DIY screwdriver charger repair

Without a doubt, the power tool greatly facilitates our work, and also reduces the time of routine operations. All kinds of self-powered screwdrivers are now in use.

Consider the device, the schematic diagram and the repair of the battery charger from the Interskol screwdriver.

First, let's take a look at the schematic diagram. It is copied from a real charger PCB.

Charger PCB (CDQ-F06K1).

The power section of the charger consists of a GS-1415 power transformer. Its power is about 25-26 watts. I counted according to the simplified formula, which I have already spoken about here.

The reduced alternating voltage 18V from the secondary winding of the transformer is fed to the diode bridge through the fuse FU1. The diode bridge consists of 4 diodes VD1-VD4 type 1N5408. Each of the 1N5408 diodes withstands a forward current of 3 amperes. The electrolytic capacitor C1 smooths out the voltage ripple downstream of the diode bridge.

The basis of the control circuit is a microcircuit HCF4060BE, which is a 14-bit counter with elements for the master oscillator. It drives the pnp bipolar transistor S9012. The transistor is loaded on the S3-12A electromagnetic relay. A kind of timer is implemented on the U1 microcircuit, which turns on the relay for a given charge time - about 60 minutes.

When the charger is connected to the network and the battery is connected, the contacts of the JDQK1 relay are open.

The HCF4060BE microcircuit is powered by the VD6 zener diode - 1N4742A (12V). The zener diode limits the voltage from the mains rectifier to 12 volts, since its output is about 24 volts.

If you look at the diagram, it is not difficult to notice that before pressing the “Start” button, the U1 HCF4060BE microcircuit is de-energized - disconnected from the power source. When the “Start” button is pressed, the supply voltage from the rectifier goes to the 1N4742A zener diode through the resistor R6.

Further, the reduced and stabilized voltage is supplied to the 16th pin of the U1 microcircuit. The microcircuit starts to work, and the transistor also opens S9012that she runs.

The supply voltage through the open transistor S9012 is supplied to the winding of the electromagnetic relay JDQK1. The relay contacts close and supply voltage to the battery. The battery starts charging. Diode VD8 (1N4007) bypasses the relay and protects the S9012 transistor from a reverse voltage surge that occurs when the relay coil is de-energized.

The VD5 diode (1N5408) protects the battery from discharge if the mains supply is suddenly turned off.

What happens after the contacts of the "Start" button open? The diagram shows that when the contacts of the electromagnetic relay are closed, the positive voltage through the diode VD7 (1N4007) goes to the Zener diode VD6 through a damping resistor R6. As a result, the U1 microcircuit remains connected to the power source even after the button contacts are open.

Replaceable battery GB1 is a block in which 12 nickel-cadmium (Ni-Cd) cells, each 1.2 volts, are connected in series.

In the schematic diagram, the elements of the replaceable battery are circled with a dotted line.

The total voltage of such a composite battery is 14.4 volts.

A temperature sensor is also built into the battery pack. In the diagram, it is designated as SA1. In principle, it is similar to the thermal switches of the KSD series. Thermoswitch marking JJD-45 2A... Structurally, it is fixed on one of the Ni-Cd cells and fits tightly to it.

One of the terminals of the temperature sensor is connected to the negative terminal of the storage battery. The second pin is connected to a separate, third connector.

When connected to a 220V network, the charger does not show its work in any way. Indicators (green and red LEDs) are off. When a removable battery is connected, a green LED lights up, which indicates that the charger is ready for use.

When the “Start” button is pressed, the electromagnetic relay closes its contacts, and the battery is connected to the output of the mains rectifier, and the battery charging process begins. The red LED lights up and the green one goes out. After 50-60 minutes, the relay opens the battery charging circuit. The green LED lights up and the red one goes out. Charging is complete.

After charging, the voltage at the battery terminals can reach 16.8 volts.

This algorithm of work is primitive and eventually leads to the so-called "memory effect" of the battery. That is, the capacity of the battery decreases.

