Converting a 12v electric screwdriver to lithium

Replacing the batteries in an electric screwdriver with lithium ones with your own hands: step-by-step instructions

In order to convert an electric screwdriver to a lithium battery, you will need the unit itself, batteries and a simple arsenal of tools. The appropriateness of the transformation is caused by the performance characteristics of lithium-ion models.

Battery conversion of Black & Decker Cordless Screwdriver

Their electrical density is considerably superior to that of NiCd batteries. Lower weight and longer life. In addition Li-Ion batteries are deprived of such disadvantage of Ni-Mh analogues as memory effect. Accordingly, they can be charged at any time, regardless of the operating level.

But Li-Ion batteries are less effective in cold weather. They already begin to discharge rapidly at a temperature of 10°C. If the work is predominantly done in an open space, it is better to do without the transformation. With basic skills, the electric screwdriver can be replaced with a lithium battery with your own hands.

converting, electric, screwdriver, lithium

The preparatory stage

Hurrying will never produce the expected result. Step-by-step instructions for changing the batteries begin with a preparatory step.

Before starting work, it is necessary to determine the number of blocks used in the battery, which will significantly affect the level of the final voltage. Choosing the correct lithium component is equally important. Particular attention should be paid to the indicator of discharge current and capacity. Don’t forget about the controller.

The characteristics of the part are compared to the nominal voltage and discharge current. In other words, to assemble 14V power supplies, you will need a controller with the same voltage level.

Preparing an old battery for rebuilding

When converting your electric screwdriver to lithium-ion batteries you will need high-current cells like 18650. Batteries from old laptop computers can not be used, because they have a current capacity of 3 to 4 A, and the battery of an electric screwdriver must be able to give at least 15 A. In addition, the capacity and other characteristics of the batteries should be nearly identical. So it is better to buy them together from the same seller.

Batteries must be charged equally, so they should be charged separately. And only then reassemble them together.

Those who don’t want to solder can buy a ready-made assembly.

Dismantling process of the battery case

Before an electric screwdriver is converted to lithium batteries, it is disassembled. The body of the tool can be joined with a c:

A model with a laminated case is the most difficult to convert. It is carefully disassembled along the joints, tapping with a hammer with a soft plastic head. If you accidentally damage the halves of the box, it will be difficult to assemble, and subsequently problematic to work. Easily disassemble the casing, connected with latches and self-tapping screws.

The process of disassembling the battery case

The case can be assembled with screws, locking mechanisms, and glue. In the latter case, converting an electric screwdriver to lithium batteries will become significantly more difficult. A laminated case must be carefully disassembled along the joining seams. They need to be smashed with a mallet with a plastic soft head. Do not damage parts of the box, otherwise it will be extremely problematic to assemble it back, as well as work with the tool. Self-tapping screws and latches are easy to loosen.

From the disassembled box must be removed all the contents. At the subsequent assembly you will need a contact plate (in some models it is a complete terminal assembly). It will be used to make the connection to the charger, etc.д.

Methods for Connecting the Battery Elements

The energy storage unit is assembled in one of three ways:

  • Spot welding. If you don’t have a welder at home, you can ask an expert. This technique is the preferred method of connecting elements in a block.
  • Soldering. Every home must have a soldering iron. But when soldering, all manipulation must be done very quickly, because the solder cools almost instantly. Avoid prolonged heating of the batteries. High temperatures will damage the cells. If you don’t know how to solder, it is better to let a specialist do the work.
  • Cassettes. An alternative, but not the most reliable way. The contacts obtained in the process will have a significant transient resistance. So, you need to be prepared for the fact that at high currents it will quickly deteriorate. Using special cassettes, a quick connection of the batteries into a block is carried out.

Finishing stage

Now you need to combine all the parts into one unit. exactly solder the wires to the assembled block and not to the protective board. All actions should be coordinated with the wiring diagram. Assembly recommendations:

  • Wires with a cross-section of 1 mm are soldered to the batteries.5 mm2. For other purposes you can take thinner contacts. 0.75 mm2 in cross section.
  • You can use heat shrink tubing to eliminate the contact of the parts of the unit.
  • Connect the assembly with the “plus” and “minus” outputs.
  • Test soldered circuits.

If everything works, the case can be assembled.

Converting a screwdriver battery to Li-Ion

I will not say anything new in this article, but I just want to share my experience with upgrading the batteries of my old Makita screwdriver. Originally this tool was designed for nickel-cadmium batteries (which are long dead, as dead and bought to replace them). Disadvantages of Ni-Cd are known: low capacity, short life, high price. That’s why cordless tool manufacturers switched to lithium-ion batteries a long time ago.

