Measuring the voltage helps you to get a clear idea about the recently charged status of a car battery. It is unnecessary to say what’s the importance of a battery to start cars. Understanding the battery’s condition and voltage, you can use any multimeter, or voltmeter, or manually. Now, the question is how many volts is a car battery?
A car’s battery voltage varies depending on the engine conditions. When the battery is fully charged and the engine is ON, the voltage is from 14.1 to 14.8 Volts. It can drop to 12.1 Volts when the charge is 50%.
If you prefer to learn more about car battery voltage charts, you will turn to our writing.
How Many Volts Is a Car Battery?
The standard and the most common nominal voltage of a car have 12 volts. It is only a traditional calculation. But, this amount of voltage can be up or down depending on the engine’s position. Sometimes it reaches 0 volts and sometimes over 15 volts. While the engine is turned on or turned off, the voltage is changed quickly.
Chemistry is also important to check the voltage of a car battery. The very common car battery chemistry is lead-acid batteries. They can be Absorbent Glass Mat (AGM) batteries, enhanced AGM batteries, wet/flooded batteries, enhanced wet/flooded batteries, batteries with calcium plates, Gel-Cell batteries, batteries with pure lead plates, and similar.
These batteries have different voltages especially in the condition of fully charged, fully discharged, or semi-charged. Even though there are several temperatures. Now, we talk about the voltage level when the engine turned ON and turned OFF.
Engine Turned ON
You know, at the time of engine running, the alternator will charge the battery. Even with the new car battery, you don’t need to charge for starting the car. Check this helpful post to know the details.
Engine running, the voltage will be from 13.5 to 14.7 volts. Somehow the car battery voltage can be below 13.5 volts. Then, use the alternator to recharge the battery. So, start the engine again. The battery starts charging automatically.
Ultimately, if the turning in your engine and voltage is up to 13.7 volts, your battery is charged fully.
On the other hand, to get actual data about lead-acid batteries, you should know about charging voltage-temperature charts. The average value is -4mV/°C/cell and the starting to maximize range -3mV/°C/cell to -5mV/°C/cell.
Engine Turned OFF
Another engine condition is turned OFF. At this moment, you have to disconnect the battery and turn OFF the light, fan, multimedia, audio, and others. If necessary, you can keep ON your hazard lights. But, it is harmful to the car battery to continue for 60 to 90 minutes.
The drain current is not a major fact in voltage measurement. Here is a table of standard wet/flooded and standard AGM batteries measurement of charge at 77°F or 25°C.
|Type of SoC||0% SoC||25% SoC||50% SoC||75% SoC||100% SoC|
|Flooded/Wet||11.89 Volts||12.06 Volts||12.24 Volts||12.45 Volts||12.65 Volts|
|AGM||11.80 Volts||12.00 Volts||12.40 Volts||12.60 Volts||12.80 Volts|
So, the above standard flooded/wet and AGM batteries voltage chart is not enough to understand it completely. The voltage rate can be different for several brands. Such as Odyssey AGM batteries have different SoC/voltage relations:
|Percent of SoC||Voltage|
|100% SoC||12.84 volts or higher|
|75% SoC||12.50 volts|
|50% SoC||12.18 volts|
|25% SoC||11.88 volts|
Fortunately, if you have a digital multimeter, you can measure the voltage with ease and accuracy. Remember, the temperature is another important thing when you measure the car battery voltage, charge, or discharge rate.
At the condition of engine OFF, the battery is not charged automatically. Considering the battery SoC and temperature, you will find the rate of voltage-temperature of the
standard flooded and AGM battery. See the table where find 0 to 120°F or -17.8 – 49°C temperature range of voltage.
|% of the SoC||Standard Flooded Battery||Standard AGM Battery|
|100% SoC||12.52 to 12.66 V||12.67 to 12.81 V|
|75% SoC||12.32 to 12.46 V||12.47 to 12.61 V|
|50% SoC||12.11 to 12.25 V||12.27 to 12.41 V|
|25% SoC||11.93 to 12.07 V||11.87 to 12.01 V|
|0% SoC||11.76 to 11.90 V||11.67 to 11.81 V|
Note: It is tough to check the voltage by observing SoC and temperature range.
An actual CCA rating is also crucial to test the battery voltage. How?
First of all, Cold Cranking Amps (CCA) means the ultimate currency of the 12 volts battery or fully charged, or a new battery delivering for 30 seconds. The low voltage is not below 7.2 volts at -18° C.
CA and MCA?
CA (Cranking Amps) and MCA (Marine Cranking Amps) also indicate the ultimate current of a new, fully charged, 12V battery delivering for 30 seconds. The low voltage is not below 7.2V at 32°F (0°C).
So, CCA, CA, and MCA are very useful to test the indicated stress.
Average Voltage Chart
The following chart indicates what the average voltage is at various states of charge and operating situations. This is intended as a guide only.
|Engine Position||Average Voltage Chart|
|Engine Starting||10.0 Volts|
|Engine Running||13.5 to 14.7 Volts|
|Fully Charged (Engine On)||14.1 to 14.8 Volts|
|Fully Charged (Engine Rest)||12.6 Volts|
|50% Charged (Engine Rest)||12.1 Volts|
|25% Charged (Engine Rest)||11.7 Volts|
|0% charged||10.0 Volts|
So, fully charged automotive batteries can measure 12.6 volts. When your car engine is running, this measurement might be 13.5 to 14.7 volts. And, the measurement should be 10.0 volts when the engine is starting.
Instead of using a multimeter to find the voltage, it is possible to check the electrical system to start a car along with turning on the headlights. When you notice that headlights are dim or often light off, the battery has no charge or low battery. Lights can be bright if your engine starts. But, this alternator current is not sufficient to fully charge your battery.
What is a Good Voltage for a Car Battery?
12.6 volts is a good voltage when the engine is at rest. This voltage indicates that 12-volt automotive batteries are fully charged.
What Voltage Is Too Low for a 12 Volt Battery?
For any 12 volts battery, the minimum voltage is needed at 12.0 volts. If the voltage is less than 12.0 V, it should be recharged again as fast.
Are 11.9 Volts Enough to Start a Car?
11.9 volts suggests the battery is fully discharged. Less than 12.2 volts, the battery is starting to discharge. If your battery is healthy, the multimeter display should exhibit a reading of 12.6 volts. So, 12.2 to 12.6 volts is a great range of batteries to start a vehicle.
What Voltage is too Low for a Car Battery?
11.75 volts to 11.89 volts is too low and the vehicle can die due to the low voltage. In this situation, if you try to start the engine, the engine fails frequently.
Don’t think that a fully charged battery or 12.6 volts don’t always work for producing the required current. You should check the battery from time to time. Remember, when the car battery has not enough charge or less than 12.2, car owners have to recharge the battery as soon as possible.
Anyway, this article already provided plenty of information about the car battery voltage and necessary charts.
Good luck and happy riding!
About This Writer
Hi, I am responsible for the 'Homeowners Power Solutions' category. My name is Liam Jaxon and a licensed technician with 7 years of experience in vehicle batteries, electrical gadgets, and home appliances. My working experience in different residential & light commercial electrical sectors and the automobile industry helped to acquire vast knowledge in this industry.