The charger for an electric screwdriver 12v with their own hands

Charger for electric screwdriver with his own hands. scheme and principle of charging

Battery. an assistant for the autonomous operation of an electric screwdriver and other household tools. Charger is intended for charging the battery. Charger diagram for an electric screwdriver is different in different devices, depending on the voltage of the power supply. They come in 12, 14 and 18 volt versions.

The working principle of the charger for different screwdriver batteries is as follows:

  • When the device is plugged into the mains, the 220V voltage passes through the fuse.
  • AC voltage is fed to the step-down transformer. Converts voltages up to 18.
  • The charge is transferred to the diode bridge.
  • It is rectified and fed to the capacitor C1, which has a capacity of 330 uF. The voltage is converted to 24V.

The relay closes after being switched on by pressing a button. The battery starts to charge at the output of the line rectifier. The average time to fully charge the battery in an electric screwdriver is 50-60 minutes. These are average values that apply to 12, 14 or 18 volt batteries.

Adapter as a battery charger for lithium-ion batteries of an electric screwdriver.

Last time I looked at replacing the nickel-cadmium NiCd batteries of an electric screwdriver with lithium-ion. Now there is a question of charging these batteries. Lithium ion batteries of the 18650 format can usually be charged to a voltage of 4.20V per cell with a maximum tolerance of 50 millivolts because an increase in voltage can damage the structure of the battery. The charging current can range from 0,1C to 1C (C-capacitance of the battery). It is better to choose this value according to the datasheet of the particular battery. I have used Samsung INR18650-30Q 3000mAh 15A batteries in re-design of the electric screwdriver. Looking at the datasheet. charging current.1,5А. The most correct way to charge lithium batteries is to use the CC/CV (constant current, constant voltage) method in two steps. First step is to have a constant current of charge. The value of the current is 0.2-0.5С. For a battery with a capacity of 3000 mA/h, the nominal charging current at the first stage is 600-1500 mA. The second stage is charging the battery with constant voltage, the current is constantly decreasing. Maintains battery voltage within 4.15-4.25 В. The charging process will be terminated when the current falls to 0.05-0.01С. At this stage the charger maintains the battery voltage of 4.15-4.25 volt and controls the current value.As you gain capacity, the charging current will decrease. As soon as it drops to 0.05-0.01C, charging process is complete. Taking into consideration the above said I used ready made electronic modules from Aliexpress. CC/CV derating board with current limitation on XL4015E1 chip or LM2596. I prefer the board on XL4015E1 as it is more convenient to set up. Characteristics of XL4015E1 board. Maximum output current up to 5 Ampere. Output voltage: 0.8V-30V. Input voltage: 5V-32V. LM2596-based circuit board has similar parameters, but the current is slightly less. up to 3 Amps. The board for controlling the charge of the lithium-ion battery is selected earlier. As a power supply, you can use any of the following parameters. the output voltage of 18 volts (circuit 4S), current is not less than 2-3 Amps. As a first example of building a battery charger for lithium-ion batteries of an electric screwdriver, I used a 220/12 volt, 3 Amp adapter. I checked beforehand how much current it can deliver at rated load. I connected a car lamp to the output and waited for half an hour. Outputs freely without a preload of 1.9 Ampere. I also checked the temperature of the transistor heatsinks at 40 degree Celsius. Pretty good-normal mode. But in this case there is not enough voltage. This is easily fixed, with only one penny radio component, a variable resistor (potentiometer) of 10-20 kOhm. Let’s look at a typical adapter circuit. There is a TL431 controllable switch on the circuit, it is in the feedback circuit. Its task is to keep the output voltage stable according to the load. Through the divider of two resistors it is connected to the plus output of the adapter. We need to solder to the resistor (or solder it out and solder in its place, then the voltage will be adjusted in a smaller way), which is connected to pin 1 of the TL431 regulator and to the minus bus a variable resistor. Turn the potentiometer axis and set the voltage. In my case I have set it to 18 volts (a small margin of 16.8 volts for the drop in the CCCV board). If you have a voltage indicated on the cases of electrolytic capacitors at the output of the circuit will be higher than the new voltage they can explode. Then you have to replace them with a 30% voltage reserve. Next, connect the board to the adapter for charge control. We set the voltage of 16,8 Volt with the trimmer on the board. We use another resistor to set the current of 1,5 Ampere, preliminarily connect the tester in the ammeter mode to the output of the board. Now you can plug in the lithium-ion assembly of an electric screwdriver. Charging went fine, the current dropped to a minimum by the end of the charge, the battery was charged. The temperature of the adapter was in the 40-43 degree Celsius range, which is normal. In the future you can drill holes in the housing of the adapter for better ventilation (especially in summer). The end of the battery charge can be seen by the LED on the XL4015E1 board turning on. In this example I used another board with LM2596 because I accidentally burned XL4015E1 during the experiments. I advise to do the charging better on the XL4015E1 board.

