How many 18650 batteries do you need for a 12v electric screwdriver

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Conversion of an electric screwdriver to lithium batteries 18650

Every craftsman is faced with the problem of reduced tool performance, or complete failure due to the battery. Manufacturers use nickel-cadmium batteries in 12, 14, 18 volt screwdrivers. The sequential assembly of several elements creates the desired voltage. Replacing nickel-cadmium batteries with lithium batteries extends battery life by making the design lighter. Mandatory BMS board installation adds reliability. Therefore, the conversion of an electric screwdriver to lithium batteries, mainly to the 18650 form factor, is justified.

Conversion of the “Hitachi” 12 V electric screwdriver to 18640 lithium batteries

Features of alteration of the 12 V Hitachi electric screwdriver for lithium batteries. The very compact battery compartment is designed for finger cells. Therefore, you should prepare a place for 18650 cells. It is necessary to cut one side of the partition in order to tightly place 1 element.

You need to get a gumboil, a flat metal connecting tape, hot glue. It is necessary to install lithium batteries in an electric screwdriver during rework through a protective controller. It should service 3 18650 cells, 3.7V and rated for 20-30 amps.

Remove the old battery from the socket, carefully disconnect the contacts in the assembly with the temperature sensor and the power-on indicator. Clean up and sign contacts. They should be brought out to one side, connected with solder to the leads from thick wires and filled with hot melt glue on the assembly.

Assemble a power source with one of the 3 cell controllers. Build a serial circuit of 3 Li-ion cells. Connect the controller. The conversion of the 12-volt lithium battery is completed when the structure is installed in the unit, secured, and the charging indicator lights up. After fully charging, the measurements show 12.17 volts in the external network. But this is enough for trouble-free long-term operation of the device.

The meaning and procedure for converting screwdrivers to lithium batteries

Why do nickel cadmium batteries fail quickly? In a garland of series-connected cans, each one is special. The chemical process is individual, the charge in closed systems is different. In the event of a malfunction in one bank, the design does not provide the required voltage. Control system and charge balancing in individual components is not provided.

  • Each Ni-Cd bank provides 1.2V and Li-ion 18650 3.6V.
  • The capacity of a lithium battery is 2 times that of a nickel-cadmium battery, similar in size.
  • An overheated li-ion battery threatens an explosion and fire, therefore, the installation of control of the uniformity of the charge in the banks is mandatory. BMS is not installed in nickel-cadmium batteries. the manufacturer is not interested.
  • Lithium cells have no memory effect, unlike Ni-Cd, they can be charged at any time and within an hour.
  • an electric screwdriver becomes much easier after converting the battery to li-ion, using 18650 cells.

There are only two obstacles to converting an electric screwdriver for lithium batteries. it is impossible to work with it at minus. The capacity of cans decreases, starting from a decrease already from 10 0 C. Lithium batteries are expensive.

Knowing what input voltage is required for an electric screwdriver, the charger is reworked, taking into account the placement of the lithium battery cans and control elements in the factory container. You can also do with a flashlight by upgrading the socket for a block of 18650 cells.

Let’s say you need to convert a 12 V electric screwdriver using Ni-Cd cans to li-ion. If you use 3 cans, the output voltage is not enough: 3.6 x 3 = 10.8 V. With 4 components, the power of the apparatus will be higher: 3.6 x 4 = 14.4 V. This will make the instrument 182 g lighter. its power will slightly increase, capacity. solid pluses. But when dismantling, it is necessary to leave the terminals and the native thermal sensor.

Conversion of an electric screwdriver to lithium batteries 18650 14 V

When converting screwdrivers of different power and flashlights from Ni-Cd to Li-ion, batteries of the form factor 18650 are more often used. They easily fit into a container or a nest, since instead of two or three relatives, one lithium is installed. Alteration of the battery of an electric screwdriver should be carried out taking into account the characteristics of lithium batteries for 18650.

This type of energy source does not tolerate deep discharge and excessive charge. Hence, it is necessary to use voltage control boards. Since each battery has its own character, their charge is corrected by a balancer. The point of reworking an electric screwdriver with a voltage of 14.4 V lies in the creation of a device using lithium batteries to facilitate a hand tool and increase its performance. Lithium 18650 batteries are most suitable for these purposes.

When selecting components, it should be taken into account that the starting current of the electric screwdriver is high, you must select the appropriate BMS for the required number of cans and at least 30 A. jumpers.

