Device for measuring the capacity of the battery. Basic methods

Each car owner wonders what a device is needed to measure the battery capacity. The measurement of this value is often carried out during the passage of the planned maintenance, but it will be useful to learn how to determine it.

Battery capacity meter

Battery capacity is a parameter that determines the amount of energy that the battery gives at a certain voltage for one hour. It is measured in A / h (Ampere per hour), and depends on the density of the electrolyte, which is determined by a special device - a hydrometer. When buying a new battery, all technical parameters are indicated by the manufacturer on the package. But this value can be determined by yourself. For this, there are special instruments and methods.

The easiest way is to take a special tester, for example "Pendant". It is a modern device for measuring the capacity of a car battery, as well as its voltage. In this case, you will spend a minimum amount of time and get a reliable result. For testing, it is necessary to connect the device to the terminals of the battery and within a few seconds it will determine not only the capacity, but also the battery voltage and the state of the plates. However, there are other methods for determining the capacity of batteries.

The first method (classical)

For example, a multimeter can be used as an instrument for measuring the capacity of a car battery, but with its help you will not get accurate readings. A mandatory condition for this method (it is called the control discharge method) is the full charge of the battery. To begin with, you need to connect a powerful consumer to the battery (a normal 60W lamp is suitable).

After that, it is necessary to assemble the circuit, which consists of a multimeter, battery, consumer, and supply the load. If the bulb does not change its brightness within 2 minutes (otherwise the battery can not be restored), we take the reading of the device at certain intervals. As soon as the indicator falls below the standard battery voltage (under the load it is 12V), its discharge will begin. Now, knowing the time interval that it took to completely empty the energy reserve and the load current of the consumer, it is necessary to multiply these values. The product of these quantities is the actual capacity of the battery. If the values obtained are different from the passport data, the battery needs to be replaced. This method makes it possible to determine the capacity of any battery. The disadvantage of this method is a large time expenditure.

The second method

You can also use the method in which the battery is discharged through a resistor, applying a special circuit. Using the stopwatch we determine the time spent on the discharge. Since the energy will be lost at a voltage within 1 Volt, we can easily determine the current by using the formula I = UR, where I is the current strength, U is the voltage, and R is the resistance. In this case, it is necessary to avoid a complete discharge of the battery, using, for example, a special relay.

How to make the device yourself

If there is no possibility to purchase a finished device, it is always possible to assemble a device for measuring the capacity of the battery with one's own hands.

To determine the degree of charge and capacity of the battery, you can use the load fork. On sale there are many models of ready-made plugs, but you can assemble it yourself. Then one of the options is considered.

In this model, an extended scale is used, so that high measurement accuracy is achieved. There is built-in load resistance. The scale is divided into two ranges (0-10 V and 10-15 V), which further reduces the measurement error. The device also has a 3-volt scale and the other terminal of the measuring device, allowing the testing of individual battery cans. The 15V scale is achieved by reducing the voltage across the diode and the zener diode. The value of the device current increases if the voltage value exceeds the zener diode opening level. When a voltage is applied with an incorrect polarity, the diode performs a protective function.

On the diagram: R1- transmits the required current to the zener diode; R2 and R3 are the resistors selected for the microampere M3240; R4 - defines the width of the narrow scale range; R5 - load resistance, switched on by tumbler SB1.

The load current is determined by Ohm's law. The load resistance is taken into account.

Device for measuring the capacity of the battery AA

The capacity of AA batteries is measured in mA / h (milliampere per hour). To measure these batteries, you can use special chargers that determine the current, voltage and capacity of the battery. An example of such a device is a device for measuring the battery capacity AccuPower IQ3, which has a power supply with a voltage range from 100 to 240 volts. To measure, you need to insert batteries into the device, and all necessary parameters appear on the display.

Determination of capacity using a charger

Also, the capacity can be determined using a conventional charger. Having determined the value of the current strength of the charge (it is indicated in the characteristics of the device), it is necessary to fully charge the battery and note the time spent on it. After multiplying these two values, we get an approximate capacity.

More accurate readings can be obtained using another method, for which you need a fully charged battery, stopwatch, multimeter and consumer (you can use, for example, a flashlight). Connect the consumer to the battery, and using a multimeter to determine the current consumption (the less it is, the more reliable the results). We record the time during which the flashlight was shining, and multiply the result by the current consumption.