Redance power supply for lithium batteries. Pros and cons of installation…

Alteration of an electric screwdriver for lithium batteries

Is the alteration of an electric screwdriver or other power tools for lithium batteries possible and how to do it correctly. In this article, we tried to clarify some points for beginner home.made people and picked up budgetary components of good quality.

The rules for using nickel-cadmium and nickel-metall-gidrid oblige to discharge the battery in front of the charge, otherwise its capacity is rapidly falling. Without observing these rules, the battery cannot serve for a long time. And their full charge lasts about 10 hours, which is not very fast.

Lithium batteries are deprived of this drawback. They can be charged from any level. And the charge is possible many times faster. A full charge cycle is from 0 to 100% when using the correct charger can occupy about one and a half hours. And for batteries with the possibility of fast charge. less than an hour.

With the same volume and mass of the same with Nicd or Ni MH, the lithium battery will be several times more capacious, which means it will be enough for a greater volume of work. In addition, lithium batteries have a low self-discharge, durable and lighter than nickel-cadmium and nickel-metal-hydride battery.

In a similar way, it is possible to remake not only an electric screwdriver, but also other batteries and devices with power supply from batteries.

Selecting the type of lithium battery chemistry

First of all, you need to decide on the choice of the type of chemistry of lithium batteries. There are two options-either phosphate iron lithium (lifepo4), or ion lithium (Li-Ion). But in any case, when working on such a powerful load, you need to consider that the battery must be able to give the required current without harm to its well.being! We will briefly analyze the features of these types of batteries.

Working temperature

If it is supposed to use an electric screwdriver at minus temperatures, then it is better to choose phosphate iron lithium (Lifepo4) Batteries. Temperature range at which you can discharge them.20 ~ 65 ° C. Li-Ion has a faster container faster. If the work is mainly planned at plus temperatures, then both are suitable for both. But both types of batteries (with the exception of some Lifepo4 models) cannot be charged at a negative temperature. And the upper temperature limit when charge in both is about 60 ° C.

Dimensions and weight

With the same capacity, lifepo4 batteries are almost one and a half times heavier and more in the volume than Li-Ion.

Durability

The number of full cycles of the charge/discharge of Lifepo4 batteries of more than 1000, in Li-Ion less than 500. But! If you are not up to 0% and not to 100% charge, then the number of cycles increases significantly. Storage of any lithium batteries best tolerate half charged at a temperature of 0 10 ° C. Read more about storage in this article.

Work voltage

One LI-Ion Battery cell with 100% charge has a voltage of 4.2 V, with a full discharge of about 3-2.5 V. Average operating voltage 3.7 in.

One lifepo4 cell of the battery with 100% charge has a voltage of 3.6 V, with a full discharge of about 2 V. Average operating voltage 3.2 V.

Based on this, we consider the number of sequentially connected cells to obtain the required voltage at the output of the battery. This is customary to indicate the number of sequential cells symbol S (serial. consistent). The voltage with this connection is summarized.

Li-Ion: 1S-4.2 V, 2S-8.4 V, 3S-12.6 V, 4S-16.8 V, 5S-21 V.

Lifepo4: 1S-3.6 V, 2S-7.2 V, 3S-10.8 V, 4S-14.4 V, 5S-18 V.

That is, for example, for a 12 voluntary electric screwdriver, you need a LI-Ion 3S battery, or Lifepo4 4s.

Working current

The characteristics of the battery usually indicate the nominal and maximum (peak) discharge current. With a rated current, it is able to work for a long time, and with a peak. for a few seconds. Therefore, for such a powerful load as an electric screwdriver, it is necessary to pay attention to this indicator and choose high.precision batteries.

At idle 12, 12 volt electrical screwdriver consumes current 1-2 A, and with maximum load (especially in a inhibited state), the current can reach 30 A. Therefore, if it is supposed to use, for example, the GTF HG2 18650 3000 3000 mAh with a nominal and peak currents, respectively 10A and 25A, then you need to assemble a minimum of 3S2P so as not to overload the batteries. With a parallel connection of two batteries, the permissible currents are doubled, when connecting three. triple and t.D.

Details and tools for remaking

To transfer the existing electric screwdriver to lithium, you must purchase:

• a soldering iron with a capacity of at least 40 watts with a set of consumables, including an acid flux;
• small locksmith tool (screwdrivers, scalpel, etc.P.).

The process itself is quite creative, depends on the existing initial conditions and the design of the electrical screwdriver, therefore, in the course of the alteration, something else will be required. You have to be prepared for this.

