Convert electric screwdriver battery to 14v lithium
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. Control system and charge balancing in individual components is not provided.
- Each Ni-Cd bank provides 1.2V and Li-ion 18650 3.6V.
- The capacity of a lithium battery is 2 times that of a nickel-cadmium battery, similar in size.
- An overheated li-ion battery threatens an explosion and fire, therefore, the installation of control of the uniformity of the charge in the banks is mandatory. BMS is not installed in nickel-cadmium batteries. the manufacturer is not interested.
- Lithium cells have no memory effect, unlike Ni-Cd, they can be charged at any time and within an hour.
- an electric screwdriver becomes much easier after converting the battery to li-ion, using 18650 cells.
There are only two obstacles to converting an electric screwdriver for lithium batteries. it is impossible to work with it at minus. The capacity of cans decreases, starting from a decrease already from 10 0 C. Lithium batteries are expensive.
Knowing what input voltage is required for an electric screwdriver, the charger is reworked, taking into account the placement of the lithium battery cans and control elements in the factory container. You can also do with a flashlight by upgrading the socket for a block of 18650 cells.
Let’s say you need to convert a 12 V electric screwdriver using Ni-Cd cans to li-ion. If you use 3 cans, the output voltage is not enough: 3.6 x 3 = 10.8 V. With 4 components, the power of the apparatus will be higher: 3.6 x 4 = 14.4 V. This will make the instrument 182 g lighter. its power will slightly increase, capacity. solid pluses. But when dismantling, it is necessary to leave the terminals and the native thermal sensor.
Conversion of the “Hitachi” 12 V electric screwdriver to 18640 lithium batteries
Features of alteration of the 12 V Hitachi electric screwdriver for lithium batteries. The very compact battery compartment is designed for finger cells. Therefore, you should prepare a place for 18650 cells. It is necessary to cut one side of the partition in order to tightly place 1 element.
You need to get a gumboil, a flat metal connecting tape, hot glue. It is necessary to install lithium batteries in an electric screwdriver during rework through a protective controller. It should service 3 18650 cells, 3.7V and rated for 20-30 amps.
Remove the old battery from the socket, carefully disconnect the contacts in the assembly with the temperature sensor and the power-on indicator. Clean up and sign contacts. They should be brought out to one side, connected with solder to the leads from thick wires and filled with hot melt glue on the assembly.
Assemble a power source with one of the 3 cell controllers. Build a serial circuit of 3 Li-ion cells. Connect the controller. The conversion of the 12-volt lithium battery is completed when the structure is installed in the unit, secured, and the charging indicator lights up. After fully charging, the measurements show 12.17 volts in the external network. But this is enough for trouble-free long-term operation of the device.
Conversion of an electric screwdriver to lithium batteries 18650 14 V
When converting screwdrivers of different power and flashlights from Ni-Cd to Li-ion, batteries of the form factor 18650 are more often used. They easily fit into a container or a nest, since instead of two or three relatives, one lithium is installed. Alteration of the battery of an electric screwdriver should be carried out taking into account the characteristics of lithium batteries for 18650.
This type of energy source does not tolerate deep discharge and excessive charge. Hence, it is necessary to use voltage control boards. Since each battery has its own character, their charge is corrected by a balancer. The point of reworking an electric screwdriver with a voltage of 14.4 V lies in the creation of a device using lithium batteries to facilitate a hand tool and increase its performance. Lithium 18650 batteries are most suitable for these purposes.
When selecting components, it should be taken into account that the starting current of the electric screwdriver is high, you must select the appropriate BMS for the required number of cans and at least 30 A. jumpers.
- Lithium-ion cans in the amount of 4 pcs.
- 4-cell li-ion battery controller, CF-4S30A-A works well. It has a built-in balancer that controls the charge of each element.
- Hot melt glue, flux for soldering TAGS, solder.
- Heat-resistant tape;
- Connecting jumpers or thick insulated wire with a cross section of at least 0.75 squares, cut for bridges.
The procedure for converting an electric screwdriver for 18650:
- Disassemble the case and remove a bundle of 12 Ni-Cd cells from the container.
- Remove the garland, leaving the connector with the “” and “-” pins. Instead of a temperature sensor, a thermocouple from the controller will be installed.
- Solder the assembly, considering that you cannot use acid, only neutral flux and pure solder. During the connection period, do not warm up the covers. Work pointwise.
