Converting a screwdriver to Li-Ion batteries and to a network one with your own hands. How to convert a screwdriver battery to lithium-ion: step by step instructions

The industry has been producing screwdrivers for a long time, and many people have older models with nickel-cadmium and nickel-metal hydride batteries. Converting a screwdriver to lithium will improve the performance of the device without buying a new tool. Now many companies offer screwdriver battery conversion services, but you can do it yourself.

Benefits of Lithium Ion Batteries

Nickel-cadmium batteries have a low price, withstand many charging cycles, and are not afraid of low temperatures. But the capacity of the battery will decrease if you put it on a charge without waiting for a full discharge (memory effect).

Lithium-ion batteries have the following advantages:

• high capacity, which will provide more time for the screwdriver;
• smaller size and weight;
• keeps the charge well when not in use.

But a lithium battery for a screwdriver does not withstand a full discharge, therefore, factory tools on such batteries are equipped with additional boards that protect the battery from overheating, short circuit, overcharge in order to avoid an explosion, a complete discharge. When the microcircuit is inserted directly into the battery, the circuit is opened if the unused battery is separated from the tool.

Difficulties in remodeling

Li-Ion batteries have objective disadvantages, such as poor performance at low temperatures. In addition, when converting a screwdriver to 18650 lithium batteries, a number of difficulties may occur:

1. The 18650 standard means that the diameter of one battery cell is 18 mm with a length of 65 mm. These dimensions do not match the dimensions of the nickel-cadmium or nickel-metal hydride elements previously installed in the screwdriver. Replacing batteries will require placing them in a regular battery case, plus installing a protective microcircuit and connecting wires;
2. The voltage at the output of lithium cells is 3.6 V, and for nickel-cadmium cells it is 1.2 V. Let's say the nominal voltage of an old battery is 12 V. Such a voltage cannot be provided when Li-Ion cells are connected in series. The range of voltage fluctuations during charge-discharge cycles of an ion battery also changes. Accordingly, converted batteries may not be compatible with a screwdriver;
3. Ion batteries differ in the specifics of their work. They do not withstand a recharge voltage of more than 4.2 V and a discharge of less than 2.7 V until they fail. Therefore, when the battery is being reworked, a protective board must be installed in the screwdriver;
4. It may not be possible to use an existing charger for a screwdriver with a Li-Ion battery. You will also need to redo it or purchase another one.

Important! If the drill or screwdriver is cheap and not of very high quality, then it is better not to rework. This can be more expensive than the cost of the tool itself.

Battery selection

Often, 12 V batteries are used for screwdrivers. Factors to consider when choosing a Li-Ion battery for a screwdriver:

1. In such tools, elements with high discharge current values ​​\u200b\u200bare used;
2. In many cases, the capacitance of the cell is inversely related to the discharge current, so you cannot choose it only by capacitance. The main indicator is the current. The value of the operating current of the screwdriver can be found in the passport of the tool. Usually it is from 15 to 30-40 A;
3. It is not recommended to use elements with different capacity values ​​when replacing the screwdriver battery with Li-Ion 18650;
4. Sometimes there are tips to use a lithium battery from an old laptop. This is absolutely unacceptable. They are designed for a much lower discharge current and have unsuitable specifications;
5. The number of elements is calculated based on the approximate ratio - 1 Li-Ion per 3 Ni-Cd. For a 12-volt battery, you will need to replace 10 old cans with 3 new ones. The voltage level will be slightly reduced, but if you install 4 elements, then the increased voltage will shorten the life of the motor.

Important! Before assembly, it is necessary to fully charge all elements for equalization.

Battery Case Disassembly

The case is often assembled with self-tapping screws, other options are with latches or glue. The glued block is the most difficult to disassemble, you have to use a special hammer with a plastic head so as not to damage parts of the case. Everything inside is removed. Only contact plates or the entire terminal assembly can be reused for connection to a tool, charger.