Before remaking the power tool for working on Li-Ion batteries, future operating conditions must be taken into account. Lithium-ion elements are unsuitable for working at low temperatures.

How many and which batteries to purchase

In most cases, to remake any electrical screwdriver for lithium batteries use elements of size 18650. This figure means linear dimensions:

These batteries belong to the category of finger. have a cylindrical shape with conclusions of positive and negative poles from opposite sides. The voltage of one element in a fully charged state is 3.6 volts. For each electric screwdriver, you need to dial the required voltage. It can be found on the body of the old battery.

Obviously, out of 3.6-volt elements, it is not always possible to gain voltage strictly equal to the face value. So, for 18, everything turns out perfectly, and for 12 V you will have to be content with either a slightly smaller or slightly high voltage. It must be understood that in the first version the torque will fall a little, and in the second it will increase, but you must be prepared to reduce the resource of the mechanical part. In addition, there is a chance that increased voltage can disable the electronic control circuit. Although the reviews on the network say that everything works fine in this regard.

What tools will be needed to redo the screwdriver for a 12 volt lithium battery

To remake batteries for lithium-ion batteries, you will need such tools as:

• a soldering device with a capacity of more than 40 watts with some consumables, including an acid flux;
• Repair tools such as screwdrivers, pliers, scalpel, hammer, nippers, knife.
• In some cases, an insulation tape may be required;
• It is also mandatory when using a welding machine to use a specialized protective mask.

Dismantling of the power supply for new charging

All parts are removed from the body, leaving contact terminals or plates. Perform a sequential connection of new batteries with point welding or soldering, due to the sequence, the container and voltage will be constant. Connect with wires with cross section 2.5 mm². They withstand great voltage, which is created during operation.

First, they clean all parts of the case, think about where to place a new charging block. In size, the converted battery will be much smaller than the native, because it must be well fixed inside the case. If this is not done, then due to vibration when working the instrument, the block after a short period of time will fail. For fastening, you can use the glue moment or sealant. The wires are soldered to the assembled block. When working, the connection schemes adhere to. The wires with a cross section of 4 mm2 are soldered to the batteries. So that the details do not contact each other, use the heat.shrink tube. A terminal with soldered wires is installed in the same place. If there are no grooves in the case for him, it needs to be fixed. The assembly is connected to the “plus” and “minus”.

The assembly of the protective fee provides for the connection of all parts of the battery unit. Be sure to check the reliability of placement.

You can connect the battery elements in different ways

Methods for connecting battery elements

A block that accumulates energy can be collected in different ways. There are three types of assembly:

It is necessary to solder as soon as possible, so you need a powerful soldering iron by about 100 watts. Lithium batteries are afraid of overheating, so they cannot be heated for a long time, high temperature leads to damage. In the absence of experience, it is worth resorting to the services of a professional.

The technique of connecting elements into the unit using spot welding is considered the best. A master who has a special welding machine has better handle work.

Special cassettes are considered not very reliable. The received contacts have a significant transition resistance, which at a high current will begin to quickly collapse.

Elements are connected sequentially. Then the voltage is summarized, and the size of the container does not change. Consistently connected batteries not everyone fails at the same time, because in some cases, one working jar can be restored from two batteries of electric screwdriver by choosing serviceable. But it must be borne in mind that it will not last long. Therefore, experts advise to resort to such repair in rare cases.

Charger Makita DC9710 and lithium-ion battery

Previously, the battery was controlled by the device itself. When reached the full level, it stopped the process and signaling the completion of charging with a green indicator. But now the level of the level of the BMS scheme is engaged in the level of level and the power outage. Therefore, at the end of charging, the red LED on the charger will simply turn off.

If you have just such an old device, you are lucky. Because everything is simple with him. Diode burns. charging is going on. Went out. charging is completed, the battery is completely charged.

Charger Makita DC1414 T and lithium-ion battery

There is a small nuance that you need to know. This is more it and it is intended for charging a wider range of batteries from 7.2 to 14.4 V. The charging process on it goes as usual, the red LED burns:

But when the battery (which, in the case of NIMH elements is supposed to have a maximum voltage of 10.8 V) reaches 12 volts (we have Li-Ion elements in which the maximum total voltage can be 12.6 V), the charger will take the roof. Because he will not understand what kind of battery he charges: either 9.6-volt, or 14.4-volt. And at that moment, Makita DC1414 will enter the error mode, alternately blinking red and green LED.