I also have a regular charger from another electric screwdriver. It is designed to charge Ni-Cd batteries. I want to use this regular charger to charge both Ni-Cd and Li-Ion batteries. It was solved simply soldered to the output wires (red plus, black minus) wires to the board CCCV. The no-load voltage at the output of the standard charger was 27 volts, this is quite suitable for our charger board. After that, connected the same way as with the adapter. The end of the charging, we see here by the change of color of the LED (switch from red to green). I put the CCCV board itself in a suitable plastic box, bringing the wires outside. If you have regular transformer charger you can connect the CCCV card after the diode bridge of the rectifier. The way of transforming the adapter for beginners and may be useful for other purposes, as a result we get a budget unit to power various devices. I wish you all good health and success in shopping and life. details about the charger for a converted electric screwdriver can be seen in the video

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Goods provided for writing the review store. The review is published in accordance with p.18 Site Rules.

Possible power sources

In order for any electric screwdriver to function from the mains, it needs to provide voltage conversion: the tool requires only 12, 16 or 18 volts. All power supplies fall into 2 large groups: they can be pulsed or transformer.

Impulse systems

In these power supplies the input voltage is first rectified, then converted into high frequency pulses. They are fed through a transformer or through ordinary resistors. The second method makes it possible to obtain a small-sized design, since the circuit does not have a massive power transformer.

This power supply for an electric screwdriver usually has a fairly high efficiency of up to 98%. The plus side of the solution is the short circuit protection, the safety guaranteed by the locking without load. The following are some disadvantages of pulse units. This is a lower wattage when compared with the transformer version. If the lower load limit is minimal, such a power supply will not work. Another disadvantage. more complicated repair in case of failure of pulse PSU.

charger, electric, screwdriver, their

Transformer unit

This is a classic device. A linear power supply includes a step-down transformer and a rectifier that turns alternating current into direct current. The last element comes in two forms: a single half-periodic diode, consisting of one diode, or a double half-periodic diode bridge, consisting of 4 electronic elements.

The circuit of the transformer unit may include a capacitor, stabilizer, high-pass filter and short circuit protection. Advantages of the device: simplicity, reliability, maintainability, no interference, and very expensive elements. Disadvantages. large size and the same weight, low efficiency. Since part of the voltage is drawn by a regulator, the output value must be higher than that required to operate an electric screwdriver. For example, for tool with 12 V power supply you need PSU, which has output voltage from 12 to 14 volts.

Charging a faulty battery

Sometimes it happens that the electric screwdriver itself works, but the battery is broken. There are several solutions to the problem:

  • Buying a new one.
  • Repairing an old one. If you do it yourself, you need special knowledge. Besides, not everyone wants to work with harmful substances.
  • Wiring via a power supply. For example, if you have a common “Chinese” for 14.4 V, a car battery will do. You can build your own from a 15-17V transformer. You’ll need a diode bridge (rectifier) and a thermostat to prevent overheating. The rest of the components. only to control the input and output voltage. You don’t need a regulator.
  • The “native” battery or its substitutes can be excluded from the construction altogether. electric screwdriver will be powered directly from the mains.

