Converting an electric screwdriver to 12v lithium batteries

How to charge the battery of an electric screwdriver without the original charger

A cordless electric screwdriver is a indispensable tool for every craftsman engaged in repair and construction. And in everyday life it does not lie idle much, if you like to do craft work. The special beauty of these tools is that they are not tied to the socket. But a screwdriver needs a systematic recharging. What to do if there was no charger? In this article we will find out how to charge the battery for an electric screwdriver without the usual charger.

How to convert an electric screwdriver to lithium (li-ion) batteries with your own hands

How to convert an electric screwdriver from old nickel cadmium batteries to lithium ones at home.

Hello to all lovers of making things with their own hands! Today, almost everyone has a cordless electric screwdriver, and even more than one. In today’s article I want to show how you can transfer your hands to an electric screwdriver on a lithium battery.

Most electric screwdrivers have nickel cadmium batteries, but they don’t have a very long life and are very tricky to charge.е. They can not be charged until they run out of power because they have a memory effect and their capacity will decrease as a result. Just the price of the original batteries is also quite high.

This screwdriver is 4 years old. I won it on this site, participating in one of the contests. I want to take this opportunity to thank the site useful DIY and in particular the administrator Alexander for such a wonderful prize! Good luck and prosperity to this site.

As I have already mentioned, the screwdriver is 4 years old and the battery has already started to give up. The charge lasts for a very short time and even the standstill will cause the battery to run down. Still, I believe that 4 years is a long time for such batteries.

Pros and cons of the upgrade

Before you convert an electric screwdriver to lithium 18650 batteries, you need to understand what the wizard will get as a result. The advantages of these manipulations are as follows:

  • A multiple increase in the operating time of the electric screwdriver;
  • increase the speed of the battery charge. lithium batteries take approximately 1 hour to fully gain power;
  • Increasing the charge current capacity to 1-2 C;
  • reducing the cost of regular purchase of new NiCd batteries due to their insufficient service life;
  • complete absence of memory effect in lithium batteries.

Also, before you convert the battery with your own hands to a more modern technology, you should be aware of the negative consequences:

  • it is necessary to connect the controller to determine the level of charge, as the device can not be charged more than 4.2 V and discharged less than 2.7 V;
  • Li-Ion batteries for Li-Lon series screwdrivers lose their abilities when operated in low temperature conditions;
  • when converting an electric screwdriver to a lithium battery, there may be difficulties with the adaptation of the charger from NiCd, here you will have to use a universal device.

Which lithium battery to choose?

In 7 of 10 cases 12-volt batteries are used for screwdrivers.

Voltage is the deciding factor in your choice. It can be found in the technical documentation of the device, on the Internet. New batteries are selected with the following in mind:

  • The value of the discharge current. Screwdrivers are powered by batteries with a high discharge current parameter. Check the technical documentation for the required parameter for a specific model. It is a mistake to choose a battery only by its capacity, because the main parameter is the current. It can range from 15-30A, sometimes up to 40A.
  • Characteristics of lithium-ion cells. 18650 batteries should have the same capacity specifications.
  • Number of new batteries. The calculation is easy. The ratio is as follows. 3 Ni-CDs equals 1 Li-ion. Replace the old 12 volt block with a block of 3 lithium ion cells.

Counting the number of new sources remember that the higher voltage (for example, instead of 3 Li-CD instead of 10 Ni-CD take 4 lithium batteries) will increase wear and tear of the equipment will reduce life. But the power will increase. So you need to weigh the pros and cons. Do not hurry with the installation of sources in the tool. Initially they need to be fully charged.

The first thing to think about is whether I need this conversion? Because this would be a blatant “homemade” and in some cases can lead to failure of both the battery and the screwdriver itself. So let’s take a look at the pros and cons of this procedure. It is possible that after this some of you will decide not to convert the Ni─Cd battery for your screwdriver to lithium cells.

Arguments for

  • The energy density of lithium─ion cells is much higher than the nickel─cadmium cells that are used by default in electric screwdrivers. That is, the lithium can battery will have less weight than the cadmium battery with the same capacity and output voltage;
  • Charging of lithium battery cells is much faster than in the case of 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 have to be fully discharged before putting them on charge.

