How to charge a screwdriver

Power supply for 12v screwdriver

One of the most important advantages and at the same time a disadvantage of a battery-powered screwdriver is the ability to work remotely without stationary power sources. To carry out work on such objects for 8. 10 hours, without being able to recharge the batteries, you need to have high-quality batteries and properly charge it. This is especially important for low-power 12V screwdriver power supplies, which do not have high energy consumption.

Capacity or voltage

The elementary sources from which the battery for the screwdriver is assembled have different voltages, so the Ca-Ni battery has 3.2 V., Li-ion. 3.6 V. If we connect three batteries in series, we get 12, 6V and 13.2V. A series connection is a connection in which the positive terminal is connected to the negative terminal of the next battery, and the positive terminal to the negative terminal of the next one, forming a continuous chain. With this connection, the battery voltage is added. If you connect the batteries plus to plus, and the minus terminal to minus, then the voltage remains the same, but the capacity will double. Thus, if it is necessary to increase the voltage, we collect a serial (series) connection, if the capacity is a parallel connection (parallel).

Improved performance in terms of power and stability

Let’s see how to do it. First, you need to unsolder all unnecessary wires from the circuit, leaving only 12V fishing line. You also need to look at the 12V output circuit from the microcircuit, perhaps there is an electrolytic capacitor of 16 Volts at the junction, it needs to be changed to at least 25 V. Since we will raise the operating voltage to 16 Volts.

charge, screwdriver

To raise the voltage in the circuit, we redo the installation according to the indicated circuit on the right. Once again, you need to check the output circuit for 12V, checking that the resistance R7 is 12 kOhm and re-solder the regulating resistance R9 to a variable value of 10 kOhm. The adjustment knob can be brought out to the front panel.
Check the output voltage, for example, with a multimeter, by setting the voltage with a variable resistor to 15. 16V. This voltage is quite enough for the reliable operation of a screwdriver with an operating voltage of 12-14V.
After closing the cover, mount the terminal clamps for the cables (suitable from household power outlets or switches), an ammeter and a voltmeter can be mounted on the front panel to monitor the parameters of the circuit.

After that, we can assume that the switching power supply for the 12v screwdriver is complete.

Battery assemblies

the power supply for an electric hand tool may differ in the configuration of the case, group of contacts, beautiful color, but one thing is invariable. they are assembled from piece elements. Each of the manufacturing firms produces branded batteries paying great attention to quality, since the performance of the tool directly depends on the power source by which the manufacturer is judged.

Now on the market there are different batteries for sale: by the active component; size; capacity; stress.
Elements with an active Ca-Ni component appeared in devices as source of autonomous power supply from the very first. Actually, after his invention, it became possible to manufacture hand tools on batteries. These elements have a number of advantages and disadvantages.

One of the main advantages: these elements work well at temperatures close to frost down to.20 ° C and are sold at a low price.

One of the biggest problems is the so-called “memory effect”. This phenomenon is expressed in the ability of active components to oxidize during prolonged charging, i.e. if the battery remains charged for several days, then the capacity, and, accordingly, the performance will decrease several times. And, although the manufacturers in the instructions warn about the procedure for the mandatory discharge of the battery after the end of work on an additional load, for example, on an incandescent light bulb, but forgetfulness of users can damage the battery. With proper use, the number of charge-discharge cycles is up to 500. 600 times without limitation of the service life.

Metal. a hydride battery in which an oxide. nickel alloy acts as a contact plate, the active layer is made of powder with a nickel filler with the inclusion of rare earth elements.

With the correct operating mode, the discharge cycle. the charge of such batteries is brought up to 700 times. With the introduction of new active elements, the product received an additional capacity in comparison with Ca.Ni by almost one and a half times, but also acquired a drawback: in the event of a controller breakdown in the battery circuit, when overcharged, the active nickel was activated and overheated. In the updated batteries, the “memory effect” was greatly reduced, but not completely ruled out. The service life was limited to three to four years of operation.

Li. ion. The Li-ion battery uses components with lithium ions. The very first lithium batteries were made from lithium. They had good characteristics. high operating voltage and capacitance, however, they had a problem: with a slight overvoltage or internal short circuit of the cells, lithium became active and reacted with the filler, which led to ignition or heating to high temperatures. In order to avoid battery fires, manufacturers were forced to turn the production of batteries towards the use of materials with lithium ions, such batteries received a prefix. lithium-ion. During operation, it turned out that if you systematically recharge the battery, then active release of lithium begins and its deposition on the walls of the battery. With a certain accumulation, he could go into an active phase with the same consequences.