This is fine! Your new battery will still charge. however, not until the end. The voltage will be approximately 12 volts.

That is, you will miss some part of the container with this charger, but it seems to me that this can be experienced.

Total modernization of the battery cost about 1000. New Makitovsky Makita PA09 is more expensive. over, we ultimately received twice as much capacity, and further repairs (in the event of a sooner failure) will be only in replacing lithium-ion elements.

Attention: this article and images in it are objects of copyright. Partial or complete reproduction on other resources without coordination is prohibited.

Replacement of batteries in a screwdriver with lithium

What needs to be estimated before starting work?

It is necessary to decide on the number of elements in the battery, which ultimately solves the voltage value. For three elements, the ceiling will be 12.6, and for four ─ 16.8 volts. We are talking about remaking widespread batteries with a face value of 14.4 volts. It is better to choose 4 elements, because when working, the voltage will quickly pass to 14.8. The difference in several volts will not affect the work of the screwdriver.

In addition, a larger number of lithium elements will give a large capacity. So, more work of the screwdriver.

Lithium battery elements 18650

Next, you need to choose the right lithium elements themselves. Form factor without options-18650. The main thing you need to look at is a discharge current and capacity. According to statistics with the standard work of the screwdriver, the current consumed is in the range of 5─10 amperes. If you sharply press the start button, then the current can jump up to 25 amperes for a few seconds. That is, you need to choose lithium batteries 18650 with the maximum value of the discharge current 20─30 amperes. Then, with a short.term increase in current to these values, the battery will not be damaged.

The rated voltage of lithium elements 3.6─3.7 volts, and the capacity in most cases is 2000─3000 mAh. If the battery housing allows, you can take not 4, but 8 elements. Two to combine them in 4 parallel assemblies, and then connect them sequentially. As a result, you can increase the battery capacity. But far from every case it will be possible to pack 8 cans 18650.

And the last preparatory stage is the choice of controller. In its characteristics, it must correspond to the rated voltage and discharge current. That is, if you decide to collect the battery of 14.4 volts, then select the controller with this voltage. The working current of the discharge is usually chosen half as much as the maximum permissible current.

Above, we found that the maximum permissible short.term discharge current for lithium elements is 25─30 ampere. This means that the charge controller should be designed for 12─15 amperes. Then the protection will work with an increase in current to 25─30 amperes. Do not forget about the dimensions of the protection board. Its with elements will need to be fitted into the housing of the battery of the screwdriver.

Replacement of batteries

Well, then the assembly process itself goes. First disassemble the battery housing. If this is a model for 14.4 volts, then there will be 12 nickel ─ cadmium batteries with a face value of 1.2 volts.

All this garland needs to be soldered or bite off. You should only have a connector with a plus and minus conclusion. You can also remove the thermal sensor, and instead of it, select a controller with a thermocouple, which will turn off the jars when overheating.

After that, you need to solder the purchased elements in the assembly with a sequential connection. Next, the controller is solder to it in accordance with its scheme. At the same time, balancing points are connected. The board has a special connector for them, and often wires with a connector are delivered in the kit.

After assembling the battery, conclusions are soldered to plus and minus, and the whole structure is placed in the case. In principle, the process on this is completed. Problems can arise only with a charger. But in most cases, standard charges for screwdrivers charge lithium elements without problems. At the same time, the charge of the cans goes through the controller, so nothing terrible with the elements themselves will happen.

On the network you can find recommendations for saving on the controller board. That is, a cheaper model is bought, designed for a smaller current. And so that it does not limit the work of the screwdriver, the discharge is not made through the controller, but directly from the cans. And their charging, as expected, goes through the controller. Return

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Also remade an electric screwdriver 14.4v on Li-Ion also took a ready-made controller from the Chinese, but the other. The indicator made on TL431, on them (TL431), in principle, the balancer can be done.

You write better to use 4 batteries, since the voltage will quickly pass to 14.8V, here I agree, but the words that we will increase the volume are not true, during the sequential connection the capacity does not change, and the capacity of one battery is even, the capacity is increased during parallel connection.

Dilyaver, and here you are already right only partly. The fact is that the tank in the mAC will remain the same, this is a fact, but the capacity in watt watches will increase.