  • Lithium-ion cans in the amount of 4 pcs.
  • 4-cell li-ion battery controller, CF-4S30A-A works well. It has a built-in balancer that controls the charge of each element.
  • Hot melt glue, flux for soldering TAGS, solder.
  • Heat-resistant tape;
  • Connecting jumpers or thick insulated wire with a cross section of at least 0.75 squares, cut for bridges.

The procedure for converting an electric screwdriver for 18650:

  • Disassemble the case and remove a bundle of 12 Ni-Cd cells from the container.
  • Remove the garland, leaving the connector with the “” and “-” pins. Instead of a temperature sensor, a thermocouple from the controller will be installed.
  • Solder the assembly, considering that you cannot use acid, only neutral flux and pure solder. During the connection period, do not warm up the covers. Work pointwise.
  • Connect the balancing points to the controller according to the diagram. The board has connectors.
  • Connect assembly with plus and minus pins.
  • Check the functionality of the circuit. If everything works, assembled the battery, place the controller in the socket, secure with a sealant.

If the charger is not universal, additional alteration will be required. Screwdrivers for 12 V with a universal charger are assembled in the same way, but a protective connection circuit 3×18650 3.7 V for lithium batteries is used. In the same way, a screwdriver is reworked using a set of 18650 batteries in the amount of 2 elements.

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Conversion of the Makita electric screwdriver to a lithium battery

There is a “Makita” electric screwdriver with a 1.3 A / h battery and a voltage of 9.6 V. To change the power source to a lithium-ion one, you will need 3 18650 components. charge, will add power as the operating voltage rises to 10.8 V.

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The design will require the use of a BMS, a control controller that maintains the lithium cell operating mode within operating limits. With this breaker, each cell will be charged evenly without exceeding 4.2 V, the lower voltage is 2.7 V. The built-in balancer is used here.

The parameters of the controller should accompany the operation of the instrument when the operating current rises to 10-20 A. The Sony VTC4 30 A board, designed for a capacity of 2100 A / h, can ensure operation without shutdown. Of the 20 amperes, the Sanyo UR18650NSX accepting 2600A / h energies is suitable. The board is needed for 3 elements, which is marked in the 3S classification. In this case, the board must have 2 contacts, plus and minus. If the conclusions are designated with the letters “P-“, “P”, “C-“, they are intended for later models of screwdrivers.

Step-by-step instructions for converting a Makita electric screwdriver to lithium batteries looks like this.

  • You can disassemble the battery with glue if you tap the junction with a soft-headed hammer while weighing. Direction of impact downwards, butt-joint along the lower part of the body.
  • Take only the contact plates from the old assembly, carefully disconnecting them from the battery. Leave the sensor and breaker.
  • Solder 3 elements in series using TAGS flux and insulated jumpers. The wire cross-section must be greater than 0.75 mm2.
  • Assemble the circuit with the controller, and connect the power supply to the contact connectors with 1.5 square wires.
  • Check the functionality of the circuit and reassemble the case by placing it on the glue again.

In an electric screwdriver with an old DC9710 charger, once the 18650 lithium battery has finished charging, the red LED on the panel will turn off. The built-in controller monitors the charge level.

The Makita DC1414 T charger is used to charge 7.2-14.4 V power sources. While charging, the red light is on. But when charging a lithium battery, its voltage does not fit into the standards of salt products, and after 12 V, the charger will flash red and green. But the necessary charging is already there. electric screwdriver ready to work.

Conversion of the Interskol electric screwdriver to lithium batteries 18650

Sooner or later, the nickel-cadmium assembly of 15 cans fails. One or two elements are lazy, and it is no longer possible to get the output voltage. Modern DS “Interskol” with lithium batteries serve much better. Alteration of an electric screwdriver for 18 volt lithium batteries mastered by craftsmen.

It is necessary to purchase a protection board for 5S, 3.7 V and 40-50 A. You will need a balancing board and the energy sources themselves. 5 lithium 18650 batteries, you can leave them with factory thermistors by extending the wires. During installation, create a contact pad, insert the assembly, check the functionality, secure. The assembly features of the wizard’s advice are given in detail in the video. See here for full details on reworking an 18 volt lithium electric screwdriver

Parts and tools for rework

To convert an existing electric screwdriver to lithium, you need to purchase:

  • set of Li-Ion batteries;
  • charge controller board (BMS):
  • wires with a cross section of at least 2.5 sq. mm (better in silicone insulation).
  • a soldering iron with a capacity of at least 40 watts with a set of consumables, including an acid flux;
  • small locksmith tools (screwdrivers, scalpel, etc.).

The process itself is quite creative, depending on the existing initial conditions and the design of the electric screwdriver, so something else may be needed along the way. You need to be ready for this.