Consider the design of a block for a screwdriver from a computer

It may happen that the battery charger breaks down or the batteries fail to charge. Almost every home has old electronic equipment, including an old computer, from which the power unit can be used as a computer unit to power a 12V screwdriver. This will not harm the engine of technology, since the device will provide for current stabilization and can practically replace the battery assembly in terms of parameters.
From parts of already unnecessary electrical engineering, you can assemble a network rectifier by installing it directly into an empty battery box, having previously freed up space from the elements. Sources can be: power; impulse

Power supply from an old computer

To implement the plan, almost any unit based on the tl 494 microcircuit or an analogue of the ka 7500 (domestic kr1114 EU4) is suitable. Before proceeding with the alteration, you need to make sure that the computer’s power supply is working. To do this, you need a 12 volt light bulb and a jumper wire. The power supply has three connectors with colored wires, first we take which is average in terms of the number of suitable wires, we look: red wire. 5 V; 2 black wires are negative wires; yellow wire. 12 volts.

We connect a 12V x 25W light bulb (automotive) to the 12V mowing line by connecting the contacts with the yellow and black wires. this will be a kind of indicator that the current source is working.

On the largest connector, we use the green and black wires, which need to be closed together with a wire jumper. Such a schematic snag is needed to outline the protection circuit. After supplying 220V, the fan spun, the light came on. this indicates that the unit is working and can be upgraded. The wiring of the TL494 microcircuit must be changed as shown in the diagram, connecting the elements as shown in the diagram. This is done to remove the protection of the operation of the pulse generator, so that it works stably and does not turn off under load. After a simple alteration, it is necessary to check the operability of the device again by connecting the light bulb according to the previous scheme, while the protection is turned off and the pulse generator will work without interruption.

Soldering of the elements is quite enough for the unit to work, but the performance can be improved even further. Radio magazine for 2009 (you can download at the end of the article).

Charging

In order for the battery assembly to work for a long time and efficiently, it needs high-quality charging. But, even self-respecting manufacturers, producing low-power sources for charging batteries, make them according to a simplified scheme. This is due to the fact that high-quality charging is expensive, starting from 2 thousand rubles. and more. A simplified diagram, as a rule, is: a step-down transformer; rectifier bridge from a diode assembly or individual diodes; several zener diodes and capacitors that smooth out the ripple. Yes, and the original app. parts for repair will not be easy to find. A high-quality power supply unit can be assembled from domestic parts. One of these is shown in the figure. As you can see, the alteration is quite simple, there is not even a step-down transformer, the mains voltage is extinguished by capacitors. Having passed through the diode bridge, the current becomes constant. A simple alteration provides a stabilized power supply to electronic devices at the output.

Why do you need a battery?

The universal battery comes in handy when traveling. You won’t need to carry all the chargers with you. You can make a battery that will meet all your needs in terms of size and usability.

You can also make an automatic battery charger yourself, which will come in handy during the winter season. Even if the garage or parking lot is heated, the battery still lacks heat. So it erupts quickly.

It is possible during breaks to replenish the reserve of its work with the help of homemade charging, and then it will be possible to safely travel long distances even in the most severe weather conditions.

AA battery charger

To make a do-it-yourself AA battery charger, you will need:

  • flux;
  • solder;
  • soldering iron;
  • tweezers;
  • tester;
  • screwdriver.

A tester is needed to check the performance of radio components for comparison with standard indicators.

You will also need a battery compartment and case. We take the compartment from any children’s toy (for example, from “Tetris”, which was very popular in the 90s). Any plastic case will also work.

Then the process looks like this:

  • We fasten the battery compartment to the body with screws. You can take a game console board as a basis. We cut everything according to this pattern and leave the power socket.
  • We connect the parts with a soldering iron, focusing on the diagram. Remember to consider the polarity: plus is soldered to plus.
  • For the cord, you can use a cable from a computer mouse with a USB input.
  • We check the voltage from the cord. The tester will display a reading of 5V.
  • We set the charging current. We connect the tester so that the minus is connected to the battery, and the plus is connected to the diode.
  • We set the current mode to 200 mA and turn it on. The LED lights up. it means you did everything right.
  • Now you need to set the charging current indicator by changing the resistance. In the same way, we make a second AA battery.

