Components needed for the conversion
Beforehand, it is necessary to select the components that will help to transform the electric screwdriver. The composition is determined by the peculiarities of the process, namely, soldering, using special cassettes or spot welding. Cassettes are not recommended due to their vulnerability to current. Otherwise, the list includes:
- Li-ion18650 batteries;
- protection board or a module that provides a uniform load during charging;
- contact welding machine. It is preferable to soldering because lithium batteries are sensitive to heat and can fail;
- Wire cross-sections of 0.75 mm², 1.5 mm², 2.5 mm²;
- heat shrink;
- circular knife.
The battery must match the capacity of the old components in the proportion of 1/3. Т.е. The lithium cell is a full-fledged replacement for 3 nickel-cadmium batteries. Usually use 3 pcs. Li-ion instead of 10 Ni-Mh, which will slightly reduce the power of the unit. It is possible to install 4 batteries, but this will reduce the operating life of the motor.
The key is the current value given in the work certificate of the electric screwdriver. It varies in the range of 15-40A, respectively, selected elements with similar parameters of the output. This applies to both batteries and protection boards. Universal option BMS module for 25 A or 30 A. It is undesirable to use batteries from an old laptop, because they are not designed for a high load.
How to convert an electric screwdriver to lithium ion batteries
Screwdrivers, like other construction equipment, are bought with a good longevity in mind. So a fast drain on the battery or a slow recharging process becomes a real problem. When the original battery is dead or functioning frankly badly, using the tool becomes impossible. You should buy a battery or make one yourself. In this article there is a detailed manual on how to solder the batteries for an electric screwdriver with your own hands.
Preparing an old battery for conversion
When converting an electric screwdriver to lithium-ion batteries, you will need high-current cells type 18650. Batteries from old notebooks cannot 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 not less than 15 A. In addition, the capacity and other characteristics of the batteries should be almost the same. That is why it is better to buy them together from a single seller.
Batteries must be charged equally, so they should be charged separately. And only then assemble them together.
Those who don’t want to solder can purchase a ready-made assembly.
Features of choosing lithium batteries
When choosing a Li-ion cell, you should pay attention to the number of available cycles of discharging and charging. The latest models are endowed with the ability to discharge up to 600 times. When choosing, you should consider that the higher the capacity, the longer the tool can work. If a weak model is fitted with a higher capacity battery, the electric screwdriver will fail faster. A 12-volt battery on a tool that is designed for 18 volts will limit its power. because the voltage rating of the drive must correspond exactly to the value on the electric screwdriver.
Conversion of a Hitachi electric screwdriver to lithium batteries
Nickel-cadmium batteries are uncomfortable because of their “memory effect”, so the transition to lithium-ion batteries is expedient and profitable.
Preparation: selection of necessary devices, cells
The battery pack that has lost its performance, must be dismantled. The halves of the housing can be fastened with glue and/or screws, locks. To separate the glued seam it is gently knocked with a rubber mallet so that the halves of the plastic housing are separated from each other, but not cracked. From the opened case remove the cells assembled in a “cassette”. The contact pad is carefully separated, it will need to be attached to the new lithium batteries.
A new Li-Ion battery for a Hitachi electric screwdriver requires the purchase of additional accessories, and the following circumstances must be taken into account:
- New batteries must be similar to the old ones in size and voltage.
- It is advisable to choose batteries that are already equipped with nickel plates, so as not to spend time on soldering.
- A lithium-ion battery needs a BMS board (Battery Management System). It evenly distributes energy between the banks, protects the device from sudden voltage glitches, shuts it down if the charging time is exceeded, or the batteries are discharged to almost zero. To protect against overheating, a thermal detector is connected to the board.
- To connect the cassette to the contact pad you will need a power insulated wire of suitable thickness.
Rebuilding a screwdriver battery for Li-Ion
I won’t say anything new in this article, but I just want to share my experience with upgrading the batteries of my old Makita screwdriver. This tool was originally designed for nickel-cadmium batteries (which died a long time ago, as died and bought the same ones to replace them). The disadvantages of Ni-Cd are well known: low capacity, short life span, high price. That’s why cordless tool manufacturers switched to lithium-ion batteries long ago.