- Connect the balancing points to the controller according to the diagram. The board has connectors.
- Connect assembly with plus and minus pins.
- Check the functionality of the circuit. If everything works, assembled the battery, place the controller in the socket, secure with a sealant.
If the charger is not universal, additional alteration will be required. Screwdrivers for 12 V with a universal charger are assembled in the same way, but a protective connection circuit 3×18650 3.7 V for lithium batteries is used. In the same way, a screwdriver is reworked using a set of 18650 batteries in the amount of 2 elements.
Conversion of an electric screwdriver to lithium batteries 18650
Every craftsman is faced with the problem of reduced tool performance, or complete failure due to the battery. Manufacturers use nickel-cadmium batteries in 12, 14, 18 volt screwdrivers. The sequential assembly of several elements creates the desired voltage. Replacing nickel-cadmium batteries with lithium batteries extends battery life by making the design lighter. Mandatory BMS board installation adds reliability. Therefore, the conversion of an electric screwdriver to lithium batteries, mainly to the 18650 form factor, is justified.
Conversion of the Makita electric screwdriver to a lithium battery
There is a “Makita” electric screwdriver with a 1.3 A / h battery and a voltage of 9.6 V. To change the power source to a lithium-ion one, you will need 3 18650 components. charge, will add power as the operating voltage rises to 10.8 V.
The design will require the use of a BMS, a control controller that maintains the lithium cell operating mode within operating limits. With this breaker, each cell will be charged evenly without exceeding 4.2 V, the lower voltage is 2.7 V. The built-in balancer is used here.
The parameters of the controller should accompany the operation of the instrument when the operating current rises to 10-20 A. The Sony VTC4 30 A board, designed for a capacity of 2100 A / h, can ensure operation without shutdown. Of the 20 amperes, the Sanyo UR18650NSX accepting 2600A / h energies is suitable. The board is needed for 3 elements, which is marked in the 3S classification. In this case, the board must have 2 contacts, plus and minus. If the conclusions are designated with the letters “P-“, “P”, “C-“, they are intended for later models of screwdrivers.
Step-by-step instructions for converting a Makita electric screwdriver to lithium batteries looks like this.
- You can disassemble the battery with glue if you tap the junction with a soft-headed hammer while weighing. Direction of impact downwards, butt-joint along the lower part of the body.
- Take only the contact plates from the old assembly, carefully disconnecting them from the battery. Leave the sensor and breaker.
- Solder 3 elements in series using TAGS flux and insulated jumpers. The wire cross-section must be greater than 0.75 mm2.
- Assemble the circuit with the controller, and connect the power supply to the contact connectors with 1.5 square wires.
- Check the functionality of the circuit and reassemble the case by placing it on the glue again.
In an electric screwdriver with an old DC9710 charger, once the 18650 lithium battery has finished charging, the red LED on the panel will turn off. The built-in controller monitors the charge level.
The Makita DC1414 T charger is used to charge 7.2-14.4 V power sources. While charging, the red light is on. But when charging a lithium battery, its voltage does not fit into the standards of salt products, and after 12 V, the charger will flash red and green. But the necessary charging is already there. electric screwdriver ready to work.
Conversion of the Interskol electric screwdriver to lithium batteries 18650
Sooner or later, the nickel-cadmium assembly of 15 cans fails. One or two elements are lazy, and it is no longer possible to get the output voltage. Modern DS “Interskol” with lithium batteries serve much better. Alteration of an electric screwdriver for 18 volt lithium batteries mastered by craftsmen.
It is necessary to purchase a protection board for 5S, 3.7 V and 40-50 A. You will need a balancing board and the energy sources themselves. 5 lithium 18650 batteries, you can leave them with factory thermistors by extending the wires. During installation, create a contact pad, insert the assembly, check the functionality, secure. The assembly features of the wizard’s advice are given in detail in the video. See here for full details on reworking an 18 volt lithium electric screwdriver
High current 18650 batteries
The second main element when reworking an electric screwdriver. Good batteries with a current output of at least 15A are required. LG HE4 2500mah, Samsung 25R 2500mah, Samsung 30Q 3000mah and LG HG4 3000mah (“chocolates”) are ideal in terms of price / quality ratio. You can use medium-current banks of 10A, but only in the 2P scheme (two in parallel).