What to make a charger for a car

Specific options such as activated carbon or table salt batteries should not be considered if you value your car. There is a safer and easier option, which is with. Any driver will bring success to life.

Today, lithium polymer and lithium-ion batteries are used for the production of batteries. They also work on the basis of a chemical reaction, but without the use of an electrolyte. This allows us to talk about their safety, because during the operation of such charges, a chemical reaction will not occur.

In addition, lithium batteries are inexpensive, stable, and suitable for making chargers for any purpose. They are widely used in the manufacture of flashlights, telephones and electronics.

How many batteries to take?

To make a simple car battery charger, you need to calculate how many lithium batteries to take.

One keg has a voltage of 3.7 volts and a weight of about 100 grams. The capacity is different and can vary by 1.505 Ah. Not enough for a car, but you can just take more batteries to meet all power ratings.

The car needs a pulse charger of three batteries. In total, a voltage of 11-12 volts should be obtained. But it is better to pay attention to the capacity indicators. For car batteries, it is approximately 60 Ah.

Three accumulators provide 5 A. H. This means that the required voltage and current can be obtained using 38-40 such batteries. They are quite enough to charge the car battery.

DIY battery charger. drawings, projects and diagrams for creating a charger (75 photos)

Battery problems are common. A normal device is expensive, and cheap charging only spoils the technology. Many have already learned how to make chargers for mobile batteries with their own hands and saved themselves from the agony of choosing these devices of dubious quality.

  • Why do you need a battery?
  • AA battery charger
  • What to make a charger for a car
  • How many batteries to take?
  • Is it worth making such a charger?
  • DIY battery charger photo

Is it worth making such a charger?

This solution has its advantages:

  • light weight;
  • ease of manufacture;
  • low cost;
  • compactness.

But of the minuses, it is worth highlighting the problems with charging from the generator and the difficulty in operation at low temperatures. Also, the charger has low reliability and may not work at the most crucial moment. However, using it as a backup charge is not a bad option.

Now you know why you had to teach physics at school. Everyone can try to make a DIY lithium battery charger. This is not only saving money, but also new knowledge!

Types of batteries used

Nickel-cadmium batteries do not have problems when charging at high speed. Such batteries have a high load capacity, a low price and can easily tolerate work at sub-zero temperatures. The disadvantages include: memory effect, toxicity, high self-discharge rate. Therefore, before charging this type of battery, it must be completely discharged. The battery has a high self-discharge rate and discharges quickly even when not in use. Currently, they are practically not produced due to their toxicity. Of all types, they have the smallest capacity.

Nickel metal hydride is superior to NiCd in all respects. They have less self-discharge, less pronounced memory effect. With the same dimensions, they have a large capacity. They contain no toxic material, cadmium. In the price category, this type occupies an average position, therefore, it is the most common type of capacitive elements in a screwdriver.

Lithium-ion is characterized by high capacity and low self-discharge. These batteries do not tolerate overheating and deep discharge. In the first case, they are capable of exploding, and in the second, they will no longer be able to restore their capacity. They are also capable of working at subzero temperatures and have no memory effect. The use of a charger with a microcontroller made it possible to protect the battery from overcharging, thereby making this type the most attractive for use. For the price, they are more expensive than the first two types.

In addition, the main characteristic of rechargeable batteries is their capacity. The higher this indicator, the longer the screwdriver works. The unit of measure for capacity is milliamperes per hour (mAh). The design of the battery consists in connecting the batteries in series and placing them in a common housing. For Li-Ion, the voltage on one cell is 3.3 volts, for NiCd and NiMH. 1.2 volts.

The principle of operation of the memory

If the charger fails, it makes sense to first try to restore it. For repairs, it is advisable to have a charging device circuit and a multimeter. The circuitry of many charging devices is based on the HCF4060BE microcircuit. Its switching circuit forms the delay of the charging time interval. It includes a crystal oscillator circuit and a 14-bit binary counter, making it easy to implement a timer.