Bosch 12V Battery Upgrade from Nicd to Lithium-ion

The arguments against

  • Lithium battery cells should not be charged above 4.2 volts and discharged below 2.7 volts. In real life, this interval is even narrower. Exceeding these limits can damage the battery. Therefore, in addition to the lithium battery packs themselves, you need to connect and install a charge-discharge controller in the screwdriver;
  • The voltage of one Li─Ion cell is 3.6─3.7 volts, and for Ni─Cd and Ni─MH this value is 1.2 volts. So there are problems with the assembly of a battery for screwdrivers with a voltage rating of 12 volts. Three lithium batteries connected in series can make a battery with a voltage rating of 11.1 volts. Four ─ 14.8, five ─ 18.5 volts and so on. Naturally, the charge-discharge voltage limits will also be different. That is, there may be problems of compatibility of the converted battery with the screwdriver;
  • In most cases, 18650 standard cans are used as lithium cells for the conversion. In terms of size they are different from Ni─Cd and Ni─MH batteries. In addition, you will need room for a charge-discharge controller and wiring. All of this will need to fit into a standard screwdriver battery case. Otherwise it will be extremely inconvenient to work with them;
  • Battery charger for cadmium batteries may not be suitable for charging the battery after it has been rebuilt. You may need to modify the charger or use universal chargers;
  • Lithium batteries become unusable at sub-zero temperatures. This is critical for those who use the screwdriver outdoors;
  • Lithium batteries are more expensive than cadmium batteries.
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Converting a screwdriver to lithium 18650 batteries

In this article, you will learn how to economically convert your screwdriver battery from nickel cadmium batteries to 18650 lithium ion batteries, thereby improving your screwdriver battery, making it more powerful and increasing battery life. All steps of modification are described in detail, so there should be no problems, all the necessary components are specified and available.

Components needed for the modification

To replace the batteries in my screwdriver (12V) used batteries 18650 with a capacity of 2500 mAh. These batteries already have soldered solder wires for soldering, which is very handy and also saves a lot on battery compartments.

You’ll also need two 12.6V 40A BMS boards for the modification, I bought them here:

Rebuilding a battery

The first step is to carefully disassemble the battery compartment and throw away the old, discharged NiCd batteries.

Then disconnect the battery terminal.

You need to solder two wires, preferably with a large cross-section; for this application we used 4 mm² and a length of approx. 100 mm. In the photo above you see the red wire, it was left on so as not to mix up the polarity, the red wire should preferably be soldered to this wire so there is no trouble and you will know exactly what it is

Solder the negative wire to the shiny contact:

Then you need to insert the terminal with the soldered wires into the case in its place, making sure to observe the polarity!

To fix the terminal you can pour hot glue inside of the glass, I couldn’t find a better way of fixing, the more so that it holds very well!

DIY New 12V Lithium Battery from old style NiMh Case For MAKITA

Now you can solder the batteries. Remove the heat shrink tubing from the batteries and bend them so that they can be welded one by one.

converting, electric, screwdriver, lithium, batteries

Next, apply hot glue to the resulting side of the battery where the contacts protrude upward, and glue the BMS board as shown in the photo below. Note that the plus and minus sides of the board and the batteries are facing each other.

Then bend the battery contacts over the board contacts and solder them starting from the minus!

We solder a short wire to the B1 board contact and solder its other end to the battery connection point!

In the same way we solder a short wire to pin B2, the other end of which we solder to the battery junction on the opposite side!

And finally we weld the last positive contact.

Now it remains to connect the terminals of the housing with the resulting battery, to do this solder the red wire to the terminal “P “, and the blue, negative wire to the terminal “P-“.

Just in case anyone is confused, here is the wiring diagram of the BMS depending on the number of batteries (power voltage of the screwdriver).

I would also like to point out that it is worth paying attention to the charging. For this you can either buy a ready made charger or you can buy a current and voltage regulator (aka DC-DC) and use it to modify your own charger for the voltage and current you need.

This completes the battery conversion! It remains to repair the fabricated battery and put in place the second part of the case. After the tests, the electric screwdriver worked just as well as with the factory battery, and in terms of power I would say much better and the charge lasts longer. I recommend everyone to convert their old and tired batteries!))

Buy prefabricated 12V 2A battery charger

That’s it, I hope this article was useful and if you liked it, thumbs up, write Комментарии и мнения владельцев, don’t forget to share it on social media at the links below.

