Cordless tools are more mobile and easier to use than their corded counterparts. But we must not forget about the significant drawback of the cordless tool, as you yourself understand the fragility of the batteries. Buying new batteries separately is comparable in price to purchasing a new tool.
After four years of service, my first screwdriver, or rather the batteries, began to lose capacity. To begin with, I assembled one from two batteries by choosing working "banks", but this modernization did not last long. I converted my screwdriver to a network one - it turned out to be very inconvenient. I had to buy the same, but a new 12 volt Interskol DA-12ER. The batteries in the new screwdriver lasted even less. As a result, two serviceable screwdrivers and not one working battery.
There is a lot of writing on the Internet about how to solve this problem. It is proposed to convert used Ni-Cd batteries to Li-ion batteries of size 18650. At first glance, there is nothing complicated about this. You remove the old Ni-Cd batteries from the case and install new Li-ion ones. But it turned out not to be so simple. The following describes what to pay attention to when upgrading a cordless tool.
For conversion you will need:
I'll start with 18650 lithium-ion batteries. Purchased at.
The nominal voltage of the 18650 cells is 3.7 V. According to the seller, the capacity is 2600 mAh, marking ICR18650 26F, dimensions 18 by 65 mm.
The advantages of Li-ion batteries over Ni-Cd are smaller dimensions and weight, with a larger capacity, as well as the absence of the so-called "memory effect". But lithium-ion batteries have serious disadvantages, namely:
1. Negative temperatures drastically reduce capacity, which cannot be said about nickel-cadmium batteries. Hence the conclusion - if the tool is often used at low temperatures, then replacing with Li-ion will not solve the problem.
2. A discharge below 2.9 - 2.5V and overcharging above 4.2V can be critical, complete failure is possible. Therefore, a BMS board is needed to control charge and discharge, if it is not installed, then new batteries will quickly fail.
On the Internet, they mainly describe how to convert a 14 volt screwdriver - it is ideal for retrofitting. With a series connection of four 18650 cells and a nominal voltage of 3.7V. we get 14.8V. - just what you need, even when fully charged, plus another 2V, this is not scary for the electric motor. And what about the 12V tool. There are two options, install 3 or 4 18650 elements, if three then it seems to be not enough, especially with partial discharge, and if four - a bit too much. I chose four and in my opinion made the right choice.
And now about the BMS board, it is also from AliExpress.
This is the so-called charge control board, battery discharge, specifically in my case CF-4S30A-A. As can be seen from the marking, it is calculated for a battery of four "cans" of 18650 and a discharge current of up to 30A. It also has a built-in so-called "balancer", which controls the charge of each element separately and eliminates uneven charging. For the correct operation of the board, the batteries for the assembly are taken from the same capacity and preferably from the same batch.
In general, there are a great many BMS boards with different characteristics on sale. I don’t advise you to take it for a current below 30A - the board will constantly go into protection and to restore work on some boards you need to briefly apply charging current, and for this you need to remove the battery and connect it to the charger. There is no such drawback on the board that we are considering, just release the trigger of the screwdriver and in the absence of short circuit currents, the board will turn on by itself.
To charge the converted battery, the native universal charger was perfect. In recent years, Interskol began to equip its tools with universal chargers.
The photo shows to what voltage the BMS board charges my battery together with a standard charger. The voltage on the battery after charging 14.95V is slightly higher than what is needed for a 12 volt screwdriver, but it is rather even better. My old screwdriver became faster and more powerful, and fears that it would burn out gradually dissipated after four months of use. That seems to be all the main nuances, you can start reworking.
We disassemble the old battery.
We solder the old cans and leave the terminals together with the temperature sensor. If you remove the sensor as well, then when using a standard charger, it will not turn on.
According to the diagram in the photo, we solder 18650 cells into one battery. Jumpers between the "banks" must be made with a thick wire of at least 2.5 kv. mm, since the currents during the operation of the screwdriver are large, and with a small section, the power of the tool will drop sharply. The network writes that it is impossible to solder Li-ion batteries because they are afraid of overheating, and they recommend connecting using spot welding. You can only solder a soldering iron with a power of at least 60 watts. The most important thing is to solder quickly so as not to overheat the element itself.
It should look like it fits into the battery case.
