How To Charge A Screwdriver Without A Charger
Making a charger for a screwdriver with your own hands Types and types of chargers. How they work. Simple schemes for self-repetition. Methods for charging the battery of a screwdriver without a charger.
Types of batteries used
Nickel-cadmium batteries do not have problems when charging at high speed. Such batteries have a high load capacity, a low price and easily tolerate work at sub-zero temperatures. The disadvantages include: memory effect, toxicity, high self-discharge rate. Therefore, before charging this type of battery, it must be completely discharged. The battery has a high self-discharge rate and discharges quickly even when not in use. Currently, they are practically not produced due to their toxicity. Of all types, they have the smallest capacity.
Nickel metal hydride is superior to NiCd in all respects. They have less self-discharge, less pronounced memory effect. With the same dimensions, they have a large capacity. They contain no toxic material, cadmium. In the price category, this type occupies a middle position, therefore, it is the most common type of capacitive elements in a screwdriver.
Lithium-ion is characterized by high capacity and low self-discharge. These batteries do not tolerate overheating and deep discharge. In the first case, they are capable of exploding, and in the second, they will no longer be able to restore their capacity. They are also capable of working at subzero temperatures and have no memory effect. The use of a charger with a microcontroller made it possible to protect the battery from overcharging, thereby making this type the most attractive for use. They are more expensive in price than the first two types.
Besides, the main characteristic of rechargeable batteries is their capacity. The higher this indicator, the longer the screwdriver works. The unit of measurement for capacity is milliamperes per hour (mAh). The design of the battery consists in connecting the batteries in series and placing them in a common housing. For Li-Ion, the voltage on one cell is 3.3 volts, for NiCd and NiMH 1.2 volts.
Homemade charging devices
It is quite simple to make your own charging for a 12 volt screwdriver with your own hands, by analogy with the one used in the Interskol memory. To do this, you need to take advantage of the ability of the thermal relay to break the contact when a certain temperature is reached.
In the circuit, R1 and VD2 are a charge current flow sensor, R1 is designed to protect the VD2 diode. When voltage is applied, the transistor VT1 opens, a current passes through it and the LH1 LED starts to glow. The voltage value drops on the R1, D1 chain and is applied to the battery. The charge current flows through the thermal relay. As soon as the temperature of the battery to which the thermal relay is connected exceeds the permissible value, it is triggered. The relay contacts switch, and the charge current begins to flow through the resistance R4, the LH2 LED lights up, indicating the end of the charge.
The principle of operation of the memory
If the charger fails, it makes sense to first try to restore it. For repairs, it is advisable to have a charge device circuit and a multimeter. The circuitry of many charging devices is based on the HCF4060BE microcircuit. Its switching circuit forms the delay of the charging time interval. It includes a crystal oscillator circuit and a 14-bit binary counter, making it easy to implement a timer.
The principle of operation of the charger circuit is easier to disassemble with a real example. This is how it looks in the Interskol screwdriver:
This circuit is designed to charge 14.4 volt batteries. It has an LED indication showing the connection to the network, LED2 is on, and the charging process is on, LED1 is on. The U1 HCF4060BE microcircuit or its analogs: TC4060, CD4060 is used as a counter. The rectifier is assembled on VD1-VD4 power diodes of the 1N5408 type. The Q1 PNP transistor operates in the key mode, the control contacts of the S3-12A relay are connected to its terminals. The key operation is controlled by the U1 controller.
When the charger is turned on, an alternating voltage of 220 volts is fed through a fuse to a step-down transformer, at the output of which its value is 18 volts. Further, passing through the diode bridge, it is straightened and goes to the smoothing capacitor C1 with a capacity of 330 μF. The voltage across it is 24 volts. When the battery is connected, the relay contact block is in the open position. Microcircuit U1 is powered through a Zener diode VD6 with a constant signal equal to 12 volts.
The used SK1 button works momentarily. When it is released, all power is supplied through the VD7, VD6 chain and the limiting resistance R6. And also power is supplied to LED1 through resistor R1. The LED lights up, signaling that the charging process has started. The operating time of the U1 microcircuit is set for one hour of operation, after which the power is removed from the Q1 transistor and, accordingly, from the relay. Its contact group breaks and the charge current disappears. LED1 goes out.
This charger is equipped with an overheating protection circuit. Such protection is realized using the SA1 thermocouple temperature sensor. If during the process the temperature reaches more than 45 degrees Celsius, then the thermocouple will work, the microcircuit will receive a signal and the charge circuit will break. After the end of the process, the voltage at the battery terminals reaches 16.8 volts.
