How to test the battery of an electric screwdriver with a multimeter. How to recover a lithium battery from a DeWALT screwdriver?
Dewalt Lithium Ion Battery Won’t Charge? Try Resetting It With This Easy Fix.
How to check the battery capacity of an electric screwdriver with a multimeter
There are a huge number of battery technologies, but the most common and popular among them are the following:
- Lead-acid batteries are the most popular for automotive applications due to ease of manufacture and low cost. But further, for use in power tools, they did not prove themselves much, because they have low power with large size and high weight.
- Nickel-cadmium batteries have greatly surpassed lead-acid cells. In fact, they produce a lot of power with a low weight and compact size. But, of course, there are also its negative sides, in particular the toxicity of the battery. Since the production of this kind of battery cells is harmful to the environment. For example, this type of battery is prohibited in the European Union.
- Nickel-metal hydride cells are considered to be a more advanced version of the previous type of batteries. After all, they are completely safe for the environment. But there is a disadvantage in the form of high self-discharge in terms of current.
- Lithium-ion batteries, although they have almost ideal parameters, as they have a high capacity, small size and small weight, are not very popular. All because such a progressive element has a high cost, and therefore not affordable to every average citizen.
Varieties of batteries
To date, the most common is the nickel-cadmium type of battery. Its undoubted advantage is considered to be:
The maximum voltage of a single cell reaches 1.38 volts.
The nickel-metal hydride type is in fact the competitor of the above type of battery. However, its parameters are significantly worse, but the elements are completely safe from an environmental point of view.
It is necessary to send the named batteries in charged condition for storage, otherwise they will fail in a month already.
It is not too long ago that they started making batteries for screwdrivers:
They have the advantage of small size and high capacity. There are two disadvantages:
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How to Test an Electric Screwdriver Battery with a Multimeter
For the very first diagnosis, you need to determine the voltage and strength of the acb while charging the electric screwdriver. Normally, the device should indicate 13 V after 30 minutes of connection to the mains. After 1 hour the value will change to 0.5В.
The maximum voltage of an electric screwdriver should reach 17V.
The current strength when connected to the network at a well working device should reach more than 1 amp for 1 hour.
The multimeter itself is switched to DC mode to check the battery voltage. At the same time the mode switch must be set to 20V. This means that the voltage at the electric screwdriver will not exceed 20 volts.
When measuring the voltage of an electric screwdriver that is already fully charged, the value must be equal to the number of “cans” multiplied by the voltage of each battery.
Usually the number of batteries in the device is 10-12. With a nickel-cadmium battery voltage of 1.2V, the required value will reach a maximum of 14.4V.
The first stage of the test
Checking the battery of an electric screwdriver at the first stage is the easiest, the indicators of current and voltage are taken from the battery while it is on charge.
The readings are taken several times, at certain time intervals:
- 30 minutes after charging has started, the 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 deliver 17 volts.
Regarding the current increase (amperage) during charging, if the battery is in good working order, the amperage will steadily increase during the first hour. In addition to the volts, measure the amperage an hour after the start of the process. If it passes the “1 amp” mark, your battery is in good health and does not need to be disassembled or repaired.
To find out which “tank” of the battery is faulty, you need to unsolder each battery and measure the voltage on the poles.
To connect to the device use the probes, one of which (red) is connected to the positive and the second (black) is connected to the negative terminal of the accumulator. The multimeter display will show the value in volts.
Makita brand screwdrivers with Li-lon should show a voltage of 3.6 to 3.8V. This corresponds to the characteristics of lithium-ion batteries. In simple Chinese models, the Russian Interskol with Ni-cd value should be 1.4V, the minimum value is 1.2V.
It is possible that checking this way does not show any malfunctions, although the battery runs out quickly. Then test each battery with a light bulb (25 Watt and 12V). Also use a resistor to measure the resistance level, for example 10 ohms.
If you connect them to each other for a couple of minutes the brightness should not change. If it goes out or flickers, then the battery has insufficient capacity.
Also compare resistance values of all the batteries by first disconnecting them from the temperature sensor.
The resistance level in the battery is calculated using the formula:
where N is voltage, A is current, S is resistor resistance.
Let’s assume the value of the first battery is 0,60 Ohm and the second is 5 Ohm. This means that the second battery is unusable.
A nickel cadmium battery can be restored by trying to make up for the lack of electrolyte. For this purpose it is necessary to make a hole in the case of battery from the minus side with an awl. Pour 1 cc of distilled water using a syringe. Plug the hole with epoxy glue and assemble the battery.
All other types of batteries (Li-lon, Ni-mh) cannot be restored. In this case it will be necessary to buy a similar battery and conduct a replacement.