High-current accumulators 21700
The most promising battery format, gaining popularity at a frantic pace. It has a higher energy consumption, but at the same time it is slightly larger in size. The only drawback is that they may not fit in the case, so check this point before buying. When using them, you will get a very impressive autonomy.
Designed to connect batteries to a battery. It can be used for both resistance welding and soldering. It has a low resistance and does not heat up at serious currents, moreover, it has a flat profile, which does not add much in size and allows the assembly to fit in compact cases.
One of the main elements when converting a battery to lithium power. The BMS board is required to protect the batteries against over-discharge, over-discharge, over-current and short-circuit (short-circuit). For 12-volt screwdrivers we purchase 3S BMS, for 14-volt. 4S BMS. For a more complete use of the batteries, the 4S BMS is perfect.
High-quality copper stranded wires in heat-resistant silicone insulation. Alternative to nickel tape. They are easy to tin, bend well, the insulation melts only at high temperatures. A good option for a budget rework. In critical projects I use the same.
Designed for additional electrical insulation of the battery terminals and increase the survivability of the battery as a whole. It is especially important to use them in powerful instruments with high consumption currents. They will also be useful when using not very high-quality wires, which heat up at significant currents and can short-circuit the leads.
Conversion of screwdrivers to lithium still does not lose its relevance, since it does not require significant investment and is easily carried out even by an unprepared person. At the same time, you get your favorite and time-tested tool with a much longer operating time without the disadvantages that are inherent in Ni-Cd batteries.
Assembling the battery
After checking the internal resistance of each cell, it is allowed to proceed with the assembly of the battery. The collected cells are placed in the bag, taking into account the polarity. Then the balancers and power wires are connected, the packages are connected to each other.
There are 2 techniques for connecting the battery. soldering and bolting. Soldering the part means ensuring the reliability of the connection, but if you are not confident in your own skills, it is better to choose an alternative option and select the elements intended for bolting.
How to convert cordless drill’s 14.4 Volts Ni-Cd battery into Li-on 18650 battery / Hx-4S-A01 BMS
After the tie, all the elements are placed in a pre-prepared box with a hole for cables. BMS board and balancers are mounted. After the output of the power wires, the holes are sealed.
Types of cell connections in batteries
- Series connection. positive pole connects to negative.
- Parallel connection. positive pole attaches to positive, negative to negative.
Important. Lithium batteries cannot be soldered, as they become unusable from high temperatures.
Soldering power supplies
There are several methods of soldering, the most common is soldering with a metal strip that can be removed from the can. Places of future contacts on both sides are tinned with a heated soldering iron with a drop of solder. Without bringing to strong overheating, a tape is applied.
How to convert an electric screwdriver to lithium-ion batteries
Screwdrivers, like other construction equipment, are purchased based on a good service life. Therefore, quickly depleting a charge or a slow recharging process becomes a real problem. When a regular battery is out of order or functions frankly poorly, it becomes impossible to use the tool. You should buy a battery or do it yourself. The presented article provides detailed instructions on how to solder batteries for an electric screwdriver with your own hands.
Removing the battery case
Each user is able to independently disassemble the case, which consists of two parts connected with screws and glue. The screws are unscrewed, the glue layer is broken with a thin object, which is pushed along the entire perimeter.
After the repair, the screws are installed in their original place, and the adhesive layer is renewed.
Knowing the most crucial points will help to avoid mistakes when reworking batteries:
- Use of exclusively high-quality and original components.
- Replacement with lithium substitutes is made by calculating the number of batteries.
- The quantity is calculated from the calculation of 3.7 V per cell.
- The sizes of the cans are different compared to Ni-Cd, which requires additional installation of the charging and discharging controller cells.
- Do not rush to dispose of your own battery, by means of diagnostics, the possibility of its repair is established.
Electric screwdriver batteries
Features of the choice of lithium batteries
The lithium-ion generation is the most modern. When choosing a battery, you need to pay attention to the following indicators:
- Number of discharging and charging cycles available (latest models are capable of discharging up to 600 times).
- Charging speed (maximum 2 hours).
- Price (no more than 50% of the cost of an electric screwdriver).
- Full Power Feature.
- Battery level memory.
- Dimensions (edit).
- Resistance to temperature extremes.
