How to repair an anchor at home
The armature is the cause of one-third of all screwdriver failures. In the case of daily intensive work, malfunctions may occur already in the first six months, for example, if the brushes are not replaced in time. If used sparingly, the screwdriver will last a year or more.
Anchor can be saved if the balance is not disturbed. If an intermittent hum and strong vibrations can be heard during use, it is not balanced. Such an armature must be replaced. And the winding and collector can be repaired. Short circuits can be repaired. If a substantial portion of the winding is damaged, it can be rewound. Protract, rebuild, or solder worn or badly damaged lamellae. Also, do not attempt to repair the armature if you are unsure of your capabilities. It is better to replace it or have it repaired.
Nickel-cadmium type batteries are the most common today. Its undoubted merit is considered:
The maximum voltage of an individual element reaches 1.38 volts.
The nickel-metal hydride type is actually a competitor of the above type of battery. True, its parameters are much worse, but the cells are completely safe from an environmental point of view.
It is necessary to send the named batteries in charged condition for storage, otherwise they will fail in a month.
How to make an electric screwdriver: malfunctions of the mechanical part
It will be necessary to check the state of the armature windings, since this element can be purchased and changed by yourself. To check the armature, you will need to measure the resistance on the adjacent collector plates, all the way around. The value should approach zero. If in the process of checking will be found plates with a resistance that differs from zero, then it will be necessary to repair the armature or make its replacement.
Problems in the mechanical part can be identified as follows:
- During operation, the electric screwdriver makes strange noises that were not there before.
- The tool vibrates a lot during operation.
- Clamping chuck breakage.
- Tool can be turned on, but cannot be used because it is jammed.
If you hear crackling noises during operation, the bushings or bearing may be worn out. To fix this, you need to disassemble the electric motor and check the bearing and bushing for wear. The anchor should rotate freely, there should not be any friction or distortion. You can buy these tools at a hardware store and replace them yourself.
The most common failures of the geared design include the following:
In all cases, defective gearbox parts must be replaced. All of the above actions must be carried out carefully. Disassembly of an electric screwdriver must be done in a clear sequence, otherwise some of the parts may be lost.
To perform the repair of an electric screwdriver can anyone, you only need to correctly identify the faulty element.
Any device that combines electrical and mechanical components, over time, comes into disrepair. It is associated with both operating conditions, and natural wear and tear of the parts. The electric screwdriver is no exception. In the process of work, its mechanical components quickly become clogged with dust, the motor works in harsh conditions, the battery capacity is lost. Screwdriver repair can be entrusted to service centers, but to conduct it yourself is more profitable, because this process is not complicated at all.
How to check the button on an electric screwdriver
The electric screwdriver button is the main control element that performs several functions at once:
Each of the controls built into the button assembly cannot work properly on its own. Except for the directional switch, which is often a separate function block. The body in most cases consists of three conventional compartments in which the working nodes and mechanisms are located.
- In the lower part of the housing there is a control unit for switching on/off and adjusting the motor speed.
- In the middle part there is the “trigger” of the soft starter (the deeper you push it in, the higher the chuck rotation speed). Button when pressed slides in a special block on guides, for the speed regulation is responsible variable resistor.
- There is a reversing button at the top of the unit. the chuck rotation direction switch. Direction is reversed by reversing the polarity of the voltage applied to the switch.
Approximately this is how all the control units of different brands of screwdrivers are designed. To become acquainted with the construction of the button of a particular model of tool in more detail, we recommend to study the diagram of the electric screwdriver button (it is in the manual).
Getting ready to check the battery of an electric screwdriver with a multimeter
Improper charging and self-discharge tendencies can create a “memory effect” in the battery. It is the buildup of crystals that interferes with a full charge. Batteries self-discharge as a result: Ni-cd up to 20%, Ni-mh. 30%, Li-lon. 8%. You need to get rid of this effect before you start testing.
It is enough to feed the load through a 12V incandescent bulb and carry out several cycles of charging-discharging. After three or four repetitions, the battery will fully recover and may not even need further repair. To test the battery of an inoperative electric screwdriver, you need to prepare:
- pliers and a screwdriver;
- knife and soldering iron;
- tester and multimeter;
- DC voltmeter (15V);
- DC voltmeter and ammeter.
Although the tester and the multimeter have overlapping functions, it is a good idea to have both. Тестер дает более точные показания по основным параметрам, что важно при поиске проблемной точки.
Types of storage in batteries and their properties
Batteries are based on a process of electrolysis. It is based on conversion of energy through reduction and decay reactions. Is made by anode and cathode.