Almost all modern lithium-ion batteries have excellent energy intensity, as well as high compact performance. It is with their help that you can power high-power devices with the greatest efficiency. And it is absolutely not necessary to buy a ready-made charger in the store for this, because there is a more budgetary option that radio amateurs will especially like - to assemble a charger for lithium-ion batteries with your own hands.
Precautions: overcharging is not allowed
It is extremely important to remember one simple thing before starting to assemble a battery for batteries - lithium batteries are strictly forbidden to be recharged. They have very strict requirements for charging and operating mode, so they cannot be charged to a voltage of more than 4.2 V. It is even better to be guided by the information on the safe threshold for each individual cell. By the way, even a smaller threshold, which is considered acceptable for this instance, can be specified there.
Even better, if you are going to do your own lithium battery charging, check the materials and equipment used several times. If you have doubts about the accuracy of your voltmeter readings or the origin of the cans, as well as the maximum allowable power of their charge, it is better to set the threshold even lower. It will be optimally within 4.1–4.15 V. In this case, it will be safe for you to charge batteries that do not have a built-in protection board.
Otherwise, there is a high probability of strong heating and swelling of the cans, abundant release of gas with a sharp unpleasant odor, and even their subsequent explosion. Check everything several times before proceeding with assembly and charging.
How to assemble a lithium battery charger do-it-yourself batteries
One of the simplest, if not the easiest, way to create a charger. It involves the use of the LM317 chip. It is cheap and widely available, plus it is equipped with a charge indicator.
The setting comes down to setting the output voltage to a nominal value of 4.2 Volts using the trimming resistor R8. Just make sure you don't have a battery connected. And also the charging current is set by selecting resistors R4 and R6. The recommended power of the resistor R1 in this case should be at least 1 watt.
When the LED on the diagram goes out, this indicates the completion of the battery charging process. At the same time, the indicators of the charging current will never decrease to zero.
Chips such as LM317, like its counterparts, are very widely used in various current and voltage stabilizers. At the same time, you can buy them on any radio market, and they will cost mere pennies.
The disadvantage of the circuit can be considered the supply voltage, which must necessarily be from 8 to 12 V. This is due to the fact that for the normal functioning of the microcircuit, a difference between the voltage at the automatic transmission and the supply voltage is required to be at least 4.25 V, that is, power the device using the USB port will not work.
The sequence for collecting charging lithium batteries with your own hands is as follows:
- choose the right case;
- attach a power supply (5 V) and elements of the specified circuit to it (necessarily in the correct order);
- take brass and cut out two strips from it, fasten them to the nests;
- using a nut, set the distance between the contacts and the battery that you are going to connect;
- fasten the switch if you want to later be able to change the polarity on the sockets (if not, leave everything as it is).
But if the task is to assemble a charger designed to work with 18650 batteries, then you should immediately move on to more complex circuits, or buy a ready-made device. Without the appropriate technical skills, it will not work to assemble the knot. Sometimes it's really easier to spend a little more money, but take a factory charger with the necessary parameters and protection.
How to assemble a charger for lithium-ion batteries with your own hands?
Since Li-Ion batteries are sensitive to sudden voltage during charging, special microcircuits are built into branded batteries. They provide voltage control and do not allow exceeding the allowable limits. Therefore, in order to assemble a charger for 18650 lithium batteries with your own hands, you need a more complex circuit than the one discussed above.
This version of the battery will be much more difficult to create than the previous one, and at home this is only possible if there are certain skills and relevant experience. In theory, you can get a charger that, in terms of characteristics, will be in no way inferior to branded batteries. But in practice this is not always the case.
Have you collected memory at home from improvised materials? Tell us about your results in the comments.
We assemble a simple charger for Lithium-ion batteries, almost from trash.
I have accumulated a large number of batteries from laptop batteries, 18650 format. Thinking about how to charge them, I decided not to bother with Chinese modules, and I had run out of them by that time. I decided to put together two schemes. Current sensor and BMS board from mobile phone battery. Proven in practice. Although the circuit is primitive, it works and successfully, not a single battery was damaged.
Charger circuit
Materials and tools
- USB cord;
- crocodiles;
- BMS protection board;
- plastic egg from Kinder;
- two LEDs of different colors;
- transistor kt361;
- 470 and 22 ohm resistors;
- two-watt resistor 2.2 ohm;
- one diode IN4148;
- instruments.
Charger manufacturing
We disassemble the USB cable and remove the connector. I have it from some kind of iPad.
We solder the wires to the crocodiles.