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Well, what to do if you have an old tool? Yes, everything is very simple: throw out the Ni-Cd cans and replace them with a Li-Ion of the popular format 18650 (marking indicates a diameter of 18 mm and a length of 65 mm).

What board and what elements are needed to convert the screwdriver to lithium-ion

So, here is my battery at 9.6 V and a capacity of 1.3 Ah. At maximum charge it has 10.8 volts. Lithium-ion cells have a nominal voltage of 3.6 volts and a maximum voltage of 4.2 volts. Consequently, to replace the old nickel-cadmium cells with lithium-ion cells, I need 3 cells, their operating voltage will be 10.8 volts, the maximum. 12.6 volts. Exceeding the rated voltage will not damage the motor in any way, it will not burn out and with a larger difference, there is no need to worry.

Lithium-ion cells, as it is known for a long time, categorically do not like overcharge (voltage above 4.2 V) and excessive discharge (below 2.5 V). If you exceed that operating range, the cell will degrade very quickly. Therefore, lithium-ion cells always work together with an electronic circuit board (BMS. Battery Management System) which controls the cell and monitors both the upper and lower voltage limits. It is a protection board that simply disconnects the can from the circuit when the voltage is outside the operating range. Therefore, in addition to the cells themselves, you will need such a BMS board.

Now two important points that I have experimented with unsuccessfully several times until I have come to the right choice. This is the maximum allowable operating current of Li-Ion cells themselves and the maximum operating current of the BMS-board.

In a screwdriver the operating currents at high load are up to 10-20 A. That is why you should buy cells that are able to deliver high currents. Personally, I successfully use 30 amp 18650 cells manufactured by Sony VTC4 (2100 mAh) and 20 amp Sanyo UR18650NSX (2600 mAh). They work fine in my electric screwdrivers. But, for example, Chinese TrustFire 2500 mAh and Japanese light green Panasonic NCR18650B 3400 mAh are not suitable, they are not designed for such currents. That’s why it is not necessary to be overly concerned with cell capacity. even 2100 mAh is more than enough; the main thing is not to miscalculate the maximum allowable discharge current.

And in the same way, BMS board must be designed for high operating currents. I’ve seen on YouTube how people build batteries on 5 or 10 amp boards. I don’t know, personally I’ve had such boards go into protection immediately when I turn on the screwdriver. I think it’s a waste of money. I can tell you that Makita itself puts 30-amp boards in its batteries. That’s why I use a 25 amp BMS bought on Aliexpress. They cost about 6-7 dollars and search for “BMS 25A”. Since you need a board for a 3-cell assembly, you should look for a board that has “3S” in its name.

One more important point: some boards have different contacts for charging (marked “C”) and loading (marked “P”). For example, the board might have three pins: “P-“, “P” and “C-“, like the native Makita lithium-ion board. This board will not work for us. Charging and discharging (charge/discharge) should be done through one contact! That is, the board should have 2 working contacts: just “plus” and just “minus”. Because our old battery charger also has only two pins.

All in all, as you might have guessed by now, I threw a lot of money away with my experiments on both the wrong elements and the wrong boards, making all the mistakes one could make. But I gained invaluable experience.

How to Disassemble a Screwdriver Battery

How to disassemble an old battery? There are batteries where the halves of the body are attached with screws, but there are also adhesive. My batteries are just the latter and for a long time I thought they couldn’t be disassembled. Turns out it’s possible if you have a hammer.

In general, with the help of intensive blows to the perimeter of the edge of the bottom of the case (hammer with a nylon head, the battery must be held in the hand in the weight) gluing place is successfully disconnected. The case is not damaged in any way, I have already taken apart 4 units.

From the old circuit you need only the contact plates. They are firmly welded to the top two elements by spot welding. You can open the welding with a screwdriver or pliers, but you have to be very careful not to break the plastic.

Almost done for the next job. By the way, I kept the stock temperature sensor and disconnect switch, though they’re not really relevant anymore.

But it is very likely that the presence of these cells is necessary for the normal operation of the regular charger. So I strongly recommend to keep them.

Assemble the lithium-ion battery

Here are new cells Sanyo UR18650NSX (by this part number you can find them on Aliexpress), the capacity of 2600 mAh. For comparison, the old battery had a capacity of only 1300 mAh, half as much.

I have to solder the wires to the cells. Wires cross section should be not less than 0,75 sq.mm, because we will have considerable currents. Wire with such a cross section works well with currents of more than 20 A at 12V voltage. You can solder lithium-ion cans, short-term overheating won’t hurt them in any way, it’s been tested. But you need a good fast flux. I use TAGS glycerine flux. Half a second and it’s done.

Solder the other ends of the wires to the board according to the diagram.