The principle of operation of the charger circuit is easier to disassemble with a real example. This is how it looks in the Interskol screwdriver:

This circuit is designed to charge 14.4 volt batteries. It has an LED indication showing the connection to the network, LED2 is on, and the charging process is on, LED1 is on. The U1 HCF4060BE microcircuit or its analogs: TC4060, CD4060 is used as a counter. The rectifier is assembled on VD1-VD4 power diodes of the 1N5408 type. The Q1 PNP transistor operates in a key mode, the control contacts of the S3-12A relay are connected to its terminals. The key operation is controlled by the U1 controller.

When the charger is turned on, an alternating voltage of 220 volts is fed through a fuse to a step-down transformer, at the output of which its value is 18 volts. Further, passing through the diode bridge, it is straightened and goes to the smoothing capacitor C1 with a capacity of 330 μF. The voltage across it is 24 volts. When the battery is connected, the contact block of the relay is in the open position. Microcircuit U1 is powered through a Zener diode VD6 with a constant signal equal to 12 volts.

When the “Start” SK1 button is pressed, a stabilized signal is supplied to the 16th output of the U1 controller through the resistor R6. Key Q1 opens and current flows through it to the relay outputs. The contacts of the S3-12A device are closed and the charging process begins. Diode VD8, connected in parallel with the transistor, protects it from a voltage surge caused by a relay disconnection.

The used SK1 button works non-latching. When it is released, all power is supplied through the VD7, VD6 chain and the limiting resistance R6. And also power is supplied to LED1 through resistor R1. The LED lights up, signaling that the charging process has started. The operating time of the U1 microcircuit is set for one hour of operation, after which the power is removed from the Q1 transistor and, accordingly, from the relay. Its contact group breaks and the charge current disappears. LED1 goes out.

This charger is equipped with an overheating protection circuit. Such protection is realized using a temperature sensor. thermocouple SA1. If during the process the temperature reaches more than 45 degrees Celsius, then the thermocouple will work, the microcircuit will receive a signal and the charge circuit will break. After the end of the process, the voltage at the battery terminals reaches 16.8 volts.

This charging method is not considered intelligent, the charger cannot determine the state of the battery. Because of this, the battery life of the screwdriver will decrease due to the development of the memory effect. That is, the capacity of the battery decreases every time after charging.

Types of chargers

The popularity of the screwdriver is due to the fact that it simplifies the process of twisting or unscrewing various fasteners. Characterized by mobility and small size, it is indispensable for assembling furniture structures, disassembling equipment, roofing and other construction work. The tool owes its mobility to the batteries included in its design.

charge, screwdriver

Fix Ryobi HP44L Quickturn Cordless Lithium Ion Screwdriver Repair

The advantage of using batteries is the possibility of their repeated use. Batteries, giving the accumulated energy to the device, periodically need to be recharged themselves. To restore the value of their capacity, chargers are used.

The screwdriver battery is charged in two ways: with a built-in or external charger. The built-in charger allows you to charge the battery without removing it from the screwdriver. The capacity recovery circuit is located directly with the battery. While the remote means their extraction and installation in a separate charging device. Distinguish chargers according to the type of recoverable batteries. The batteries used are:

  • nickel-cadmium (NiCd);
  • nickel metal hydride (NiMH);
  • lithium-ion (LiIon).

The final cost of a screwdriver depends not least on the type of batteries used and the capabilities of the charger. Chargers are available in 12 volts, 14.4 volts and 18 volts. In addition, memory devices are divided according to their capabilities and may have:

  • indication;
  • fast charging;
  • different type of protection.

The most used chargers use a slow charge due to a low current. They do not contain an indication of operation in their design and do not turn off automatically. This is more true for built-in capacity recovery devices. Chargers built on pulsed circuits provide the possibility of accelerated charging. They automatically turn off when the required voltage is reached or in the event of an emergency.

Homemade charging devices

It is quite simple to make your own charging for a 12 volt screwdriver with your own hands, by analogy with the one used in the Interskol memory. To do this, you need to take advantage of the ability of the thermal relay to break the contact when a certain temperature is reached.

In the circuit, R1 and VD2 are a charge current flow sensor, R1 is designed to protect the VD2 diode. When voltage is applied, the transistor VT1 opens, a current passes through it and the LH1 LED starts to glow. The voltage value drops on the R1, D1 chain and is applied to the battery. The charge current flows through the thermal relay. As soon as the temperature of the battery to which the thermal relay is connected exceeds the permissible value, it is triggered. The relay contacts switch, and the charge current begins to flow through the resistance R4, the LH2 LED lights up, indicating the end of the charge.