If you follow the correct algorithm for charging the battery, for a start, each of its elements must be discharged to 1 volt. Those. a block of 12 batteries must be discharged to 12 volts. In the charger for the screwdriver, this mode not implemented.

Here is the charging characteristic of one 1.2V Ni-Cd battery cell.

The graph shows how the cell temperature changes during charging (temperature), the voltage across its terminals (voltage) and relative pressure (relative pressure).

Specialized charge controllers for Ni-Cd and Ni-MH batteries, as a rule, operate according to the so-called delta -ΔV method... The figure shows that at the end of the cell charging, the voltage decreases by a small amount - about 10mV (for Ni-Cd) and 4mV (for Ni-MH). From this change in voltage, the controller determines whether the element is charged.

Also, during charging, the temperature of the element is monitored using a temperature sensor. Immediately on the graph you can see that the temperature of the charged element is about 45 0 WITH.

Let's go back to the charger circuit from the screwdriver. It is now clear that the JDD-45 thermal switch monitors the temperature of the battery pack and breaks the charge circuit when the temperature reaches somewhere 45 0 C. Sometimes this happens before the timer on the HCF4060BE chip goes off. This happens when the battery capacity has decreased due to the “memory effect”. At the same time, a full charge of such a battery occurs a little faster than in 60 minutes.

As you can see from the circuitry, the charging algorithm is not the most optimal and, over time, leads to a loss of the battery's electrical capacity. Therefore, a universal charger such as the Turnigy Accucell 6 can be used to charge the battery.

Over time, due to wear and tear and moisture, the SK1 "Start" button begins to work poorly, and sometimes even fails. It is clear that if the SK1 button fails, we will not be able to supply power to the U1 microcircuit and start the timer.

There may also be a failure of the VD6 Zener diode (1N4742A) and the U1 microcircuit (HCF4060BE). In this case, when the button is pressed, charging does not turn on, there is no indication.

In my practice, there was a case when the zener diode struck, with a multimeter it “rang” like a piece of wire. After replacing it, the charging began to work properly. Any zener diode for a stabilization voltage of 12V and a power of 1 W is suitable for replacement. You can check the Zener diode for “breakdown” in the same way as a conventional diode. I already talked about checking diodes.

After repair, you need to check the operation of the device. Press the button to start charging the battery. After about an hour, the charger should turn off (the “Network” indicator (green) will light up. We take out the battery and make a “control” measurement of the voltage at its terminals. The battery must be charged.

If the elements of the printed circuit board are in good order and do not cause suspicion, and the charging mode does not turn on, then the thermal switch SA1 (JDD-45 2A) in the battery pack should be checked.

The scheme is quite primitive and does not cause problems when diagnosing a malfunction and repairing, even for novice radio amateurs.

The screwdriver is a very useful tool in the household. Perhaps not to list all the situations when it can come in handy, this is the assembly of furniture, and the screwing of shelves and fixing cabinets and much more. The work of screwing the screws, which our fathers did for a long time and tediously by hand, 20 years ago, is done in a matter of minutes with the help of a screwdriver. Therefore, a screwdriver malfunction at the right time is very unsettling. Malfunctions, of course, can be different, but we will talk about one of the most popular - charging does not charge our instrument. Let's figure out what to do in this case and whether it is possible to repair the screwdriver charger yourself.

The manifestations of this type of malfunction can be quite varied. For example, charging basically does not charge our instrument. Or it charges, but it discharges too quickly. Sometimes the charger may not fully charge the screwdriver. We will consider these situations.

So you have a great screwdriver. You actively use it, but at one not-so-wonderful moment the battery starts to discharge very quickly. The reason for this most often lies either in the general deterioration of our battery, or in the charger, which is faulty and charges it poorly. If everything is clear with the first case - you cannot do without replacing the battery, then with the second we will try to figure it out. Moreover, it is better to understand right away in practice, so we will take a specific charger and will "treat" it.
In our case, this is a Bosch charger, which works with a nickel-cadmium battery.

