Conversion of charging a screwdriver to lithium
Converting a 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 required 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 a screwdriver to lithium batteries, mainly to the 18650 form factor, is justified.
Conversion of a 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 screwdriver battery should be carried out taking into account the peculiarities of lithium 18650 batteries.
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 a screwdriver with a voltage of 14.4 V lies in creating 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 screwdriver is high, you must select the appropriate BMS for the required number of cans and at least 30 A. To convert the charging of the screwdriver to a lithium battery, you must stock up on a good soldering iron, non-acidic flux and thick wires to make 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 a 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 circuit for connecting 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.
Accumulators and batteries
Energy storage information website
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. The 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.
- The screwdriver becomes much easier after converting the battery to li-ion, using 18650 cells.
There are only two obstacles to converting a 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 the 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 rework a 12 V screwdriver using Ni-Cd cans on 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 increase slightly, capacity. solid pluses. But when dismantling, it is necessary to leave the terminals and the native thermal sensor.
Alteration of the “Hitachi” 12 V screwdriver for lithium batteries 18640
Features of reworking the 12 V Hitachi 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 a screwdriver during rework through a protective controller. It should serve 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 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.
Conversion of the Makita screwdriver to the lithium battery
There is a “Makita” 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. The alteration will give the old tool new possibilities: it will increase the operating time on a single charge. will add power as the operating voltage rises to 10.8V.
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 4.2V, the lower voltage is 2.7V. 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 screwdriver to lithium batteries looks like this.
- It is possible to disassemble the battery with glue if you tap the junction with a soft-headed hammer on the weight. Direction of impact downward, butt-joint along the lower part of the body.
- Take only the contact plates from the old assembly, carefully disconnecting them from the battery. The sensor and the breaker must be left.
- 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 a screwdriver with an old DC9710 charger, after charging the 18650 lithium battery, 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. The screwdriver is ready to work.
Alteration of the Interskol screwdriver for 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 DSh “Interskol” on lithium batteries serve much better. Alteration of a 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 operability, 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 screwdriver
Ways to restore the battery at home
It should be noted that recovery is only possible for Ni-Cd batteries that have a pronounced memory effect, due to which the battery capacity is lost. As a result, the battery quickly dries up, and after a short break it starts working again. This problem can be fixed quite simply.
- Fully charge the battery in the usual way, ideally, charge should be done at low current.
- Next, you should completely discharge the battery by connecting a load to it. As the latter, you can use an ordinary 12 V light bulb with a power of up to 40 W. Thus, a soft discharge will occur, as a result of which not only the outer layer of the battery will be discharged, but also its inner plates.
- It is possible to carry out 3 to 5 charge-discharge cycles. After that, the memory effect of your battery will be erased, and the battery capacity will increase significantly.
In some cases, when it is not possible to purchase new cans for the battery pack, they can be revived by adding distilled water to them, since over time the electrolyte in the cans boils away and they fail. You can restore the battery as follows.
- Identify defective batteries using the method described above.
- Fully discharge the battery by connecting a 12V (40W) light bulb to the terminals.
- Disconnect the unusable items (marked) from the rest.
- Remove a small piece of paper insulation from the top of the can to expose a small grooved area. If you remove all the paper, you will have to wrap the battery with tape.
- Using a thin drill with a diameter of 1 mm, make a hole in the battery case, namely, in the groove, as shown in the photo below.
- Next, you need to draw distilled water into a syringe and slowly pour it into a jar. In order to restore the battery, the capacity must be completely filled.
- Wait a little so that the water is well absorbed, then seal the holes with epoxy or tape.
- Now you can solder recovered banks by placing them in their original places.
- Assemble the unit and do 3-5 cycles, including a full charge and a full discharge of the battery. Only after carrying out these procedures will it be possible to use the tool.
How to diagnose a malfunctioning battery
The main malfunctions of a screwdriver battery include the following:
- the battery does not charge;
- The battery charges quickly and discharges just as quickly;
- The battery does not hold charging for a long time.
A screwdriver battery malfunction can be caused by the failure of one or more storage elements. Failure of all cans in the battery pack is very rare, so it is quite possible to restore the battery. Since all banks are connected in series, it will be necessary to disassemble the unit and find faulty.
A complete battery check is carried out in several stages, with a fully charged battery.