Two-transistor circuit

Another simple device can be performed on the available elements. This circuit works on two transistors KT829 and KT361.

How To. Electric screwdriver repair

The magnitude of the charge current is controlled by the KT361 transistor to the collector, to which the LED is connected. This transistor also controls the state of the KT829 composite element. As soon as the capacity of the battery begins to increase, the charge current decreases and the LED, accordingly, smoothly goes out. Resistance R1 sets the maximum current.

The moment the battery is fully charged is determined by the required voltage on it. The required value is set with a variable resistor of 10 kOhm. To check it, you will need to put a voltmeter on the battery connection terminals without connecting it itself. Any rectifier unit designed for a current of at least one ampere is used as a constant voltage source.

Making a charger for a screwdriver with your own hands

When using a screwdriver, users often encounter damage to the charger (charger). First of all, this is due to the instability of the parameters of the electrical network to which the charger is connected, and secondly, with the failure of the battery. This problem is solved in two ways: buying a new charger for a screwdriver or repairing it yourself.

Using a specialized microcircuit

Manufacturers of screwdrivers are trying to reduce the of their products, often this is achieved by simplifying the memory scheme. But such actions lead to the rapid failure of the battery itself. Using a universal microcircuit designed specifically for the MAXIM MAX713 charger, you can achieve good performance in the charging process. This is what the charger circuit for an 18 volt screwdriver looks like:

The MAX713 microcircuit allows you to charge nickel-cadmium and nickel-metal hydride batteries in a fast charge mode, with a current of up to 4 C. It can monitor the battery parameters and, if necessary, reduce the current automatically. At the end of charging, the microcircuit-based circuit consumes almost no energy from the battery. It can interrupt its work on time or when a temperature sensor is triggered.

HL1 is for power indication and HL2 is for fast charge display. The setup of the scheme is as follows. To begin with, the charging current is selected, usually its value is equal to 0.5 C, where C is the battery capacity in ampere hours. The PGM1 pin is connected to the positive supply voltage (U). The power of the output transistor is calculated by the formula P = (Uin. Ubat) Isar, where:

  • Uin. the highest voltage at the input;
  • Ubat. battery voltage;
  • Isar. charging current.

The resistance of R1 and R6 is calculated by the formulas: R1 = (Uin-5) / 5, R6 = 0.25 / Isar. The choice of time after which the charging current will turn off is determined by connecting the PGM2 and PGM3 contacts to different terminals. So, for 22 minutes, PGM2 is left unconnected, and PGM3 is connected to U, for 90 minutes, PGM3 is connected to the 16th leg of the REF chip. When you need to increase the charging time to 180 minutes, the PGM3 is shorted to the 12 leg of the MAX713. The longest time of 264 minutes is achieved by connecting PGM2 with the second leg, and PGM3 with the 12th leg of the microcircuit.

How to charge a screwdriver

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Indicator for charging a screwdriver 14.4 volts

I bought a cheap Chinese SKIL-2007 screwdriver, a battery of 14.4 V. 1.2A / h, in principle, it is possible to work normally, but it had two drawbacks. First. there is no adjustment of the rotation speed, I coped with it quickly, I put a switch with a speed regulator. The set includes two batteries and a simple charger made in two separate parts. In a small case, which is plugged into an outlet, there is a transformer with a rectifier, it gives out 18 V 200 mA at the output, a piece of wire with a connector leaves from it. The second part of. the charger itself with indicators, here is its diagram. fig. 1.

A green LED indicates that the device is online. Red indicates that the battery is charging, it will remain lit as long as the battery is connected to the charger. According to the mat, the charge time is 3-5 hours. Since it is impossible to control the end of charging with this charger, I decided to add my own. Searches on the Internet did not give anything, came across too abstruse on controllers, the program to which is sent for a separate fee, or schemes according to which the charge is determined by the brightness of the LED glow, but this is also not the best option, since during the day in sunlight, the brightness seems small, but in the dark big.

I decided to make a simple, reliable battery charging indicator from available parts. As a basis, I took a car voltage indicator (found on the shelves in the garage), they are still on sale, it is a cylindrical body that plugs into the car’s cigarette lighter, at the end there are three LEDs arranged in a row, red at the edges, green in the middle. Here is its diagram (Fig. 2.) and passport data.