Parts and tools for conversion

To convert your existing electric screwdriver to lithium you need to buy one:

  • a soldering iron with at least 40 watts of power with a set of consumables including acid flux;
  • Small locksmith tools (screwdrivers, scalpel, etc.п.).

The process itself is quite creative, depends on the initial conditions and the design of the electric screwdriver, so in the course of the conversion may need something else. You have to be prepared for this.

Before you modify your power tool for Li-Ion battery powered operation, you should consider your future operating conditions. Lithium-ion cells are not suitable for low temperatures.

Electric screwdriver conversion to lithium batteries

The conversion of an electric screwdriver to lithium batteries almost all models of old-style screwdrivers worked on nickel-cadmium batteries. This type of battery is an inexpensive product, but it does not have enough power for a screwdriver, in addition it has a memory effect.

It is this property of the battery that contributes to a gradual decrease in the value of its capacity. For this reason, most owners of such a tool will benefit from its conversion to lithium batteries 18650 with a voltage of 12v. Of course the work with the conversion is not quick and requires some expense, but if everything is done correctly, then the end result is worth it.

Positive and negative sides of remaking

The first thing we need to be clear about is what we will have as a result of upgrading an electric tool by installing Li-ion batteries in it.

The main advantages of Li-Ion batteries:

  • significantly increase the operating time of the electric screwdriver from one charge;
  • the speed of charging the battery increases dramatically, to get a fully charged battery Li-Ion, it takes about one hour;
  • at least twice the specific capacity compared to Ni-Cd;
  • the economy of purchasing new Nickel-Cadmium batteries due to their short life cycle;
  • lithium batteries do not have the memory effect of charging;
  • Can be recharged as needed.

Disadvantages of Li-Ion batteries:

  • lose their effective properties when stored for a long time, i.e. the possibility of aging;
  • difficulties in operation at negative ambient temperatures;
  • the need to use a special charger designed for them;
  • high price.
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The stages of preparatory work

First of all you need to find out the highest value of voltage for the charge, this is done by calculating the number of cells. If three capacitors are used, the most effective voltage will be 12v, and for four capacitors 16v.

Consider an electric screwdriver rated at 14.4v. In this case, it is necessary to apply four capacitors, hence the difference in volts and increase in capacitance. As a result, the tool on the Li-Ion battery can work much longer.

Regarding the type of cells, the device conversion to lithium batteries is considered more reliable with the use of batteries format 18650. At this stage we need to determine the capacity and the discharge current. Under the condition of standard operation of the device, the current consumption is in the range of 5A to 10A. However, in the case of an unexpected sudden drop, it can be as much as 25A. In order to protect the batteries from damage if such surges occur, you should use cells with a discharge current of 30A.

18650 cells with increased discharge current

It is possible to combine an eight-capacity lithium-ion battery pack by connecting two banks in parallel. Now these pairs should be connected in series, the main thing is to fit eight capacitors in the case.

When converting an electric screwdriver to lithium batteries, an important factor is the selection of the controller based on the operating voltage and discharge current. The battery voltage should be the same as the voltage of the controller, but the current to discharge relative to the maximum, should be half as much.

To give you an example the charge/discharge controller should have a current of approx 14A and the protection function should trip with a current spike of 30A.

Also, when converting an electric screwdriver to a lithium battery, do not forget to calculate in advance the size of the protection board. It must necessarily fit freely in the case, but if it does not, you will have to increase the space of the case.

Step-by-step assembly process

When you have all the necessary components for converting your electric screwdriver to lithium batteries ready, you can begin the assembly process. In this part of the article we will look at how to reconstruct a 12v electric screwdriver. It consisted of twelve NiCd batteries with a voltage of 1.2v each. Our goal is to replace it with a Li-Ion.

      1. The first thing we do is to separate the battery case and remove the battery that was installed there. For this procedure you will need side cutters or wire cutters, but the connector must remain in its seat.
      2. At this step we are going to install the controller board and the thermocouple. These components are installed in place of the temperature sensor.

Due to the fact that the capacitance is not current, two banks were installed in parallel to ensure their correct operation.

      3. Now connect all the pairs in series. According to the circuit diagram, solder the controller to the board, remembering that it is necessary to connect the balance points. To perform this step, the circuit has a special connector and wires.
      4. The final step involves connecting the positive and negative voltage wires.