Restoration, alteration and repair of the screwdriver battery
It’s no secret that the cost of a new battery for a screwdriver equals 70% of the total cost of the device. During operation, any rechargeable battery (accumulator battery) begins to lose its capacity and, as a result, completely or partially fails. But do not throw away the used-up battery, because it can be reanimated at home.
How to replace faulty batteries
In addition to restoring unusable battery elements of a screwdriver, the most effective repair of a screwdriver battery is replacing the batteries that make up it with new ones. Before repairing, you must purchase suitable batteries online. Their technical characteristics must be identical to those indicated on the body of the cans in the battery pack of the screwdriver.
To change the batteries in the unit with your own hands, you will need a soldering iron and soldering materials: tin and alcohol flux (for rosin).
Replacing batteries requires some rules.
- To connect the cans, you need to use the plates previously sealed from the batteries. They have the correct cross-section and the required resistance indicator.
- In order not to overheat the cans during soldering, it should be done quickly. Excessive heating of batteries can render them unusable.
- The batteries are connected in series: the minus of each can is connected to the plus of the next.
- After assembling the battery pack, carry out at least 3 cycles of full discharge and charge of the battery.
Conversion of a screwdriver to lithium
Owners of screwdrivers with nickel-cadmium batteries often change them to lithium-ion batteries when the “native” batteries completely fail. Converting a screwdriver to 18650 lithium batteries is not a big deal. You just need to acquire the necessary parts: finger batteries in the required quantity and a charge management board BMS (Battery Management System). All parts can be purchased on China websites.
BMS is designed to control the charging / discharging process of all elements separately, the level of current consumption and temperature. BMS is also capable of balancing batteries. This controller is selected depending on the number of cans that need to be charged.
For example, the designation BMS 5S means that the controller is designed for 5 elements.
The abbreviation “18650” refers to the dimensions of the battery, that is, the diameter is 18 mm and the length is 65 mm. Batteries of this size are enough to fit in the power supply housing of a screwdriver.
For example, the transfer of a screwdriver from a Ni-Cd battery to 4 lithium batteries will be considered. Accordingly, the BMS will be designed for 4 elements. Below is the diagram for connecting BMS to batteries.
Next, it is necessary to connect the batteries by soldering them in series with each other, as shown in the diagram, and then connect them to the controller board.
All components are placed in the body of the battery pack. At this stage, the rework of the screwdriver battery is completed.
During the operation of the screwdriver, the controller monitors the voltage level on each bank. If on one of them the voltage drops below 3 V, the discharge is turned off. The same thing happens when charging. If the voltage rises to 4.2V, charging stops.
Thus, the controller prevents the battery from completely discharging and overcharging, which is very important for lithium-ion batteries.
Checking under load
To find out how long it takes for the battery to completely drain, you need to test the battery under load. The latter is selected in accordance with the battery capacity.
As a rule, it is customary to select the load for testing the battery in the range of 35-40 W. To do this, you can use a 12 V light bulb with a power of 40 W.
Connect the battery through the ammeter to the light bulb for 2-3 minutes. All measurements must be carried out with a voltmeter. The voltage at the battery outputs should be slightly more than 12.4 V. If during this time the readings have dropped and are in the range of 12-12.4 V, then this indicates that there are damaged banks in the circuit. Also, the fact that there are faulty elements in the unit can signal a drop in the brightness of the connected lamp.
Checking with a multimeter
Since all components of the battery pack must have the same voltage level, it will not be difficult to find a faulty cell. For these purposes, a multimeter is usually used, switching it to the voltage measurement mode. When measuring, take into account the nominal voltage for different types of batteries:
- Li-Ion (lithium-ion) battery has a nominal voltage of 3.6-3.8V;
- Ni-Cd (nickel-cadmium) and Ni-MH (nickel-metal hydride) batteries have a voltage rating of 1.2-1.4V.
The search for a faulty battery is as follows.
- Connect the battery to the charger and wait until it is fully charged.
- Disassemble the battery case, remove all banks from it and measure the voltage on each of them.
- Banks with a rated voltage below the norm must be marked.
- Assemble the unit, installing all the removed elements into it, and connect it to the screwdriver.
- At the next stage, it is necessary to turn on the tool and perform several operations with it in order to achieve a noticeable drop in power.
- After discharging, you should again disassemble the battery pack and measure the voltage on all batteries in the circuit. Pay special attention to labeled cans.