  • red LED VD3. 12V;
  • green LED VD4. 12.5 to 14.5 V;
  • red LED VD4. more than 15 V.
  • red VD3 and green VD4. 12.0 to 12.5 V;
  • red VD2 and green VD4. 14.5 to 15.0 V.

This circuit will work without modification for a 12-volt screwdriver. Does not contain scarce parts and can be easily assembled by a novice radio amateur.

In my screwdriver, the voltage of a fully charged battery while charging is 16.5. 16.8 V, it will not rise higher, even though it will charge for a day. The alteration of the car indicator is as follows: the case is disassembled and thrown out, leaving a 16×38 board with three LEDs. Zener diode VD1, replaced by D814G, instead of R2, set a variable resistor of 1 kOhm.

Setting: a power supply with an adjustable voltage of up to 20 V is connected to the input “±” of the indicator. We set the voltage of 16.5 V at the output of the power supply and by rotating the variable resistor slider we achieve that only the green LED is on, as soon as the red VD3 goes out, the rotation stops. This completes the setup.

I got the following charging values: Red VD3. up to 15 V (battery discharged). Red VD3 and green VD4. 15.16.5V (50-80% charged).

Green VD3. 16.5. 19.3 (100% charged). Red VD2. more than 19.3V (this indicator is practically not used).

Then, instead of a variable resistor, set a constant one, in my case it turned out R2 = 470 Ohm, but you can leave the construction one as well. the indicator is connected to the standard charger to the “±” terminals of the battery. Three holes are drilled in the case for the LEDs and the indicator is inserted into the case of the charger, there is a lot of space there, and it is fixed. Everything native remains in its place.

When you turn on the charger without a battery, VD2 lights up. We insert the discharged battery into the charger, VD2 goes out, the VD3 indicator lights up, as the charging voltage reaches 15 V, the green indicator VD4 starts to light up, and the brightness of VD3 decreases and finally VD3 goes out red, and the green VD4 lights up with full glow, charging can be considered completed.

As a result of this addition to the charger, charging, instead of 3-5 hours according to the passport, ends much earlier. At any time, by the glow of the indicators, you can determine at what stage the battery being charged is. According to the tuning method, this circuit is also suitable for other chargers, for a different voltage. To do this, the battery is fully charged, as stated in the instructions for 3-5 hours, then without removing the battery from the charger, the voltage of the fully charged battery is measured. This voltage is set at the output of the regulated power supply and by selecting the Zener diode VD1 and the resistor R2, they achieve a clear operation of the indicator, as mentioned above.

See other articles of the section Chargers, batteries, galvanic cells.

Read and write helpful comments on this article.

Comments on the article:

xav83
And where in the VD4 circuit?

Arthur
It feels like the diagram was drawn by one, and the article was written by another person.

Alexander
The alteration scheme is not bad, but there are many inaccuracies and confusion in the description.

Charger circuits for screwdrivers

The same screwdrivers can use different types of batteries with different parameters and technical characteristics. In this regard, they require different chargers. Therefore, before purchasing or making a charger for a screwdriver with your own hands, you need to determine the type of battery and operating conditions. In addition, it is recommended that you study the basic circuits most often used in chargers.

Microcontroller charging. Placed in a regular case, equipped with sound and light signaling of the beginning and end of the charge. This circuitry ensures correct battery charging. At the beginning of work, the LEDs light up and then go out. The indication is accompanied by a sound signal. In this way, the functionality of the device is tested. After that, the red LED starts blinking evenly, which indicates the normal charging process.

When the battery reaches a full charge, the red LED stops blinking, and instead of it, the green one lights up, accompanied by a sound signal. This means that charging is over.

Setting the voltage level that should be on a full charge is carried out using a variable resistor. In this case, the value of the input voltage is equal to the voltage of a fully charged battery plus one volt. The circuit uses any field-effect transistor that has a P-channel and is most suitable for current characteristics.

In order to ensure charging at 14V, the voltage applied to the input must be at least 15-16V. The threshold that disconnects the charger is set with a variable resistor at 14.4V. The charging process itself takes place in the form of pulses displayed on the LED. In the intervals between the pulses, the voltage on the battery is monitored and upon reaching the desired value, a sound signal is given together with the flashing of the LED about the end of charging.