Before converting a power tool to use Li-Ion batteries, future operating conditions must be considered. Lithium ion cells are not suitable for low temperature environments.

How to convert an electric screwdriver to lithium batteries

It is known that the resource of the mechanical part of the power tool in most cases is much higher than the battery life. The batteries are nearing the end of their life and the electric screwdriver may well continue to work. It is only necessary to resolve the issue of nutrition. In some cases, purchasing new batteries of the same type is difficult, expensive, or even impossible. Therefore, you will have to make a decision. to alter the power tool for operation from the network, while losing mobility, or to adapt a different type of battery to work.

If the second option is chosen, then it is most rational to use lithium-ion batteries. they have an increased electrical capacity per unit of geometric volume, they have practically no memory effect (although this type of batteries also has certain disadvantages).

Controller selection

For all its merits, lithium-ion cells are sensitive to:

  • deep discharge;
  • overcharged;
  • excessive charging current;
  • overheating.

It is difficult to independently control these parameters for several hours, which will be required to replenish the battery energy. Therefore, these functions are assigned to the PCB system (Power Control Board) or SOF (function support system). It is a small board, which is often built into the battery case (because of this, the length of the 18650 cell is slightly longer than the promised 65 mm). This system stops charging when the required voltage is reached and disconnects the battery when discharging to the set level. These elements are labeled Protected on the body. If the marking is absent or Unprotected is directly indicated, then the battery is not equipped with such a system and the charge parameters will have to be controlled manually or this function must be assigned to an external device.

Do not confuse PCB (SOF) with BMS system. Battery Management System or PCM. Power Charge Module. This system is designed for element-by-element control of the charge of the accumulators connected to the battery according to a sequential scheme. The elements that make up the battery have a certain range of parameters, so a situation is possible when some of the cells are already charged, and the other part still needs to be charged. Obviously, this mode is unfavorable for batteries. This problem is designed to solve the BMS (“balancer”). And in the case under consideration, this system cannot be dispensed with.

A typical BMS connection diagram is shown in the figure. When the nominal parameters are reached, the cell is shunted with an internal key, the rest of the batteries continue to charge.

For boards from different manufacturers, the marking may slightly differ (instead of “B-” there is the designation “0V”, instead of the serial number of the battery, the total voltage at the connection point). You can buy a ready-made device on the Internet at well-known trading platforms. You need to choose according to the following parameters:

  • operating current. not less than 30 A;
  • the number of connected cells must correspond to the number of batteries in the battery.

And, of course, you need to measure the dimensions of the board with the available mounting space.

Battery assembly process

The first step is to determine if the new elements will fit into the old case. It should be borne in mind that in addition to batteries, you will also have to place a BMS board (about it below). In most cases, there will not be enough space in the old case, and first you need to try to remove everything unnecessary from there (partitions, unnecessary fasteners, etc.)

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An alternative option is to “print” the new body on a 3D printer. Not everyone has such an opportunity, but if it works out, the elements can be placed in an optimal way.

It is not known what material the strips are made of (manufacturers claim that they are made of nickel), but they are easily soldered. This means you can eliminate the acidic flux and use a conventional rosin-based formulation. Eliminates additional corrosion factor.

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If you wish, you can glue a miniature digital voltmeter or a voltage indicator in the form of a light strip into the case. Usability will improve slightly. Such a device is connected in parallel to the battery chain through a button. so as not to increase the discharge of the batteries in the pauses of work.

The next step is to install the BMS board in the case and connect it according to the diagram.

The board is connected to the contact group with conductors with a cross section of at least 2.5 sq. Mm. To do this, it is convenient to use wires in soft silicone insulation. it is not afraid of overheating (it can occur during soldering or during operation).

This completes the battery replacement, you can finally assemble the battery pack, charge the battery and try the electric screwdriver in operation.

How many and which batteries to buy

In most cases, 18650 cells are used to convert any electric screwdriver to lithium batteries. This figure means the linear dimensions:

  • length 65 mm (actually a little more);
  • diameter 18 mm.

These batteries are classified as finger-type batteries. have a cylindrical shape with positive and negative terminals on opposite sides. The voltage of one cell 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 case of an old battery.

