Why does the battery of an electric screwdriver hold a charge or does not charge at all??

In the arsenal of any good owner there is probably a common power tool in today’s home. a screwdriver. Its main advantage is mobility. After all, this device works on removable batteries, which makes it most convenient to use, because you do not need to connect to a power outlet. But what to do if the battery of a screwdriver fails? It will be quite expensive to buy a new one, because its cost in some models reaches up to 50-70% of the price of the screwdriver itself. It is much more practical to buy a new tool with two batteries at once. But it is still possible to extend the life of an old screwdriver by repairing a failed battery.

If the electric screwdriver is equipped with a rechargeable battery, then the charger must necessarily be attached to it. If at one point you find that the tool’s battery is not charging after you put it on charge, there could be several reasons for this:

  • Battery failure, which happens quite often if the tool is mishandled.
  • Charger malfunction. Very often it happens with Chinese tools which are much cheaper than brand-name products.

Although there are two reasons for the lack of battery charging, the first thing to do is to check if the battery is in good condition. It can be checked by connecting a voltmeter or multimeter to the battery terminals. If the instrument will show at least a similar value (12V, 16V, 24V) then the problem is most likely in the charger.

Important to know! Most battery chargers have warning lights (diodes) that indicate when charging is complete. If after connecting the battery, these elements do not show charging mode, or do not light up at all, then the problem is in the charger itself.

Typical electric screwdriver battery charger faults

Typical charger malfunctions include:

  • Fuse blown.
  • Rectifier failure, if the device lowers the voltage from 220V to 12V.
  • Breakdown of the high voltage transistor in the inverter.

The other components, as practice shows, work long and trouble-free, so if you suspect a malfunction of the charger, you should check these three main nodes. Repair of the electric screwdriver charger can be done independently. To do this you will need to disassemble it, which is possible with a regular square screwdriver.

Electric Screwdriver Charger Repair

Repair of the electric screwdriver charger begins with the fact that initially you need to identify the possible cause of malfunction. After all, quite often the cause of the lack of charging the battery is oxidation of the contacts or their clogging on the charger. To begin with carry out a visual inspection of the product, assessing its condition. If there is an odor of burning, it indicates that the internal elements are burned out.

Repair the charger with their own hands by doing the following steps:

  • First remove the housing cover by unscrewing the 4 or 6 fasteners.
  • Remove the cover and you can see that the charger consists of two parts: a transformer and a board.
  • Repair begins with checking the voltage at the output of the transformer. For this purpose the tester is set in “Voltmeter” mode. The plug must be plugged into the socket.

After the repaired charger should be checked for proper operation and function. Standard battery charging time is 1 to 4 hours with a fully discharged battery.

Important to know! Do not store your electric screwdriver for a long time with a fully discharged battery. Also, do not store the electric screwdriver for a long time without using it.

To summarize, you don’t need to be an expert to repair an electric screwdriver battery charger. The design of this product is quite simple, but do not forget that this element runs on electricity, which is dangerous to life. Remember to observe safety precautions when doing repair work.

Until recently, the main helper in the hands of the master was a drill, but today it has been replaced by an electric screwdriver. This portable power tool is used for screwing and unscrewing fasteners, drilling holes and even sanding surfaces. However, the tool for various reasons breaks down, and how to repair it is described here. The description will consider how to repair the charger for an electric screwdriver, and whether it is possible to restore the integrity of the electronic unit.

You rider or repair of flooded GTX 760

Hi there. From this post from time to time there will be repairs done by me at the service center where I work (if interested, all links will be in the telegram).Anyway, received video card Palit GTX 760 with 2GB of video memory.

The defect, according to the owner. Filled, after that is no longer detected in the system. Inspecting the video card and yes, there are traces of flooding. A lot of traces of flooding.

Okay, I thought, I’ll have to trouble finding the right resistors and capacitors. Whatever. I disassemble the video card and.

And that’s where I go nuts. That’s my practice I have never seen. The liquid is even leaking from under the screw fixing the cooling system. Sighing heavily disassemble the graphics card carefully (in order not to get soiled with this substance) and just fell into shock. See for yourself:

Yeah, I certainly did not expect that. Okay, I put a price tag on it and send it to the customer for approval. After a while I get an answer from the client that it is necessary to repair. Eh, I didn’t want to do it, but I guess I have to. I replace the rotten elements and run it in my test bench.