Connecting battery cells

CompoundLi– Ionbatteries for screwdriverperformed in several ways:

1. The use of special cassettes. The method is fast, but the contacts have a large contact resistance, can quickly collapse from relatively high currents;
2. Soldering. A method suitable for those who know how to solder, since you need to have certain skills. Soldering must be done quickly, because the solder cools quickly, and long heating can damage the battery;
3. Spot welding. Is the preferred method. Not everyone has a welding machine; specialists can provide such services.

Important! The elements must be connected in series, then the battery voltage is added, and the capacity does not change.

At the second stage, wires are soldered to the contacts of the assembled battery and to the protective board according to the connection diagram. Wires with a cross-sectional area of ​​​​1.5 mm² are soldered to the contacts of the battery itself for power circuits. For other circuits, you can take thinner wires - 0.75 mm²;

Then a piece of heat shrink tubing is put on the battery, but this is not necessary. You can also put heat shrink on the protective microcircuit to isolate it from contact with the batteries, otherwise the sharp protrusions of the soldering can damage the cell shell and provoke a short circuit.

Further battery replacement consists of the following steps:

1. The disassembled parts of the case are well cleaned;
2. Since the dimensions of the new battery cells will be smaller, they must be securely fixed: glued to the inner wall of the case with Moment glue or sealant;
3. The positive and negative wires are soldered to the old terminal block, it is placed in its original place in the housing and fixed. The protective board is laid, the parts of the battery pack are connected. If they were previously glued, then the “Moment” is used again.

The lithium-ion battery of the screwdriver will not function properly without the BMS protection board. The copies for sale have different parameters. Marking BMS 3S suggests, for example, that the board is designed for 3 elements.

What you need to pay attention to to choose the right chip:

1. The presence of balancing to ensure the uniformity of the charge of the elements. If it is present, the value of the balancing current should be in the description of the technical data;
2. The maximum value of the operating current that can be sustained for a long time. On average, you need to focus on 20-30 A. But it depends on the power of the screwdriver. Low-power enough 20 A, powerful - from 30 A;
3. The voltage at which the batteries are switched off during recharging (about 4.3 V);
4. The voltage at which the screwdriver turns off. It is necessary to select this value based on the technical parameters of the battery cell (the minimum voltage is about 2.6 V);
5. Current of operation of protection against an overload;
6. Resistance of transistor elements (minimum value is selected).

Important! The magnitude of the tripping current during overload does not matter much. This value is detuned from the operating load current. With short-term overloads, even if the tool is turned off, you must release the start button, and then you can continue to work.

Whether the controller has an auto-start function can be determined by the presence of the "Automatic recovery" entry in the technical data. If there is no such function, then in order to restart the screwdriver after the protection has been triggered, it will be necessary to remove the battery and connect it to the charger.

Charger

The lithium-ion battery of the screwdriver cannot be charged by connecting to a conventional power supply. For this, a charger is used. The power supply simply produces a stable charge voltage within the specified limits. And in the charger, the determining parameter is the charge current, which affects the voltage level. Its value is limited. There are nodes in the charger circuit that are responsible for stopping the charging process and other protective functions, for example, turning off when the polarity is incorrect.

The simplest memory is a power supply with a resistance included in the circuit to reduce the charging current. Sometimes a timer is also connected, which works after a set time period has elapsed. All of these options do not contribute to long battery life.

Charging methodsLI Ionscrewdriver batteries:

1. Using a factory charger. Often it is also suitable for charging a new battery;
2. Alteration of the charger circuit, with the installation of additional circuit elements;
3. Buying a ready-made memory. A good option is IMax.

Let's say there is an old Makita DC9710 charger for charging a 12 V Ni-Cd battery, which has an indication in the form of a green LED signaling the end of the process. The presence of the BMS board will allow you to stop the charge when the specified voltage limits per cell are reached. The green LED will not light up, but the red LED will just turn off. The charge is finished.

The Makita DC1414 T charger is designed to charge a wide range of 7.2-14.4 V rechargeable batteries. In it, if the protective shutdown is triggered at the end of the charge, the indication will not work correctly. There is a flashing of red and green light, which also signals the end of the charge.

