Car battery voltage under load and without it. How to measure car battery voltage

Modern vehicles can have different types of lights, music players, televisions and other elements that create a load on the power source. Insufficient battery voltage of the car will not allow to ensure the full functioning of all devices and accessories. In this case, to achieve comfortable operation of the machine simply will not succeed.

Car battery voltage

The main causes of stress reduction

A car battery works on the principle of converting chemicals directly into electrical energy. When charging happens the opposite is true. During the operation of the device current is generated due to the deposition of sulfates on the plates.The concentration of the electrolyte decreases, and at the same time the internal resistance increases.

Most often, the vehicle battery voltage is lost for the following reasons:

  • battery life has completely expired;
  • the generator broke;
  • there is a leakage current through the wiring;
  • The circuit was not designed for a specific load.

The situation can be fixed in almost all cases, if we are not talking about the wear of the device. Normal voltage can be restored even when using the unit for several years. The mere measurement of current cannot be the basis for assessing the quality characteristics of a battery.

Normal car battery voltage

Indicators in normal condition

Ideally, the normal battery voltage of the car should not be less than 12.4-12.8 volts. With a decrease in performance, the power source is not able to ensure the full operation of the engine, but it can be started up with a good generator. However, it is not recommended to continue the operation of such a device, as coarse-grained lead sulfate may appear on the plates, which leads to a decrease in battery capacity.

The drop in performance to 11.6 volts indicates a complete discharge of the device. Its use in this state is not possible. It will require special recharging that can restore factory standards and get the output voltage of a normal car battery.

Auxiliary table

Knowing how many volts a measuring instrument shows, it is impossible to know the degree of wear of an electrical power source. However, to determine the approximate percentage of charging is quite realistic. To do this, use the table below.

Indications in volts

Percentage charge



































What should be the voltage on the car battery

Parameters under load

Above indicated the normal battery voltage of the car without load. However, it is impossible to determine the performance of the battery in this way. To do this, the device with a special plug must be given a load twice as high.

The duration of the working phase should be 4-5 seconds. The voltage should not fall below 9 volts. With a strong drawdown, first charge the battery and retest.The situation will not change if the battery resource is completely exhausted.

Normal voltage on the vehicle battery when the engine is running

Measured the number of volts and with the established motor. Under normal conditions, the operating voltage of a car battery should vary from 13.5 to 14 V. When the battery is low, the indicator exceeds the maximum value, since the generator is forced to operate in an enhanced mode.

In most cases, the increased voltage poses no danger. If everything is normal with electrical equipment, then it returns to its normal state 5-10 minutes after the engine starts. A constant increase in performance can lead to a recharge of the power source, which will boil the electrolyte.

Car battery voltage without load

When measuring, there is also a low voltage in the car battery. This indicates that the battery does not have time to fully charge. For testing, it is necessary to gradually turn on electrical consumers (lights, music, air conditioning and other devices), making measurements. With a faulty generator, the figures will fall by more than 0.2 V.

Influence of the winter season

Often, vehicle owners complain that battery parameters deteriorate at low temperatures. However, this is not quite true. When frost occurs, a change in the density of the electrolyte, which affects the production of current. However, with sufficient charge nothing threatens the battery. Therefore, to remove it in the cold season and bring in the heat is not necessary.

Removal of indicators using special devices

The above is theoretical information that allows you to familiarize yourself with the basic rules. However, you also need to know how to measure the voltage of a car battery. For the removal of indicators should be used special devices that are connected directly to the battery terminals. Testing is recommended at an electrolyte temperature of 25 degrees.

When carrying out measurements without load, a tester is usually used. It selects a specific mode of operation. The red contact is connected to the positive pole terminal, and the black contact to the negative terminal. The display should show the current value.

Indications in a closed circuit allows you to lock the load plug.It simulates the situation with the start of the engine, measuring the operating voltage in such conditions. The measuring device is connected to the release in the same way. A load is applied to the battery for 5 seconds.

Voltage on the vehicle battery when the engine is running

additional information

It is worth checking even the voltage of a new car battery after a long period of operation. With a poorly operating generator, it can gradually be discharged, which means that the voltmeter readings can be much lower than normal. To restore the allowable values ​​will require recharging.

It is not recommended to make measurements using the onboard PC, since the final result will have a significant error, which is explained by the specifics of connecting the device to the network. Approximate data to identify problems should not be used.

A comprehensive check of the battery should be carried out regularly. If the vehicle has not been used for several days, and the meter has shown a significant reduction in voltage, then the life of the power source will expire.

Features of battery operation

In order for the car battery voltage to be normal for a long time, you should follow certain rules.

  1. Immediately before starting the engine, it is necessary to disconnect electrical consumers. Load in one attempt should not exceed the time interval of 5-10 seconds. If the engine does not start from the fourth or fifth time, then it is necessary to diagnose the systems of ignition and fuel supply.
  2. Periodically required to check the integrity of the wiring of the car. The current leakage in the circuits leads to a rapid discharge of the battery, and hence the loss of operating voltage. Measurement of power loss should be made at service stations.
  3. When driving in the city in winter, when the engine runs at low speed, and there are quite a few consumers involved, it is advisable to recharge the battery with the help of stationary charging devices. In this case, the power supply device will last longer, producing the necessary current.
  4. The battery should be kept clean, especially for places near the pole terminals. It is recommended to wipe it with a cloth that is wetted in a solution of soda ash. You can also use ammonia mixture.

Car battery operating voltage

Battery recharge rules

The battery must be charged in a timely manner so that the voltage during the operation of the vehicle is optimal. In the implementation of this event it is necessary to follow a number of rules.

  1. Charging should be done at a temperature of more than 0 degrees.
  2. Before connecting to the electrical network, the filler plugs are unscrewed and left in the mounting holes.
  3. It is necessary to use a device capable of providing a voltage of 16 volts.
  4. Twist the plugs should not be within 20 minutes after completion of charging, so that the accumulated gases were able to freely go outside.
  5. The room must have ventilation.
  6. The criterion for the completion of the charge will be the achievement of the optimal voltage or density of 1.27 g / cc. cm.
  7. The temperature of the electrolyte inside the device connected to the network should not exceed 45 degrees.
  8. Current measurement is recommended 8 hours after charging.
  9. If there is an indicator, the time of disconnecting the device from the network is determined by it.

Voltage new car battery

Final part

Each driver does not hurt to study the information about what should be the voltage on the vehicle battery.With its help, he will be able to accurately determine the level of charge and battery performance. Measurements should be carried out in both static and dynamic mode using the aforementioned devices. If necessary, the power source should be charged in accordance with the basic rules.

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