Checking the battery helps to identify the cause of the battery malfunction and eliminate it. This saves the cost of buying a new device.
We check the battery of an electric screwdriver with a multimeter
The most vulnerable part of an electric screwdriver is the battery. You can check the battery yourself with a multimeter (tester). Use it to measure the DC current and voltage in volts. How to check the battery of an electric screwdriver with a multimeter. described in the article.
The battery is a device arranged as source of direct current, which is transmitted from the batteries. When charging a rechargeable device, energy is stored in the system on the contrary.
The structure of the acb in electrical devices has the same elements:
The energy of the batteries is stored and transmitted by connecting them in series. A characteristic feature of “batteries”: the same size and voltage of the individual cells.
If the battery of an electric screwdriver breaks, usually only one or more batteries fail.
In addition to batteries, battery operation is affected by contact damage. The power terminals allow the device to receive a charge and release energy. The temperature sensor protects the electric screwdriver against overheating. And the service wire equalizes the charges in all cells.
In addition, the operation of the device is affected by the type of battery.
The “memory effect” and what to do about it?
If we are talking about ni cd batteries, there is such a concept as “memory effect” for them. This “painful symptom” is defined quite simply. If the battery quickly discharges after going through a full charge cycle and then, after a short pause, continues to function again, it is a true diagnosis, which with the right skill can be cured.
What must be done to cure the “memory effect”?
first subject the battery to a full charge (preferably at a low current). Then a light load is applied to it in order to achieve complete discharge. This simple method allows to activate the internal plates of the battery as fully as possible. As an example of a successful load, you can use an ordinary incandescent light bulb on 220V with a power of 60W. The process of slow charging and discharging should be repeated at least 4-5 times. The result of these steps is a return to 80% of the battery’s original capacity.
By the way, if you work on a disassembled battery, where you already know the “weakened” batteries, a high current shock can bring them back into operation. If the electrolyte is present in the battery, it is always possible to restore the battery using this method.
Batteries in a battery work on the basis of electrolysis, the process of breaking down and reducing molecules, during which energy is created. An anode and cathode initiate the process.
They can be identified by the marking Li-lon. Expensive, reliable and high-quality batteries are used by leading repair equipment manufacturers, including Makita or Bosch. Lithium disintegrates into ions during operation, which explains its name. Lithium batteries do not create a “memory effect” and can withstand more charge-discharge cycles.
Nickel combined with cadmium Ni-cd (nickel-cadmium) or Ni-mh (metalhydride). They are used not only in screwdrivers, but also in cell phones and home appliances. They have a large capacity, but quickly accumulate the ability to self-discharge. But they are not afraid of cold and can be stored in a discharged state.
Are the least popular because they have a low capacity and can be harmful to health. The basic element is PbO2. But for now they are most often used, especially in computers and cars. Lead models are famous for their ability to withstand heavy loads and durability.
Batteries and batteries
Testing of rechargeable batteries
To find out which “tank” of the battery is faulty, it is necessary to unsolder each of them and measure the voltage on the poles.
The probe is connected to the meter with one of the probes (red) connected to the positive pole and the other (black) connected to the negative pole of the drive. The multimeter display will read in volts.
Makita brand Li-lon screwdrivers should show a voltage of 3.6 to 3.8V. This is consistent with the characteristics of lithium-ion batteries. In simple Chinese models, the Russian Interskol with Ni-cd value should be 1.4V, the minimum value is 1.2V.
It happens that the test in this way does not show any faults, although the battery quickly shrinks. Then check each battery with a light bulb (25 Watt and 12V). Also use a resistor to measure the resistance level, e.g. 10 ohms.
When you connect them to each other for a couple of minutes the brightness should not change. If it goes out or flickers, then the battery has insufficient capacity.
Also compare the resistance of all the batteries by first disconnecting them from the temperature sensor.
The resistance level in the battery is calculated by the formula:
where N is voltage, A is current, S is resistor resistance.
Let’s assume that the value of the first battery is 0.60 ohms and the second battery is 5 ohms. This means that the second battery is unusable.
Nickel-cadmium batteries can be restored if you try to compensate for the lack of electrolyte. For this purpose in the case of an accumulator from a minus side it is necessary to make an aperture with an awl. Using a syringe, fill in 1 cc of distilled water. To plug a hole with epoxy glue and assemble the battery.
All other types of “banks” (Li-lon, Ni-mh) can not be restored. In this case you will need to buy a similar battery and replace it.
A battery check helps to diagnose and repair the cause of a malfunctioning battery. This saves the cost of a new device.