battery shown below is NOT reliable because it doesn’t have settings for SLI, AGM, or Spiral, so it will produce inconsistent results.
© 2012 Rick MuscoplatPosted on by Rick Muscoplat