Soldering the battery wires with the module
Before soldering the wire, the surface is treated with flux, the ends of the wire are stripped. A classic 25 watt soldering iron is used to connect the wire to the contact area of the block. A low-melting compound is used for the solder. Final melting should take no more than 3 seconds.
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 this some of you will decide to abandon the conversion of the Ni─Cd battery for a screwdriver to lithium cells.
Well, then the assembly process itself goes. 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.
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.
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.
- 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.
Replacing batteries in a screwdriver with lithium
What you need to estimate before starting work?
It is necessary to determine the number of cells in the battery, which ultimately decides the voltage value. 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.
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.
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 consider some moments of the process of replacing batteries.
- The energy density of lithium-ion cells is significantly higher than that of nickel-cadmium cells, which are used by default in electric 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.
Conversion of an electric screwdriver to lithium batteries 18650
The industry has been making screwdrivers for a long time, and many people have older models with nickel-cadmium and nickel-metal hydride batteries. Converting an electric screwdriver to lithium will improve the performance of the device without buying a new tool. Now many companies offer services for altering batteries for an electric screwdriver, but you can do it yourself.
Conversion of an electric screwdriver to lithium batteries
Difficulties in rework
There are objective disadvantages in Li-Ion batteries, such as poor performance at low temperatures. In addition, when converting an electric screwdriver to lithium 18650 batteries, a number of difficulties can be encountered:
- The 18650 standard means that a single cell has a diameter of 18 mm and a length of 65 mm. These dimensions do not match the dimensions of the nickel-cadmium or nickel-metal hydride cells previously installed in an electric screwdriver. Replacing batteries will require placing them in a standard battery case, plus the installation of a protective microcircuit and connecting wires;
- The voltage at the output of the lithium cells is 3.6 V, and on the nickel-cadmium cells. 1.2 V. Let’s say the nominal voltage of the old battery is 12 V. This voltage cannot be ensured when Li-Ion cells are connected in series. The range of voltage fluctuations during the charge-discharge cycles of the ion battery also changes. Accordingly, converted batteries may not be compatible with an electric screwdriver;
- Ionic batteries differ in the specifics of their work. They do not withstand overcharging voltage more than 4.2 V and discharge less than 2.7 V until they fail. Therefore, when a battery is being reworked, a protective board must be installed in an electric screwdriver;
- An existing charger may not be used for an electric screwdriver with a Li-Ion battery. You will also need to redo it or purchase another.
Important! If the drill or electric screwdriver is cheap and not of very high quality, then it is better not to rework. This can cost more than the cost of the tool itself.
Tips for choosing a security chip
The lithium ion battery of the electric screwdriver cannot function normally without the BMS protection board. Instances on sale have different parameters. BMS 3S marking assumes, for example, that the board is designed for 3 elements.
What you need to pay attention to in order to choose a suitable microcircuit:
- The presence of balancing to ensure the uniformity of the charge of the cells. If it is present, the value of the balancing current should be in the description of the technical data;
- The maximum value of the operating current withstood for a long time. On average, you need to focus on 20-30 A. But this depends on the power of the electric screwdriver. Low-power enough 20 A, powerful. from 30 A;
- Voltage, upon reaching which the batteries are disconnected when overcharging (about 4.3 V);
- Voltage at which the electric 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);
- Overload protection operation current;
- Resistance of transistor elements (minimum value selected).
Important! The magnitude of the overload tripping current is not very important. This value is offset from the workload current. In case of short-term overloads, even if the tool has turned off, you must release the start button, and then you can continue to work.
Connection diagram of elements with a protective board
Whether the controller has an autorun function can be determined by the presence of an “Automatic recovery” entry in the technical data. If there is no such function, then in order to restart the electric screwdriver after the protection is triggered, it will be necessary to remove the battery and connect it to the charger.
Further battery replacement consists of the following steps:
- The disassembled parts of the case are well cleaned;
- 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;
- The positive and negative wires are soldered to the old terminal block, it is placed in the same place in the case and fixed. The protective board is laid, the parts of the battery pack are connected. If they were previously glued, then “Moment” is used again.
Disassembling the battery case
The body is often assembled on self-tapping screws, other options are assembled 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 the parts of the case. Everything is removed from the inside. You can reapply only the contact plates or the entire terminal assembly for connecting to the tool, charger.