There are other charger circuits as well. For example, a charger for a drill / screwdriver works with a voltage of 18 volts. When charging a 14.4V battery, the charging current is selected using a resistor.

How to make a charger for a screwdriver

All battery powered screwdrivers are equipped with chargers. However, some of them charge the battery very slowly, which creates certain inconveniences with intensive use of the tool. In this case, even the two batteries included in the kit do not allow the normal duty cycle to be set. The best way out of this situation would be a self-made screwdriver charger according to the most suitable scheme.

Screwdriver device

Despite the variety of models, the general device of the screwdrivers is quite universal, and the principle of operation is almost the same. They may differ only in appearance, in the arrangement of individual parts, in the presence or absence of additional functions. The power supply of screwdrivers can be 220V mains or rechargeable. The general design of a screwdriver includes the following elements and components:

  • Housing. It is made of hard plastics, which contributes to a lighter construction and lower costs. Some models use metal alloys for increased strength. It is a pistol with a comfortable grip, when disassembled it is divided into two halves.
  • Cartridge. The attachments are fixed in it, to which the rotational movement is then transmitted. Typically a three-jaw, self-clamping and self-centering device is used. Inside there is a hexagonal recess where the nozzle shank is inserted. To fix in the chuck, nozzles are inserted between the cams and clamped by rotating the coupling.
  • Electrical part. Consists of a small-sized electric motor of the collector type. Mains powered devices use two-phase AC motors rated for 220V. They are started using a starting capacitor. DC motors are installed in cordless screwdrivers. Direct current comes from a battery made in the form of a set of elements combined in a common housing. The power of the screwdriver is determined by the output voltage of the battery.
  • Chain elements. To turn it on, a special button located on the handle is used. Typically, pushbutton switches are paired with voltage regulators. That is, the amount of voltage applied to the motor depends on the force applied when the button is pressed. The shift lever is also installed here, which provides a reverse rotation of the shaft due to the change in the polarity of the electrical signal. From the button, the signal goes directly to the rotor through the manifold. Electrical contact is provided by graphite brushes of certain sizes.
  • Mechanical parts and details. The design is based on a planetary gearbox, with the help of which the torque is transmitted from the shaft to the output spindle. The carrier, ring gear and satellites are used as additional elements. All parts are inside the body and in turn interact with each other.

An important component is the rotation control clutch, which sets a certain torque. With its help, the rotation of the shaft stops after screwing in the screw. Stopping occurs due to increased resistance to rotation. This measure prevents the breakdown of the threaded part of the screw and the failure of the screwdriver itself.

Charging for a screwdriver with your own hands

The problem of making a charger with your own hands does not arise so often, due to the large number of options suitable for almost all models of screwdrivers. It’s just that sometimes situations arise when there is no charging, or it suddenly failed, and there is no way to get a new one. In this case, you can try to make your own charger.

You should first stock up on all the necessary materials. You will need an inoperative battery, a battery glass, a soldering iron, a heat gun, a regular Phillips screwdriver, a drill, and a sharp knife with replaceable blades. After that, you can start making the charger. First of all, the charging cup is opened, after which all conductors are soldered from the terminals. Next, the internal electronics are removed. When performing this operation, the polarity of the terminals must be observed so that in the future there will be no confusion and errors.

Open the case of a non-working battery and carefully unsolder the wires from the terminals. For further work, you will need a connector and a top cover. Plus and minus on the terminals are marked with a pencil or marker. At the base of the charging cup, holes are outlined through which the prepared cover and the leads of the supply wires will be attached. Conductors are carefully passed through the holes, observing polarity, after which they are connected to the terminals and connectors by soldering.

Next, the body must be fastened with special hot melt glue, the bottom cover is attached to the base of the glass using self-tapping screws. The resulting structure must be inserted into the battery and the charging process begins. A flashing light will indicate correct assembly of the device. Few chargers are equipped with so-called smart systems that significantly extend battery life. This problem can be solved by a charger for an 18 volt screwdriver.

A voltage stabilization system and a charging current limitation are added to the design of conventional charging. The result is a design of a nickel-cadmium battery with a capacity of 1200 mAh. Charging will be performed in a safe mode, with a maximum current not exceeding 120 mA, but it will take more time for this than usual.

Cordless drill screwdriver Makita DF331DWYE