Reworking an electric screwdriver for mains power. Power supply options

How to turn a cordless electric screwdriver into a cordless screwdriver

A cordless electric screwdriver was created primarily to provide mobility. It is much more convenient to work with the tool without thinking about whether the wire is long enough, whether it gets caught, etc. д.

But without batteries, such a handy tool, like an electric screwdriver, becomes a simple piece of iron, although it is fully functional. Batteries have a service life of about 3 years, and it is often impossible to find complete or similar batteries on sale. For example, the manufacturer has already stopped producing such a model, and other batteries are not suitable according to various parameters.

To throw away a tool, for which at one time the money was paid, sometimes quite a considerable amount, can be very pathetic. Besides, the cost of batteries is often up to 80% of the price of an electric screwdriver, and it is more reasonable to buy a new tool. As a rule, the old tool is sent to a distant shelf and lies there uselessly. But there is a way to make it work again, and that is to convert it to 220 volt power.


It is necessary to disconnect the battery of the electric screwdriver, disassemble it, and remove the batteries.

The latter are carefully detached from the batteries, and a 4 kV wire is soldered to Then the terminals are inserted into the holders.

Next, you need to drill the battery case, remove the chamfer on the hole to screw the terminal holder through it with an M3 screw, because without batteries it will not hold.

Before installation, a capacitor is soldered to the terminals, so that the power supply from the PC does not go into inrush currents protection.

Since the capacitor will interfere with holding the nut when tightening the screw, it is better to glue it to the terminal holder. On the side of the battery case, the hole for the wire is shined through.

Then the terminal holder is screwed on and everything is put back together. It is important to remember which terminal of which color the wire is soldered to.

According to the label on the power supply unit, you need to determine which of its wires have a 12 V output, and connect to them. If there are 2 such lines, then they are twisted together.

To make the power supply turn on without a computer, you need to short any black wire to the green. This can be done with a paper clip jumper.

If the power supply turns out to be weak for your electric screwdriver, it will go into protection even with a capacitor. Then you need to connect a separate load to it. It could be an old hard drive. It also helps to have a 5W 6V light bulb installed on a 5V trimmer line unit. By modifying your electric screwdriver in this way, you save the possibility at any time to disconnect the modified battery case from it, and put a regular battery.

Electric screwdriver battery design

Converting an electric screwdriver to lithium 18650 batteries

The design of the battery is independent of the brand. In all devices, the design of batteries is similar and differs in appearance, housing and contacts.

The device of the rechargeable battery

The case contains several cells connected in series. Their number depends on the voltage of each cell and the battery as a whole. When using the most common, nickel-cadmium cells with a voltage of 1.2 V, to supply a device rated 12 V, you need 10 pcs. The capacity of the battery is indicated in ampere hours.

Interesting. When connected in series, the output voltage increases, and the capacity does not change and is equal to the capacity of the individual cells.

Basic Materials:

To transfer the power of an electric screwdriver from the battery to the mains, you need to get to its power contacts. To do this, you need to disassemble the case of the battery pack. The batteries present in it are removed.

Since the contacts of the batteries remain on the removed batteries, it is necessary to refine them in order to return them to the case. To do this, I cut two short tubes from a 20-meter polypropylene pipe. Their length should match the height of the battery pack removed. It is necessary that the sections fit into the battery housing of the electric screwdriver.

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Most likely one of the edges of the tubes will have to be trimmed a bit as it will rest against the ledge on the cover.

Next, remove the contact plates from the batteries and transfer them to the tubes. To make them fit snugly, each tube should be wrapped in duct tape, thus increasing the seating diameter. After that, a cable of a convenient length is soldered to the pins and they are finally attached to the tubes.

Now you need to connect the cable from the terminals of the electric screwdriver to the power supply wire. Here it is important to observe the polarity. The plus side of the block should connect to the plus terminal and the minus side to the minus terminal. It’s better to solder the twist to be sure. Its insulation can be done with electrical tape or heat shrink.