For those who are very concerned about issues of originality, we will immediately explain that it was made in China, but at the same time it is factory-made and produced in compliance with all the necessary standards.

At the connector, we can see three pins, two of which are power, and one is control.
Most often we come across a case when the battery is on charge, but the charge does not go, although the battery is not charged.

In any case, the problem can be solved only by disassembling our device. To do this, unscrew the fastening screws and carefully remove the case cover. Our charger is divided into two parts, in one of them there is a place for an AC current transformer, in the other for a rectifier. There are also power connectors and a control chip, as you can see for yourself in our illustration.

To check our charger, you need to plug it in and replace the voltage indicator. If voltage is present, then most likely you will need repair related to the contacts of the device.
This work is quite laborious, but quite real. As we said above, the charger has power contacts, there are two of them, and a control contact. We have to check them, and all three of them. This will require some preparatory work. Our task is to take measurements of the voltage at the terminals of each contact at the moment when there is a charge. To do this, we need a tool - a soldering iron and thin wires. These wires need to be soldered to the contacts, they will help us measure the voltage indicators when the charger is working.
To avoid confusion, we recommend choosing different wire colors for plus and minus.

After completing these preparatory work, you can start charging testing. To do this, we measure the voltage value with a mutitimeter at the moment when an electric charge is applied to the terminals.

What do we see from the measurement results? If the voltage "jumps" and does not show stable values, then this is an indicator that this is where the cause of the malfunction is.In this case, it also happens that with the slightest movement, the tension disappears altogether. This problem is most likely due to the fact that the contact terminals are unbent, which means that the contact does not fit tightly and does not provide a stable voltage required for normal charging of our device.

The malfunction of the control contact affects the quality of charging especially strongly, since it is he who is responsible for supplying normal voltage to the terminals.

The instability of the contacts violates the logic of charging the device. What can we do in this case? We cannot close the contact. This is due to the fact that the battery includes a thermistor device as an integral part, which changes the resistance value in response to a change in temperature in the battery. This means that it acts as a safety device to keep the battery from overheating or overcharging.

Knowing this feature of the battery, we should take the following actions. First of all, you need to bend the terminals. And after that, during the charging period, you need to monitor the voltage with a multimeter. We will see that first there is an increase in its value, and then - a decrease. And of course, you should pay attention to the charge indicator lamp on the device itself, it signals whether charging is in progress.

When measuring voltage, it is very important to pay attention to how fast it builds up. If the speed is high enough, the battery is in good health. But if the voltage rises at a very low rate, then this signals the deterioration of the battery. You should pay attention to this signal and replace the battery. So, as you can see, we also need the voltage rise indicator to assess the degree of battery wear.

As a rule, after carrying out the above manipulations, the charger works normally. Only you may still need additional fixation of the charging socket; this can be done with electrical tape.
As you can see, repairing a charger with a screwdriver with your own hands is a rather painstaking, but quite real process. So do not rush to throw away the faulty charger, but try to figure out the causes of the breakdown and eliminate them. And your "shura" will again serve faithfully!

A Skil 2301 screwdriver (made in China) was gathering dust in the closet. He worked poorly - he was discharged for 5-10 minutes. finally decided to fix it - and that's what happened.

I checked the batteries with a tester - they turned out to be working properly. The reason was the charger. The declared power of 400 mA was not enough for the power supply: the manufacturer's savings on copper in the transformer prevented a full charge from occurring (see Fig. 1 on page 18).

I decided to make a charger on a specialized microcircuit (MS) that would control the charge. The choice fell on the MAX 713 - affordable and inexpensive. The battery pack contains 10 charging capacities of 1.2 V, 1200 mA. After reading the nomenclature for the microcircuit, I came to an almost typical circuit solution suitable for me:

1. Input voltage - 21.5 V.
2. 10 batteries (photo 1).
3. Charging current - 0.5 A.
4. Timer switch-off time - 180 min.

The MC has a very delicate node, it has its own power supply, so it is undesirable for the current to exceed 10 mA. Otherwise, the MS fails and the internal power supply of the microcircuit is damaged. To strengthen the circuit, I introduced a simple current regulator on the LM 317.

