How to check the capacity of a car battery?

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

The battery is a reusable current source used for autonomous power supply of various devices, and in this case, a car. Therefore, over time, the volume of capacity may decrease, as a result, the time of its operation without additional charge decreases.

Battery units

Nominal capacity - this unit is most often used to determine the electric charge of power sources. The nominal capacity of a car battery is expressed in Ah, that is, in ampere-hours, or Ah (Ah - ampere - hour in the English abbreviation).

Electrical voltage is measured in volts, V. Batteries used in passenger cars most often have a standard value of 12 V. This is a characteristic indicated in the technical data sheet. And the voltage value is often indicated next to the brand, for example, BOSCH 63 Ah, where 63 is the capacity of the automobilebattery, Ah.

Check with a tester

So, for starters, a car enthusiast is wondering how to determine the residual capacity of a car battery.

Special testers are used to determine what the volume of capacity is and to understand how it is still operable. These are indispensable devices for testing all types of batteries, their functionality is huge. The tester is not at all difficult to operate and in most cases has only one button, with the help of which indicators of various parameters are determined, for example, both the volume of the capacitance and the current strength. The results obtained will not necessarily accurately reflect the condition of the battery, but if desired, using simple formulas, you can also make the final calculation of the capacity of the car battery.

Using a multimeter

A multimeter (or an avometer, from the word ampervoltmeter) is also a combined instrument used to measure the performance of electrical appliances.

It also has several modes of operation, it is not difficult to operate.

There are several ways to measure and find out what the capacity of a car battery is.

Load testing

An ordinary light bulb will act as a load. If during measurements the level of its brightness decreases, then testing immediately stops, as this will indicate poor battery performance - there is not enough charge or the device circuit is broken.

To calculate the required load for the tankcar battery, the first thing to consider is the number of amperes. If the capacitance rating is, for example, 7 Ah (Ah), then the corresponding load value will be 3.5 volts. If you don't have the right light bulb handy, a regular car headlight is perfect.

Measuring process

How to determine the capacity of a car battery, every car enthusiast should know!

To determine battery capacity measurements, follow these steps, in exact order:

1. First you need to disconnect the battery from the generator.
2. Next, connect the load in the form of a light bulb and let the battery run for just a couple of minutes. Then turn it off.
3. Then a multimeter is connected to the battery and a measurement is taken for 20 seconds.

The indicators are being recorded.

If the voltage is 12.5 volts, the battery is in good condition. But if the indicators are 11, 5 or even lower, then the battery needs to be replaced.

Check digit method

In order to measure the capacity of a car battery in this way, you need to know the discharge current of a particular power source. To do this, you can see the technical documentation attached to it. The capacity discharging current will be equal to the required load level to be applied to the battery.

In such a measurement of the volume of capacity, the multimeter should remain connected to the battery for as long as the current drops to 60, and preferably 50%. As a resulta value will be obtained, which must be compared with the value in the data sheet of the battery. Most likely, they will not match, since each charge / discharge of the battery gradually reduces its working capacity, but the numbers should not vary greatly! If the discrepancy is large, there is only one conclusion - battery replacement.

Measuring other indicators

Modern multimeter is a device with great functionality. It is suitable for measuring other parameters of the power supply.

Voltage measurement

If the battery type is alkaline-acid or lithium-ion, then you can measure the battery voltage by switching it to voltmeter mode. Depending on the load level of the measured device, set up the multimeter by setting the appropriate indicator. After that, a black wire is connected to the negative terminal of the battery, and a red wire, respectively, to the positive terminal. Literally within the next 2 seconds, the voltage indicator will be displayed on the screen of the multimeter.

If the battery is good, then the value of the indicator will be 12-12.5 Volts. This will indicate that the state of the power supply is normal.

Internal resistance test

Here, again, you will need a 12 V light bulb and, of course, a multimeter.

The internal resistance of a battery is also an important he alth indicator.

To take a measurement, a motorist or master acts in the following order:

1. Connected to the batterybulb. The battery will never charge!
2. After a couple of seconds, a multimeter is connected to the battery terminals and the first voltage measurement is taken.
3. The lamp turns off.
4. And the second voltage measurement is made.

If there is a difference in the received figures, but it is not higher than 0.05 V, then the battery is considered to be in good condition. If the difference is higher, then either replacement or inspection and additional tests are required. Internal resistance should not exceed the norm!