Next, the contacts with tubes are placed in the battery case. To do this, a side hole is made in it right at the junction with the cover for wire entry. To prevent the tubes with contacts from slipping and falling out, everything is fixed with hot melt adhesive. To be sure, you can also apply it to the joint between the housing and the lid, so that it does not open.

electric, screwdriver, mains, power, supply

Now when you plug the power supply into the socket, the electric screwdriver can work from the mains for as long as you want without recharging.

How to make an electric screwdriver from the mains video

You can see how to convert an electric screwdriver in detail at

If after the batteries have become unusable to remake the electric screwdriver to power from 220 V, then this will allow to continue to use the tool without significant cost.

When the batteries stop working, many people wonder how they can convert a cordless electric screwdriver to a mains. It is impossible to repair batteries with ruined cells. The cost of new power supplies is almost equal to the price of an electric screwdriver. Finding the right elements is not always possible, models are often removed from production. But for Zealous and skillful owners there is a way out. to power an electric screwdriver from the mains.

The converted tool has one disadvantage: it is tied to the outlet. But this is not so important for indoor work. But there are more advantages. Now you do not have to worry about recharging the battery, there will be no downtime. The current strength at all times remains stable and does not depend on the battery discharge, and this means a constant torque.

Before you go looking for a power supply (hereinafter. PSU), study the parameters of the electric screwdriver, which are listed on the case or in the passport. Pay attention to the voltage. 12-volt tools are more common, and it’s not hard to find a power adapter for them. If the voltage is higher, the search may take longer. It is required to find out the current consumption, which is not indicated in the technical specification. Purchased unit must deliver an average current value (between the battery capacity and regular charger). You can read the data from the markings.

There are two main options for converting a cordless electric screwdriver to 220 volts. The first is to use an external PSU. Any rectifier capable of delivering the necessary DC voltage is suitable. Even if it is large and bulky, there is no problem. After all, you do not have to carry it around the room. The unit is installed near the outlet, and the cord to the tool makes the required length.

Remember that with a decrease in voltage the current increases, if the power remains the same. This means that the cross section of the low-voltage cord must be larger than that of the 220 V mains.

The second option is that the PSU is mounted in a housing from the battery. The only obstacle to this method may be the size of the transformer. Mobility is retained, the radius of use depends on the length of the power cord. It is important to remember that the tool is powered by 220 V, so the cord must be reliable and the input itself must be neatly made, carefully insulated.

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Available power supplies can be used as an external source:

You can inexpensively buy an old charger at the market. Pulse chargers are now mostly used, and older devices are often sold out of necessity. This is the charger with the ability to manually adjust the voltage and current is ideal for any electric screwdriver, regardless of its operating voltage. All remodeling consists of connecting the low-voltage cord to the output pins of the charger.

The power supply of the computer is purchased from older models, it must have a shutdown button. It will not be needed, but it is the format option “AT”, which is needed. At flea markets, choose a unit rated at 300-350 watts, which will ensure the reliable operation of low-power and medium screwdrivers. All technical specifications are indicated on the sticker on the case. The unit has a cooling fan and overload protection. To remake a computer PSU with your own hands on an external power supply for an electric screwdriver, perform simple operations:

  • disassemble the case;
  • On the large square connector, find the green wire and any black wire;
  • connect the two wires together, insulate them;
  • On the other smaller connector remove all the wires, leaving the yellow and black;
  • solder the low voltage cable to them.

To observe the polarity you should know: yellow wire. positive, black. negative. From the computer power supply works tool with up to 14 volts.

Most laptop chargers have characteristics that allow them to be used as a power source of an electric screwdriver. You can use a charger with a 12 to 19 volt output voltage. The only changes that need to be made are to the output plug. It should be cut, stripped the wires and soldered to them a cable of the desired length.

People who have an idea of electrical engineering can make a homemade power supply. Its circuit is quite simple and includes a step-down transformer, diode rectifier and two capacitors. All parts can be bought or borrowed from old radio equipment. A transformer from a tube TV set with a 24-30V output is just fine. The presence of a rectifying diode bridge is mandatory. Capacitors are used non-deficient, from old equipment: one at 0.1 uF and the other electrolytic at 4700 uF.

Warning! Be sure to enclose the construction in a case. To protect against short circuits, you must install fuses on the input and output.