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I always run even thicker 1.5 kv wire to the battery terminals.mm. because space allows. Before soldering them to the mating pins, I put a piece of heat shrink tubing on the board. It is necessary for additional isolation of the board from the battery cells. Otherwise, the sharp edges of the solder can easily rub or puncture the thin film of the lithium-ion cell and cause short circuits. You don’t have to use shrink tubing, but it is absolutely necessary to put at least something insulating between the board and the board.

The contact part can be reinforced in the battery case with a couple of drops of superglue.

It’s good when the case is screwed on, but that’s not my case, so I just glue the halves back together with Mint.

Charging the battery is done with the regular charger. True, the algorithm of work changes.

I have two battery chargers, a DC9710 and a DC1414 T. And they work differently now, so I’ll tell you exactly how.

The Makita DC9710 charger and the Li-Ion battery

Previously, the battery was controlled by the device itself. When it reached full, it would stop the process and signal when it was done charging with a green light. But now the level control and power off is done by the BMS circuit we installed. So when the charger is done charging the red LED on the charger will simply turn off.

If that’s the kind of old device you have, you’re in luck. Because it’s so simple. Charging LED is on. Off. charging is complete, the battery is fully charged.

The Makita DC1414 T battery charger and the lithium-ion battery

There’s a little nuance to be aware of here. This charger is newer and is designed to charge a wider range of batteries from 7.2 to 14.4 volts. The charging process on it is going as usual, the red LED is on:

But when the battery (which in the case of NiMH-cells should have a maximum voltage of 10.8 V) will reach 12 volts (we have Li-Ion cells, which can have a maximum total voltage of 12.6 V), the charger will blow the roof off. Because it doesn’t know what kind of battery it’s charging, whether it’s a 9.6 volt or a 14.4 volt. At this point the Makita DC1414 will go into error mode, alternately flashing red and green LEDs.

That’s normal! Your new battery will still charge, but not completely. The voltage will be about 12 volts.

That is, you will miss some of the capacity with this charger, but it seems to me that this can be survived.

All in all, the battery upgrade cost about 1000. The new Makita PA09 costs twice as much. And we ended up with twice the capacity, and further repair (in case of an early failure) will only consist of replacing the lithium-ion cells.

Note: This article and the images in it are copyright. Reproduction in part or in full on other resources without permission is prohibited.

Converting a DeWalt 12V Cordless Drill from NiCad to Lithium LiFePO4

Hitachi Electric Screwdriver Conversion to Lithium Batteries

Some screwdriver owners want to recycle batteries from their condition to lithium battery cells.

On this subject is written many articles and in this article I would like to summarize the information on this topic.

Black & Decker cordless screwdriver conversion to Lithium Ion.

First of all, let’s look at the reasons for and against converting the screwdriver to lithium batteries. And of course consider the individual moments of the process of changing batteries.

The first thing to think about is whether I need this redesign? It would be a blatant “homemade” and in a number of all sorts of cases leads to wear and tear of both the battery and the screwdriver itself. Therefore, it is necessary to consider what remains for and against this procedure. It is possible that then some of you decide to give up on converting the Ni─Cd battery pack for your screwdriver to lithium cells.

  • The power density of lithium─ion parts is much higher than the nickel─cadmium ones, which are used in electric screwdrivers by default. In other words, a lithium bank battery has the least weight than a cadmium battery with the same capacity and output voltage;
  • Charging of the lithium battery parts is much faster than if Ni─Cd is passed. 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 completely discharged before they are put on charge.

Now about the shortcomings and complexities of lithium batteries.

  • Lithium battery cells cannot be charged above 4.5 volts and discharged below 4.7 volts. In real criteria this interval is even narrower. If go beyond these limits, the battery has the option of failing. Therefore, apart from the lithium batteries themselves you will need to connect and install a charge-discharge controller in the screwdriver;
  • The voltage of 1 cell of a Li─Ion is 3,6─3,7 volt, for Ni─Cd and Ni─MH this value is 1,3.5 volt. In other words, there are problems with assembling a battery for screwdrivers with a voltage rating of 12 volts. With three lithium batteries connected in series, it is possible to assemble an 11.1 volt battery. Of 4 ─ 14.8, of 5 ─ 18.5 volts, etc.д. Than the charge-discharge voltage limits will also be different. In other words, there are problems with the compatibility of the converted battery with the screwdriver;
  • As a rule, as lithium parts for remaking used banks standard 18650. They are different in size from Ni─Cd and Ni─MH batteries. Today, you will need space for the charge-discharge controller and wiring. All of this will need to fit into a standard screwdriver battery case. Otherwise, it will be very awkward to work;
  • Battery charger for cadmium batteries may not be suitable for charging the battery after it has been rebuilt. You will need to refine the charger or otherwise implement a universal charger;
  • Lithium batteries lose their charge-discharge capability at sub-zero temperatures. This is critical for those who use the screwdriver just on the street;
  • The cost of lithium batteries is higher than cadmium batteries.
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It is necessary to determine the number of parts in the battery, which ultimately decides the value of voltage. For three parts the ceiling will be 12.6, for four ─ 16.8 volts.