The cost of replacing screwdriver batteries with lithium-ion batteries depends on the power of the tool, the need to buy a charger, etc. But if the drill driver is in good functional condition, the charger does not require a thorough alteration or replacement, then for a couple of thousand rubles you can get an improved power tool with an extended battery life.

Video

The advantages of cordless power tools are obvious, it makes no sense to discuss this issue. The negative factors include some inconvenience associated with the need to charge the batteries, as well as the high cost of batteries (we are talking about high-quality power packs).

If you have to put up with charging, then the second problem is solved by manufacturers not in the best way for the consumer. Most screwdrivers in the affordable price range are equipped with nickel-cadmium batteries (Ni-Ca), the performance of which leaves much to be desired.

In the battery case there are 10-12 interconnected finger-type Ni-Ca batteries (typical voltage - 14 volts). Such elements have a limited service life, and a rather low capacity, which is gradually lost during operation. As a result, after 2-3 years, the charge retention time can be reduced by 3-5 times. You have to regularly change damaged "barrels", or even buy a new battery pack.

The best option in terms of price and quality is lithium batteries of the 18650 series. Structurally, they look like ordinary finger batteries, the size is 25% larger than the AA format.

Parameters of a typical Li-ion battery:

• voltage 3.6-3.7V
• capacity from 800 to 4500 mAh
• recoil current - about 35A

The optimal capacity is 2500 mAh, too high values ​​do not correspond to reality, and entail an unjustified increase in cost. A 2500 mAh battery from a more or less decent manufacturer (for example, LG) can be bought for 300-600 rubles.

How to calculate the parameters of a new battery

1. The current consumption of a screwdriver usually does not exceed 10-15 amperes. Accordingly, the typical recoil (discharge) current of a Li-ion battery (30-35A) is enough with a margin.
2. The supply voltage is calculated from an old Ni-Ca battery. Typically, a block consists of 12 batteries of 1.2 volts, that is, a total of 14.4 V. Lithium batteries must not be discharged to a voltage below 2.74 volts. The operating voltage is 3.0-3.5 V, that is, for replacement, it is necessary to connect 4 18650 batteries in series.

The resulting operating voltage of 12V to 14V is more than enough. Even relatively fresh regular Ni-Ca batteries rarely give out more than 12 volts.

If volume allows, you can connect 2 consecutive assemblies of 4 batteries in parallel, doubling the battery capacity. At the same time, the relative position can be anything - according to the shape of the body. The main thing is to ensure a reliable connection of wires.

1. In addition, it is desirable to place a charger in a common case. Then you do not have to remove the batteries from the case every time.

Charger - manufacturing options

Optimal design - "all in one". That is, both batteries and a charger with a 220 volt input are placed in the battery case. You simply connect the network cable and charge.

There is another option - the charger is placed in a separate case to save space (this allows you to put more batteries in the battery case).

Most chargers (we are talking about factory boards that can be purchased at radio stores, or on the same Aliexpress) are designed for a certain number of Li-ion batteries in the assembly. You just choose the right option.

You can assemble such a circuit yourself if you have the skills of a radio amateur. In this case, the cost of alteration will decrease.

In any case, a charge (discharge) control device must be installed. It can be indicator LEDs, or a digital display.

Built-in lithium battery monitoring

Cells of this type are sensitive to overdischarge. If the battery voltage drops below 2.75 V, degradation begins and the module loses capacity. Therefore, it is necessary to monitor the parameters during operation.

Some 18650 cells are equipped with built-in discharge control boards, and simply turn off the battery when a critical voltage is reached. When buying items, you need to clarify this point. If your batteries do not have protection, it can be installed additionally. Such ready-made boards are also commercially available.

The circuit is installed in a common battery case, and does not interfere with charging the batteries at all.

Option with a ready-made kit for vapers

18650 batteries are popular with the so-called. vapers - lovers of electronic cigarettes. Ready-made kits are available for sale, consisting of a charger and Li-ion batteries. To use such a set in a screwdriver, you will have to install a container with contacts in the battery case, and each time remove the modules for charging.

If the dimensions of the screwdriver body allow, and there is no desire to mess around with diagrams, this is an option for you. Of course, the costs will rise slightly.