There are more horseradish in this review than real tips (and video from YouTube chose the same gundose, empty). Such an example was remembered. The controller in China (according to their remarks) stands like a new lithium battery!? Yes, where and when it was. For about ten minutes ago, Aliexpress looked by the specialist. littered, see. Such as I need, for 18 V-with delivery from 1.8-to 3-4-6 dollars, and this is with a thermal attribute and soldered wires!

good afternoon! Please give advice which BMS controller is needed for an electrical screwdriver 18V, 1.2 A. Thank you in advance.

For an electric screwdriver 18V, you need to take a controller at 21V! ru.Aliexpress.COM/Item/Aihasd-21-1005S-BMS-LMO-Ternary/32831689172.HTML

Hello! Please give a link to the charging module for 14V for 4 batteries, as you describe in your video. Could not find.

Hello! I have a question: if the protective fee to batteries without balancing, whether it is necessary to connect intermediate wires? I have 3S, I connected a minus to 0V from the first battery, and from the last plus to 12.6V. Load and charging on other terminals (.). But at 3.7V and 7.4v I did not connect anything. Shurik twisted so much, with a clamped cartridge, he turned off, and does not twist more. It seems to have charged everything, but with a multimeter on connectors shows 7.6V. And in the batteries themselves 12.6V there is. Tell me what is wrong there?

The controller believes that the banks are dead, it is necessary to connect the intermediate banks, and not to consider yourself smarter than the developers!

I will express, hehe, since such a booze went I have a second Shurik, with a capacity of 18 in. I am not a techie, I do not have summer cottages, garages, enterprises, hack. Just- such a way in life- I do not like to get a break,- including matches, salt, cigarette, all the more so, kiyanka, vise, tens, a steamer-bomber, a turret, a hammer, a rubbish, a sherhbel, a hacksaw, a chisel, glass cutter, a square, a square, a square Level, painting brushes, spatula, jigsaw, drill, corner grinding grinder, naturally, Shurik and so on., so on. I used separate manual and power tools once or twice, I bought it for some specific work-for example, I made slopes from the laminate for the front door. In Shurik, nickel-cadmium batteries are standing, the third year ends-I regularly pump them (category-discharge-detachment). Sometimes for testing the power I screw a couple of 100 mm into an oak bruusak-with a creak, on a dry. There is enough power with excess. Very satisfied. In a lot of work, the new Shurik was four times. the balcony remade (dismantled the plastic by lining), ennobled the basement and under. I think the batteries will last another three or four years. I look after them, most importantly, I know that they got them obviously new, when buying, more precisely (a whole story), when I present me with a sales representative of the plant. It is convinced that 50-70% of the problems are the users of users of the nickel-cadmium battery-they are injected with a tightly stained product, one that, in fact, had to write down or discerned 50-80% a year or two ago. Due to the half.striped, or even dead battles of batteries (one. accurate). Shurik was also stolen to me, and the condition of the cans as you determine. no one will allow you to tear off the battery. It’s good that Shurik gave to finish the repair in the kitchen, collect new furniture, even install slopes. And both batteries died right away. I split-two or three-straight leaking jars. Well, what do you order to do?A year of warranty took place two weeks ago. Okay, I think that I remoded everything primary, where there are trifles. you can also be a screwdriver. A year later, there was still work for Shurik. He began to think about buying a shurik of an electric And suddenly anger broke out on the Internet seller of a dead Shurik (he did not find traces-changed the deployment, name?). Began to look for the manufacturer address. And he once found, wrote a complaint In the spirit that your Shurik is excellent, no worse than Makit and Hilti, but the battery put some half-dead And the manufacturer just on the year of my circulation launched a new model of Shurikov-the painting became brighter, beautifully and everything became more vague. Well, the representative of the plant comes to me and takes the old Shurik from me, and gives out fresh. The suitcase for the suitcase changed. I don’t need the best. If the nickel-cadmium battery is obsolete, I will insert lithium, or through the workshop (Star already) and buy a new lithium charging. I will give Shurik a son.in.law. Let it join here are the new batteries for three years already, and the powerful ones are like tigers. I shore them. I’ll see how many normal batteries are able to live with the most terrible semi.slaughter for them. Most of the consumers of Shuriks take them for some one.time, and then periodic service. For nickel cadmium, this is a terrible life. They need complete discharge and complete charging, at least 1-2 times a month. It is desirable to store in dry and cool (cold) room. Shurik. separately from the battery.