This charging method is not considered smart, The charger cannot determine the state of the battery. Because of this, the battery life of the screwdriver will decrease due to the development of the memory effect. That is, the capacity of the battery decreases every time it is charged.
Types of chargers
The popularity of the screwdriver is due to the fact that it simplifies the process of twisting or unscrewing various fastenersand. Characterized by mobility and small size, it is indispensable for assembling furniture structures, disassembling equipment, roofing and other construction work. The tool owes its mobility to the rechargeable batteries included in its design.
The screwdriver battery is charged in two ways: with a built-in or external charger. The built-in charger allows you to charge the battery without removing it from the screwdriver. The capacity recovery circuit is located directly with the battery. While the remote means their extraction and installation in a separate charging device. Distinguish chargers according to the type of recoverable batteries. The batteries used are:
- Nickel cadmium (NiCd);
- Nickel metal hydride (NiMH);
- Lithium ion (LiIon).
The final cost of a screwdriver depends not least on the type of batteries used and the capabilities of the charger. Chargers are available in 12 volts, 14.4 volts and 18 volts. In addition, storage devices are divided according to their capabilities and can have:
- Fast charging;
- Different type of protection.
The most used chargers use a slow charge due to a low current. They do not contain an indication of operation in their design and do not turn off automatically. This is more true for built-in capacity recovery devices. Chargers built on impulse circuits provide the possibility of accelerated charging. They automatically turn off when the required voltage is reached or in the event of an emergency.
Making a charger for a screwdriver with your own hands
When using a screwdriver, users often encounter damage to the charger (charger). First of all, this is due to the instability of the parameters of the electrical network to which the charger is connected, and secondly, with the failure of the battery. This problem is solved in two ways: buying a new charger for a screwdriver or repairing it yourself.
Using a specialized microcircuit
Manufacturers of screwdrivers are trying to reduce prices for their products, often this is achieved by simplifying the memory scheme. But such actions lead to the rapid failure of the battery itself. Using a universal microcircuit designed specifically for the MAXIM MAX713 charger, you can achieve good performance in the charging process. This is what the charger circuit for an 18 volt screwdriver looks like:
The MAX713 microcircuit allows you to charge nickel-cadmium and nickel-metal hydride batteries in a fast charge mode, with a current of up to 4 C. It can monitor the battery parameters and, if necessary, reduce the current automatically. At the end of charging, the microcircuit-based circuit consumes practically no energy from the battery. It can interrupt its work on time or when a temperature sensor is triggered.
HL1 is for power indication and HL2 is for fast charge display. The setup of the scheme is as follows. To begin with, the charging current is selected, usually its value is equal to 0.5 C, where C is the battery capacity in ampere hours. The PGM1 pin is connected to the positive supply voltage (U). The power of the output transistor is calculated by the formula P = (Uin Ubat) Isar, where:
- Uin is the highest voltage at the input;
- Ubat battery voltage;
- Isar charging current.
The resistance of R1 and R6 is calculated by the formulas: R1 = (Uin-5) / 5, R6 = 0.25 / Isar. The choice of time after which the charging current will turn off is determined by connecting the PGM2 and PGM3 contacts to different terminals. So, for 22 minutes, PGM2 is left unconnected, and PGM3 is connected to U, for 90 minutes, PGM3 is connected to the 16th leg of the REF chip. When you need to increase the charging time to 180 minutes, the PGM3 is shorted to the 12 leg of the MAX713. The longest time of 264 minutes is achieved by connecting PGM2 with the second leg, and PGM3 with the 12th leg of the microcircuit.
Using a car charger
The main danger when using this method is overcharging the battery. The batteries used in power tools differ in their characteristics from automotive lead-acid batteries. A charger equipped with electronic current and voltage control is suitable.
The charging current is selected at the rate of 0.5 to 0.1 of the battery capacity in Ah. So, with a capacity of 1.3 Ah, the charging current is set from 650 to 130 mA. Lead acid chargers are designed to handle high currents, and the required value may be out of range. In this case, a ballast resistor connected in series with the battery is used to limit the current. A car lamp can be used as a resistance.