Conclusion - the advantages and disadvantages of converting a screwdriver battery to lithium cells

Any modification must be economically justified. If we spend money and time, we need to understand what benefits will come from it.

Advantages of Li-ion batteries

• The energy intensity of lithium batteries is much higher. Therefore, with the same dimensions and weight, the duration of battery use between recharges will be higher.
• The charging process is faster. This means that downtime during recharging is reduced.
• Unlike nickel batteries, lithium batteries do not have the so-called memory effect. They can be charged without waiting for full discharge.

Disadvantages of replacing batteries from Ni-Ca to Li-ion:

• First of all, the cost part. The total cost of rework can reach 2-3 thousand rubles.
• Dependence on external temperature: lithium batteries lose their performance at low temperatures. Therefore, in winter, on the street, it is impossible to use such tools.
• The non-standard voltage of Li-ion batteries (3.6-3.7 V) leads to inaccuracies in the selection of the final value.
• 18650 batteries differ in size from standard Ni-Ca “cans”. To place them in the standard case of a screwdriver, it is necessary to solve a number of design problems.

The standard screwdriver device is not suitable for charging lithium batteries. We have to make a new scheme.

Many craftsmen in the service have a cordless screwdriver. Over time, the battery degrades and holds a charge less and less. Battery wear has a huge impact on battery life. Constant recharging does not help. In this situation, “repacking” the battery with the same elements helps. The most commonly used elements in screwdriver batteries are the "SC" size type. But the most valuable thing for a master is a do-it-yourself repair.
Let's remake a screwdriver with a 14.4 volt battery. Screwdrivers often use a motor for a wide range of supply voltages. So in this case, only three Li-ion cells of the 18650 format can be used. I will not use control boards. The discharge of elements will be visible in the work. As soon as the self-tapping screw does not twist, for example, it's time to put it on charge.

Converting a screwdriver to Li-ion without a BMS board

First, let's disassemble our battery. Inside it are 12 elements. 10 pieces in one row and 2 in the second row. A contact group is welded to the second row of elements. We leave a couple of elements with a contact group, we recycle the rest.

Now you need to solder the wires for further work. The contacts turned out to be from a material that cannot be tinned, so we solder the wires to the elements. Minus to the body of the element, and plus directly to the plus patch. Old elements play the role of a support and are not involved in the work.

I will use lithium-ion batteries of the 18650 format. Elements bu. High-current elements are needed for refinement. I “changed” my elements into thermal shrinkage from Sanyo, the old one was pretty shabby. Checked the residual capacity Imax.
We connect the batteries in series and solder the elements of the head. The battery is almost ready.

Now we will provide comfortable charging. You need to install a four-pin connector. I used the connector from the old motherboard for the number of pins I needed. I took the mate from an old computer power supply.

Cut out a hole for the connector. We fill the connector with epoxy glue or super glue with soda. We also solder the wires.

Solder the wires to the elements. Wire from the first contact of the connector to the plus of the battery. The wire from the second contact of the connector to the plus of the second element, it is also the minus of the first element, and so on. Since I will be charging with a “smart” charger, I need to make a balancing wire.

As a connector for connecting to the charger, I will use the wire from the computer's power supply. The wire through which the floppy drive was powered. We cut off all the keys from the connector and it fits perfectly under the charger. It dissolves simply. Red wire to the first contact of the battery connector. Black wire to battery connector pin 2, etc.

Has the meaning. The advantage is that they have a high electrical density. As a result, by installing such a device in the body of a screwdriver, we can achieve an increase in the duration of the tool many times over. The charging current for high-power lithium batteries, especially for new modifications, it can reach 1-2 C. You can recharge such a device in 1 hour, without overestimating the parameters recommended by the manufacturer and without spoiling the quality of the product.

What do lithium batteries look like?

Most lithium devices are enclosed in a prismatic case, but some models are cylindrical. Rolled electrodes and separators are used in such batteries. The body is made of aluminum or steel. The positive pole goes to the housing cover.