We weight the deep part of the plastic kinder, I filled the M6 nut with hot glue.
We solder our simple circuit. Everything is done by surface mounting and soldered on the BMS board. I used a dual LED, but two single-color ones are possible. The transistor fell out of the old Soviet radio equipment.
We thread the wires into the hole in the second, small, half of the plastic kinder. We solder the scheme.
We stuff everything compactly into a plastic egg. We make a hole for the LED.
We connect to the USB port of a PC or Chinese charging, they still have little current.
Lights up orange while charging. Those. both LEDs are lit.
When the charge is over, green is on, the one that is connected through the IN4148 diode.
You can check the circuit by disconnecting from the battery, the green LED will light up, indicating the end of the charge.
Many may say that for little money you can order a special board from China, through which you can charge lithium batteries via USB. It will cost about $1.
But it makes no sense to buy something that can be easily assembled in a few minutes. Do not forget that the ordered board will have to wait about a month. And a purchased device does not bring as much pleasure as a hand-made one.
It was originally planned to assemble a charger based on the LM317 chip.
But then a voltage higher than 5V would be required to power this charge. The chip would need to have a 2V difference between the input and output voltages. A charged lithium battery has a voltage of 4.2 V. This does not meet the requirements described (5-4.2=0.8), so another solution must be found.
The exercises that will be discussed in this article can be repeated by almost everyone. Her scheme is quite simple to repeat.
One of these programs can be downloaded at the end of the article.
To fine-tune the output voltage, you can change the resistor R2 to a multi-turn one. Its resistance should be about 10 kOhm.
Attached files: :
How to make a simple Power Bank with your own hands: a diagram of a homemade power bank Do-it-yourself lithium-ion battery: how to properly charge
The invention and use of tools with autonomous power sources has become one of the hallmarks of our time. More and more active components are being developed and introduced to improve the performance of battery assemblies. Unfortunately, batteries cannot work without recharging. And if on devices that have constant access to the mains, the issue is solved by built-in sources, then for powerful power sources, for example, a screwdriver, separate chargers for lithium batteries are needed, taking into account the characteristics of different types of batteries.
In recent years, products based on a lithium-ion active component have been increasingly used. And this is quite understandable, since these power sources have proven themselves from a very good side:
- they have no memory effect;
- almost completely eliminated self-discharge;
- can work at sub-zero temperatures;
- hold the discharge well.
- the number was brought up to 700 cycles.
But, each type of battery has its own characteristics. So, the lithium-ion component requires the design of elementary batteries with a voltage of 3.6V, which requires some individual features for such products.
Recovery features
With all the advantages of lithium-ion batteries, they have their drawbacks - this is the possibility of an internal short circuit of the cells during charging overvoltage due to active lithium crystallization in the active component. There is also a limitation on the minimum voltage value, which leads to the impossibility of receiving electrons by the active component. To eliminate the consequences, the battery is equipped with an internal controller that breaks the circuit of elements with a load when critical values are reached. Such elements are stored best when charged at 50% at +5 - 15 ° C. Another of the features of lithium-ion batteries is that the battery life depends on the time of its manufacture, regardless of whether it was in operation or not, or in other words, it is subject to the “aging effect”, which limits the service life to five years.
Charging lithium-ion batteries
The simplest single cell charger
In order to understand more complex lithium-ion battery charging schemes, consider a simple lithium battery charger, more precisely for a single battery.
The basis of the circuit leaves control: a TL 431 microcircuit (acts as an adjustable zener diode) and one reverse conduction transistor.
As can be seen from the diagram, the control electrode TL431 is included in the base of the transistor. Setting up the device is as follows: you need to set the output of the device to a voltage of 4.2V - this is set by adjusting the zener diode by connecting to the first leg of the resistance R4 - R3 with a nominal value of 2.2 kOhm and 3 kOhm. This circuit is responsible for adjusting the output voltage, the voltage adjustment is only set once and is stable.
Next, the charge current is regulated, the adjustment is made by the resistance R1 (in the circuit with a nominal value of 3 ohms) if the emitter of the transistor is turned on without resistance, then the input voltage will also be at the charging terminals, that is, it is 5V, which may not meet the requirements.
Also, in this case, the LED will not glow, and it signals the current saturation process. The resistor can be from 3 to 8 ohms.