12 V batteries are often used for screwdrivers. Factors to consider when choosing a Li-Ion battery for an electric screwdriver:
- In such instruments, elements with high values of the discharge current are used;
- In many cases, the cell capacity is inversely related to the discharge current, so it cannot be selected based on capacity alone. The main indicator is the current. The value of the operating current of an electric screwdriver can be found in the instrument’s passport. Usually it is from 15 to 30-40 A;
- It is not recommended to use cells with different capacities when replacing the battery of an electric screwdriver with a Li-Ion 18650;
- 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 inappropriate technical characteristics;
- The number of elements is calculated based on the approximate ratio. 1 Li-Ion to 3 Ni-Cd. For a 12-volt battery, you will need to install 3 new ones to replace 10 old cans. The voltage level will be slightly reduced, but if 4 cells are installed, the overvoltage will shorten the life of the motor.
Important! Before assembly, it is necessary to fully charge all elements to equalize.
The advantages 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 charge without waiting for a full discharge (memory effect).
Lithium-ion batteries offer the following benefits:
- high capacity, which will provide a longer operating time for the electric screwdriver;
- smaller size and weight;
- keeps charge well when inoperative.
But a lithium battery for an electric screwdriver does not withstand a full discharge, so 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.
How to determine the maximum current in an electric screwdriver?
Converting a 12V electric 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 that is consumed by an electric screwdriver will rise to the 5 A mark. Now you should sharply pull the trigger. This will short-circuit the power supply. 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 fixing it. This will be a short load current when the trigger of the electric screwdriver is pressed sharply. Any model of such a device will react in the same way.
Lithium Battery BMS Nicd/Nimh Charger, Is it possible? Bosch cordless drill 14.4V PSR 1440
Next, clamp the tip of the electric screwdriver with a vise and observe to what value the current consumption will increase during operation, when the ratchet is triggered in the electric screwdriver. The current indicator in this case increases to 10-12 A.
Ryobi 14.4V running 18V lithium battery
So you can determine the magnitude of the load current. In this case, it will be equal to 5 A at idle and 30 A at a sharp start, and at a maximum load it will be 12 A. The manufacturer must choose lithium cells, the nominal load current of which will be 10-20 A, and the pulsed one. 25-30 BUT.
Conversion of an electric screwdriver to lithium batteries: instruction
Converting an electric screwdriver to lithium batteries makes sense. The advantage is that they have a high electrical density. As a result, by installing such a device in the body of an electric 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 versions, it can reach 1-2 C. You can recharge such a device in 1 hour, without overstating the parameters recommended by the manufacturer and without spoiling the quality of the product.
How long does it take to replace batteries?
Converting an electric screwdriver to lithium batteries will take approximately 2 hours. If all parameters are checked, then it will take 4 hours.
Everything can be done on your own, without the help of another person. But contact welding and the choice of batteries cannot be carried out without specialized equipment.
What else can you test the state of charge besides the controller?
The electric screwdriver was converted to lithium batteries. The built-in charger 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 the special RC helicopter lipo battery AKKU portable voltage meter tester alarm 2-6S AOK. The cost of the device is very low. It has a balance and charge connector similar to the iMax6. The device is connected to the battery via an adapter. This voltage level monitor is very convenient. It can measure from two to six lithium cells connected in series, and also give the total indicator or the voltage of each element separately with extreme accuracy.
Disassembly and assembly
Converting an electric screwdriver to lithium batteries includes the following steps:
- Open the old battery by unscrewing five screws.
- Remove the Ni-Mh battery from the housing. It will be noticeable that the contact pad engaging with the contact group of the electric screwdriver is welded to the negative contact of one of the Ni-Mh cells. The welding points should be cut using a tool with a DREMEL 4000 cut-off stone built into it.
- Wires are soldered to the contacts, the cross-section of which is at least 2 mm 2 for the power terminals and 0.2 mm 2 for the thermistor. The contact pad is glued to the battery case with hot melt glue.
- According to the indicator of internal resistance, four cells are selected on the meter. The value must be the same for all four fixtures.
- Lithium cells are glued with hot melt glue so that they are compactly located in the housing.
- Welding of cells is carried out on a resistance welding machine using a welding strip made of nickel (its cross-sectional index should be equal to 2X10 mm).
How many cells will fit in the case?
Assembling 4S2P (four serial connections and two parallel) will not work. Converting an electric screwdriver to 18650 lithium batteries assumes the presence of eight cells. How can they meet four? Each cell will carry the maximum current load.