In prismatic configurations, the electrodes are in the form of rectangular plates. To ensure safety, the battery has a device that acts as a regulator of all processes and opens the electrical circuit in critical situations. The increased sealing of the case prevents the electrolyte from leaking out and oxygen and moisture from penetrating inside.

What precautions should be taken to avoid damaging the lithium battery?

• Due to technology limitations, the charge indicator of lithium batteries should not exceed 4.25-4.35 V. The discharge should not reach 2.5-2.7. This condition is indicated in the technical data sheet for each specific model. If these values ​​are exceeded, you can disable the device. Special charging and discharging controllers are used, which keep the voltage on the lithium cell within normal limits. Converting a screwdriver to a lithium battery with a controller will protect the device from malfunction.
• The voltage indicator of lithium batteries is a multiple of 3.7 V (3.6 V). For Ni-Mh models, this figure is 1.2 V. This phenomenon is understandable. in lithium devices is stored in a separate cell. The 12 volt lithium battery will never be assembled. The rating will be 11.1V (three consecutive cells) or 14.8V (four consecutive cells). In addition, the voltage indicator of the lithium cell changes when operating when fully charged by 4.25 V, and when fully discharged - by 2.5 V. The voltage indicator 3S (3 serial - three serial connections) will change when the device is operating from 12.6 V (4.2x3) up to 7.5 V (2.5x3). For a 4S configuration, this figure ranges from 16.8 to 10 V.
• Converting a screwdriver to 18650 lithium batteries (the vast majority of products have this particular size) requires taking into account the difference in dimensions with Ni-Mh cells. The 18650 cell has a diameter of 18 mm and a height of 65 mm. It is very important to calculate how many cells will fit in the case. It should be remembered that for a model with a power of 11.1 V, you will need the number of cells in multiples of three. For a model with a power of 14.8 V - four. The controller and switching wires must also fit.
• The lithium battery charger is different from the Ni-Mh charger.

The article will look at how a screwdriver is converted to lithium. The tool is equipped with a pair of Ni-Mh batteries with a voltage rating of 12 V and a capacity of 2.6 Ah. A remake of a Hitachi screwdriver will be considered. Lithium batteries will provide the device with a long service life.

Choosing the rated voltage

First of all, you should decide on the choice of voltage rating for a lithium-based device. The choice should be made between the 3S model (its voltage range is from 12.6 to 7.5 V) and the 4S-Li-Ion battery (its voltage range is from 16.8 to 10 V).

Advantages of the second option

The second option is more suitable, because the voltage in the battery drops quite quickly from the maximum to the minimum (from 16.8 to 14.8 V). For an electric motor, which, in fact, is a screwdriver, an excess of 2.8 V is not a critical mark.

The lowest voltage rating is for the 3S-Li-Ion modification. It is equal to 7.5 V, which is insufficient for the normal functioning of the electrical device. By mounting four configurations, we will increase the battery.

How to decide on the choice of lithium cells?

In order to select lithium-based cells, limiting factors must be identified. Currently, lithium devices are produced with a permissible current load value of 20-25 A.

Impulse current values ​​(short, up to 1-2 seconds) reach 30-35 A. The battery configuration will not be disturbed.

How many cells will fit in the case?

Collecting 4S2P (four serial connections and two parallel) will not work. Converting a screwdriver to 18650 lithium batteries involves eight cells. How can they meet four? Each cell will bear the maximum current load.

How to determine the maximum current in a screwdriver?

Converting a 12V screwdriver to lithium batteries involves connecting the device to a laboratory power source with a maximum current of 30 A. The limiter regulator is set to the maximum value. Having created the voltage level of the power source close to the nominal value of the future battery, we begin to smoothly pull the trigger. The current consumed by the screwdriver will rise to 5 A. Now you should sharply pull the trigger. This will short out the power circuit. The current will reach a power of 20-30 A. Perhaps its indicator would be much higher, but the power of the power source will not allow this to be fixed. This will be a short load current when you sharply press the trigger of the screwdriver. Any model of such a device will react similarly.