Many do not install VT2 transistor, but the manufacturer recommends it when the input voltage exceeds 15 V (Fig. 2).

You can buy an inductor, but I wound it myself (photo 2). Its current is at least 1.5 A. Dimensions of the coil L1 - N 48 23x14x10 mm, where da (outer) = 23 mm, di (inner) = 14 mm, h (ring thickness) = 10 mm.

He wound 60 turns of PEL d 0.6 mm (Fig. 3).

The most difficult thing was to place the entire circuit in the box of the device's native charger (photo 3-6).

After assembly, I carried out a test - the batteries were charged for 2 hours 40 minutes. at 500mA, the fast charge will automatically shut down. It follows from this that the microcircuit was calculated correctly, the device is working properly.

Similarly, on the basis of this microcircuit, you can create this device for any charging by changing the circuit.

Often, the native charger that comes with the screwdriver works slowly, taking a long time to charge the battery. For those who use a screwdriver intensively, this is very interfering with their work. Despite the fact that the kit usually includes two batteries (one is installed in the handle of the tool and in operation, and the other is connected to a charger and is in the process of charging), often the owners cannot adapt to the duty cycle of the batteries. Then it makes sense to make a charger with your own hands and charging will become more convenient.

Batteries are not of the same type and may have different charge modes. Nickel-cadmium (Ni-Cd) batteries are a very good source of energy, capable of delivering a lot of power. However, for environmental reasons, their production has been discontinued and they will be encountered less and less. Now they have been superseded by lithium-ion batteries everywhere.

Sulfuric acid (Pb) lead gel batteries have good characteristics, but they make the instrument heavier and therefore are not very popular, despite the relative cheapness. Since they are gelatinous (a solution of sulfuric acid is thickened with sodium silicate), there are no plugs in them, the electrolyte does not flow out of them and they can be used in any position. (By the way, nickel-cadmium batteries for screwdrivers also belong to the gel class.)

Lithium-ion batteries (Li-ion) are now the most promising and advanced in technology and on the market. Their feature is the complete tightness of the cell. They have a very high power density, are safe to use (thanks to the built-in charge controller!), Are beneficially disposed of, are the most environmentally friendly, and have low weight. In screwdrivers, they are currently used very often.

The nominal voltage of the Ni-Cd cell is 1.2 V. The nickel-cadmium battery is charged with a current from 0.1 to 1.0 of the nominal capacity. This means that a 5 amp-hour battery can be charged with a current of 0.5 to 5 A.

The charge of sulfuric acid batteries is well known to all people holding a screwdriver in their hands, because almost every one of them is also a car enthusiast. The nominal voltage of the Pb-PbO2 cell is 2.0 V, and the charging current of the lead sulfuric acid battery is always 0.1 C (current fraction of the nominal capacity, see above).

The lithium-ion cell has a nominal voltage of 3.3 V. The charging current of the lithium-ion battery is 0.1 C. At room temperature, this current can be gradually increased to 1.0 C - this is a fast charge. However, this is only suitable for those batteries that have not been over-discharged. When charging lithium-ion batteries, be sure to observe the voltage exactly. The charge is made up to 4.2 V for sure. Exceeding dramatically reduces service life, decreasing - decreases capacity. Watch the temperature when charging. A warm battery should either be limited to a current of 0.1 C, or turned off before it cools down.

ATTENTION! If the lithium-ion battery overheats when charged over 60 degrees Celsius, it may explode and catch fire! Do not rely too much on the built-in safety electronics (charge controller).

When charging a lithium battery, the control voltage (end-of-charge voltage) forms an approximate series (the exact voltages depend on the specific technology and are indicated in the passport for the battery and on its case):

The charge voltage should be monitored with a multimeter or a circuit with a voltage comparator tuned exactly to the battery being used.But for “entry-level electronics engineers”, you can really only offer a simple and reliable scheme, described in the next section.

