The vehicle relies on car battery voltage for the most basic function which is starting the engine. One of the main reasons why the car won’t start is when the battery cannot produce the necessary voltage.
Diminishing car battery health can result from electrical system problems. For example, Blown fuses, faulty wiring, corrosion, faulty alternator amongst others.
The standard car battery charge goes up to 12 Volts. Therefore, if you’re using a car battery charger after your car battery capacity is depleted, it will automatically shut down after reaching the standard 12 volts.
By now you have noticed that we aren’t talking about the electric car battery. Instead, we are focusing on the combustion engine car battery.
Car battery voltage.
The car battery voltage varies between when the engine is running and when it is off. It is recommended that you test the car battery voltage when the engine has been off for a substantial amount of time.
It is important to test the battery voltage on a regular basis so as to identify a bad car battery before it causes you to become stranded.
Fully charged car battery voltage.
When buying a new car battery, it usually has a battery life of up to 3-5 years. Before starting the vehicle, the battery voltage is usually between 12 volts to 12.8 volts. However, this changes when the car engine starts and runs for sometime.
Because the vehicle charging system recharges the battery and gets the voltage up to 13.5-14.7 volts. A 12 volt engine will not have a battery that exceeds 14.7 volts.
However, you will not need the full charge battery capacity to start the car engine. The only amount of voltage that you need for engine starting purposes is 10.8-11.8 volts.
Therefore, the battery doesn’t have to be fully charged when starting the vehicle. If the battery cannot maintain this amount of volts, then you might need a car battery replacement.
Car battery charge chart.
| Battery use | Starting battery voltage | Impacts on the vehicle |
| Before start | Less than 10.8 Volts | Will not start the vehicle. |
| Before start | 10.8 to 11.8 Volts | Vehicle starts if applieances are off. |
| Before start | 11.8 to 12.8 Volts | Starts normally. |
| After start | 12.8 to 13.2 Volts | Battery won’t recharge. |
| After start | 13.2 to 14.8 Volts | Battery recharges normally. |
| After start | More than 14.8 Volts. | Excess volts damage battery. |
You will need a car battery voltage tester to check on the battery voltage as a regular car maintenance activity. If your car battery test reveals that the charge is below 10.8 volts, then you may have to jumpstart the car battery.
How to measure car battery voltage
You should not use the car battery charge up to below 10.8 volts. Because at this voltage point, the battery won’t be able to power the vehicle engine starting process.
Car battery life varies from one type of battery to another. For example, lead-acid battery and lithium-ion battery. But their voltage reading will be very close or even similar.
In order to measure the battery voltage, you will need a multimeter device. You do not need to be a mechanic for this.
The multimeter is a device that’s used to measure an electrical sources’ resistance, amps and volts. When it comes to car batteries it provides accurate information which can help you to conclude on the battery health.
Make sure that the vehicle engine has been off for a substantial amount of time. At least an hour and more.
a]. Car battery preparation.
Before you sort out any car battery issues, you need some basic knowledge about its location and the two terminals (+ve and -ve ). After locating the battery, differentiate the two terminals.
You can do this based on the different colors of their plastic covers. Whereby the positive (+ve) terminal commonly wears a red cover and has a + sign on it. Alternatively, the negative (-ve) terminal commonly wears a black top cover and has a – sign on it.
Follow the correct process of disconnecting the car battery in order to clean off any corrosion caused by battery acid and other elements. Otherwise, if you don’t clean the corrosion, you will not get an accurate voltage reading. Further, battery safety demands that you wear protective gloves during this activity. Additionally, remove your watch and ring before handling the car battery.
b]. Set up the multimeter.
First thing you need to do is to choose the right multimeter measurement setting. Make sure that you select the DC or DCV for direct current voltage measurement. Understand that the multimeter devices vary from one to another. Next, set up the dial meter voltage range to 20 volts.
i.] Connect the probes.
Before you connect the probes there is a step that you have to undertake while the vehicle engine is off. It is going to ensure that you get the correct reading.
Make sure that you turn on the headlights for around two minutes before even disconnecting the battery terminals. This will get rid of the surface charge that had accumulated when the charging system recharged the battery after the engine was running.
There is a constant battery safety rule that states that only one terminal needs to be connected during disconnection and reconnection. Therefore, you will start with connecting the positive multimeter cable to the positive battery terminal.
Afterwards, just touch the negative battery terminal with the negative multimeter cable. You will not have to connect the negative multimeter cable clump onto the negative terminal.
c]. Read and interpret the voltage.
One reading is not enough to determine the battery health unless the multimeter shows the reading of a fully charged battery. Otherwise, there’s a little more that needs to be done.
The device display should show a voltage that is between 12.2 to 12.6 volts. This is an indication that your car battery is fully charged. Therefore, the battery and the vehicle electrical system are in a good condition.
Alternatively, if the reading shows anything less than the 12.2 voltage mark, it is an indication that there are some care battery issues. It could be a sign that you need a new car battery or you need to investigate the vehicle’s electrical system components.
Recharge the car battery using a charger or start the engine so that the vehicle’s alternator can recharge the battery. The first reading is known as a resting battery voltage.
i]. Crank cycle battery voltage reading.
This is the second test you will need to undertake. Though it is not compulsory, this car battery voltage test will help you determine the health of your car’s electrical system components that recharge the battery.
Ensure that all the battery terminal connections are in place. Next, start the car engine while the multimeter device is also connected to the battery terminal clumps.
Check the multimeter reading to see that the voltage drops due to the cold cranking amps used in the engine starting process. The standard drop should go from 12.6 volts to 9.8 or 10.8 volts.
In case the voltage falls below this level, it means that you need a new battery. After a minute or two, the voltage should start rising again steadily. It should rise up to 13.8 or 14.5 volts while the engine is idle.
How to test car battery voltage without a multimeter.
This type of test will only indicate the car battery health condition in relation to holding charge. However, you will not find out the amount of voltage through this test.
- Make sure that the gear is set to park mode and engage the parking brake.
- The engine must be turned off.
- Turn on the vehicle headlights while the engine is off.
- Get a friend to turn the engine on while you’re in front of the car and you’re looking at the headlights.
If the headlights loose brightness while the engine turns over, the battery has insufficient charge.
Perform an alternator test.
Car battery technology is designed in such a way that the battery recharges when the engine is running. Despite whether, the engine is idle or you’re driving.
This is possible because of the alternator. Therefore, how do you test that your alternator is in a good condition to recharge your car battery?
- Starting the car engine and let it idle.
- Connect the multimeter cables to the battery terminal clumps.
- Turn on all electrical appliances in the vehicle. For example, the stereo, lights, ac and accessories.
- Observe the multimeter reading.
When all electronic appliances are turned on while the engine is running, the exert a certain level of energy up-take on the car’s electrical system. Therefore, if you observe that the multimeter voltage reading drops below 13.5 volts, there is a problem with the alternator.
Because the alternator should be responsible for supplying electric current to the electrical system appliances. Therefore, a drop in the multimeter voltage reading means that there is an electric current demand overflow to the car battery’s charge.