An easy way to convert a screwdriver from nickel-cadmium to lithium-ion batteries

Probably every screwdriver owner has had this problem at least once: you charge your old battery, but after 5 minutes of use it runs out again. This is very unpleasant, but we can solve this problem ourselves.
Nickel-cadmium (Ni─Cd) batteries are still installed in many models of screwdrivers, but they are far from the most ideal energy carriers. They have low current output, memory effect, high self-discharge, support low charging current (they charge for a long time with low current) and have a relatively low specific capacity. Taking into account all of the above factors, it just begs to be replaced, for example, with lithium ion (Li─Ion).

But is this replacement any good?

This issue is worth paying attention to. For the screwdriver user, installing lithium-ion batteries opens up some previously inaccessible "chips":

• 1 – you can recharge the batteries after a short period of operation, this will not reduce their capacity;
  
• 2 – batteries will work out a greater number of charge-discharge cycles. When the resource is exhausted, they can be easily replaced.
  
• 3 - Charging will take place many times faster (about 1-3 hours, versus 13-15 for nickel-cadmium).

But there will also be disadvantages:

• 1 - Lithium-ion batteries are more expensive. You will have to pay 250-500 rubles for one piece.
  
• 2 - The next disadvantage is their fastidiousness to charging - they do not tolerate overcharging or overdischarging and, frankly, it is better to charge them with a “smart” charger, which, when a certain voltage is reached, reduces the current supplied to the batteries.

What batteries should I buy?

In order not to overpay and get exactly what you need, look at the characteristics of your screwdriver. The power consumption and voltage should be indicated there. The first must be divided by the second - you will get the maximum value of the current consumed by the screwdriver. When choosing a battery, you need to focus primarily on its current output (you can look at its specifications), since if too much current is removed from the battery, fire, heating, or the release of gases hazardous to health may occur.
The following models are popular among batteries with high current output: Samsung 25R, LG HE2, LG HE4, Sony VTC5.

How many batteries should I buy?

Charged 18650 battery produces 4.2 volts. Divide the voltage from which the screwdriver operates by 4.2 and round up (for a 12-volt screwdriver - 3 batteries).

Disassembly.

Unscrew the screws located at the bottom of the battery compartment.

After this, carefully open the battery compartment. It will contain a battery made from nickel-cadmium batteries.

The upper batteries are attached by spot welding to the contact group of the battery compartment of the screwdriver. You can disconnect the batteries from the terminals with a knife; if this does not work, cut off the contact pad running from the terminal to the battery, above the welding site. Dispose of the removed battery at a designated disposal point.

Assembly.

The project involves quick removal of batteries (so that after finishing work, you can easily charge them on a stationary charger, for example, NITECORE I4 (On the website https://home.washerhouse.com there are also articles on how to assemble a budget charger for these batteries)), so 2 x holders were used 18650.

To achieve the desired voltage, you need to connect the batteries in series (With this connection, the plus of the battery is connected to the minus of the next one). Since I used 2 holders, they need to be connected to each other for current exchange
The original holder wires were too thin, which could cause heating losses; to avoid this, they were soldered to larger diameter wires, taking into account the new location of the batteries.

For an approximate indication of the battery charge level, Light-emitting diode at 12V, connected in series with a 1 kOhm current-limiting resistor.

Don't forget about isolation.

Nutrition LED must be output parallel to the power supply of the screwdriver. To do this, wires of a smaller cross-section are soldered to the thick plus and minus wires of the battery pack.

Wires of a larger cross-section must be soldered to the terminals of the battery pack of the screwdriver; in my case, they are placed on a separate plate, and then the plate is returned to its normal position, if desired, fixed with glue.

For observation LED You need to make a hole in the battery compartment body (a heated nail works well for this).

Because Light-emitting diode performs the function of an indicator, and not a lighting device; you can fix it in the hole by applying hot glue to it (due to this the glow will become softer). Photo of the screwdriver after processing.




A video demonstrating the capabilities of a screwdriver using new batteries is attached.

Please note that for the batteries to work correctly in a series connection, they must be “married”, in other words, they must be taken from the same batch, the same capacity and model. If this rule is followed, they will be discharged simultaneously. To check the charge of batteries and prevent them from overdischarging, use Light-emitting diode (the lower the charge, the dimmer the light it emits. Without proper training, this is not so easy to do, so be sure to check the voltage on the batteries with a voltmeter).