The charger below will provide the correct charging current for any of the listed batteries. Screwdrivers are powered by batteries with different voltages of 12 volts or 18 volts. It doesn't matter, the main parameter of a battery charger is the charge current. The voltage of the charger when the load is disconnected is always higher than the rated voltage, it drops to normal when the battery is connected while charging. During the charging process, it corresponds to the current state of the battery and is usually slightly higher than the nominal at the end of charging.

The charger is a current generator based on a powerful composite transistor VT2, which is powered by a rectifier bridge connected to a step-down transformer with sufficient output voltage (see the table in the previous section).

This transformer must also have sufficient power to provide the required current for continuous operation without overheating the windings. Otherwise, it may burn out. The charge current is set by adjusting the resistor R1 with the battery connected. It remains constant during charging (the more constant, the higher the voltage from the transformer. Note: the voltage from the transformer should not exceed 27 V).

Resistor R3 (at least 2 W 1 Ohm) limits the maximum current, and the VD6 LED is on while the charge is in progress. By the end of the charge, the LED light decreases and it goes out. However, do not forget to accurately monitor the voltage and temperature of lithium-ion batteries!

All details in the described scheme are mounted on a printed circuit board made of foil-coated PCB. Instead of the diodes indicated in the diagram, you can take the Russian diodes KD202 or D242, they are quite available in the old electronic scrap. It is necessary to arrange the parts so that there are as few intersections as possible on the board, ideally not a single one. You should not get carried away with the high density of installation, because you are not assembling a smartphone. It will be much easier for you to solder the parts if 3-5 mm remain between them.

The transistor must be installed on a heat sink of sufficient area (20-50 cm2). It is best to mount all parts of the charger in a convenient homemade case. This will be the most practical solution, nothing will interfere with your work. But here great difficulties can arise with the terminals and connection to the battery. Therefore, it is better to do this: take an old or faulty charger from friends, suitable for your battery model, and rework it.

• Open the case of the old charger.
• Remove all the former filling from it.
• Pick up the following radioelements:

Perhaps the most demanded tool of any home craftsman is the screwdriver. But this device, like any other, sometimes breaks down. If this happens, then in some cases you can replace the screwdriver with an electric drill. But if the work cannot be done with a drill, then you need to carry the screwdriver to the service center so that the craftsmen can repair the device. But this can be time-consuming and expensive. Therefore, it makes sense to try to repair the screwdriver yourself.

Before starting repair work, you need to get acquainted with the design of this tool and identify elements, which will be required to fix the screwdriver, among them:

The main element is the start button, it performs a number of functions: turning on the power supply and the engine speed governor. If you hold down the button all the way, the power supply circuit of the electric motor will close, resulting in maximum power. The number of revolutions in this case will also be maximum. The device contains an electrical regulator consisting of a PWM generator... This item is on the board.

The contact placed on the button will move along the board, taking into account the pressure on the button. The level of the impulse applied to the key depends on the location of the element. The key is a field-effect transistor. The principle of operation will be as follows: the harder you press the button, the higher the value of the pulse on the transistor and the greater the voltage on the motor.

Motor rotation is reversed by reversing the polarity at the terminals. This process takes place using contacts that are switched using the reverse handle.

As a rule, screwdrivers contain collector single-phase DC motors. They are quite reliable and very easy to maintain. Standard screwdriver consists of the following elements:

The gearing system converts the high rotations of the motor shaft into the revolutions of the chuck. Screwdrivers use classic or planetary gearboxes. The first ones are installed very rarely. Planetary gearboxes consist of the following parts:

• sun gear;
• ring gear;
• drove;
• satellites.

The sun gear works by means of the armature shaft, its teeth activate the satellites that rotate the carrier.

A special regulator is installed to regulate the force with which it is supplied to the screw. Typically, there are 15 adjustment positions.

The main signs of breakage spare parts in this case are:

• impossibility of adjusting the number of revolutions;
• impossibility of switching to reverse mode;
• breakdown of the charger;
• the screwdriver does not turn on.

