How to check the battery capacity of an electric screwdriver with a multimeter


To check the power supply of an electric screwdriver for operability, you just need to take off the current and voltage readings at the time of charging. over, it is necessary to repeat the procedure several times in order to obtain the most accurate values.

  • after 30 minutes of charging. 13 V;
  • after 60 minutes of charging. 13.5 V;
  • after 2 hours. 14 V;
  • at the end of charging. 17 V.

Such observations indicate that the battery is completely intact and functional. In most cases, no further analysis is required.

At the same time, for a working battery, the current strength will also steadily increase within an hour after the start of charging. If after an hour the indicator has reached a value of 1 A, then this indicates the serviceability of the device.

There is also a method for accelerated testing of the battery, which consists in measuring the voltage at no load (no load). This voltage must reach the required value, which is directly related to the operating voltage of the battery cells (cells). If the indicator is lower, then there is a high probability of failure of one or more elements.

A separate type of battery capacity test with a multimeter from an electric screwdriver can be considered load testing. Additional equipment is used here, which needs recharging. Incandescent lamps are ideal for this. The power of such a lamp must match the power of the battery. Otherwise, the test results may not be accurate enough. In most cases, the power is equal to half the current that the battery delivers multiplied by the voltage. For standard screwdriver batteries, 12 V lamps are used for testing.

The battery is connected to the load through a multimeter, which is then used to take readings. After a few minutes, you need to measure the voltage. It should be higher than 12.4 V. If this value has not been achieved, then there is clearly some kind of malfunction. Additionally, it is recommended to pay attention to the brightness of the light bulb. It must be stable enough.

Nickel cadmium battery

check, battery, capacity, electric, screwdriver

The most common type of battery. They charge quickly enough and have a good volume. They are distinguished by their durability and resistance to external influences. The average number of charge / discharge cycles can reach 3500. When using accelerated chargers, the battery does not wear out faster and can last for a long time. Separately, it is worth noting the cheapness of such batteries and the ability to operate at temperatures below zero.

But there are also disadvantages, the main one of which is the so-called “memory effect”. Batteries are quite toxic in the event of a malfunction and have a high self-discharge rate. Due to toxicity, manufacturers are now trying to rapidly reduce the percentage of such devices.

To prolong the life of such a battery, it is recommended to completely discharge it before recharging.

General recommendations before testing the battery

Immediately before checking the battery, it is necessary to clearly determine what type of battery the battery belongs to. Depending on this type, the approach may be different. For example, the most common nickel-cadmium batteries are highly sensitive to operating conditions. Infrequent or irregular full recharges will significantly reduce the capacity of the battery and the battery will not fully utilize its resources. We will consider the types of batteries in more detail below.

How to check for bad rechargeable batteries with a multimeter

It is also recommended to fully charge the battery before checking. This will allow you to make more accurate conclusions about the performance of the device. It has been proven that the most accurate readings are taken under load. And the full charge is a very suitable type of load.

Before testing, it is necessary to minimize the influence of the “memory effect” on the device. Since this effect appears with batteries in case of improper use, in order to eliminate it, it is necessary to use the battery several times in accordance with all the rules.

It is enough to carry out the charge / discharge cycles 3 times to significantly reduce the effect of the effect. For an accelerated discharge, it is best to use an incandescent lamp, which, together with a multimeter, will need to be connected to the battery.

If everything is done correctly, then after a few full cycles the battery will be able to restore its capacity and can again be used in an electric screwdriver. If the operation did not help, then the problem was different.

How to check the battery of an electric screwdriver with a multimeter?

During intensive use of the electric screwdriver, there is a possibility of its breakdown. And one of the most vulnerable parts is the battery. Consider how to check the battery of an electric screwdriver for performance by different methods.

Li-ion battery

A much more expensive analogue, which, however, has a number of undeniable advantages. Such batteries are used in advanced models of screwdrivers from well-known brands.

These batteries have a large capacity and a much lower percentage of charge loss due to self-discharge. However, such batteries are strictly not recommended to be overheated and left completely discharged for a long time. This can lead to degradation of the crystals and damage to the battery. If overheated, there is a risk of explosion of such a device.

Like the first type, the lithium-ion battery is capable of functioning in cold weather.

How to check

Battery voltage

After the first stage of verification, it will become clear whether the device is working properly or not. If the testing indicated a mismatch in the parameters, then it is logical to proceed with the repair, accompanied by the replacement of faulty cans.

You need to open the battery case and identify the malfunction. For this, a multimeter is also used, which is connected to each element separately. The voltage of each jar must be at least 1.2 V. All discrepancies indicate a breakdown of the element. Defective cans must be removed from the common circuit and replaced with new ones.