- If you notice a voltage drop of 0.5-0.7 V on any battery, then such a battery can be considered unusable, and it will have to be replaced.
Battery charger malfunctions and repairs
To repair the charging, you must have at least minimal knowledge in the radio model, as well as a device for “dialing” the radio components of the device. a tester. All chargers for screwdrivers are similar to each other and have the following components:
- a low-voltage part, which includes a converter rectifier, as well as a circuit that provides power supply for charging the battery;
- step-down inverter;
- mains rectifier.
Network rectifiers can be called the most durable battery charger elements if they are properly operated. But if the charging is designed to operate from a 120-130 V mains, and while connecting it through the converter, the fuse burns out, then in order to fix it, the fault should be looked for in the rectifier. In chargers operating from 220 V, the high-voltage transistors of the inverter are often lit. At the same time, the rest of the charging electronics and the inverter rectifier fail very rarely. Also, the reason that the charger does not work can be considered broken or swollen capacitors.
Disassembly of the charger case is required before troubleshooting. This should be done carefully, since most cases are assembled on 1 screw and latches, which break easily.
All components of the electronic charging circuit must be checked with a tester. Most often, the rectifier capacitor turns out to be faulty. Even if, upon visual inspection, you see swollen electrolytes, they must be re-soldered, replacing them with serviceable analogs. Further, by installing a fuse with the required rating, you can check the operation of the board in the battery charging mode. If no problems are found, the current and voltage indicators are within normal limits, then the board can be mounted in the case.
If the charger board still refuses to work, and the battery does not charge, then you need to look for problems further. The serviceability of the fuse, as well as the presence of voltage on the capacitor, indicates that the fault is in the inverter. Inverter diagnostics is a complex task and requires certain experience, as well as special equipment. an oscilloscope. If there is no experience and equipment, then the charging can be repaired by alternately checking all radio components, changing the transistors and converter microcircuits, and each time checking the board for operability.
Also, upon visual inspection, you can see punctured diodes. They will differ in their yellowness due to overheating. If at least one diode (diode bridge) breaks through, it short-circuits the transformer. What happened causes overheating of the remaining diodes, as a result of which there is an overheating of the transformer windings and their turn-to-turn short circuit. Therefore, you need to check with a tester all suspicious diodes and both windings of the transformer. The check most often shows an open in the primary winding.
It is worth knowing that almost all transformers of this type have thermal protection, which is triggered at a temperature of 130 ° C. Typically, this sensor is located under the top layers of the transformer insulation. If there is nothing to replace the sensor with, then at your own peril and risk, you can simply solder the sensor legs, eliminating an open circuit. Next, you should return the insulation removed from the windings to its place and check the performance of the charger. In most cases, this transformer malfunction is eliminated in a fairly simple way.
Features of the
The design of a lithium rechargeable battery is not too different from the design of batteries based on other chemistry. But a fundamental feature is the use of anhydrous electrolyte, which prevents the release of free hydrogen during operation. This was a significant disadvantage of the batteries of the previous designs and led to a high probability of fire.
The anode is made of a cobalt oxide film deposited on an aluminum base-current collector. The cathode is the electrolyte itself, which contains lithium salts in liquid form. The electrolyte impregnates a porous mass of electrically conductive chemically neutral material. Loose graphite or coke is suitable for it. Current collection is carried out from a copper plate superimposed on the back of the cathode.
For normal battery operation, the porous cathode must be pressed tightly enough to the anode. Therefore, in the design of lithium batteries, there is always a spring that compresses the “sandwich” from the anode, cathode and negative current collector. The ingress of ambient air can upset the carefully balanced chemical balance. And the ingress of moisture and does threaten the danger of fire and even explosion. Therefore, the finished battery cell must be carefully sealed.
A flat battery is simpler in design. All other things being equal, a flat lithium battery will be lighter, much more compact, and provide significant current (that is, more power). But it is necessary to design a device with flat-shaped lithium batteries, which means that the battery will have a narrow, specialized application. Such batteries are more expensive than their counterparts.
Battery conversion of Black & Decker Cordless Screwdriver
To make the sales market wider, manufacturers produce battery cells with universal shapes and standard sizes.