Alteration of an electric screwdriver for lithium batteries

Over time, nickel-cadmium batteries of electric screwdriver lose their container, the charge is enough for a couple of screws, and charging occurs in a couple of minutes. If you are faced with such a problem, the first thing that comes to mind is to buy a new battery or electric screwdriver. But you can give a second life a screwdriver and convert to a lithium battery (of course, if an electric screwdriver is not killed and advisable). As an example, I will use an electric screwdriver »Sohamash ASH-14M» with a voltage of 12 V.

Necessary details: Electric screwdriver Sohamash ASH-14M x 1 pc; Liitokala HG2, 18650, 3000 MAH X 3 pcs; BMS 3S, 40A, 12.6V with balancing x 1 pc; Reducing voltage converter XL4015 x 1 pc; Wire 1.5 mm (black, red). 20 cm.

Dismantling of the case: in my case, the battery housing is fastened with screws, there is also an option with latches or glue. The most difficult thing to disassemble from the glued block, a special hammer with a plastic base is used to analyze. Everything is removed from the inside of the battery block, we need only contact plates, to connect to a screwdriver and charger station.

The choice of batteries: the ASH-14M electric screwdriver is designed to work from 14 in the battery, so I will use three lithium batteries with a total voltage of 12.6 V, of course, you can use four batteries and raise the voltage to 16.8, but then it will be necessary to use a separate power supply, as well as high voltage, reduce the service life of an electric screwdriver. Not all batteries will approach the redistribution of the battery, so it is necessary to take into account several factors:

It is not recommended to use batteries with different containers; You can not choose batteries only according to the container, the main parameter is the discharge current. Some recommend using lithium batteries from old laptops, this is not right, they are designed to work with less discharge current.

In the article I use Liitokala HG2 batteries, such as size 18650, with a capacity of 3000 MAH and a 2AA discharge current, there are already soldered “tails” and without, in my case, for convenience, I advise you to buy with “tails”

BMS selection: lithium-ion battery cannot be used without BMS protection board. There are a different amount with different parameters on the market. BMS 3S marking indicates that the fee is designed for three batteries. BMS 3S marking suggests, for example, that the board is designed for 3 elements. What you need to pay attention to:

The presence of balancing ensures the uniformity of the battery charge. Maximum long.term working current.

In the article I use BMS 3S, 40A, 12.6V with balancing, she has proven herself well.

Alteration of the battery (assembly): I use the battery without soldered “tails”, so I will solder the wires directly to the contacts, for this I better use the soldering iron at 60W or high power so as not to overheat the battery.

Attention! In no case do not overheat the battery.

We take acid, solder and pour on both sides of the contacts of the batteries and solder the wires, also instead of wires you can use the nicki-fuel tape, which can be bought or taken from the old battery. In my case, I use a wire with a thickness of 1 square, since the place will not allow the battery evenly and the tape will not reach. After all the wires were soldered, we take and fasten all the battery with electrical tape. Various batteries are already available now.

Now according to the scheme, we sequentially solder each output of the batteries from 0 o 12.6, that is, first we solder to 0, then 4.2, then 8.4, then 12.6 to the BMS 3S board

Next, we solder the wires, with a cross section of at least 1.5 squares to the contact plates and with the help of a heat.mock, fasten them in the battery housing. Also, some leave two old batteries so that the contact group does not fly out.

We solder the wires from the contact plates to the BMS board, observing the polarity and in the reverse order we collect the battery housing and everything is ready.

Alteration of the charger: complete with an electrical screwdriver So-Uz-14M, there is a charger, but it is designed to charge nickel-cadmium batteries, for charging lithium-ion must be finalized. Of course, some use charging devices without alteration, but this is not right.

The revision is that it is necessary to add a fee to lower the voltage and limiting current, the board on the chip XL4015 has proven itself well.

I do not see meaning to describe the refinement as for each charger it is different, but the essence is that it is necessary to cut a couple of paths on the charging device and from the output circuit of the transformer to fall to the entrance from XL4015. Next, it is necessary to set voltage 12.6 V, in my case 3S or 16.8 V for 4S and set the current 1A, if the current is set more, the charging will pass faster, but the batteries will quickly fail if less charging will be longer than the charging.

An example of a replacement of the Ni-CD battery with Li-Ion in an electric screwdriver

After the selection and acquisition of the necessary configuration, you can begin to repair an electric screwdriver by replacing a faulty NI-CD battery with Li-Ion.

Even before ordering above the presented set of parts, the battery building of the electrical screwdriver was disassembled to convenient to measure the value of the electric motor consumption and evaluate the possibility of placing batteries and an indicator of the degree of their charge. A photograph of the extracted NI-CD batteries is shown at the beginning of the article.