If the kit has the original charger, then there should be no problem with it. Devices of this type are perfectly suitable for Li-Ion batteries. The charge passes through the circuit of the controller. And this in turn completely removes the possibility of critical heating of the battery as a result of voltage surges.

In case the instrument was designed for 12v, then the most suitable for the assembly will be this scheme:

Based on the fact that the sale of new batteries cost in the range of three thousand, and the cost of modification will cost somewhere in the region of 1000 Therefore, such an upgrade of an electric screwdriver is well worth it.

Converting an electric screwdriver to lithium batteries

Converting the Ni-Cd battery of an electric screwdriver to Li-ion. Colossal capacity 4400mAh!

A guide for converting a screwdriver and charging to Li-Ion. Easy current reduction in the MT3608 to charge converted Ni-Cd to Li-Ion batteries for the screwdriver

If you have (or you know) an old screwdriver for Ni-Cd and all batteries are dead, and the charger broke (burned out), order at ali MT3608 board for 40 rubles, look for an old charger from a cell phone (all in bulk) and old batteries from a laptop (they need batteries Li-Ion 18650).

Today we will be converting an old screwdriver from nickel-cadmium batteries to lithium-ion, and accordingly modify its charger.

Everything is easy to remake. Let’s start with the batteries.

If the screwdriver was 12V, we would need 4 18650 batteries (16.8V max) if at 14.4 V 5 pieces (21 V max.), if 18 V, then 6 pieces (25.2V max). The safety margin of the electric motor and other mechanisms in the screwdriver is great, and we could use more power.

At first, the batteries 18650 Li-Ion are tested and, if there are some to choose from, they have the same capacity. Expensive and accurate this can be done with a BT-C3100 V2.2 or similar. Factory capacity 18650 batteries from laptops 2000-2200 mAh, written on them, if not, you can divide by 2 the capacity written on the nameplate beech battery. The run will be better if you give 3 charge/discharge cycles. If the measured capacity is 5-10% lower than the written capacity, then it is acceptable, but if the capacity is much lower, then the batteries have lost capacity. Also measure the internal resistance of the batteries in the device, which must also be the same.

Without precision instruments, it is sufficient to charge the Li-Ion 18650 batteries to 4.2V in any matching voltage-limited charger, give them the same load, and after the same amount of time, measure the voltage across them. If it has dropped to the same values then it’s ok. For example, load a fully charged 18650 with 3-5 ohms load (current from 1.5 to 0.8 A), and after equal time (e.g. three minutes) measure the remaining 4.2V under load and without load. If the final voltage under load and without load is the same, the batteries are suitable. This indicates the same load capacity and the same internal resistance.

Out of the removable battery case, we throw out the old Ni-Cd batteries that are dead/short-circuited, and solder instead Li-Ion batteries of the desired voltage. The Li-Ion batteries themselves are better to leave the flat connectors from the laptop, but if you do solder to Li-Ion wire, the soldering point should be cooled by blowing, solder quickly with flux or acid, to reduce the time of heating the battery surfaces, to avoid failure. Use soldering wire from an old computer power supply, or thicker.

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It’s better if you solder the batteries with a 4S or 6S balance protection board, it will prevent the batteries from overcharging above 4.2V. Also with this board will be charged better capacitive batteries, but in the case of different batteries will be much faster degrade less capacitive batteries, because they will be discharged below the minimum voltage 2.8V, while higher-capacity ones will still have a voltage reserve. The screwdriver will still spin, but the weaker batteries are already degrading.

Then we check how the screwdriver spins on Li-Ion batteries, usually this increases the power by 20-40% and reduces the weight of the replacement battery.

Now move on to redesigning the battery charger, especially if it’s burned out, or doesn’t have one. They are different from company to company, Bosch, Shturm, Hitachi, everything is different. From the case of the charger you can take out all the stuffing except the terminal block. Basically, all we need is a terminal block to connect the replacement battery. Of course, everything is better in the case. I had too much current from the heavy transformer and it was heavy, so I found a better use for it (in a lab PSU).

We solder the output of cellular charger to the MT3608 board on the VIn pins, plus, minus. Turn it on, turn up the resistor to the desired output voltage, it’s 16.8, 21 or 25.2V accordingly, which battery you have Li-Ion.