Among lithium batteries, the 18650 version actually dominates today. Such batteries have a form similar to the cylindrical finger batteries familiar in everyday life. But the 18650 standard specifically provides for a slightly larger size. This avoids confusion and prevents such a power supply unit from being mistakenly replaced in place of a conventional saline battery. But this would be very dangerous, since the lithium battery has two and a half times the standard voltage (3.6 volts versus 1.5 volts for a salt battery).
For an electric screwdriver, lithium cells are sequentially collected into a battery. This allows the voltage to the motor to be increased to provide the power and torque required by the tool.
The rechargeable battery necessarily contains in its design temperature sensors and a specialized electronic device. a controller.
- monitors the uniformity of the charge of individual elements;
- controls the charge current;
- does not allow excessive discharge of elements;
- prevents overheating of the battery.
Batteries of this type are called ionic. There are also lithium-polymer cells, this is a modification of lithium-ion. Their design is fundamentally different only in the material and design of the electrolyte.
How to charge correctly?
Lithium batteries are quite finicky about charger specifications. Such batteries can be charged fairly quickly with a significant current, but excessive charging current leads to severe heating and fire hazard.
To charge a lithium battery, it is imperative to use a special charger with electronic control of the charge current and temperature control.
It should also be borne in mind that when cells are connected in series in a battery, lithium sources are very prone to uneven charging of individual cells. This leads to the fact that it is not possible to charge the battery to its full capacity, and the cell, which regularly works in undercharged mode, simply wears out faster. Therefore, chargers are usually built according to the “charge balancer” scheme.
Fortunately, all modern factory-made lithium batteries (except for outright fakes) have built-in protection and balancing circuits. However, the charger for these batteries must be specialized.
Features, advantages and disadvantages of lithium batteries for screwdriver
- Features of the
- Advantages and disadvantages
- Difference from nickel cadmium batteries
- How to choose?
- How to remake and assemble?
- How to charge correctly?
- How to store?
If a hand-held power tool powered by a household power supply is tied to an outlet with a wire, limiting the movement of a person holding the device in his hands, then battery-operated counterparts of the units “on a leash” provide much more freedom of action in work. Battery is essential when it comes to using screwdrivers.
Depending on the type of battery used, they can be conditionally divided into two groups. with nickel and lithium batteries, and the features of the latter make this power tool the most interesting for the user.
How to choose?
When it comes to choosing a battery for a screwdriver, the task comes down to the selection of the electrical device itself, which will include a battery of a specific model.
The rating of inexpensive cordless screwdrivers this season looks like this:
- Makita HP331DZ, 10.8 volts, 1.5 Ah, lithium;
- Bosch PSR 1080 LI, 10.8 volts, 1.5 Ah, lithium;
- Bort BAB-12-P, 12 volt, 1.3 Ah, nickel;
- Interskol DA-12ER-01, 12 volts 1.3 Ah, nickel;
- Kolner KCD 12M, 12 volt, 1.3 Ah, nickel.
The best professional models are:
- Makita DHP481RTE, 18 volts, 5 Ah, lithium;
- Hitachi DS14DSAL, 14.4 volts, 1.5 Ah, lithium;
- Metabo BS 18 LTX Impuls 201, 18 volt, 4 Ah, lithium;
- Bosch GSR 18 V-EC 2016, 18 volts, 4 Ah, lithium;
- Dewalt DCD780M2, 18 Volt 1.5 Ah, lithium.
The best cordless screwdrivers in terms of reliability:
- Bosch GSR 1440, 14.4 volts, 1.5 Ah, lithium;
- Hitachi DS18DFL, 18 Volt, 1.5 Ah, Lithium
- Dewalt DCD790D2, 18 Volt, 2 Ah, Lithium.
You can see that the best screwdrivers in the semi-professional and professional segments have 18 volt rechargeable batteries.
This voltage is considered the industry professional standard for lithium batteries. Since a professional tool is designed for long-term active work, and also implies an additional level of comfort, a significant part of the produced 18-volt screwdriver batteries are fully compatible with each other, and sometimes even interchangeable between tools from different manufacturers.
In addition, the 10.8 volt and 14.4 volt standards are widely used. The first option is found only among the most inexpensive models. The second is traditionally a “middle peasant” and can be found both among professional models of screwdrivers and in models of the middle (intermediate) class.
But the designations of 220 volts in the characteristics of the best models cannot be seen, since this indicates that the screwdriver is connected with a wire to a household power outlet.