First you need to check the tool battery. If the screwdriver was set to charge, but this did not give results, then you need to prepare a multimeter and try to determine the breakdown with it.

First you need to measure the voltage value of the battery. This value must correspond approximately to the one that is written on the case. If the voltage is low, then you need to identify the faulty part: the charger or the battery. What do you need a multimeter for? We plug this device into the network, then we measure the voltage at the terminals idling. It must be several volts higher than indicated on the design. If there is no voltage, then the charger needs to be repaired.

Very often the problem when working with a screwdriver is the rapid discharge of the battery. The reason or the deterioration of the battery, or improper charging. Let's tell you more about the repair of the charger. For example, we will use a charger from BOSCH AL 60DV - this device is used in tandem with nickel-cadmium batteries.

As a rule, all chargers, like most spare parts, are not original, and they are manufactured not in Germany or Switzerland, but in China... But there is nothing wrong with that, the quality usually corresponds to the standard.

BOSH connector is three-pin: one control connector and two power connectors.

Most often, this situation appears - the battery is installed in charging - but the charging process ends in just a few minutes, and the battery is discharged, and the charger stops.

To understand the problem and find the faulty part, you need to disassemble the charger. We unscrew the four screws at the bottom and open the case. In the case, in one compartment there is an AC voltage transformer, and in the other - a rectifier circuit with power connectors and a control chip.

Then we plug in the charger and we measure the current strength on the transformer - if everything is fine, then proceed to the next procedure.

You don't need to touch the control chip and rectifier, they are most likely fine. We pass to the contact group - one control contact and two power contacts. To determine what the malfunction may be, we need to measure the current at the power terminals when the charge is working.Why do we solder to all contacts along a thin wire - so that the voltage can be measured when charging is working.

It is advisable to use several colors of wires in this scheme and, accordingly, to solder them plus and minus. Then we collect the charging and test with a multimeter the current at the terminals when charging.

If the current on the device is unstable and fluctuates in the range from 3-4 to 14-18 volts. Moreover, if you move the battery, then the contact disappears. It is here that the reason lies - during the operation of the device - the terminals are bent and poor contact leads to unstable charging of the screwdriver battery.

That is, it is clear that unstable contact breaks the charging logic - in particular, the third contact, control, it is he who is responsible for what current is supplied to the terminals. It will not be possible to close it, since there is a thermistor inside the circuit of any battery and its resistance changes taking into account the temperature of the spare parts inside the battery. That's right, it protects the battery from overheating and overcharging at the same time. But in this case, there is a way out. We again disassemble the charging, bend the terminals, then use a multimeter to watch the charging process - the current at the terminals will slowly increase and then decrease, and the indicator light on the charging is an additional indicator of operation.

The rate of growth of the current at the terminals indicates another important factor - battery wear. If the current rises very quickly and reaches 18-19 volts, then the battery is in good condition. When the battery is slowly taking charge, there is a high probability that some part of the battery is already unusable and needs to be replaced.

Thus, after the restoration of contact between the charger and the battery, we see normal charging process... If the charging seat is loose, then you need to fix the battery in the desired position with electrical tape. The wires that were soldered for indication, we advise you to leave them with the help of them, it is very easy to determine which spare part is faulty, the battery or charging.

If the battery is faulty, then it is necessary to disassemble the unit, carefully examine all the places for the quality of the wires. If there are no damaged fasteners, then it is necessary to measure the current strength with a multimeter on each element. It must be 0.8-1.1 volts or higher. If there is a spare part with a lower amperage, then it must be replaced. The type and capacity of the element must certainly correspond to the installed elements.

If the charger and the battery are in good order, but the screwdriver still does not work, then you need to disassemble this device. Several wires come out from the battery terminals, you need to take a multimeter and measure the current at the input of the button... If it is present, then you need to get the battery, using the clamps, short-circuit the wires from it. The multimeter should determine the resistance, which should tend to zero. In this case, the spare part is working properly, the problem is with the brushes or other elements. If the resistance is different, then the button will need to be changed. To repair the button, sometimes it is enough to clean the contacts on the terminals with sandpaper. You also need to check the reverse spare part. Repair takes place by cleaning the contacts.

