Batteries with open cells may read fully charged in idle, but they fail under a load test every time. Once a battery reaches this point, there is no going back. The best thing to do is recycle the thing. … The only tools you really need are a battery charger and a digital voltmeter.
Can a car battery have 12 volts and still be bad?
Yes it can be bad if it’s output is 12 volts with no load and the engine not running… Load it down and watch the voltage drop… The starter is a good load to use for measuring the output under load.. Even a new battery voltage will drop with the starter running, but the battery should easily crank the car….
Can a car battery test good but be bad?
As long as battery voltage remains above 9.6 volts, the battery is considered “good.” But if it drops below 9.6 volts by the end of the test, the battery may be “bad,” or the battery may have to be recharged and retested if it was not fully charged prior to the test.
What should a fully charged car battery show?
Fully charged automotive batteries should measure at 12.6 volts or above. When the engine is running, this measurement should be 13.7 to 14.7 volts.
How do you know if you have a bad car battery?
How Do I Know if My Car Battery is Bad?
- Battery light illuminated on the dashboard.
- Engine cranks slowly when starting.
- Vehicle requires frequent jump starts.
- Clicking when you turn the engine.
- Lights are dim.
- Car won’t start.
At what voltage is a car battery dead?
A fully charged battery should register at 12.7 volts or more. If the voltage falls below this number, the battery should be recharged. A battery is only charged by one quarter at just 12 volts. Once it drops to 11.9 volts, your battery is considered dead.
What voltage should a 12 volt car battery read when fully charged?
12.6V volts or above – Your battery is healthy and fully charged. No further action is required. 12.5 volts – Your battery is at a healthy state of charge, but we’d recommend re-checking it within a few days to ensure the voltage hasn’t dropped any further.
How do I know when my car battery needs replacing?
How to Know When it is Time to Replace Your Car Battery
- 1) Your Battery Struggles to Combat Seasonal Challenges. …
- 2) Your Car Has Been Sitting For Too Long. …
- 3) Your Vehicle Struggles When Starting. …
- 4) Your Battery Is Older and Triggers a Dashboard Light. …
- Alternative Starting and Battery Problems.
Why does my car keep dying with a new battery and alternator?
Some of the most common reasons for a car battery to die repeatedly include loose or corroded battery connections, persistent electrical drains, charging problems, constantly demanding more power than the alternator can provide, and even extreme weather.
Can battery testers be wrong?
They may also provide a code for the failed test. The best way to check a battery is still with a carbon pile tester similar to the one Eric uses in his videos. I’ve had expensive digital testers give false results on batteries that will immediately pass a carbon pile test.
How do you tell when a battery is fully charged on a battery charger?
What should a battery charger read when fully charged. On the 12 amp charging setting, the needle will settle at around 6 amps, or just under. This is showing that the battery is fully charged. On the 2 amp setting, the needle will settle near the end of the small red triangle.
How accurate are car battery testers?
Measuring the open circuit voltage and checking the internal resistance do not provide conclusive evidence of battery state-of-health. A dead battery is easy to check and most testers are 100 percent accurate. The challenge comes in evaluating a battery in the 80–100 percent performance range while in use.
How do I know if my alternator is bad?
7 Signs of a Failing Alternator
- Dim or Overly Bright Lights. …
- Dead Battery. …
- Slow or Malfunctioning Accessories. …
- Trouble Starting or Frequent Stalling. …
- Growling or Whining Noises. …
- Smell of Burning Rubber or Wires. …
- Battery Warning Light on Dash.