A typical 12-volt auto battery will have around 12.6 volts when fully charged. It only needs to drop down to around 10.5 volts to be considered fully discharged. If it drops down below that, the battery will become damaged due to excessive sulfation.
If the measured reading is less than 12.2 volts, the battery's resting voltage is weak, which means it most likely needs to be charged or replaced.
With the engine off, you should get a reading of 12.6 volts. If the battery isn't fully charged, it will diminish to 12.4V at 75%, 12V when it's only operating at 25%, and down to 11.9V when it's completely discharged.
When the voltage of the starting power supply is lower than 11.8V, it will be difficult to start the car. You can choose to turn off all other electrical appliances and try several times. When the battery voltage is lower than 10.8V, it is generally impossible to start the car.
12.0 volts or below - At 12.0 volts your battery is considered to be fully discharged or 'flat' and should be recharged as soon as possible. The lifespan of your battery will be severely affected if it remains within this voltage range for extended periods of time.
Generally, when the engine is not running, the battery voltage should be at least 12.6-12.8 volts. If the voltage is around 12V, the battery will probably be able to crank the engine. If the voltage is below 11.7-11.8V, the battery will probably NOT be able to crank the engine.
Your battery is fully charged when the reading is between 12.65 and 12.77 volts. You are 75% charged if you have 12.45–12.54 volts, 50% charged at 12.24–12.29, and 25% charged at 11.99–12.06 volts. 11.75–11.89 volts indicate a dead battery.
voltage is too low if your multimeter measures anything less than 12.45 volts. If your multimeter measures anything less than 11.6 volts, your car battery should be replaced.
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.
The next step in determining whether your battery is bad is performing a load test. Have a friend start the car while you watch the voltage on the multimeter. It should drop no more than two volts while the engine cranks. If it drops any more or dips below 9.5 volts, you need a new battery.
11.9v indicates the battery is completely discharged. Anything under 12.2v means the battery is in a state of discharge, and a healthy battery should show 12.6v in a static state. Yours needs to be replaced.
When the battery measures only 11.6 volts that indicates about 15% of fully charged, so it is mostly discharged or weak, or on its way to dead. It might start the car, but is barely strong enough.
A fully charged car battery should have a voltage of around 12.6 volts. When the battery voltage drops below 12 volts, there is a possibility that it won't have enough power to start the car. It is recommended to have a battery with a voltage of at least 12.4 volts to ensure a reliable start.
Answer: You would rather be safe than sorry when it comes to your car battery, as it is best to avoid getting stuck without a functional vehicle due to a dead battery. Therefore, most mechanics will recommend that you get your battery replaced when it reaches 50% of its full capacity charge.
A car battery that is providing 12 volts may still have a low SOC, which means that it does not have enough power to start the engine or run the vehicle's electrical systems.
A 12V battery with a voltage of 11.4V or less is fully discharged. Under 10.7V, a lead acid battery is dead. Lithium-ion and Lithium-polymer batteries also have a dead voltage – what this is depends on the battery configuration.
What Voltage Should My 12v Battery Show? A fully charged 12 volt battery should read at 12.6 volts on the multimeter. If the reading is lower than this, you'll want to charge your battery with either a battery charger or by taking your car for a drive.
So, how low are we talking? A typical 12-volt auto battery will have around 12.6 volts when fully charged. It only needs to drop down to around 10.5 volts to be considered fully discharged. If it drops down below that, the battery will become damaged due to excessive sulfation.
Anything below 12 volts is flat & 12 volts is about 50% charged,12.4 volts is 75% charged & 12.6+ volts is 100% charged ! In short: if it measures 12V or less then it is around 20% charged or less. A fully charged battery should measure 12.7V.
The resting voltage should ideally be no lower than 12.6V. Bear in mind that when a battery goes down to 12.2V it's actually only 50% charged, and below 12V it's classed as discharged.
As you can see, a voltage of 12.1V means your battery is operating at only 50% of its total charge. If your battery drops to a voltage of 11.9V or less, you're going to notice a serious drop-off in performance. Once it goes down to 11.6V, the battery is almost completely discharged.
The National Electrical Code says that a voltage drop of 5% at the furthest receptacle in a branch wiring circuit is passable for normal efficiency. For a 120-volt 15 ampere circuit, this means that there should be no greater than a 6 volt drop at the furthest outlet when the circuit is fully loaded.