Need to check quality of armature windings, since this spare part can be bought and replaced with your own hands. To check the armature, you need to measure the resistance on the collector plates located nearby. The value must tend to zero. If, during the check, plates with a resistance other than zero are found, then it is necessary to repair the armature spare part or change it.

Mechanical breakdowns defined in this way:

• The screwdriver vibrates a lot during operation.
• During operation, the screwdriver emits extraneous noise.
• The screwdriver turns on, but it does not work because of jamming.
• Hits the chuck.

If during operation the screwdriver emits extraneous noise, this means that the bearing or bushings are worn out. To fix this, you need to disassemble the engine, then check the wear level of the bushing and the integrity of the bearing. The anchor must spin freely, there should not be any distortions or friction. These accessories can be purchased at the store and replaced with your own hands.

To the most common malfunctions gearbox designs include the following:

• break in the pin where the satellite is attached;
• abrasion of gears;
• shaft malfunction.

In all cases, it is necessary to replace the defective spare part of the gearbox. All the actions described above must be performed very carefully. Disassembly of the screwdriver must be done in a clear sequence, since some of the spare parts may be lost. Anyone can make an independent repair of a screwdriver, you just need to correctly identify the broken part.

Almost all screwdrivers operate on batteries. The average battery capacity is 12 mAh. And in order for it to always be in working order, a constant recharge is needed. This requires a charger specific to each type of battery. However, they differ greatly in their characteristics.

Currently producing 12-18 V models... It is also worth noting that manufacturers use different components for different charger models. To figure this out, you should familiarize yourself with the standard circuit diagram for these chargers.

The basis of the standard scheme is three-channel type microcircuit... In this version, four transistors are attached to the microcircuit, very different in capacitance and high-frequency capacitors (pulse or transient). To stabilize the current, thyristors or open-type tetrodes are used. The current conductivity is regulated by dipole filters. This circuitry handles network overloads with ease.

The purpose of power tools is primarily to make our daily work less tedious and chore. In the home, a screwdriver is an indispensable assistant in the repair or disassembly (assembly) of furniture and other household items. Autonomous power supply screwdriver makes it more mobile and convenient to use. The charger is a power source for any cordless power tool, including a screwdriver. For example, let's get acquainted with the device and the schematic diagram.

For circuit diagrams of chargers of 18 V screwdrivers are used transistors several capacitors and a diode bridge tetrode. Frequency stabilization is carried out by the grid trigger. Charging current conductivity for 18 V is 5.4 μA. Sometimes chromatic resistors are used to improve conductivity. The capacitance of the capacitors, in this case, should not be higher than 15 pF.

The "banks" of the battery are enclosed in a housing that has four contacts, including two power plus and minus for discharge / charge. Upper control contact switched on via thermistor (thermal sensor) that protects the battery from overheating while charging. When it gets too hot, it limits or cuts off the charge current. The service contact is connected through a 9 kOhm resistor, which equalizes the charge of all elements of complex charging stations, but they are usually used for industrial devices.

1. Interskol chargers use transceivers with increased conductivity. Their maximum current load reaches 6 A, and even higher in new models. The standard charger of the Interskol screwdriver uses a two-channel microcircuit, 3 pF capacitors, pulse transistors and open-type tetrodes. The current conductivity reaches 6 μA, with an average battery capacity of 12 mAh.
2. Quite often, the Russian manufacturer Interskol uses a battery charging circuit with IRLML 2230 transistors. In this case, a three-channel type microcircuit and capacitors with a capacity of 2 pF are used in 18 V chargers, which are well tolerated by network loads. The conductivity index in this case reaches 4 μA. When choosing a screwdriver, you need to take into account its power, which affects its service life. The higher the power rating, the longer the tool will last.