Battery charger 12.6V 3A, or continuing the conversation about converting an electric screwdriver battery

At the end of last year I posted a couple of reviews on the subject of converting screwdriver batteries. Today I’m going to talk about an alternative way to charge a rebuilt battery using an off-the-shelf battery charger. Anyway, as always, inspection, disassembly, schematics, tests.

Last time I suggested using an old charger with a separate converter board for charging. This is not a bad alternative, but I was wondering what to do if the old charger is broken, is broken, was eaten by a cat. So I accidentally came across a charger option in a store that would work with 3S batteries, t.е. 12.6 Volt. Since this option is one of the most common when converting old screwdrivers, I decided to order it for review.

Packaging is very ascetic, however, as well as the inscription indicating the voltage and charging current.

The package is very simple, the cable and the charger itself.

The cable is basically not bad, but the plug is bad, the options. cut, change or look for the adapter.

The charger is made in a power supply format, it is quite weighty, the housing is sturdy.

On one side of the housing is a two-pin power connector, on the other side of the cable with the usual 5.5/2.1mm plug. Cable length of about 1 meter.

The charger, not the power adapter you use to charge your smartphone/tablet, so it has an end of charge indicator. But it’s not very bright, in a bright sunlight it would not be noticeable, such as in a flashlight.

At the bottom there is a sticker with the characteristics, nothing new, other than what was stated on the package, I saw.

As I wrote above, the case is quite robust but it can not resist a hammer and knife, and there is no other way to disassemble this product.

The board is very firmly seated inside. Partly double sided adhesive tape, partly silicone glued to the power section. In the picture you can see the inside of the case, in addition there is some gluey mass.

It looks economical but it is of high quality. The radiators are insulated and held in place by the power element itself, an additional lobe, and a silicone sealant. Also the transformer and the input choke are glued to the case. In general it was pretty hard to take the board out.

At the input a fuse is present, and the input filter. Unfortunately there is no thermistor, instead of that there is a jumper.

The capacity of the input capacitor is 68μF, about 40 Watts of power is enough. 2. A CS7N60F high voltage transistor in a fully insulated package. 3, 4. On one side of the transformer is a feedback optocoupler, and on the other side is a correct noise suppression capacitor Y class, so it won’t kill you with current. 5. 10 Amp 100 Volt diode output assembly, with both current and voltage to spare. 6. Output capacitors have capacity 1000 uF and voltage up to 25 Volt, no questions here either. Along the way there is room to install a noise suppression choke and a third capacitor.

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Even more components on the bottom of the board.

The “hot” side of the power supply. Here I also had no questions, well almost none 🙂

The “cold” side. Here you can find voltage and current stabilization elements, as well as end of charge indication.

My only complaint about the “hot” side was the soldering, or to be more precise its quality. I have a feeling, that PWM controller was re-soldered, because all other parts are soldered carefully. No questions to the output side, everything is neat, the elements are additionally fixed with glue. An LM358 operational amplifier.

Since I don’t have a review of such a device yet, it was impossible not to redraw the schematic. However, the primary part of the power supply turned out to be almost identical to the power supply I have already reviewed. Power Supply 12 Volt 1 Amp. The unit is very reliable and of good quality. The only difference is the nominal values of some components and their number, the chip has the same pinout.

Since the circuit is big, I split it into two parts, primary and secondary, to make it more understandable. The secondary side is different from the usual power supply circuits because it has more nodes.

I will list the parts separately. 1. The green one is the output voltage regulator which is responsible for the CV mode. 2. Red. Current Stabilization, CC mode. 3. Blue. display unit. On the top left two rectifiers, primary and secondary (D3, C5) to power the operational amplifier and the LED. Additional power is necessary that these elements do not consume current when the battery is connected and the charger is not plugged in. Between the red and blue node is source of reference voltage for the indication and current stabilization node.