If such a check does not reveal a breakdown, then you need to resort to stress testing again. And here the level of resistance is of fundamental importance, which is directly related to voltage and current strength. Each element is tested separately and resistances are calculated as well. In the event of a malfunction, this indicator will clearly deviate from the norm and quickly identify a broken element.


The malfunction may lie not only in the battery, but also in the charger itself. Therefore, you first need to check the charger for an electric screwdriver with a multimeter.

On it, the mode of measuring direct current is turned on and, using probes, it is connected to the charger. The value of the current on the meter should be as close as possible to what is indicated on the case. If this is not the case, then it is better to replace the device with a new one.

Checking the battery of the screwdriver

In the battery of the screwdriver, nickel cells with a voltage of 1.2V are connected in series. Usually, the entire battery loses capacity due to the failure of one element. Therefore, if it quickly loses its charge, then the device should be disassembled, check each element separately and replace the faulty one.

Checking the battery cells of the screwdriver

Output voltage

The measurement is made according to the instructions for the voltmeter. The nominal value of the battery is indicated in the documentation or on the case:

  • Nickel-cadmium or nickel-metal hydride. 1.2V. Such cells are used instead of AA and AAA batteries in electric screwdrivers and similar devices. Sets of such batteries in these electrical appliances are assembled into batteries. If necessary, the parameters of an individual cell or the entire battery are determined;
  • In car batteries. 12.7V. Similar devices are used in the UPS. Some models of scooters and motorcycles have a battery voltage of 6.3V;
  • Lithium-ion. used in phones, tablets and other mobile equipment. The voltage value depends on the specific model.

Important! Measurements are taken with the load off so that the voltage drop inside the power supply does not introduce errors in the result.

How to check the battery capacity with a multimeter

A battery is a device that stores electricity and delivers it to lamps, electric motors and other electrical appliances. One of the important parameters of these devices is capacity. To check it, special expensive devices are used, but there is an alternative option. This article tells you how to find out the battery capacity with an ordinary multimeter.

Interesting. There are multimeters with the function of checking the battery capacity.

Measuring capacity with a multimeter

Battery capacity is measured in ampere-hours. This is the product of the current consumed by the device and the operating time that the battery can provide. You can find out the nominal capacity of the battery by the markings on its case. Before measuring the battery capacity, you need to check the voltage and, if necessary, recharge the device.

To measure the battery capacity, a load, for example, an incandescent lamp, is connected to a power source charged to the rated voltage Unom, and the current consumed by it is measured by the tester. After some time t, the battery voltage Uwork is measured and the discharge level Urez is determined. This is done using the formula:

and the expected running time is determined:

This formula is only suitable for acid batteries that discharge to “0”. Elements of other types are disconnected when the voltage drops below 0.83Unom. Therefore, in the formula for calculating the phone battery, instead of Unom, 0.17Unom should be used.

To calculate the capacity of the storage battery, the obtained value is multiplied by the current Cap = Itwork.

Battery parameters

The main parameters of the device can be measured or calculated without the use of special expensive devices.

Battery capacity

This parameter shows how long the device connected to the battery will work until the battery is completely discharged.

The capacity is measured in ampere-hours. This is the product of the operating time and the consumed current. It can also be calculated by taking the necessary measurements with a multimeter.

Self-discharge of the battery

During storage, the voltage at the output of the device decreases. This phenomenon is called self-discharge.

Testing current draw of cordless screwdriver at 12V with a multimeter

To determine it, it is necessary to measure the voltage in the disconnected battery with a frequency of several days, the self-discharge of the device is calculated from the difference.

Internal resistance

Another important parameter is the internal resistance of the device. At its high value, there is a significant drop in the output voltage at high load currents. This effect is observed when the car is started with a starter, while the headlights dim.

The internal resistance is determined as follows:

  • measured voltage without load. Uхх;
  • the load is connected, and its current I and voltage Uwork are measured;
  • the voltage drop inside the power supply is calculated:
  • according to the formula Rvn = Uvn / I the internal resistance of the battery is calculated.

Interesting. In a conventional battery, during discharge, the output voltage does not drop, but the internal resistance increases, and the short-circuit current drops.

What does the battery consist of?

The internal structure of the battery of any electric screwdriver, regardless of the country of origin, is absolutely identical. If you disassemble the plastic block, there are always “jars” inside, assembled in a certain sequence. The battery voltage indicator as a whole is added up based on the U level that each battery has separately. The battery also has four contacts, two of which provide charge-discharge cycles, the third is connected to a thermal sensor, and the fourth, which has a service purpose, is responsible for equalizing the charge potential in all batteries.

So, the interconnected “banks” of the battery of an electric tool are nothing more than source of current with a constant value, in which chemical reactions are constantly being converted into electricity. This is how the battery transfers the stored energy to the circuit. And when it is charging, the process takes place in the opposite direction: the battery simply takes energy from the network.