And yes, the card detected and gave a picture. Already can be happy, but the image seemed to me kind of strange. And yes, when I run some test, I see a greenish tint, which clearly should not be. I take a screenshot and it shows a normal picture.

This is the first time I encounter such a defect, so I decided to take some time to think. So while I’m thinking, I’m starting to clean the video card.

Under a stream of hot water wash off all the liquid on the casing of the cooling system (what kind of liquid I did not understand, it is very thick, but under a stream of hot water rinsed hurray).

And I put all the metal pieces in the alcohol for half an hour, and I periodically stirred them.

While it was drying, I decided to look for a boardview. I could not find it in this particular card but I found a boardview for a 760 from Asus. The parts I needed were in another place, but armed with a multimeter I found what I needed. I found a missing resistor in the end and after soldering the resistor the graphics card returned to normal.

Hurrah, I’m almost at the finish. After half a day of testing I fill all problematic spots with greenish lacquer, dry and reassemble the video card.

Putting the video card to the test for a few days:

What might be broken

There are a number of “typical” breakdowns that are common to cordless screwdrivers. On their list is a fuse, diode bridge, capacitor and high voltage transistor. Less common:

  • Power cable break and burn out;
  • Failure of the fuse;
  • transformer short circuit;
  • Rectifier diodes or insulation breakdown;
  • Oxidation of tumbler pins and output device pins.

These faults can be corrected by cleaning the contacts, and replacing small parts. transformer, power cable, automatic control unit.

fuse

Protective element built into the board of all factory chargers. Located before the rectifier bridge after the transformer. It is designed to protect against typical problems: voltage surges, short circuits and stray current, etc.д.

The current-carrying capacity rating in the circuit is calculated from the battery’s rated voltage. Most often the “hair”, the main part of the fuse, carries a current of up to 5A.

Diode Bridge

After checking the fuse, check the rectifier, also called a diode bridge. It consists of four diodes in series, which rectify alternating current and convert it to direct current.

This is how the battery is charged. Fixing a diode bridge requires replacing a diode or unsoldering a diode when there is only one faulty element.

Capacitor

The most common cause of electric screwdriver battery charger failure. The condenser is a cylindrical piece, which will swell due to overheating of the board.

This is followed by the breakage of the fuse and the subsequent burning of the rectifier. All elements of the electrical circuit are interconnected, and if one of them is broken, and the fault was not eliminated, then it will lead to other, more serious malfunctions.

If there is a suspicion of a breakage of one of the circuit elements described above, it is first necessary to check the battery of the electric screwdriver, because the tool most often stops charging due to a faulty battery. If there is nothing wrong with it, you should find the other faulty element that caused the breakdown of the charger.

Resistor

Needed to limit current in electrical circuits. Fails one of the last, most often breaks down as a result of damage to the entire electrical circuit after a short circuit.

Electric screwdriver charger repair

Main breakdowns

Screwdrivers purchased these days can be made not only for the 220 V electrical network, but also for lower voltage networks. There are such models that charge the battery from 120. 130 V and connected to 220 V power supply through a special converter.

That’s why you should be careful when buying a battery charger and check the type of power grid the battery charger is made for. And if there are problems with screwdriver work, for example, the fuse in its charger constantly blows, most likely something has gone wrong.

But the first thing to do is to check if the battery is working properly. If it is functional, the voltmeter will show the correct value when you connect it to the terminals and the engine will rotate even if the battery is not fully charged. The fuse will also not blow if the battery is worn out. So it is most likely that it is burning because of a malfunction in the charger. Most likely it was plugged into 220 V by mistake, even though it was designed for 120. 130 V.

But regardless of belonging to one or the other, all chargers are similar and contain:

  • The line rectifier;
  • step-down inverter;
  • the low voltage part, the inverter rectifier and then the circuit with the appropriate parameters to supply power to recharge the battery.

Where to look for defects

Rectifiers and rectifiers in general are one of the most reliable electronic components when working properly. But if your charger is made to run on 120 to 130 volts and won’t work, and the fuse blows repeatedly when you connect it to a 120 to 130 volt outlet, the problem is probably with the rectifier.

The next candidate for failure is the high voltage transistor in the inverter. It is most likely to malfunction in 220V battery chargers. Rectifier of the inverter and all other electronics, usually works long and trouble free.

Repairing the charger for an electric screwdriver will require the following tools:

In any case it is necessary to disassemble the case of the charger to remove the circuit board. It should be noted that manufacturers save on everything, including fasteners, using a minimum of screws and screws. For this reason the fastening is likely to be done with only one screw or bolt, and all the other elements of fixation in the case will be latches. And you have to try not to break them when disassembling.