For quick adjustment of the voltage on the load, the resistance R3 can be set adjustable (potentiometer). The voltage is adjusted without load, that is, without the resistance of the element, with a nominal value of 4, 2 - 4.5V. After reaching the required value, it is enough to measure the value of the resistance of the variable resistor and put the main part of the desired rating in its place. If there is no required rating, it can be assembled from several pieces in parallel or serial connection.
Resistance R4 is designed to open the base of the transistor, its value should be 220 ohms. As the battery charge increases, the voltage will increase, the control electrode of the transistor base will increase the emitter-collector transition resistance, reducing the charging current.
The transistor can be used KT819, KT817 or KT815, but then you have to install a radiator for cooling. Also, a radiator will be needed if the currents exceed 1000mA. In general, this classic scheme is the simplest charging.
Improvement of the charger for lithium li - ion batteries
When it becomes necessary to charge lithium-ion batteries connected from several soldered elementary cells, it is best to charge the cells separately using a control circuit that will monitor the charging of each individual battery individually. Without this circuit, a significant deviation in the characteristics of one element in a series-soldered battery will lead to failure of all batteries, and the block itself will even be dangerous due to its possible overheating or even ignition.
Charger for lithium batteries 12 volts. Balancer device
The term balancing in electrical engineering means a charging mode that controls each individual element involved in the process, preventing an increase or decrease in voltage below the required level. The need for such solutions stems from the features of assemblies with li - ion. If, due to the internal design, one of the cells is charged faster than the others, which is very dangerous for the condition of the remaining cells, and as a result of the entire battery. The circuit design of the balancer is designed in such a way that the elements of the circuit take on excess energy, thereby regulating the process of charging an individual cell.
If we compare the principles of charging nickel-cadmium batteries, then they differ from lithium-ion, first of all, for Ca-Ni, the end of the process is indicated by an increase in the voltage of the polar electrodes and a decrease in current to 0.01 mA. Also, before charging, this source must be discharged by at least 30% of its original capacity, if this condition is not maintained in the battery, a “memory effect” occurs, which reduces the battery capacity.
With Li-Ion active component, the opposite is true. Completely discharging these cells can lead to irreversible damage and drastically reduce the ability to charge. Often low-quality controllers may not provide control over the level of battery discharge, which can lead to failure of the entire assembly due to one cell.
The way out of the situation can be the use of the above circuit on an adjustable zener diode TL431. A load of 1000 mA or more can be provided by installing a more powerful transistor. Such cells are connected directly to each cell to prevent improper charging.
Choose a transistor should be on power. Power is calculated by the formula P = U*I, where U is the voltage, I is the charging current.
For example, with a current charging of 0.45 A, the transistor must have a power dissipation of at least 3.65 V * 0.45A \u003d 1.8 W. and this is a large current load for internal transitions, so it is better to install the output transistors in radiators.
Below is an approximate calculation of the value of resistors R1 and R2 for different charge voltages:
22.1k + 33k => 4.16 V
15.1k + 22k => 4.20 V
47.1k + 68k => 4.22V
27.1k + 39k => 4.23 V
39.1k + 56k => 4.24V
33k + 47k => 4.25V
Resistance R3 is a transistor-based load. Its resistance can be 471 Ohm - 1.1 kOhm.
But, when implementing these circuit solutions, a problem arose, how to charge a separate cell in the battery pack? And such a solution was found. If you look at the contacts on the charging leg, then on recent cases with lithium-ion batteries there are as many contacts as there are individual cells in the battery, of course, on the charger, each such element is connected to a separate controller circuit.
The cost of such a charger is slightly more expensive than a linear device with two contacts, but it's worth it, especially when you consider that assemblies with high-quality lithium-ion components reach up to half the cost of the product itself.
Pulse charger for lithium li - ion batteries
Recently, many leading manufacturers of self-powered hand tools have been widely advertising fast chargers. For these purposes, pulse converters based on pulse-width modulated signals (PWM) were developed to restore power supplies for screwdrivers based on a PWM generator on a UC3842 chip, a flyback AS - DS converter was assembled with a load on a pulse transformer.
Next, the operation of the circuit of the most common source will be considered (see the attached diagram): the mains voltage of 220V is supplied to the diode assembly D1-D4, for these purposes any diodes with a power of up to 2A are used. Ripple smoothing occurs on capacitor C1, where a voltage of about 300V is concentrated. This voltage is the power supply for the pulse generator with the output transformer T1.