Power supply for the electric screwdriver can be placed in the battery case or in the handle. Choices:

At the radio market pick up a PSU with the right parameters. At home it should be carefully removed from the case and placed in your electric screwdriver, fixing all components securely. If the wires are short, lengthen them so that they do not touch metal parts. Place the transformer and board separately. Place additional heat sinks on the microcircuits for better cooling. Holes in the housing are also useful to circulate air and dissipate heat during operation.

The mobility of the device

When transferring battery-powered equipment to the mains one of the main distinctive features is lost. mobility. Therefore, if you decide to make a remodeling of the screwdriver power supply, you must determine exactly what kind of device you want to use in the future.

There are two concepts on how to convert cordless type equipment to mains power:

  • The power supply (PSU) will be external. This version requires a separate unit. But don’t let this scare you, even a heavy and large rectifier can simply be near a power outlet. You will still be limited by the length of the power cable either to the socket or to the power supply unit. According to Ohm’s law, reducing the voltage for the same power increases the amperage. Therefore, the cross section of the 12-19 volt power cord of the device must be larger than the 220 volt power cord.
  • The power supply is built into the battery housing. With such a device mobility is almost completely preserved, only the length of the mains cable can limit the movement of the operator. One problem may arise if you need to install a high wattage transformer in the battery case of your screwdriver. But the modern radio industry allows us to solve this problem, there are a large number of compact rectifiers on the radio equipment markets.
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Each method finds supporters, because it has a certain set of characteristics.

Power supply options

Any electric screwdriver requires much less voltage than a regular socket. Therefore, in order to feed it, a special converter is needed, the output of which will produce the necessary voltage. All power supplies are divided into two large groups: pulsed and transformer. Let’s look at each of them separately.


The principle of impulse systems is that the voltage is first rectified, and then converted to a special impulse signal. It is important to achieve a stable voltage. A transformer winding or resistors can help.

electric, screwdriver, mains, power, supply

Switch mode power supplies are effective enough and can be used in different conditions. At the same time, they have a high level of protection against short circuits and similar effects. But the pulsed systems clearly lose out to the transformer ones in terms of power. Besides such units are very picky about the input voltage. If it is lower than the set voltage, the element can simply not work.


common power supply units which have proven reliable and efficient in many applications. It consists of a step-down transformer and a rectifier, through which a low voltage is passed. Rectifiers can be different, depending on the number of diodes used.

Such elements are simple to make, cheap and reliable. That is why they are often preferred. They provide a stable voltage without interference with high maximum power. But there are a few disadvantages. The main disadvantage is that they are bulky, with much lower efficiency than pulsed sources. This fact requires picking up a power supply for an electric screwdriver with more power than the tool needs. Because part of the power is spent on side processes.

electric, screwdriver, mains, power, supply

Selection Features

When choosing power it is worth taking into account not only what power of an electric screwdriver is specified in the information from the manufacturer. Because the output is too high, it can drive the screws too hard, forcing their heads into the surface. This spoils the appearance of the surface and makes it virtually impossible to unscrew the fasteners, if necessary.

Choosing what voltage is better for an electric screwdriver, you should consider that the voltage is the main parameter of the device. For example, the Makita DDF343SHE electric screwdriver has a motor power of 700W, a voltage of 14.4V, a battery capacity of 1,300mAh, and a torque of 36Nm. While the other Hammer ACD182 has a weaker motor (22 Nm) and a smaller battery capacity (1200 mAh) and appears to be around 40% weaker. However, due to the voltage of 18 V, “Hammer” is able to screw more fasteners without recharging, even inferior to the competitor in terms of battery capacity.

You can understand why a seemingly less productive screwdriver is inferior to a more powerful one by performing a small calculation:

When choosing a screwdriver, it is desirable to take into account the presence of a spare battery. Some models even have 2 extra batteries. On the one hand, such a set will cost more (the more so as the cost of the battery is up to 80% of the equipment price), but it will be much more convenient to work with. At the same time performing household tasks additional battery is not needed. the time of work performed with its help rarely exceeds 1-2 hours. Whereas in the process of constant use of the screwdriver (eg for repair work or furniture assembly) the second battery allows not to interrupt the work for more than a few minutes. A discharged battery is placed on charge, and a spare battery is installed in the device.

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