Choosing the rated voltage
First of all, you should decide on the choice of the voltage rating indicator 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 (voltage range is from 16.8 to 10 V).
How to Determine the Choice of Lithium Cells?
In order to make the selection of lithium-based cells, the limiting factors should be outlined. Currently, lithium devices with a permissible load current of 20-25 A are being produced.
Pulse current values (short, up to 1-2 seconds) reach 30-35 A. Battery configuration will not be violated.
Choosing the type of chemistry of lithium batteries
First of all, you need to decide on the type of chemistry for lithium batteries. There are two options. either lithium iron phosphate (LiFePO4), or lithium ion (Li-ion). But in any case, when working on such a powerful load, it must be borne in mind that the battery must be able to deliver the required current without harm to its well-being! Let’s briefly analyze the features of these types of batteries.
If you intend to use an electric screwdriver at subzero temperatures, then it is better to choose lithium iron phosphate (LiFePO4) batteries. Temperature range at which they can be discharged. 20
65 ° C. Li-ion’s capacity drops faster in cold weather. If work is mainly planned at positive temperatures, then both are suitable. However, both types of batteries (with the exception of some LiFePO4 models) cannot be charged at negative temperatures. And the upper limit of the temperature when charging for both is about 60 ° C.
A little about the advantages of lithium over the usual nickel-metal-hydride and nickel-cadmium batteries.
The rules for the use of nickel-cadmium and nickel-metal hydride oblige to completely discharge the battery before charging, otherwise its capacity drops rapidly. Without observing these rules, the battery will not be able to serve for a long time. And a full charge lasts about 10 hours, which is not very fast.
Lithium batteries do not have this disadvantage. They can be charged from any level. And the charge is possible many times faster. A full 0 to 100% charge cycle using the correct charger can take about an hour and a half. And for batteries with the ability to quickly charge. less than an hour.
With the same volume and weight as NiCd or Ni MH, the lithium battery will be many times more capacious, which means it will be enough for a larger volume of work. In addition, lithium batteries have low self-discharge, are more durable and lighter than nickel-cadmium and nickel-metal hydride batteries.
In a similar way, it is possible to remake not only an electric screwdriver, but also other rechargeable gadgets and battery-powered devices.
One cell of a Li-ion battery at 100% charge has a voltage of 4.2 V, with a full discharge of about 3. 2.5 V. Average operating voltage 3.7 V.
One cell of LiFePO4 battery at 100% charge has a voltage of 3.6 V, with a full discharge of about 2 V. Average operating voltage is 3.2 V.
Based on this, we count the number of cells connected in series to obtain the required voltage at the output of the battery. It is customary to denote by the number of consecutive cells the character S (serial). The voltage with this connection is summed up.
Li-ion: 1S-4.2 V, 2S-8.4 V, 3S-12.6 V, 4S-16.8 V, 5S-21 V
LiFePO4: 1S-3.6V, 2S-7.2V, 3S-10.8V, 4S-14.4V, 5S-18V
That is, for example, for a 12 volt electric screwdriver, you need a Li-ion 3S battery, or LiFePO4 4S.
Conversion of an electric screwdriver to lithium batteries
Is it possible to convert an electric screwdriver or other power tool to lithium batteries and how to do it correctly. In this article, we tried to clarify some points for novice DIYers and selected budget components of good quality.
The number of full charge / discharge cycles for LiFePO4 batteries is more than 1000, for Li-ion less than 500. But! If you do not discharge to 0% and do not charge up to 100%, then the number of cycles increases significantly. Storage Any lithium battery will work best when half charged at 0-10 ° C. You can read more about storage in this article.
The battery characteristics usually indicate the nominal and maximum (peak) discharge current. At rated current, it is able to work for a long time, and at peak current. for several seconds. Therefore, for such a powerful load as an electric screwdriver, it is necessary to pay attention to this indicator and choose high-current battery models.
At idle, a 12-volt electric screwdriver of average power consumes a current of 1-2 A, and at maximum load (especially in a braked state) the current can reach 30 A. Therefore, if it is supposed to use, for example, a GTF HG2 18650 3000 mAh battery with rated and peak currents 10A and 25A respectively, then it is necessary to assemble at least 3S2P in order not to overload the batteries. When two batteries are connected in parallel, the permissible currents are doubled, when three are connected, they are tripled, etc.