Next, you should clamp the tip of the screwdriver with a vise and observe to what value the current consumption will increase during the operating mode, when the ratchet works in the screwdriver. The current indicator in this case increases to 10-12 A.

So you can determine the magnitude of the load current. In this case, it will be 5 A at idle and 30 A at a sharp start, and at maximum load it will be 12 A. The manufacturer must select lithium cells, the nominal load current of which will be 10-20 A, and the pulse current - 25-30 BUT.

How to choose a controller?

So, the screwdriver is being converted to lithium batteries. Regular charging for the device is required. When choosing a controller, please note that the device must meet two parameters:

• indicator of rated operating voltage;
• indicator of the rated operating current.

With voltage, everything is very clear: if the battery is 11.1 V, then the controller will be with the same voltage.

The concept of "rated operating current" implies the carrying capacity of the board protection. Thus, a 4 A controller is designed for a current mark of 4 A, and with an indicator of 8 A, an additional load is placed on it. In this case, the protective device will operate. All these technical data are set out in the passport of each modification of the controller. In this case, one modification may have a limiting current indicator of 30 A, and the other - 50 A. And both of these devices will formally be suitable for operation. Also, when creating a lithium battery, there is a limitation in size. Therefore, you should purchase a controller that will fit in the case of the old battery.

Disassembly and assembly

Converting a screwdriver to lithium batteries includes the following steps:

• You should open the old battery by unscrewing five screws.
• Remove the Ni-Mh battery from the case. It will be noticeable that the contact pad, which engages with the contact group of the screwdriver, is welded to the negative contact of one of the Ni-Mh cells. Weld points should be cut with a tool with a cut-off stone built into it.
• Wires are soldered to the contacts, the cross section of which is at least 2 mm 2 for power leads and 0.2 mm 2 for the thermistor. The contact pad is glued into the battery case using hot glue.
• According to the indicator of internal resistance on the meter, four cells are selected. The value must be the same for all four fixtures.
• Lithium cells are glued with hot glue so that they are compactly located in the case.
• Cell welding is carried out on a resistance welding machine using a nickel welding tape (its cross section should be 2X10 mm).

Installing the protection board

This stage can show how lightweight lithium battery design is. The weight of the Ni-Mh device was 536 g. The weight of the new lithium device is 199 g, which will be quite noticeable. We managed to win 337 g in weight. At the same time, an increase in energy capacity is observed.

The battery is mounted in the case. The voids are filled with soft material from the packaging.

Screwdriver connection

• A sharp pull on the trigger triggers the current protection mechanism. But in fact, such a protective mode is unlikely to be needed when using the tool. If you do not provoke protection on purpose, then the operation of the screwdriver will be stable.
• The tip should be clamped in a vise. The power of the battery freely triggers the ratchet, which limits the increase in the number of turns of torsion.
• the screwdriver is discharged by 5A.
• The battery is inserted into the regular memory. The charge current indicator during measurement is 3 A, which is acceptable for lithium cells. For the LG INR18650HG2 configuration, the maximum charge current will be 4 A, which is indicated in the technical specification.

How long does it take to replace batteries?

Converting a screwdriver to lithium batteries will take approximately 2 hours. If all parameters are checked, then it will take 4 hours.

You can do everything on your own, without the help of another person. But resistance welding and the selection of batteries cannot be carried out without specialized equipment.

How else can you test the degree of charge other than the controller?

The screwdriver has been converted to lithium batteries. The standard charger built into the case is ideal. But the cost of the controller is quite high. The device will cost $ 30, which is equivalent to the cost of the battery itself.

To test the charge level of a lithium battery on the go, without using a charger, you can use a special indicator RC helicopter lipo battery AKKU portable voltage meter tester alarm 2-6S AOK. The cost of the device is very low. It has a balancing and charging connector similar to the iMax6 device. The device is connected to the battery via an adapter. This voltage level control device is very convenient. It can measure from two to six series-connected lithium cells, as well as give the total value or voltage of each cell individually with extreme accuracy.

How much will it cost to replace a Ni-Mh with a lithium device?

How much money will it take to convert a screwdriver to a lithium battery?