MT3608 is a Step Up converter (step up) voltage with pulse width modulation, on regular boards, the output capacitor must be soldered to a large pin of the output VOut and respectively stripped the ground next to it for soldering capacitor. This is an imperfection of the Chinese, the board is poorly working from the factory.

To limit the charging current we need a 5-15 Ohm resistor and the smallest and simplest diode. We solder the wire of VOut plus directly to the terminal block to the battery plus. And the VOut is through a resistor in the minus wire. From the measuring point of the resistor we solder the diode (with anode) to the FB signal of the chip, it’s the 3rd pin of MT3608, it’s small, but it is tested on the potentiometer on the other side of the board, it’s easier to solder.

connect the battery to charge and check the charging current, it will be from 50 mA (15 ohms) to 200 mA (5 ohms). Respectively, the current from the cellular charger would be, for example, 50mA(21V/5V/KPD) =300mA, and for 200mA(21V/5V/KPD)=1200mA (may be too much, not every cellular charger it will pull). Check the charger if it gets warm or if the voltage drops from 5V to 2V.5V, then you should reduce the current to avoid overheating.

You may ask why such a small charging current, because it will take a long time to charge. The first point, with large charging currents close to 1.0C (C-capacity of the Li-Ion battery), the charge time is about an hour, the battery dies after 1-2 years of such atrocities. Second, even old Li-Ion batteries tend to recover at low charging currents (unless of course the chemistry is leaked or blown), and low current charging will definitely extend the life of the battery. Can be viewed at for review.

converting, electric, screwdriver, lithium, batteries

Pros: higher capacity of Li-Ion batteries, increased power of the screwdriver, light weight, longer service life. Minimal rework, parts readily available. If the transformer in the charger works, that’s a bonus (for a lab PSU).

Cons: long time to fully charge (10-20 hours). It is highly undesirable to put Li-Ion batteries below 3V per cell, ie do a full discharge (when screwdriver tightens much weaker), Li-Ion batteries much earlier lose capacity in the cold, already at 0 degrees screwdriver little work (You can put a glove or scarf or only on the battery screwdriver for short-term work in the cold, or heat only the battery indoors at the heating battery).

I strongly advise against buying cheap Chinese batteries in stores! Better yet on ali take the NCR18650B Li-Ion 3400 mAh Panasonic (4pcs 1100r), they are real.

Instead of charging from a cell phone you can take 5V or 12V from a computer power supply or a PSU from a router / modem.

Cordless Drill Lithium Battery Conversion using 18650 Cells

Once I got a very weak Chinese cell phone charger. It says 5V, 450mA. Even with 21V 50mA, MT3608 overcharge and output voltage drops to 2V, charging boils. What I had to redo:

First I limited the starting voltage of Uin conversion for MT3608 (to prevent the converter from driving the charger PSU to 2V 2A when it starts to get very hot and burn out). In the schematic of simple parts resistor R2 can be replaced by a trimmer to 1-10-100kOhm (optimally 10k and R1 10k then). This allowed the StepUp converter to start only from a higher input voltage, the maximum current for the Chinese charger was at voltage 4.I wanted to increase current up to 3V, if I needed to increase it a little with the tweeter, converter stopped working and voltage jumped up to 5V.

I also wanted to raise the charging current, 21V 80mA was not enough.

The higher secondary voltage of PSU high-frequency converter transformer the more power you can take with the same current (and the maximum current depends on the wire cross section), but you can get to oversaturation or transformer overheating and PSU circuit can get protection or burn out.

At the output of the PSU charger has a feedback optocoupler and a regulator for 3-4 volts or resistors to stabilize the 5.2В. I was lucky enough to get a battery charger with a 7V regulator.5V, which I soldered in place of the measuring zenergon, and got 9V at the output of the charger. Above 10V cell phone charger is better not to overclock, usually at 11-12 volts is a failure of stabilization.

Finally I cranked the input voltage limitation to 8.2 volts, got the converter output 21V 140mA, the result is a 13 hour charge for my 2000mAh 18650 batteries is normal.

Tags: from improvised parts, can be found everywhere, easy to find, easy to redo, simplicity, it’s easier when there is nothing.

Leave your Комментарии и мнения владельцев, share your experiences, advise who had what, how best to redo. If you make a video of the conversion, post the link here.

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