Advantages and disadvantages
- The main advantage of lithium batteries is their high electrical capacity. This allows you to create a lightweight and compact hand tool. On the other hand, if the user is ready to work with a heavier device, he will receive a very powerful battery that allows the screwdriver to work for a long time.
- Another advantage is the ability to fill lithium batteries with energy relatively quickly. A typical full charge time is approximately two hours, and some batteries can be charged in half an hour with a special charger! This advantage can be an exceptional reason for equipping a screwdriver with a lithium battery.
Lithium batteries also have some specific disadvantages.
- The most noticeable is the significant drop in practical capacity when operating in cold weather. At subzero temperatures, an instrument equipped with lithium batteries has to be warmed up from time to time, while the electrical capacity is fully restored.
- The second noticeable drawback is not too long service life. Despite the assurances of the manufacturers, the best samples, with the most careful use, withstand no more than three to five years. Within a year after the purchase, a lithium battery of any common brand, with the most careful use, can lose up to a third of its capacity. After two years, hardly half of the original capacity will remain. Average life of normal operation is two to three years.
- And another notable drawback: the price of lithium batteries is much higher than the cost of nickel-cadmium batteries that are still widely used in handheld power tools.
How to remake and assemble?
Often, the master already has an old cordless screwdriver that suits him completely. But the device is equipped with outdated nickel-cadmium batteries. Since the battery will still have to be changed, there is a desire to replace the old battery with something newer. This will not only provide more comfortable work, but also eliminate the need to look for batteries of an outdated model on the market.
The simplest thing that comes to mind is to assemble a power supply from an electronic transformer in an old battery case. Now you can use the screwdriver by connecting it to the household power supply.
14.4 volt models can be connected to car batteries. Having assembled an extension adapter with terminals or a cigarette lighter plug from the body of an old battery, you get an indispensable device for a garage or work “in the field”.
Unfortunately, when converting an old battery into a wired adapter, the main advantage of the cordless screwdriver is lost. mobility.
If we are converting an old battery to lithium, we can take into account that 18650 lithium cells are extremely widespread in the market. Thus, we can make screwdriver batteries based on readily available parts. over, the prevalence of the 18650 standard allows you to choose batteries from any manufacturer.
It will not be difficult to open the case of an old battery and remove the old filling from it. It is important not to forget to mark the contact on the case to which the “plus” of the old battery assembly was previously connected.
Depending on the voltage for which the old battery was designed, it is necessary to select the number of lithium cells connected in series. The standard voltage of a lithium cell is exactly three times that of a nickel cell (3.6 V instead of 1.2 V). Thus, each “lithium” replaces three series-connected “nickels”.
By providing for the design of the battery, in which three lithium cells are connected one after the other, it is possible to obtain a battery with a voltage of 10.8 volts. Among nickel batteries, these are found, but not often. When four lithium cells are connected to a garland, we already get 14.4 volts. This will replace both 12 volt and 14.4 volt nickel batteries. these are very common standards for nickel cadmium and nickel metal hydride batteries. It all depends on the specific model of the screwdriver.
After it was possible to determine the number of successive stages, it will probably turn out that there is still free space in the old building. This will allow two cells to be connected in each stage in parallel, which will double the battery capacity. To connect lithium batteries to each other in production, a nickel strip is used. Sections of the tape are connected to each other and to lithium elements by resistance welding. But in everyday life, soldering is quite acceptable.
Soldering lithium cells should be done with great care. The joint must be thoroughly cleaned beforehand and a good flux applied. Tinning is done very quickly, with a well-heated soldering iron of sufficiently high power.
The soldering itself is performed by quickly and confidently warming up the place where the wire is connected to the lithium cell. To avoid dangerous overheating of the element, the soldering time should not exceed three to five seconds.
When designing a homemade lithium battery, you should take into account that it is charged in a special way. It is imperative to provide an electronic circuit for monitoring and balancing the charge in the design of the battery. In addition, such a circuit should prevent possible overheating of the battery and excessive discharge. Without such a device, a lithium battery is simply explosive.
It is good that now there are ready-made electronic control and balancing modules on sale at fairly low prices. It is enough to choose the solution that suits your particular case. Basically, these controllers differ in the number of series-connected “steps”, the voltage between which is subject to equalization (balancing). In addition, they differ in their permissible load current and temperature control method.