We are talking about converting the widespread 14.4 volt battery packs. It is best to choose 4 cells, because during operation, the voltage will drop quite rapidly to 14.8.

A difference of a few volts will not compromise your screwdriver’s performance.

Converting a Hitachi electric screwdriver to lithium

Already today, more lithium parts will give a huge capacity. This means a longer working time of the screwdriver.

Lithium battery cells 18650

The rated voltage of the lithium parts is 3.6─3.7 volts, and the capacity is almost always 2000─3000 mAh. If the battery case allows it, you can use 8 parts instead of 4. Two of them are connected in 4 parallel assemblies, and then they are connected one by one. After completion it is possible to increase the capacity of the battery. However far not in any case it is possible to pack 8 cans 18650.

And the last preliminary step is the choice of the controller. Its features should match the nominal voltage and discharge current. In other words, if you decided to collect the battery 14.4 volts, then choose a controller with this voltage. The operating discharge current is usually chosen to be half as much as the maximum allowable current.

Above we have established that the maximum allowable short term discharge current for lithium parts is 25─30 amperes. It means that the charge-discharge controller can be designed for 12─15 Ampere. Then the protection will be triggered when the current increases up to 25─30 amperes. Do not forget about the dimensions of the protection board as well. Together with the elements it will be necessary to fit it into the battery case of the screwdriver.

And then goes the process of assembling. At first you disassemble the battery case. If it is a 14.4 volt model, there will be 12 nickel cadmium batteries rated at 1.4 volts inside.

Converting a Hitachi 12-volt battery to lithium

After that you need to solder the acquired elements into an assembly with the connectors connected one by one. Then the controller is soldered to it according to its diagram. At the same time the balancing points are connected. There is a special connector on the board to make them, and often wires with the connector are supplied in the kit.

After assembling the battery the leads for plus and minus are soldered and the whole construction is placed into the case. Generally speaking this is the end of the process. Difficulties occur only with the charger.

But for the most part regular chargers for screwdrivers charge lithium cells freely. With all that, the charging of the jars goes through the controller, so something special will not happen to the cells themselves.

There are some tips on how to save money on the controller board. In other words, a cheaper model is bought, designed for the smallest current. And so that it does not limit the screwdriver’s work, the discharge is not done through the controller, but directly from the cans. And their charging, as it should be, goes through the controller.

Rebuilding a Hitachi 12 volt electric screwdriver for 18640 lithium batteries

Features of converting a Hitachi 12 V electric screwdriver to lithium batteries. Very compact battery cell socket designed for finger cells. Therefore, you need to prepare the battery cavity for the 18650. One side of the divider must be cut out to fit 1 cell.

We need to get some flux, flat metal adhesive tape, hot melt glue. The lithium batteries have to be inserted through a safety controller when converting the electric screwdriver. It must serve 3 18650 cells, 3.7 volts and is rated at 20-30 amps.

Remove the old battery from the socket, carefully disconnect the contacts in the assembly with a temperature sensor and power indicator. Clean and sign the pins. They should be led out to one side, soldered to the leads of thick wires and fill the assembly with hot melt glue.

Assemble the power source with one of the controllers designed for 3 cells. Assemble a circuit in series of 3 Li-ion cells. Connect a controller. Conversion of a lithium 12-volt battery is complete when the construction is installed in the unit, secured, and the charging indicator light turns on. Once fully charged, measurements show 12.17 volts in the outdoor. But this is enough for trouble-free continuous operation of the device.

Nickel-cadmium and nickel-metal hydride regulations state that the battery must be fully discharged before it is charged, or its capacity will rapidly drop. The battery will not last very long if these rules are not followed. And they take about 10 hours to fully charge, which is not very fast.

Lithium batteries don’t have this disadvantage. They can be charged at any level. And you can charge it a lot faster. A full charge cycle from 0 to 100% with the right charger can take about an hour and a half. And for batteries with the ability to quickly charge in less than an hour.

With the same capacity and weight as a NiCd or NiMH, a lithium battery will have twice the capacity, which means it will do more work. In addition, lithium batteries have a low self-discharge, longer life and lighter weight than nickel cadmium and nickel metal hydride batteries.

In a similar way it is possible to remake not only an electric screwdriver, but also other battery-powered gadgets and devices.

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