Standard battery voltage, V The number of lithium-ion cells Final voltage, V
10.8 3 10.8
12 3-4 10.8 or 14.4
fourteen four 14.4
eighteen five eighteen

Safety measures when working with batteries

When assembling the battery, it should be remembered that the currents during the operation of an electric screwdriver can reach 11-12 amperes, therefore the area of ​​the contact patch of the connecting buses between the elements should be maximum. Therefore, the spot welding option often offered on the Internet is not the best. Better to solder the busbars over the entire contact area of ​​the battery. It should be understood that the elements are very sensitive to overheating, therefore, they must be soldered quickly and confidently, using acid fluxes. the battery cases are not made of copper or brass. It is advisable to use heat sinks, which can be pliers, etc.

Care must be taken that acid splashes during soldering do not fall on other surfaces, because this will subsequently lead to corrosion in these places. Places of rations must be thoroughly rinsed.

Assembling the charger

Charging lithium-ion batteries has its own peculiarities. It is done in two stages:

  • at the first stage, energy is replenished with a constant current (the voltage for this should increase smoothly), this stage allows you to charge the battery to about 80% of the nominal capacity;
  • at the second stage, the battery is charged with constant voltage (the current falls).

The graph also shows the preliminary stage of trickle charging. It is needed for deeply discharged cells. Obviously, in order to execute such an algorithm and to fully use the battery resource, a specific charger must be used. Failure to comply with the algorithm leads to incomplete use of the battery capacity and a decrease in its resource. A device with such functions must be purchased ready-made or assembled independently, if qualifications allow. Such memory devices are based on specialized microcircuits. Converting a ready-made charger from other batteries is difficult and impractical.

Not all inexpensive chargers provide the required charging algorithm for Li-Ion cells. Many manufacturers from Southeast Asia produce chargers that charge cells only with a stabilized current.

The second stage of charging with constant voltage is not provided. Monitoring the charge level is reduced to measuring time. after a specified period, the current source is turned off, and the functions of protection against excessive charge are assigned to the internal battery protection circuit (if it is absent, then to the owner of the battery).

We recommend the video series “The Second Life of the Electric Screwdriver”

Replacing old electric screwdriver batteries with lithium batteries is a smart move. You can do it yourself, but you need to take into account the peculiarities of operating a battery of this type. After reading the materials of this review, the user will not have any fundamental questions.

How to disassemble a screwdriver battery

How to disassemble an old battery? There are batteries where the halves of the case are fastened with screws, but there are also glue ones. My batteries are one of the last ones, and I generally believed for a long time that they could not be disassembled. It turned out that it is possible if you have a hammer.

In general, with the help of intense blows to the perimeter of the edge of the lower part of the case (a hammer with a nylon head, the battery must be held in the hand by weight), the gluing site is successfully separated. In this case, the case is not damaged in any way, I have already disassembled 4 pieces this way.

From the old circuit, only contact plates are needed. They are permanently spot welded to the upper two elements. You can pick out the welding with a screwdriver or pliers, but you need to pick it as carefully as possible so as not to break the plastic.

Everything is almost ready for further work. By the way, I left the standard thermal sensor and disconnector, although they are no longer particularly relevant.

But it is very likely that the presence of these elements is necessary for the normal operation of a standard charger. Therefore, I highly recommend saving them.

775 Motor in 12v Lithium Ion Battery Pack

Converting the battery of the screwdriver to Li-Ion

I won’t say anything new in this article, but I just want to share my experience of upgrading the batteries of my old Makita screwdriver. Initially, this tool was designed for nickel-cadmium batteries (which have long since died, just as those bought for replacement have died). The disadvantages of Ni-Cd are well known: low capacity, short lifespan, high price. Therefore, cordless tool manufacturers have long since switched to lithium-ion batteries.

Well, what about those who have an old instrument? Yes, everything is very simple: throw away the Ni-Cd cans and replace them with Li-Ion of the popular 18650 format (marking indicates a diameter of 18 mm and a length of 65 mm).

What board is needed and what elements are needed to convert a screwdriver to lithium-ion

So, here is my 9.6 V 1.3 Ah battery. At the maximum charge level, it has a voltage of 10.8 volts. Lithium-ion cells have a nominal voltage of 3.6 volts, with a maximum voltage of 4.2. Therefore, to replace the old nickel-cadmium cells with lithium-ion cells, I need 3 cells, their operating voltage will be 10.8 volts, the maximum is 12.6 volts. Exceeding the rated voltage will not damage the motor in any way, it will not burn out, and with a larger difference, there is no need to worry.

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Lithium-ion cells, as everyone has known for a long time, categorically do not like overcharging (voltage above 4.2 V) and excessive discharge (below 2.5 V). When the operating range is exceeded, the element degrades very quickly. Therefore, lithium-ion cells always work in tandem with an electronic board (BMS. Battery Management System), which controls the cell and monitors both the upper and lower voltage limits. This is a protection board that simply disconnects the can from the electrical circuit when the voltage goes out of the operating range. Therefore, in addition to the elements themselves, such a BMS board is required.