Depending on the main components there are three types of batteries:
Popular in screwdrivers, home appliances, cell phones, as a replacement for AA or AAA batteries. High capacity and self-discharge capability. There are 2 types of “stuffing” used in screwdrivers: nickel combined with cadmium Ni-cd) or metalhydride (Ni-mh).
Nickel-cadmium batteries. Most common type. Specific power of each battery is 65 kWh/kg. Recharge quickly. Reliable and long-lived (number of charge-discharge cycles. 3500). Voltage is usually 1.2 volts. Among the disadvantages of Ni-cd: “memory effect.
They are used in UPSs, automotive systems with a voltage of 12.7В. Have a lower capacity, 2-4 times lower than their nickel equivalents. Last longer than all others. Can withstand heavy loads.
The most expensive versions. Used in Makita and Bosch brand screwdrivers. The basic principle of operation is the process of disintegration of the substance into ions, so ac-batteries are called lithium-ion and are labeled Li-lon.
One of the common types of lithium batteries is labeled 18650. The name of this battery indicates its size (18×65 mm). Capacity 1.6-3.6 Ah. Voltage. 3,7V.
Before checking the battery, it is necessary to eliminate the “memory effect”, which appears in the acb with improper charging and self-discharge. It is the property of batteries to accumulate crystals, which prevent the full charge.
Ni-cd self-discharge effect reaches 20%, Ni-mh. 30%, Li-lon. 8%.
To eliminate the “memory” of the battery it is necessary to spend 3-4 cycles of discharge-discharge. Do it through the load. It is provided by means of an ordinary 12V incandescent lamp connected to the multimeter and the battery (the instructions for the correct connection are described below).
When repeating the operation many times, the battery restores its original performance, if the reason was insufficient capacity and the “memory effect”.
How to check the battery capacity of an electric screwdriver with a multimeter
The main property of a battery is capacity. This value indicates the accumulated energy, that is, the amperage per 1 hour. Measured in A/h.
How to check the battery capacity with a multimeter?
- Remove the battery from the electric screwdriver.
- Charge the battery to 100%.
- Using a multimeter, a resistor and a light bulb, measure the time it takes for the light to go out, the voltage at the output of the battery.
- Calculate the capacity using the formula/
- Compare the results with those indicated in the instruction manual of the electric screwdriver.
Let’s assume the battery voltage reaches 18V. With a 10 Watt incandescent bulb, the battery drain time should reach at least 2.3 hours.
If the connected light bulb goes out after 30 minutes, then the calculated battery capacity is:
This value is significantly lower than the values of, for example, the nickel-cadmium battery of an electric screwdriver of 1.3Ah.
How to fix the screwdriver button if it doesn’t work. Detailed instruction
You will need the following tools to diagnose and repair the screwdriver:
As a result of intensive use of any power tool, dirt inevitably accumulates inside its body.
How I Fixed My Faulty Makita Battery
- Disassemble the tool body. To do this, disconnect the battery, unscrew all the screws (they can be hidden behind the decorative plates to be removed).
- Check the motor for proper operation. To do this, disconnect the two power leads from the control unit and connect them to the battery terminals (the engine should be running).
- Disassemble the screwdriver button. To do this, squeeze the plastic latches and detach the two parts of the button body.
- Visually inspect the button for dirt and damage.
- Next, you need to carefully reassemble the screwdriver button, reinstall and test.
If cleaning the control box does not work, the entire button assembly must be replaced.
- Disassemble the screwdriver (the process described above);
- Install the new button on top of the old one;
- Connect the motor to the button terminals (polarity is not required in this case);
- Reassemble the screwdriver, carefully placing the wires in the housing.
It is very important to choose a button for a specific screwdriver model, because for all external similarities and visual correspondence the part may not fit into the grooves. Typically, new buttons are sold complete with battery terminals and a transistor.
Guide to action: how to check the battery of an electric screwdriver
The internal construction of the battery of any electric screwdriver, regardless of the country of manufacture, is absolutely identical. If you disassemble the plastic block, there are always “banks” assembled in a certain sequence inside. The voltage value of the battery as a whole is added up based on the U level that each battery has individually. The battery also has four contacts, two of which provide charge-discharge cycles, the third is connected to the temperature sensor, and the fourth, which has a service purpose, is responsible for equalizing the charge potential in all cells.
So, the interconnected “banks” of a power tool battery are nothing more than a constant current source in which chemical reactions are constantly being converted into electrical energy. This is how the battery releases stored energy into the circuit. And when it is charged, the process is reversed: the battery simply draws its energy from the grid.