The price of such a device consists of the cost of several components:

• 4S lithium-based battery configuration costs 2200 rubles;
• buying a controller for charging and discharging plus a balancer costs 1240 rubles;
• the cost of welding and assembly is 800 rubles.

It turns out that a do-it-yourself lithium battery costs 4240 rubles.

For comparison, let's take a similar configuration from factory-made lithium. For example, the Makita 194065-3 device is designed for a screwdriver. It has the same settings. The cost of such a device is 6500 r. It turns out that converting a screwdriver to lithium batteries saves 2300 rubles.

The domestic industry has long been producing samples of reliable and inexpensive screwdrivers, most of which are equipped with obsolete types of built-in batteries. Self-conversion of a screwdriver to lithium allows its owner to extend the life of this product and even slightly improve performance. A modern li ion battery for a screwdriver looks like it is shown in the figure below.

Despite the fact that a large number of companies can convert a screwdriver to a new battery for a relatively modest price, it is more convenient to do it on your own.

Reasons and difficulties of alteration

Advantages and disadvantages of LI Ion

First of all, we note that the old nickel-cadmium batteries are quite reliable, inexpensive and can operate at low temperatures, withstanding a large number of charge-discharge cycles. However, they have one bad property, which consists in the gradual loss of capacity, if you put them on charge without waiting for a full discharge (the so-called "memory effect").

The need to convert a screwdriver to 18650 lithium batteries is explained by a number of advantages of the latter, the main of which are:

• Large capacity to extend the life of the device;
• Noticeably smaller dimensions and weight than other batteries (photo below);

• The ability to “keep” a charge well, while not under load;
• No memory effect typical of older batteries.

However, new lithium batteries also have a drawback, which consists in the deterioration of parameters when they are completely discharged. At voltages of more than 4.2 and less than 2.7 Volts, they “feel” not very comfortable. That is why, even during production, these products are equipped with built-in controllers that protect them from short circuits, overvoltages and deep discharges.

Note! The built-in electronic regulator automatically turns them off when the supply circuit is open, or when the battery of the screwdriver is outside the working tool compartment.

Another disadvantage of converting a screwdriver battery to lithium is the inability of new batteries to operate at low temperatures. However, all these shortcomings are more than covered by the previously considered advantages.

Problem areas

To realize the above advantages, it will be necessary to solve a number of issues that arise when converting a screwdriver battery to li- ion, namely:

• The working dimensions of the new product, determined from its designation (diameter - 18 mm, length - 65 mm) do not match the dimensions of the replaced elements;
• A full replacement of batteries is possible only if the battery compartment is improved, allowing you to place the controller board and the connecting wire harness;
• When reworking, the voltage difference of each of the elements of the combined source, consisting of several batteries, must also be taken into account (1.2 Volts for nickel-cadmium versus 3.7 Volts for LI Ion).

Important! Given this circumstance, it is necessary to try in advance to adjust the total voltage of several new cells to its old value (the figure below shows nickel-cadmium batteries).

In some cases, it is not possible to achieve a coincidence of the supply voltages at all, which forces us to abandon the alteration or look for other products that are suitable for this parameter. At the same time, it is important to observe the measure and calculate the economic feasibility of switching to li ion 18650 (otherwise the upgrade may turn out to be more expensive than the instrument itself).

Features of lithium ion battery

Before converting a screwdriver to a lithium-ion battery, you must carefully familiarize yourself with the intended modes of its operation as part of this tool. The following factors must be taken into account:

• The main operating parameter of these products is the load current (its nominal value can be found in the instrument's passport);
• When choosing a suitable type of Li-Ion 18650, one should focus on a model that provides significant discharge (or load) currents, reaching values ​​from 15 to 30-40 Amperes;
• In this case, it is not necessary to take into account the declared capacity of the selected battery, which can always be restored by additionally charging the li ion screwdriver.

Note! These features explain the inadmissibility of using a lithium battery from an outdated laptop, which is often mentioned on the Internet. Such batteries are not designed for high discharge current and do not have the required technical parameters.