Now there are two important points that I experimented with unsuccessfully several times until I came to the right choice. This is the maximum permissible operating current of the Li-Ion cells themselves and the maximum operating current of the BMS board.

In a screwdriver, operating currents at high load reach 10-20 A. Therefore, you need to buy elements that are capable of delivering high currents. Personally, I have successfully used Sony VTC4 30-amp 18650 cells (2100 mAh capacity) and 20-amp Sanyo UR18650NSX (2600 mAh capacity). They work fine in my electric screwdrivers. But, for example, Chinese TrustFire 2500 mAh and Japanese light green Panasonic NCR18650B 3400 mAh are not suitable, they are not designed for such currents. Therefore, there is no need to chase the capacity of the elements. even 2100 mAh is more than enough; the main thing when choosing is not to miscalculate with the maximum permissible discharge current.

Likewise, the BMS board must be rated for high operating currents. I saw on YouTube how people collect batteries on 5 or 10-ampere boards. I don’t know, personally, when I turned on the screwdriver, such boards immediately went into defense. In my opinion, this is a waste of money. I will say that the Makita company itself puts 30-ampere boards in its batteries. Therefore, I use 25 Amp BMS bought from Aliexpress. They cost about 6-7 and are searched for “BMS 25A”. Since you need a board for an assembly of 3 elements, you need to look for such a board, in the name of which there will be “3S”.

Another important point: some boards have different contacts for charging (designation “C”) and load (designation “P”). For example, the board can have three pins: “P-“, “P” and “C-“, as on the native Makitov lithium-ion board. Such a fee will not work for us. Charging and discharging (charge / discharge) must be done through one contact! That is, there should be 2 working contacts on the board: just “plus” and just “minus”. Because our old charger also only has two pins.

In general, as you might have guessed, with my experiments I threw out a lot of money both on the wrong elements and on the wrong boards, having made all the mistakes that could be made. But I got invaluable experience.

Putting together a lithium-ion battery

Here are the new elements of Sanyo UR18650NSX (according to this article they can be found on Aliexpress) with a capacity of 2600 mAh. For comparison, the old battery had a capacity of only 1300 mAh, half the size.

It is necessary to solder the wires to the elements. The wires must be taken with a cross section of at least 0.75 sq. Mm, because we will have considerable currents. A wire with such a cross section normally works with currents of more than 20 A at a voltage of 12 V. You can solder lithium-ion cans, short-term overheating will not harm them in any way, this has been verified. But you need a good fast-acting flux. I use TAGS glycerin flux. Half a second. and you’re done.

We solder the other ends of the wires to the board according to the diagram.

I always put even thicker wires of 1.5 sq. Mm on the battery contacts. because the space allows. Before soldering them to the mating contacts, I put a piece of heat-shrinkable tube on the board. It is necessary for additional isolation of the board from battery cells. Otherwise, the sharp edges of the solder can easily rub or puncture the thin film of the lithium-ion cell and cause a short. It is possible not to use heat shrinkage, but at least something insulating to be laid between the board and the elements is absolutely necessary.

The contact part can be fixed in the battery case with a couple of droplets of super glue.

It’s good when the case is on screws, but this is not my case, so I just glue the halves again with “Moment”.

The battery is charged with a standard charger. True, the algorithm of work is changing.

I have two chargers, DC9710 and DC1414 T. And they work differently now, so I’ll tell you exactly how.

Makita DC9710 charger and lithium-ion battery

Previously, the battery was controlled by the device itself. When the full level was reached, it stopped the process and signaled the completion of charging with a green indicator. But now the BMS circuit we have installed is engaged in level control and power off. Therefore, when charging is complete, the red LED on the charger will simply turn off.

If you have such an old device, you are in luck. Because everything is simple with him. The diode is on. charging is in progress. Off. charging completed, battery fully charged.

Makita DC1414 T charger and lithium-ion battery

There is a small nuance here that you need to know. This charger is newer and is designed to charge a wider range of batteries from 7.2 to 14.4 V. The charging process on it goes as usual, the red LED is on:

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

This is normal! Your new battery will still charge. though not completely. The voltage will be approximately 12 volts.

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

In total, the battery upgrade cost about 1000 rubles. Makitov’s new Makita PA09 costs twice as much. over, we ended up with twice the capacity, and further repairs (in the event of a slight failure) will consist only in replacing lithium-ion cells.

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