## What should a battery read when car is off?

12.2 to 12.6 volts
When the probes touch the terminals while the car is off and the battery is resting, the multimeter display should show a reading of 12.2 to 12.6 volts (full charge). This voltage range means the battery is in good condition for starting the vehicle.

## How long does a car battery last with engine off?

New Car Batteries A new and fully car battery can stay for around two weeks without needing to be recharged from a generator. This battery will fully get discharged after approximately two to three months. If you leave the battery for roughly two and a half months, you will not be able to start the car engine.

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How do battery testers work?

Battery testers work by testing the current that comes from a battery. When something conductive is touched to both the positive and negative contacts on the battery, the current is released. If the temperature is higher, the battery has more current. The gauge changes color based upon the temperature.

### How long can a car run on battery without alternator?

In this situation, the battery could last as little as 30 minutes. If you are lucky and could get up to two hours. Note: In case you have to start the car without an alternator, don’t turn off the engine once you’re going. Starting the car flattens the battery down quickly.

### How is car battery capacity measured?

Multiply this number by two to find your battery’s true AH rating. For example, if your battery’s current was 12 amps and the voltage reached 12 volts after 10 hours exactly, then the battery capacity is 12 x 10 x 2 = or a rating of 240 AH in total.

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What causes a car battery to drain fast?

A short circuit may cause excessive current draw and drain your battery. Check the charging system for a loose or worn-out alternator belt, problems in the circuit (loose, disconnected or broken wires), or a failing alternator. Engine operation problems can also cause excessive battery drain during cranking.

## How to check a car battery voltage?

You can check a car battery voltage with a multimeter or buy a car battery monitor. Both are relatively cheap and easy to use. Check out our guide on checking a car battery with a multimeter. | Why the voltage of a car battery is important.

## What should the voltage of a fully charged car battery be?

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. If you don’t have a multimeter to tell you the voltage of your battery, you can do a test of your electrical system by starting the car and turning on the headlights.