We also note that when choosing several 18650 cells inserted into one battery compartment, it is not allowed to use cells with very different capacities.

Based on the operating voltages of old and new batteries (1.2 and 3.7 Volts) indicated in the technical specifications, when selecting their quantitative ratio, a proportion of 1 to 3 should be followed. So, for a 12-volt battery compartment of nickel-cadmium cells (10 pieces), it is redesigned in such a way that 3 lithium batteries fit in it (this results in a slight voltage shortage).

We also recall that before assembly it is necessary to fully charge each of the installed elements, which will ensure the equalization of their potentials.

Compartment rework

Disassembly

Before you disassemble the case of the old battery compartment with your own hands, you should pay attention to the fact that it can be made using the following technologies:

• Separate parts are fastened together by means of small self-tapping screws;
• These elements are fixed on the base of the screwdriver using technical glue or special latches (the photo below shows the appearance of such a block).

To disassemble the glued block located on the screwdriver, it is most convenient to use a mallet with a plastic head, which eliminates possible damage to the device body. Before dismantling, remove all unnecessary parts of the structure from the compartment, leaving only the contact plates (their assembly) necessary for connecting to the tool itself and an external charger.

Connection methods

Batteries installed in the old Li-Ion compartment can be connected in the following ways:

• Use of special adapter cassettes;
• Soldering elements with a soldering iron;
• Spot welding.

The fastest of them is the first, however, when it is used, contact zones are formed with transient resistances that are noticeable at high operating currents. In addition, the dimensions of the compartment in this case increase noticeably, which is not always convenient from the point of view of ergonomics.

The connection of elements for soldering is suitable for those who have mastered the techniques of working with a soldering iron, which is very important in this case. The fact is that when soldering the battery, this operation must be done as quickly as possible so as not to overheat the contact areas of its poles.

The so-called "spot welding" is the most convenient and reliable method of all previously considered. But since the presence of a welding machine in a personal household is a rarity, you will have to turn to specialists, which is also not very cheap. Consider the most accessible of all these approaches (soldering) in more detail.

Connection of elements by soldering

When applying this method, it should be remembered that the elements converted to new operating conditions are connected in series, as a result of which their voltages add up, and the total capacitance does not change. It is recommended to use low-melting solder and low-temperature flux during the soldering process, since any overheating of the contacts of the 18650 elements can lead to their destruction.

Important! In the process of soldering batteries in the compartment that is equipped with a screwdriver or drill, it is advisable to use a soldering iron with a power of up to 40 watts. This precaution will keep the lithium battery safe and sound.

Upon completion of the connection of the elements in a serial chain, it will be necessary to solder the wires leading to the board with the control circuit (controller) to the positive and negative terminals of the assembly. Particular attention is paid to the cross section of the conductors used, which should not be less than 1.5 mm². With this size, they will not heat up during prolonged use or charging.

When carrying out this operation, it is desirable to use special insulating tubes with heat-shrink properties. Through these insulating products, it is possible to reliably protect soldering points from unwanted short circuits and oxidation (see photo below).

Direct battery assembly

All further operations to replace the battery assembly in a screwdriver with new products can be presented in the form of the following sequence of actions:

• First, all disassembled parts of the device body are thoroughly cleaned of dust and dirt accumulated during operation;
• Then, for new batteries that differ in size, it will be necessary to prepare a seat by fixing a piece of foam rubber on its bottom using the Moment universal glue;

Additional Information. In some cases, for these purposes, it is allowed to use a sealant, with which the sealing gasket is attached to the inner wall of the compartment housing.

• At the final stage of work, conductors are soldered to the contacts remaining from the old circuit, extending from the plus and minus of the lithium assembly, and it itself is placed on a bed in the case;
• A board with a controller is laid on top of it, insulated on all sides with a protective film, and then this whole structure is closed with a lid with a foam gasket.

In conclusion of the review of the known methods of alteration, we note that each of them is selected according to the capabilities and preferences of the performers. The only thing that should be carefully monitored during their implementation is the reliable isolation of all elements of the compartment, which excludes short circuits in the supply circuits.

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