How to charge a screwdriver battery without a charger
Cordless screwdrivers and drills quickly entered the domestic construction tools market and firmly established themselves on it. It is noteworthy that these devices are quite problematic. Firstly, batteries fail often, and in order to avoid regular breakdowns, you must initially buy expensive devices. Secondly, chargers break down even more often, which, by the way, are also not so cheap. The second problem, in principle, can be solved independently. You just need to figure out how to charge the battery of a screwdriver without a charger. There is a specific instruction, following which, you will be able to return the screwdriver to working condition within a minimum time.
Charging the screwdriver. Safety and Precautions
Please note that the methods below allow charging the screwdriver with constant current. In this case, it is necessary to constantly monitor the process and the full charge of the battery. The fact is that at the end of the process, the electrolytes inside the battery cells begin to boil. This contributes to a significant increase in the temperature of the battery itself. In addition, the slightest spark can cause the device to rupture.
DIY charger kit
Naturally, to do the exercises yourself, you will need additional materials and tools. It:
- An old, damaged battery.
- Two wires, from 15 centimeters long.
- Charging glass.
- Thermal gun.
- Soldering iron.
Most of the above you most likely already have, so there will not be a lot of expense to create a device. First you need to remove the terminals from the old battery. For this we use a soldering iron. To avoid reversing the polarity, make notes directly on the body of the device. Now the holes need to be adjusted to the desired size using a knife. Next, we stretch the wire through the prepared holes and solder it to the charging glass, taking into account the polarity. The structure is still quite fragile, so put cardboard into the case. Attach the bottom of the battery directly to the charging cup. You have a finished design. Now it can be inserted into the adapter and fastened to the body of the battery itself.
How to properly charge a screwdriver battery without a charger using USB
To make a USB charger you will need:
- 10A fuse.
- Any USB charger.
- 220V socket.
- Insulating tape.
The purchase of such a device is justified if, in addition to a screwdriver at home, there are other battery-powered equipment. This capacity can be laboratory power supplies or model chargers. The advantage of this type of devices is their versatility and many adjustments, with which you can set the required charging mode.
Safety and Precautions
When using any method of charging the device, you must be careful and observe the following precautions:
- Observe the process. When the battery is full of energy, the procedure is stopped. Otherwise, overfilling the battery can lead to boiling of its electrical components. When the temperature rises sharply, a small spark will cause the entire structure to explode.
- All parts must be correctly connected to the circuit. During assembly, the technical parameters of the device are strictly taken into account, ensuring the safety of the procedure and observing the polarity. Do-it-yourself chargers can completely damage the battery, excluding the possibility of its recovery in the future.
- The battery is charged in a short period of time with small differences in the characteristics of the modules (10-12 Volts)
Ways to charge a screwdriver without a charger
To carry out quick repairs, disassemble and collect removable structures, a non-stationary device is used, which is discharged in a short period of time with continuous use. There is not always a native charger at hand, so you need to know how to charge a screwdriver without a charger.
- Safety and Precautions
- How to charge a screwdriver battery without a charger
- Via USB
- Using a car charger
- Universal chargers
- Using an external current source
Using a car charger
The main disadvantage of charging with a car charger is battery overflow. The battery in the power tool differs from the lead car battery in its characteristics.
To restore the charge, a device with an electronic voltage and current regulator is used. With a battery capacity of 1.3 Ah, 150-650 mA are set.
The device for a car battery is used to work with high rates of charging current, and the required indicator for charging a screwdriver may be outside the scope of its operation. To limit the current, a 12 V lamp is required and is connected to the circuit with the battery. Without this part, it is not recommended to use this method of restoring the battery charge.
Then the device is connected to the network and the process of restoring the battery capacity is monitored. It will take 15-20 minutes to get started. When heat dissipation occurs in a charged screwdriver battery, the charger is turned off.
To charge the screwdriver, a special universal device is purchased with which you can also charge other equipment powered by batteries. This can be a mobile device or a laboratory source. This type of device has the advantages of versatility and a large number of adjustments designed to select the appropriate charging mode. The battery recovers in 1 hour. The package includes crocodile clips and adapters for common connectors.
To equip the device with a USB connector, you must prepare:
- Fuse for 10 A;
- Socket 220 V;
- USB charger;
- Electrical tape;
- Soldering iron;
First, disassemble the screwdriver. The working part of the handle is removed from above using a knife. The fuse is installed in a hole that is made in the case. The wire is soldered to the fuse and the resulting structure is inserted into the handle. You can use a heat gun to fix the parts.
How to charge a screwdriver battery without a charger
They do without memory when:
- Mounting the USB connector;
- Using a car charger;
- Using a universal charger;
- The use of third-party electrical equipment.