How To Convert A 12v Screwdriver To Lithium Batteries

Accumulators and batteries What is the difference between a lithium battery and a nickel-cadmium battery. Calculation of t component schemes of alteration. Operating conditions of the lithium battery. Features of alteration of batteries and chargers from different manufacturers.

Conversion of a screwdriver to lithium batteries 18650 14 V

When converting screwdrivers of different power and flashlights from Ni-Cd to Li-ion, batteries of the form factor 18650 are often used. They easily fit into a container or a nest, since instead of two or three relatives, one lithium is installed. Alteration of the screwdriver battery should be carried out taking into account the peculiarities of lithium 18650 batteries.

This type of energy source does not tolerate deep discharge and excessive charge. Hence, it is necessary to use voltage control boards. Since each battery has its own character, their charge is adjusted by a balancer. The point of reworking a screwdriver with a voltage of 14.4 V lies in creating a device using lithium batteries to facilitate a hand tool and increase its performance. Lithium 18650 batteries are most suitable for these purposes.

how to convert a 12v screwdriver to lithium batteries

When selecting components, it should be taken into account that the starting current of the screwdriver is high, it is necessary to choose the appropriate BMS for the required number of cans and at least 30 A.

  • 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 glue, TAGS soldering flux, solder.
  • Heat-resistant adhesive tape;
  • Jumpers or thick insulated wire with a cross section of at least 0.75 squares, cut for bridges.

The procedure for converting a screwdriver for 18650:

  • Disassemble the case and remove a bundle of 12 Ni-Cd cells from the container.
  • Remove the garland, leaving the connector with the “” and “-” pins. Instead of a temperature sensor, a thermocouple from the controller will be installed.
  • Solder the assembly, considering that you cannot use acid, only neutral flux and pure solder. During the connection period, do not warm up the covers. Work pointwise.
  • Connect balancing points to the controller according to the diagram. The connectors are provided on the board.
  • Connect the assembly to the plus and minus terminals.
  • Check the functionality of the circuit. If everything works, the assembled battery, place the controller in the socket, secure with sealant.
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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 cells.

Accumulators and batteries

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Conversion of the “Hitachi” 12 V screwdriver to 18640 lithium batteries

Peculiarities of reworking the 12 V Hitachi screwdriver for lithium batteries. The very compact battery compartment is designed for finger cells. Therefore, you should prepare a place for 18650 cells. It is necessary to cut one side of the partition to fit 1 element tightly.

You need to get a flux, flat metal connecting tape, hot glue. It is necessary to install lithium batteries in a screwdriver during rework through a protective controller. It should serve 3 18650 cells, 3.7v, and rated for 20-30 amps.

Remove the old battery from the socket, carefully disconnect the contacts in the assembly with the temperature sensor and the power indicator. Clean up and sign contacts. They should be brought out to one side, connected with solder to the leads from thick wires and filled with hot melt glue over 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.

Replacing batteries in a screwdriver with lithium

First you should think about whether I need this alteration? After all, it will be an outright “self-propeller” and in some cases can lead to failure of both the battery and the screwdriver itself. Therefore, let’s consider all the pros and cons of this procedure. It is possible that after that some of you will decide to abandon the conversion of the Ni─Cd battery for a screwdriver to lithium cells.

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The pros

Let’s start with the benefits:

  • The energy density of lithium-ion cells is much higher than that of nickel-cadmium, which are used by default in screwdrivers. That is, the battery on lithium cans will have less weight than on cadmium with the same capacity and output voltage;
  • Lithium battery cells are charged significantly faster than Ni-Cd. It will take about an hour to charge them safely;
  • Lithium Ion batteries have no memory effect. This means that they do not need to be fully discharged before charging..

Now about the disadvantages and difficulties of lithium batteries.

Making a homemade power supply

If you are familiar with the principles of building electrical circuits, you can make your own power supply. A diagram giving general concepts is shown in the illustration.

The transformer can be picked up from an old tube TV, or other household appliances. Power 220 volts 250-350W. The main thing is the power supply. The donor should not be pulsed.

The voltage on the secondary winding is 24-30 volts. The secondary winding is made from a wire of the corresponding section.

However, if the output winding current is at least 15 amperes (see transformer specification), there is nothing to worry about.

After the losses on the diode bridge (1-1.5 V on the diode), you will get the required output value.

If you have an electrical engineering education, make the calculation yourself. Or in a practical way: by connecting a 220 volt 100W incandescent lamp as a load, measure the output voltage. E

If it exceeds the needs of the screwdriver, reduce the number of turns of the secondary winding of the transformer.

Using a car battery charger

The principle is the same as using a computer power supply. It is necessary to purchase an old charger for the starter batteries. The modern fashion for compact impulse chargers has left analog linear devices with manual control of voltage and charge current behind. Therefore, such a device can be purchased on the automotive market for a symbolic cost.

Charger MAX INTER

It’s good if the voltage can be adjusted smoothly. In this case, your makeshift power supply will fit any screwdriver.

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Converting it to a power tool is reduced to connecting the input of the electric motor to the power terminals of the charger.

Battery case power supply

Mobility remains, you are limited only by the length of the network cable. The only problem is how to squeeze a sufficiently powerful transformer into a small case.

We recall Ohm’s law again, and understand that a powerful 220 volt electric motor can be compact.

External power supply

The idea is not as absurd as it might seem. Even a large and heavy buck rectifier can just stand near the outlet.

You are equally tied to the power supply, and to the stuck mains plug. And the low-voltage cord can be made of any length.

Important! Ohm’s law says. With the same power, decreasing the voltage. We increase the current! Accordingly, the 12-19 volt supply cord should have a larger cross section than 220 volts.

Using a power supply from a personal computer

On the radio market, you can purchase an old power supply from a personal computer for a small cost. We need a variant of the AT format, which had to be turned off by pressing the key after exiting the operating system.

Experienced users remember such system blocks. The advantage of such a power supply is also that it indicates an honest power. If it says 300W, it means you can safely remove 15-16 amperes from the 12-volt output (again referring to Ohm’s law). This is enough to power an average screwdriver.

Such blocks have a power button in the kit. Another advantage is the presence of a cooling fan and an advanced overload protection system.

If you are hiding the power supply in a beautiful case, do not forget to leave a hole for ventilation.

The connection is very simple. Black wire (-), yellow wire (12V).

Limitations. A screwdriver with a supply voltage higher than 14 volts will not work.

Battery case power supply

Mobility remains, you are limited only by the length of the network cable. The only problem is how to squeeze a sufficiently powerful transformer into a small case.

We recall Ohm’s law again, and understand that a powerful 220 volt electric motor can be compact.