Leakage current

If the above measurements are not so difficult to understand and remember the actions, then you need to move on to the question of how to check the capacity of a car battery for current leakage. This is an indicator on which the volume of the battery capacity itself directly depends, and hence the period of its “life”.

The level of self-discharge allowed for a battery at rest is specified in its technical documentation. However, it is worth knowing that alkaline types of batteries have the highest level!

Any leak implies an open or poor seal in the battery power circuit. And if during the measurements the leakage level was determined much higher than the technically permissible level, then the battery will be discharged even faster. But it's not just battery drain that can be a problem, as poor insulation of certain parts of the power circuit can lead to a short circuit or fire!

To test the level of battery leakage current, the multimeter is switched to the appropriate mode, and the voltage indicator is set to 10 Amps. Connectmultimeter in this way: the red wire is connected to the positive terminal, and the black one is disconnected altogether.

The leakage indicator is defined as follows: if nothing is displayed on the instrument monitor, then the car battery capacity test was successful, there is no leakage! If there are any indications, then it is urgent to check the entire on-board system.

Restoring the capacity of the power supply

After making all the necessary measurements, the next logical step is to learn how to restore the "size" of the battery capacity. After all, in any case, especially with long-term operation of the vehicle, the battery loses some of its capacity.

How to restore the capacity of a car battery?

Preparation for recovery begins with an inspection and surface cleaning of the battery. It is necessary to remove all possible smudges of the internal composition, dirt and oxidation from the terminals. Before flushing the tank itself, the contaminated electrolyte is drained. Be sure to check the lead plates for integrity, because otherwise the restoration procedure simply will not work.

Next, a control cycle is carried out for a full discharge and further charge of the battery. It is better to do it at least 4 times.

To control this cycle you can use:

• hydrometer - to determine the density of the internal composition of the battery;
• light bulb - to create the desired load;
• voltmeter or multimeter.

Immediately between the discharge cycle and furtherthe charge capacity of the car battery in mAh is set to take a break of about 12-14 hours. The duration of the charge must be at least 8 hours. The technical documentation indicates the exact parameters of the required current strength, charge time, they must be taken into account in each specific case.

The rest period between cycles is needed in order to establish a single potential from above, on the surface of the lead plates.

For each complete discharge-charge cycle, the density of the electrolyte composition will increase. If it gets very high, you can use distilled water to dilute it.

After the distilled water has been drained and all the containers are thoroughly washed, a sodium solution is poured into the battery. Its filling is also done in several approaches, 2-3 times.

Rules of manipulation

When working with any electrical appliances, everyone should be aware that power surges caused by forced disconnection from the power circuit will adversely affect the device itself. Therefore, all actions should take place, if possible, with the engine turned off. If it becomes necessary to replace the battery while the engine is running, then to minimize power surges, all electrical appliances in the car (rear window heating, headlights, radio tape recorder) must be turned on. And connect / disconnect each terminal as quickly as possible, without repeated touches. In this way, unwanted voltage drops will be kept to a minimum.

If it becomes necessary to charge the battery from other equipment, then the connectiondevices must be made with great care. Otherwise, it may also cause malfunction of the devices.

Interesting facts

The concept of "the best battery" simply does not exist. Different types serve different purposes. For example, calcium batteries have low current leakage, but at the same time they hardly tolerate deep discharges, this is especially observed in winter. At the same time, for standard "serviced" batteries, for example, lead-acid batteries with a car battery capacity of 18Ah, such a discharge will not be critical, but you will constantly have to take measurements and do flushing and topping up with distilled water.

If the temperature is low, the ability of the battery to "charge" is sharply reduced. Therefore, short trips in cold weather can lead to a faster discharge. Even if the battery is new! And this will lead to the impossibility of starting the motor!

In winter, the battery will benefit from a heated design that will accelerate the temperature rise of the internal composition of the battery. After all, it has a certain viscosity, so its temperature decreases or rises following the ambient temperature, with a delay. And in order to help the battery get a charge from the generator more efficiently, it is necessary to provide an additional source of warm air. And this, in turn, will help slow down the discharge of the battery during rest. Also, the device can be taken home and, after warming to room temperature, put on charge.

The more regularthe performance indicators of the power source and the state of the “size” of its capacity are checked, the more timely it is possible to notice an increase in current leakage, and hence to carry out restoration. The smaller the deviations, the easier it is to carry out this procedure and the more likely it is to return the lost volume. After all, the operation of the battery inevitably leads to the destruction of lead plates, the formation of electrolyte smudges, and all this contributes to its slow failure.