If the charger is connected to 120. 130 V, then we need to check the high voltage rectifier. It contains a rectifier bridge and a high capacitor. If the fuse blows, it means that there is a circuit where the corresponding current is flowing. There are only three of these circuits in the charger:

How to troubleshoot

So they need to be checked with a tester in resistance measuring mode. Most likely, the high-voltage electrolytic capacitor of the rectifier will be defective. And here’s why. Since the charger operates as a current limiter, it is unlikely that at correct operation in it something. or from overheating, or from overcurrent. Therefore, the possibility of failure due to increased mains voltage is paramount.

The detected faulty part, which will most likely turn out to be a capacitor, is replaced with a functioning analog. Then a fuse of the required rating is installed. After that you can proceed to check the functionality of the restored board. It is connected to the autotransformer. Before that you should set the output voltage to the lowest possible value. Before connecting the board, the autotransformer is disconnected from the power supply.

The probes of the tester are connected to the output in the mode of measuring DC voltage in the range corresponding to input voltage. The autotransformer is then steplessly adjusted to obtain the necessary voltage. If the problem is solved, the output LEDs will confirm it.

Then the operability of the repaired board is checked in the battery charging mode. If there are no problems in this case too, the printed circuit board can be put back into the housing. If the board is still not working and the battery is not charging, then you need to troubleshoot further. An intact fuse with the charger plugged in and the presence of voltage on the high voltage capacitor indicate that the inverter is not working.

Figuring and troubleshooting an inverter is a difficult task, especially if you don’t have a schematic diagram. To solve it you need an oscilloscope and the appropriate experience. If you have neither, the only thing to do is to use a tester to check and replace all the transistors and chips in the inverter one by one, checking the functionality of the board after each replacement. But this method, although not the cheapest, the charger will be restored.

Repair and spare parts for an electric screwdriver: charger diagram and causes of breakdown

Perhaps the most in-demand tool of any home handyman is an electric screwdriver. But this device, like any other, sometimes breaks down. If this happens, in some cases you can replace the electric screwdriver with an electric drill. But if the work with a drill can not be performed, then you need to carry an electric screwdriver to the service center so that the masters make the repair of the device. But it can take a lot of time, as well as monetary costs. So it makes sense to try to do the repair of an electric screwdriver yourself.

Before you start repair work, you need to get acquainted with the design of this tool and determine the elements that will be needed to fix the electric screwdriver, among them:

The standard design of an electric screwdriver

The main element is the start button, it performs a number of functions: switching on the power supply and the engine speed regulator. If the button is pressed as far as it will go, the motor power supply circuit closes, resulting in maximum power. The speed in this case will also be the maximum. In the device there is an electric regulator, consisting of a PWM generator. This element is located on the board.

The contact placed on the button will move along the board with the pressure on the button. The location of the element determines the level of the pulse applied to the key. The key is the field effect transistor. The principle is as follows: the stronger the button is pressed, the higher the pulse value at the transistor and the higher the voltage to the motor.

The motor is reversed by reversing the polarity on the terminals. This process is carried out by means of contacts which are switched with a reversing knob.

As a rule, screwdrivers are single-phase collector DC motors. They are quite reliable and very easy to maintain. A standard electric screwdriver consists of these parts:

The gear system converts the high rotations of the motor shaft into chuck revolutions. Screwdrivers use classical or planetary gears. The first ones are installed very rarely. Planetary gears consist of these parts:

The sun gear works by means of the armature shaft; its teeth activate the satellites that turn the driver.

A special regulator is installed to regulate the force with which it is fed to the screw. As a rule, there are 15 adjusting positions.

Electrical breakdowns

The main signs of parts failure in this case are:

  • The inability to adjust the number of revolutions;
  • Inability to switch into reverse;
  • Charger failure;
  • the electric screwdriver does not turn on.

The first thing to do is to check the battery of the tool. If the electric screwdriver has been set to charge, but this does not give results, then it is necessary to prepare a multimeter and try with its help to determine the fault.

First you need to measure the voltage of the battery. This value must correspond to approximately the value written on the housing. If the voltage is low, you need to determine the faulty part: the charger or the battery. For this you need a multimeter. This device is plugged in, then measure the voltage across the terminals at idle speed. It must be a few volts higher than indicated on the design. If there is no voltage, then you need to repair the charger.