The initial power to start the integrated circuit A1 is supplied through the resistor R1, after which the pulse generator of the microcircuit is turned on, which outputs them to pin 6. Next, the pulses are fed to the gate of a powerful field-effect transistor VT1, opening it. The drain circuit of the transistor supplies power to the primary winding of the pulse transformer T1. After that, the transformer will turn on and the transmission of pulses to the secondary winding begins. The pulses of the secondary winding 7 - 11 after rectification by the VT6 diode are used to stabilize the operation of the A1 microcircuit, which in the full generation mode consumes much more current than it receives from the resistor R1 through the circuit.
In the event of a malfunction of the D6 diodes, the source switches to the pulsation mode, alternately starting the transformer and stopping it, while a characteristic pulsating “squeak” is heard, let's see the operation of the circuit in this mode.
Power through R1 and capacitor C4 start the chip's oscillator. After starting, a higher current is required for normal operation. If D6 fails, additional power is not supplied to the microcircuit, and generation stops, then the process repeats. If the diode D6 is working, it immediately turns on the pulse transformer under full load. During a normal start of the generator, a pulsed current of 12 - 14V appears on the winding 14-18 (at idle 15V). After rectification by the diode V7 and smoothing of the pulses by the capacitor C7, the pulsed current is supplied to the battery terminals.
A current of 100 mA does not harm the active component, but increases the recovery time by 3-4 times, reducing its time from 30 minutes to 1 hour. ( source — magazine Internet edition Radioconstructor 03-2013)
Quick Charger G4-1H RYOBI ONE+ BCL14181H
Pulse device for lithium batteries 18 volts manufactured by the German company Ryobi, manufacturer in the People's Republic of China. The pulse device is suitable for lithium-ion, nickel-cadmium 18V. It is designed for normal operation at temperatures from 0 to 50 C. The circuit solution provides two power supply modes for voltage and current stabilization. The pulsed current supply ensures optimal feeding of each individual battery.
The device is made in the original housing made of impact-resistant plastic. Forced cooling from a built-in fan is used, with automatic activation when it reaches 40°C.
Characteristics:
- Minimum charge time 18V at 1.5 Ah - 60 minutes, weight 0.9 kg, dimensions: 210 x 86 x 174 mm. The charging process is indicated by a blue LED, and red when finished. There is a fault diagnosis that lights up when the assembly fails with a separate backlight on the case.
- Power supply single-phase 50Hz. 220V. The length of the network cable is 1.5 meters.
Charging station repair
If it happens that the product has ceased to perform its functions, it is best to contact specialized workshops, but elementary malfunctions can be fixed by hand. What to do if the power indicator is off, let's analyze some simple malfunctions using the station as an example.
This product is designed to work with Li-ion batteries 12V, 1.8A. The product is made with a step-down transformer, the conversion of the reduced alternating current is performed by a four-diode bridge circuit. An electrolytic capacitor is installed to smooth out the ripple. From the indication there are LEDs for mains power, the beginning and end of saturation.
So, if the network indicator is off. First of all, it is necessary to verify the integrity of the primary winding circuit of the transformer through the mains plug. To do this, through the pins of the mains plug, you need to ring the integrity of the primary winding of the transformer with an ohmmeter by touching the probes of the device on the pins of the mains plug, if the circuit shows an open, then you need to inspect the parts inside the case.
A fuse break is possible, usually a thin wire stretched in a porcelain or glass case, which burns out during overloads. But some firms, for example, Interskol, in order to protect the transformer windings from overheating, install a thermal fuse between the turns of the primary winding, the purpose of which, when the temperature reaches 120 - 130 ° C, is to break the power supply circuit and, unfortunately, it is already after the break does not restore.
Usually the fuse is located under the paper insulation of the primary winding, after opening which, this part can be easily found. To bring the circuit back into working condition, you can simply solder the ends of the winding into one piece, but you need to remember that the transformer remains without short circuit protection and it is best to install a conventional mains fuse instead of a thermal fuse.
If the primary winding circuit is intact, the secondary winding and bridge diodes ring out. For continuity of diodes, it is better to unsolder one end of the circuit and check the diode with an ohmmeter. When connecting the ends to the terminals of the probes in turn in one direction, the diode should show an open, in the other, a short circuit.
Thus, it is necessary to check all four diodes. And, if, indeed, we climbed into the circuit, then it is best to immediately change the capacitor, because the diodes are usually overloaded due to the excess electrolyte in the capacitor.
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