Options for making a power supply

There are several options on how to convert the screwdriver to work from the mains. The task is to power the electric motor of the device with an intermediate source.

We use the charger from a laptop

Make a 12 V power supply for a screwdriver with your own hands is possible, even without technical knowledge. It is only necessary to find an unnecessary charger from a laptop, which has specifications similar to those for powering a screwdriver. The main thing is that the output voltage corresponds to the desired one (12-14 volts).

To achieve this goal, you must first disassemble the battery and remove the defective elements from there. Then the following manipulations follow:

  • Taking a laptop charger.
  • Cut off the output connector, bare and tin the ends of the wires.
  • We solder the stripped wires to the battery input wires.
  • Insulate the soldering points to avoid short circuits.
  • Make a hole in the housing, so as not to squeeze the wire, and assemble the construction.

The basis. the power supply from a computer

For the manufacture of such a device we will need a block from a personal computer of format A. Т. It is not difficult to find it, this is an old model of the power supply unit which is easy to buy at any market for radio components. It is important to know that you can use a 300-350 W block with a current of 12 V at least 16 A.

AT format blocks meet these parameters. On the body of this device there is a power button, which is very convenient when working. Inside is a cooling fan and an overload protection circuit.

Here is how you are going to set up the unit:

  • Remove the lid of the housing B. П. Inside we will see the board with a lot of wires going to the connectors, as well as a fan.
  • The next step is to turn off the power protection. Find the green wire on the large square connector.
  • Connect this wire with the black wire from the same connector. You can make a jumper from another piece of wire, or you can just cut it short and leave it in the case.

Then in the outputs bunch find the smaller connector (MOLEX) and do with it the following operations:

  • We leave the black and yellow wire and cut the other two short.
  • For convenient location of the PSU during work, solder an extension cord to the black and yellow wires.
  • The other end of the extension cord is attached to the contacts of the empty battery compartment. This should be done by soldering, you can make a good twist, while it is necessary to observe the polarity.
  • Make a hole in the housing, so as not to squeeze the wire during assembly. The device is ready.

If you have the desire to ennoble your design, t. е. put it in another case, drill holes for air intake to prevent the PSU from overheating.

Power from the car charger

With a car battery charger, it’s pretty easy to make a device to power a screwdriver. To make the conversion, you just need to connect the power terminals of the charger output to power the electric motor.

If you have a battery charger with continuously variable output voltage, you can use it as a power supply for the 18 volt screwdriver.

Converting an electric screwdriver to lithium, part two, charging properly

Last time I told you how to properly convert a battery for a cordless tool. I also wrote that I would talk about the charging features, and the subject of the review this time will be the DC-DC converter board. If you are interested, please visit.

I had originally planned to limit myself to two parts, the battery and charger redesign. But while preparing the review, in my head matured the idea for the third part of the review, more complicated. And in this part I will tell you how you can remake native transformer charger, if it still works, or if the power transformer is still alive.

The converter board was ordered some time ago in quantity of several pieces (as a reserve), it was ordered specially for this modification because it has some features, however I won’t go too far ahead, let’s be consecutive.

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First I will divide the chargers into three main types: 1. The simplest ones are a transformer, a diode bridge and some parts. Such chargers complete the ultra budget instruments. 2. Signature. In fact it’s the same but it has already included simple “brains” which automatically turn off the charge at the end of the transformer. 3. “Advanced”. switching power supply, charge controller, sometimes charging several batteries simultaneously.

Tools from the first category rarely fall under the remake, because it is often easier (and cheaper) to buy a new, and the third category usually has its own difficulties for remaking. In principle it is possible to change the devices of the third group, but not within the scope of this article, because there are so many types of chargers and each needs an individual approach.

This time I will be redoing the charger from the second group, a branded, though simple. But this redesign has a lot in common with the first group, so it will be useful to most readers.