Repair the charger

A very common problem when working with an electric screwdriver is a rapid discharge of the battery. Reason either the battery is worn out or the charger is not working properly. Let’s tell more about the repair of the charger. For example we will use the battery charger from Bosch AL 60DV. this device is used with NiCd batteries.

As a rule, all battery chargers and most spare parts are not original and are not made in Germany or Switzerland, but in China. But there’s nothing wrong, the quality is usually standard.

The Bosch connector is a three-pin connector: one control connector and two power connectors.

The most common situation appears to be that the battery is placed in the charger. but the charging process ends after 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. Unscrew the four screws at the bottom and open the housing. In the case, in one compartment there is an AC voltage transformer, and in the other compartment there is a rectifier circuit with power connectors and a control chip.

Then plug in the charger and measure the current on the transformer. if everything is normal we go to the next procedure.

Do not touch the control chip and the rectifier, they are probably fine. Let’s go to the contact group. one control contact and two power contacts. To find out what the problem may be we need to measure the current on the power terminals during the charge. Why do we solder a thin wire to all the pins, so you can measure the voltage when the charger works.

It is advisable in this circuit to use several colors of wires and solder them plus and minus accordingly. Then assemble the charger and use a multimeter to test the terminal current during charging.

If the current on the device is unstable and fluctuates in the range of 3-4 to 14-18 volts. And if you move the battery, the contact disappears. This is where the cause is found. over the life of the device. the terminals are bent and poor contact entails unstable charging of the battery of an electric screwdriver.

So, it’s clear that an unstable contact disturbs the charging logic. especially the third contact, the control contact, which is responsible for how much current is applied to the terminals. It can’t be closed because there is a thermistor inside the circuit of any battery and its resistance varies with the temperature of the 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 charger, bend the terminals, then with the multimeter watching the process of charging. the current on the terminals will slowly increase and then decrease, and the indicator light on the charger is an additional indicator of work.

How else you can restore the battery cells

If for some reason it is not possible to restore the battery by replacing the defective cells, you can try to reanimate them. Only note that this cannot be done with lithium-ion banks. Only batteries with nickel-cadmium cells can be reanimated.

battery, charger, electric, screwdriver

Reanimation can be carried out in two ways:

  • Use a vice, a pair of pliers or a hammer to compress the cans with the defect detected;
  • to flash the defective cans with high voltage.

How to charge properly

After purchase and before first use, you must check the charge level, then proceed depending on the type.

If this model has no “memory effect”, you can immediately charge and get to work, otherwise you will need preparation:

  • Ni-Cd: discharge twice or three times and then fully charge to reach full capacity, then use the standard charging procedure;
  • Ni-Mh: can also be “pumped”, like the previous option;
  • Li-Ion: it does not need a full discharge at all (it is even harmful), so it can be charged immediately.
  • Recommended temperature is 10-40 Celsius (or according to the manual);
  • Ni-Mh can overheat, for this reason it is necessary to control the charging (others may also overheat, so in the heat or in a warm room it is necessary to arrange for cooling the battery, if necessary)
  • a charged battery should be disconnected from the charger.
  • it is better to disconnect the battery from the tool when it is not in use
  • if stored for a long time, it is necessary to charge periodically;
  • consider the characteristics of each type (Li-Ion and Ni-Mh should not be discharged, while Ni-Cd, on the contrary, can be stored discharged).
  • first of all. according to the instructions of the charger, additionally paying attention to the indication on the charger;
  • if the battery needs to be recharged quickly. at least half an hour (again, if not contrary to the instructions);
  • A full charge can take up to 7-8 hours; more exact time is indicated in the documentation of the device.

It is worth paying attention to the type of charger. In the amateur segment a simplified scheme is used, while professional models can be equipped with pulse variants. They are more “smart” and powerful, so full charge time can be on the order of an hour.

Design of wireless power supplies

Battery chargers convert the 220V AC current from the mains into DC current. To perform its functions, the charger has a transformer and a special printed circuit board. Batteries produce current through a chemical reaction between the two electrodes and the electrolyte. Voltage ranges from 1.2 to 24 V or more, depending on battery type and amperage. Many wireless devices are powered by a rechargeable nickel-cadmium (nicad) battery or a 20-cell rechargeable battery. Each cell provides about 1.2 volts of direct current. The packs are built directly into the tool and have snap-in terminals.

A number of batteries have permanent built-in batteries that cannot be removed and are charged in the unit.

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