We check the battery of an electric screwdriver with a multimeter

Many home craftsmen have to deal with the need to check a drill or an electric screwdriver for battery health. Over time, the battery sits down, and in order to assess the possibility of its further performance, you need to know how to check the battery of an electric screwdriver with a multimeter or tester. Multimeter. a device with voltmeter and ammeter functions.

General recommendations before testing the battery

Before you check the battery of an electric screwdriver with a multimeter for possible malfunctions, you should remind yourself that the nickel-cadmium batteries installed in most power tools have a so-called “memory effect”. In short, its essence lies in the fact that due to frequent and irregular recharging, the capacity of the “cans” of the battery decreases, and the battery does not use its resource in its entirety.

The battery should be fully charged before testing to ensure the tester’s readings are as accurate as possible. Keep in mind that testing is optimally accurate if it is done under load. This is what the battery will need a sufficient amount of charge for.

The toolkit you’ll need is simple:

How to Use Multimeter and Measure the Voltage of Power Tool Lithium Batteries

  • tester (or multimeter);
  • screwdriver;
  • knife;
  • soldering iron;
  • pliers.

The first stage of testing

Checking the battery of an electric screwdriver at the first stage is the simplest, current and voltage indicators are taken from the battery while it is charging.

Readings are taken several times, at regular intervals:

  • 30 minutes after charging has started, U will be about 13 volts;
  • after another 30 minutes, U will increase to 13.5 volts;
  • two hours after the start of the process. 14 volts;
  • a fully charged battery will give a voltage of 17 volts.

As for the increase in current (amperage) during charging, if the operating state of the battery is in order, then the current strength increases steadily during the first hour. In addition to voltage, measure the current strength one hour after the start of the process. If the indicator passes the “mark” of 1 ampere, your battery is in good health and does not need to be disassembled and repaired.

Express test method: we measure U at the poles of the battery

This method is even simpler, but with its help you can get an initial idea of ​​whether the battery is in order. If we measure U without connecting the load, then we get an indicator equal to the “idle” of the tool.

For example, if we have 12 cells in the battery with a voltage of 1.2 volts each, and the working indicator U is 14.4 volts, the “idle” U will grow to 17 volts. If the “open” voltage is less than the specified one, it means that there are “banks” in the bundle that are out of order and need to be replaced. Also, a decrease in open-circuit voltage may mean that the battery is not fully charged.

Checking performance under load

This means that we will check how long the battery of an electric screwdriver will discharge completely, provided that an additional load is connected to it. for example, an electric light bulb.

The load level must be selected based on the capacity of the battery. If it is not indicated in the operating instructions, it should be calculated independently. It will be equal to half the current delivered by the battery during operation, multiplied by the U of the current source. Usually this figure is from 35 to 40 watts, which means that the load can be a headlight from a car from 35 watts, or a 12-volt bulb.

To take readings, the battery must be connected to the lamp through an ammeter, and the readings themselves must be taken with a voltmeter. Connection time is two to three minutes, after which we measure U. If it is less than 12.4 volts, some “bank” is definitely out of order. Also, a significant decrease in the brightness of the light bulb may indicate a battery malfunction. If it goes out quickly in two or three minutes, the battery is clearly out of order, and its capacity is very small.

Checking the elements in the disassembled battery

So, if preliminary testing has shown that there may be faulty elements in an electric screwdriver, the battery should be carefully disassembled and batteries that are unusable for work should be calculated. As already mentioned, the normal voltage of each battery individually should be 1.2 volts. If this figure is less, the “can” is carefully removed from the chain using pliers. It also does not hurt to carefully examine the entire bundle for external damage: rust, leakage of electrolyte.

In the event that the voltage on all “banks individually is within the normal range, you must again use the test under load with a check on the level of internal resistance. This value is determined as follows: the voltage is divided by the current strength, and then the load resistance is subtracted from it.

To find out the voltage, we immediately connect the load. This time, you should use a resistor with a power of 25 watts and a resistance of 10 ohms. We check each battery, measuring the indicator of the working current and U.

The calculations should be something like this: for example, when measuring under load, we received the operating voltage of one element of 1.19 volts, and the current strength of 112 milliamperes. Before calculating, it is imperative to convert milliamps to amperes. It turns out 0.112 amperes, therefore: 1.19 is divided by 0.112 and we subtract the resistance of 10 ohms. It turns out the value of 0.63 Ohm. this means that the indicator is normal.

Self-checking the performance of an electric screwdriver’s battery with a multimeter is a useful skill to find out if the battery needs repair or a complete replacement of cans. Measurements of voltage indicators in general, without disassembling the battery pack, should be carried out from time to time. This will help to avoid a sudden failure of the tool and eliminate the malfunction in time. Also, to avoid the accumulation of “memory effect”, do not neglect to fully charge your battery. This will help to avoid premature drop in its capacity.