In any case, it is no longer possible to charge a homemade lithium battery with an old nickel battery charger. They have fundamentally different charging algorithms and control voltages. You will need a dedicated charger.
Difference from nickel cadmium batteries
Historically, the first truly mass-produced rechargeable batteries for handheld power tools were nickel-cadmium batteries. At a low price, they are quite capable of relatively large loads and have a satisfactory electrical capacity with reasonable dimensions and weight. Batteries of this type are still widespread today, especially in the inexpensive sector of handheld appliances.
The main difference between lithium batteries and nickel-cadmium batteries is low weight with high electrical capacity and very good load capacity.
In addition, a very important difference between lithium batteries is the significantly shorter charging time. This battery can be charged in a couple of hours. But the full charge cycle of nickel-cadmium batteries takes at least twelve hours.
There is another peculiarity associated with this: while lithium batteries tolerate both storage and operation in an incompletely charged state quite calmly, nickel-cadmium batteries have an extremely unpleasant “memory effect”. In practice, this means that in order to extend the service life, as well as to prevent a rapid loss of capacity, it is advisable to use nickel-cadmium batteries until they are completely discharged. After that, be sure to charge to full capacity, which takes a considerable time.
Lithium batteries do not have this disadvantage.
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 disconnected. At the same time, the case is not damaged in any way, I have already disassembled 4 pieces this way.
The part of interest to us.
From the old circuit, only contact plates are needed. They are permanently spot welded to the top 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.
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).
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.
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 ones, 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.
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 will be 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 30-amp 18650 cells made by Sony VTC4 (2100 mAh capacity) and 20-amp Sanyo UR18650NSX (2600 mAh capacity). They work fine in my 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 assemble 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. 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-shrink 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.
Now everything is insulated as it should.
The contact part can be fixed in the battery case with a couple of droplets of super glue.
Battery ready for assembly.
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 will tell you exactly how.
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 proceeds 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 upgrade of the oBosch battery cost about 1000 rubles. Makitovsky’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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Replacing batteries in a screwdriver with lithium
Converting a screwdriver battery to lithium cells
Many screwdriver owners want to convert their batteries to lithium battery cells. Many articles have been written on this topic and in this material I would like to summarize information on this issue. First of all, consider the arguments in favor of converting a screwdriver to lithium batteries and against it. And also we will consider some moments of the process of replacing batteries.
Let’s start with the benefits:
- The energy density of lithium-ion cells is much higher than that of nickel-cadmium, which are used by default in screwdrivers. That is, the battery on lithium cans will have less weight than on cadmium with the same capacity and output voltage;
- Lithium battery cells are charged significantly faster than Ni-Cd. It will take about an hour to charge them safely;
- Lithium ion batteries have no memory effect. This means that they do not need to be fully discharged before charging.
Now about the disadvantages and complexities of lithium batteries.
Well, then the assembly process itself follows. Disassemble the battery case first. If this is a 14.4 volt model, then there will be 12 nickel-cadmium batteries with a nominal value of 1.2 volts inside.
Assembling Nickel Cadmium Batteries
After that, you need to solder the purchased items into an assembly with a serial connection. Next, the controller is soldered to it in accordance with its circuit. In this case, balancing points are connected. The board has a special connector for them, and often wires with a connector are supplied in the kit.
Screwdriver battery housing
After assembling the battery, the terminals for plus and minus are soldered, and the whole structure is placed in the case. In principle, this is the end of the process. Problems can only arise with the charger. But in most cases, standard screwdriver chargers charge lithium cells without problems. In this case, the charge of the cans goes through the controller, so nothing terrible will happen to the elements themselves.
All pros and cons of converting a screwdriver battery to lithium cells
First, you should think about whether I need this alteration? After all, it will be a frank “self-propeller” and in some cases can lead to failure of both the battery and the screwdriver itself. Therefore, let’s consider all the pros and cons of this procedure. It is possible that after that, some of you will decide to abandon the conversion of the Ni─Cd battery for a screwdriver to lithium cells.
What you need to estimate before starting work?
It is necessary to determine the number of cells in the battery, which ultimately decides the magnitude of the voltage. For three elements, the ceiling will be 12.6, and for four. 16.8 volts. We are talking about reworking widespread batteries with a nominal value of 14.4 volts. It is better to choose 4 elements, since during operation the voltage will drop pretty quickly to 14.8. A difference of several volts will not affect the operation of the screwdriver.