In order to charge the battery you need not just connect it to the power supply, such an experiment usually ends not very well. We need to connect it to the charger. And here comes a slight misunderstanding, as quite a few people are used to calling chargers small power supplies from which they charge their smartphones, tablets and laptops. They are not battery chargers, they are power packs.

What is the difference between the charger and the power supply. The power supply is designed to deliver a stabilized voltage within the range of the stated load currents. A charger is usually more complicated, because its output voltage depends on the load current, which in turn is limited. In this case the charger has a unit which stops the charge at the end and sometimes it’s protected from connecting the battery in wrong polarity.

The simplest battery charger is just a power supply and a resistor (sometimes a bulb, which is even better) in series with the battery. This circuit limits the charging current but you understand it can do nothing else.

It is a little more complicated when they have a timer which stops the charge after a certain amount of time but this principle quickly “kills” the batteries. For example it is made in one of the inexpensive screwdriver chargers (not my photo).

The next class are more “smart” chargers, although in fact they are not much better than the previous one. For example here is a photo of brand new Bosch battery charger for charging NiCd batteries.

But all these chargers seem very simple after looking at modern options for charging lithium batteries.

Of course the last option does not fit in our rewiring concept because it would be nice if our charger not only charged right but also cost very little money.

The chargers of Chinese screwdrivers certainly look much easier, but then again, to make from scratch such a device is unlikely who wants, although that’s what I plan to do in the third part, though more accurately.

And so, to begin with let’s assume we have a battery charger which just does not fit the new type of batteries, but is serviceable. Or at least it has a functioning transformer. As I wrote above you can even use a simple resistor or a light bulb, but that’s “not our way”.

A typical diagram of a typical inexpensive battery charger looks like this: Transformer, diode bridge, thyristor and control circuit. But sometimes there is a relay instead of a thyristor, the current is not limited in any way and there may be a thermal control circuit against overheating (although it does not always save.

But we need only transformer and diode bridge from this scheme, but we’ll have to add more capacitor, so we’ll get some initial unchanged part, it’s marked red and won’t change further.

The diode bridge is usually on the board and can be used if necessary (if it is intact). Т.е. Generally speaking, you can unsolder all the radio elements from the board, leaving only four diodes and the terminals to connect the battery, and use the board itself as a base. The cathode of diodes is marked by a strip, the point where you connect two pins marked by a strip. plus, respectively, the point of connection of “unmarked” pins. minus. To the other two points of the connection a transformer is connected.

The truth having opened a charger you can see and such picture (don’t pay attention on absence of transformer): In this case it is necessary to unsolder all.

Charge modes

Nickel-cadmium (sulfuric acid) cells are charged at 1.2 (1.8-2) V, respectively, while maintaining a current of (0.1-0.15) C. For lithium-ion models, the voltage is raised to 3.3 V. A standard 18 volt electric screwdriver charger will maintain the same level while charging. The end of the operation is monitored at 21 V.

Important! Lithium cells are especially sensitive to overheating. Temperatures over 60°C can cause not only structural failure, but also fire. This parameter is carefully controlled to avoid hazardous situations.

List of radio elements

Type Nominal Quantity NoteShopMy NotebookVD1-VD4








Diode KD2998V 4 Search in the Otron store Notepad
Capacitor 1.0 μF 1 400 В Search in the Otron store In pad
Capacitor 0.47 uF 1 160 В Search in the Otron store Notebook
Electrolytic capacitor 2200 μF 15 16 В Search in Otron store To the notebook
Electrolytic capacitor 1000 uF 4 16 В Search in the Otron store To Notebook
Capacitor 1.0 μF 1 160 В Search in Otron store To the Notebook
Fuse 3.16 А 1 see. Text Search the Otron Shop In the notebook
Transformer 220/8 В 1 see. Text Search in the Otron store To Notebook
Add all

r9o-11 Published: 04.12.2015 0 1

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