The battery is the most expensive part of a screwdriver and is approximately 70% of the total cost tool. If it fails, you will have to spend money on purchasing a practically new screwdriver. But if you have certain skills and knowledge, you can fix the breakdown yourself. This requires certain knowledge about the features and structure of a battery or charger.

All elements of a screwdriver, as a rule, have standard characteristics and dimensions. Their main difference is the value of energy consumption, which is measured in A / h (ampere / hour). The capacity is indicated on each element of the power supply (they are called "banks").

"Banks" are: lithium - ionic, nickel - cadmium and nickel - metal - hydride. The voltage of the first type is 3.6 V, others have a voltage of 1.2 V.

Battery malfunction determined by a multimeter. He will determine which of the "cans" is out of order.

To repair a screwdriver battery, you need to know its design and accurately determine the location of the breakdown and the malfunction itself. If even one element fails, the entire circuit will lose its functionality. The presence of a "donor" in which all the elements are in order or new "banks" will help solve this problem.

A multimeter or 12 V lamp will tell you which item is faulty. To do this, you need to put the battery to charge until it is fully charged. Then disassemble the case and measure voltage all elements of the chain. If the voltage of the "cans" is lower than the nominal, then you need to mark them with a marker. Then collect the battery and let it run until its power drops noticeably. After that, disassemble again and measure the voltage of the marked "cans". The voltage drop across these should be most noticeable. If the difference is 0.5 V or more, and the element is working, then this indicates its imminent failure. Such elements must be replaced.

Using a 12 V lamp, you can also identify faulty circuit elements. To do this, connect a fully charged and disassembled battery to the plus and minus contacts on the 12V lamp. The load created by the lamp will be discharge the battery... Then measure the sections of the chain and identify the faulty links. Repair (restoration or replacement) can be done in two ways.

1. The defective element is cut off and a new one is soldered with a soldering iron. This applies to lithium ion batteries. Since it is not possible to restore their work.
2. Nickel - cadmium and nickel - metal - hydride cells can be recovered if an electrolyte is present that has lost volume. To do this, they are stitched with voltage, as well as enhanced current, which helps to eliminate the memory effect and increases the capacity of the element. Although it will not be possible to completely eliminate the defect. Perhaps, after a while, the malfunction will return. A much better option would be to replace the failed elements.

To repair a battery for a screwdriver, you will need spare battery, from which, you can borrow the necessary parts or purchase new chain elements. New "banks" must meet the required parameters. To replace them, you will need a soldering iron, tin, rosin, or flux.

1. Unsolder the connections of the defective parts and replace them with new ones. At the same time, do not allow them to overheat, which can damage the battery.To do this, try to perform quick soldering without delay. In the process of soldering, you can cool it with a touch of your hand, with the voltage disconnected.
2. Make the connections with native plates (maybe copper ones), otherwise overheating of the wires can trigger the necessary thermistor, which controls the heating and turns off the charging system. Remember to observe the polarity when connecting. The minus of the previous element, when connected in series, is attached to the plus of the next one.
3. Equalize the potential of the circuit elements. It differs in almost all "banks". To do this, put the battery to charge overnight, and then leave it to cool down for a day. Then, measure the voltage of the cells. Indicators should be very close to par.
4. Insert the battery into the screwdriver and give it the maximum load until it is completely discharged. Do two full discharge cycles. The result will give a complete picture of the effectiveness of the repair work.

To charge the battery device, you can make a homemade charger, USB powered... Required components for this: socket, USB charger, 10 amp fuse, required connectors, paint, electrical tape and tape. For this you need:

1. Disassemble the screwdriver into parts and cut off the upper body from the handle with a knife.
2. Make a hole for the fuse to the side of the handle. Connect the cable with the fuse and fit into the handle of the unit.
3. Fix the fuse with glue or a heat gun. Wrap the case with tape and attach the structure to the battery connector. The wires are mounted at the top of the screwdriver. The tool is assembled and wrapped with electrical tape. After that, the body is sanded, covered with paint and the resulting device is charged.

As you can see, this the process will not take long and won't be too ruinous for your family budget.