In addition, more lithium cells will give more capacity. This means longer operating time of the screwdriver.
Lithium battery cells 18650
The nominal voltage of lithium cells is 3.6-3.7 volts, and the capacity in most cases is 2000-3000 mAh. If the battery case allows, you can take not 4, but 8 cells. Connect them two by two into 4 parallel assemblies, and then connect them in series. As a result, you will be able to increase the capacity of the battery. But not every case will be able to pack 8 cans of 18650.
And the last preparatory step is choosing a controller. According to its characteristics, it must correspond to the rated voltage and discharge current. That is, if you decide to assemble a 14.4 volt battery, then choose a controller with this voltage. The working discharge current is usually chosen half of the maximum permissible current.
Charge-Discharge Controller Board
Above, we established that the maximum permissible short-term discharge current for lithium cells is 25-30 amperes. This means that the charge-discharge controller must be rated for 12-15 amperes. Then the protection will be triggered when the current increases to 25-30 amperes. Do not forget also about the dimensions of the protection board. It, together with the elements, will need to fit into the battery case of the screwdriver.
- Lithium battery cells cannot be charged above 4.2 volts and discharged below 2.7 volts. In real conditions, this interval is even narrower. If you go beyond these limits, the battery can be damaged. Therefore, in addition to the lithium cans themselves, you will need to connect and install a charge-discharge controller in the screwdriver;
- The voltage of one Li─Ion cell is 3.6─3.7 volts, and for Ni─Cd and Ni─MH this value is 1.2 volts. That is, there are problems with assembling a battery for screwdrivers with a voltage rating of 12 volts. From three lithium cans connected in series, you can assemble a battery with a nominal value of 11.1 volts. Out of four ─ 14.8, out of five ─ 18.5 volts, and so on. Naturally, the voltage limits during charge-discharge will also be different. That is, there may be problems with the compatibility of the converted battery with a screwdriver;
- In most cases, 18650 cans are used in the role of lithium cells for alteration. They differ in size from Ni─Cd and Ni─MH cans. In addition, you will need space for the charge-discharge controller and wires. All this will need to fit in a standard battery case of a screwdriver. Otherwise, it will be extremely inconvenient for them to work;
- A cadmium battery charger may not be suitable for recharging a battery after a redesign. You may need to revise the charger or use universal chargers;
- Lithium batteries lose their performance at low temperatures. This is critical for those who use a screwdriver outdoors;
- The price of lithium batteries is higher than cadmium.
I also reworked the 14.4V screwdriver for Li-ion
I also took a ready-made controller from the Chinese, but different. The indicator was made on TL431, on them (TL431), in principle, the balancer can be made.
You write it is better to use 4 batteries, since the voltage will quickly sink to 14.8v, here I agree, but the words that this will increase the volume are not correct, with a serial connection, the capacity does not change, and the capacity of one battery is equal, the capacity increases with parallel connection.
Dilyaver, and here you are only partly right. The fact is that the capacity in mAh will remain the same, this is a fact, but. the capacity in Watt hours will increase.
In this review, there is more crap than real advice (and the videos from YouTube have chosen the same dumb, empty ones). I remember such an example. The controller in China (according to their replicas) costs like a new lithium battery !? Yes, where and when it was. About ten minutes ago, a specialist looked at Aliexpress. it is overwhelmed, see the one I need, at 18 V. with delivery from 1.8 to 3-4-6 dollars, and this is with a temperature sensor and soldered wires!
Good afternoon! Please give advice on which BMS controller is needed for the 18v, 1.2 A screwdriver. Thank you in advance.
For an 18v screwdriver, you need to take a 21v controller!
Hello! Please give a link to the 14v charging module for 4 batteries, as you describe in your video. Could not find.
Hello! I have a question: if the protection board to the batteries is not balanced, do I need to connect intermediate wires? I have 3S, I connected from the first battery minus to 0v, and from the last plus to 12.6v. Loading and charging on other terminals (.). But at 3.7v and 7.4v, I did not connect anything. Shurik twisted like that a couple of times, when the cartridge was clamped, he turned off, and more and more does not twist. It seems to have loaded everything, but with a multimeter on. Connectors shows 7.6v. and in the batteries themselves there are 12.6v. Tell me what is wrong there?
The controller believes that the banks are dead, you need to connect intermediate banks, and do not consider yourself smarter than the developers!