The measurements showed that in the lower part of the battery case you can freely place a pair of Li-Ion batteries of the type 18650 (18-diameter in mm, 65-lifting in mm), BMS-2S-20A balancing fee and a connector for connecting the charger. There was no place for the indicator.

Therefore, the 8.4V-2S indicator and the button for its inclusion had to be placed in the upper part of the battery case. As it turned out, such a decision turned out to be successful, since the indicator was protected from mechanical damage during operation by an electric screwdriver.

To the cleaned and laid solder contact plates in accordance with the polarity indicated on the battery block, the red (plus) and blue (minus) flowers were soldered. Two negative plates had to be connected with a jumper. Since the launch and working currents have a large value, the cross.section of the wires should be at least 2 mm 2 2

Since the conductive plates fell off the pads, I had to fix them with armochery. These sections of the plates do not participate in the transmission of the current from the battery to the engine of the electric screwdriver.

When the NI-CD elements were installed in the battery container, they held the terminal block, so they had to be fixed in the final position, too, with the help of thermoclay.

The block was inserted into the battery compartment of an electric screwdriver and a voltage from a stationary power supply was supplied to the wires. Without load, the current current was 2.7 A, and when braking with the hand for the cartridge did not exceed 15 A. These data were necessary to select batteries and BMS protection board.

Further, after the check (photo of the check are shown above), a rectangular hole was cut out in the upper part of the battery body and the display of the LED indicator was inserted into it, and the button for its inclusion is inserted into the round hole.

Since the indicator and the button had low weight and during operation were not subjected to mechanical loads, after soldering the wires they were glued to the body of the unit with a heat.mock. After installing the indicator, it was checked by supplying a direct current with a size of about 8 V on the wires. Do not forget about the polarity of the connection.

Since the center was planned to install the connector for connecting the charger, the batteries had to be installed at a distance. For convenience, the plate was cut out of the fiberglass, the bottom of the bottom of the lower part of the battery block. Two strips of double.sided tape are glued to it.

Next, the plate is placed in the housing and batteries are glued to it so that there is a maximum distance between them. This is also good because the conditions of their cooling will be better.

When installing, you need to pay attention so that the conclusions by polarity coincide with the BMS protection board. On the part of the positive output of the battery 18560 there is a groove and the converting itself is convex with holes on the sides.

Electric screwdriver does not start. how to solve the issue

When checking the operation of an electric screwdriver with a half.charged battery, the engine was launched even under load stably. But when it was fully charged, an electric screwdriver, even at idle, was launched only after repeatedly pressing the inclusion key.

I climbed the oscilloscope with the BMS board and found out that the current protection is triggered. The fact is that at the time of starting an electric screwdriver engine, the resistance of its windings is determined by the active resistance of the wires and is tens of ohms. Therefore, the starting current at the first moment can be a hundred amperes.

To exclude false trips of protection in the BMS board, about 100 MS is usually held, which was not enough for this electrical screwdriver. For a stable engine start, it was necessary to increase the delay in the protection of protection up to half a second (500 ms). There was no electrical circuit, so I decided to increase the time of delay by scientific poke.

It was necessary to find a point in the scheme to which the condenser output relative to the minus or plus of batteries. For this, a capacitor of 0.47 Mf was taken and thin wiring was soldered to one of its ends. Its second end was soldered to the negative conclusion of the batteries.

Then, the free end of the capacitor made a sequential touch to all the conclusions of the resistances and capacitors, and each time the engine starting key was pressed on an electric screwdriver. Before each next touch, the condenser’s conclusions closed to discharge it and exclude damage to the scheme.

But the point was not possible to find relative to the minus. Therefore, the free end of the wire was soldered to the positive output of the battery and the same operation was done, which was crowned with success. Touching the output of the capacitor to the point indicated in the photograph of the engine of an electric screwdriver began to be launched confidently even under load.

For reliability, I decided to increase the capacitance of the capacitor to 2.2 mf. He was one end directly to the positive output of the battery, and the second conclusion was connected to the left output of the resistor 1 kOhm using the conductor.

Perhaps there is a more rational solution, but checking the electrical screwdriver in the work showed the effectiveness of the installation of an additional capacitor. The engine both at idle and under load were launched without fail.

Over 10 and a couple of evenings, it would seem to be returned to the system, it would seem, a useless electric screwdriver. I hope that my experience will help many decide to restore the performance of abandoned screwdrivers and other batteries.