Well, what to do for those who have an old tool? It’s very simple: throw out the Ni-Cd banks and replace them with Li-Ion batteries of the popular 18650 format (marked with a diameter of 18 mm and a length of 65 mm).
What kind of board and items are needed to convert the screwdriver to lithium-ion
So, here’s my 9.6 volt, 1.3 Ah battery. At maximum charge level it has a voltage of 10.8 volts. Lithium-ion cells have a nominal voltage of 3.6 volts and a maximum voltage of 4.2. So, to replace the old nickel-cadmium cells with lithium-ion cells, I need 3 cells and their operating voltage is 10.8 volts and the maximum voltage is 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 has long been known, categorically do not like overcharge (voltage over 4.2 V) and excessive discharge (below 2.5 V). If you exceed this operating range, the cell will degrade very quickly. That’s why lithium ion cells always work together with an electronic card (BMS. Battery Management System) which controls the cell and monitors both the upper and lower voltage limits. This is a protection board that simply disconnects the bank from the circuit when the voltage is out of the operating range. Therefore, in addition to the cells themselves, you need such a BMS board.
Now two important points that I experimented with unsuccessfully several times until I came to the right choice. This is the maximum allowable operating current of the Li-Ion cells themselves and the maximum allowable operating current of the BMS board.
In a screwdriver, the operating currents at high load reach 10-20 A. Therefore, it is necessary to buy elements that are able to deliver high currents. Personally I successfully use 30 amp 18650 Sony VTC4 (2100 mAh) and 20 amp Sanyo UR18650NSX (2600 mAh) cells. 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 aiming at the cell capacity. even 2100 mAh is more than enough; the most important is not to miscalculate the maximum allowable discharge current.
And just the same, the 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 have such boards at once went into protection when I turn on the screwdriver. I think it’s a waste of money. I will say 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 and can be searched by searching for “BMS 25A”. Since you need a board for a 3-cell assembly, you should look for one with “3S” in its name.
One more important point: some boards have different pins for charging (marked “C”) and loading (marked “P”). For example, the board can have three contacts: “P-“, “P” and “C-“, as on a native Makita lithium-ion board. That board doesn’t work for us. Charging and discharging (charge/discharge) must be done through one contact! That is, there should be 2 working contacts on the board: just “plus” and just “minus”. Because our old charger also has only two contacts.
All in all, as you might have guessed, I’ve thrown a lot of money away with my experiments, both on the wrong elements and on the wrong boards, making all the mistakes that could be made. But I gained invaluable experience.
How to disassemble the battery screwdriver
How to Disassemble an Old Battery? There are some batteries where the battery halves are attached with screws, but there are also adhesive ones. My batteries are just the latter, and I generally for a long time thought it was impossible to disassemble them. It turned out that it is possible if you have a hammer.
In general, with the help of intensive blows to the perimeter of the bottom case edge (nylon-headed hammer, the battery should be held in the hand in the weight) the gluing place is successfully disconnected. The housing is not damaged in any way, I have already taken apart 4 pieces.
From the old circuit need only contact plates. They are firmly welded to the upper two elements by means of spot welding. You can unscrew the weld with a screwdriver or pliers, but pick as carefully as possible so as not to break the plastic.
Everything is almost ready for the next work. By the way, I kept original temperature sensor and circuit breaker, although they are not really relevant anymore.
But it is very likely that the presence of these elements is necessary for normal operation of regular charger. So I strongly recommend to keep them.
Assemble the lithium-ion battery
Here are new cells Sanyo UR18650NSX (you can find them on Aliexpress under this part number) with 2600 mAh capacity. To compare, the old battery had only 1300 mAh, half as much.
It is necessary to solder wires to the elements. Wires cross section should be not less than 0,75 kV.mm, because we will have considerable currents. A wire with such a cross section is good for currents over 20A at 12V. You can solder lithium-ion battery banks, overheating won’t do them any harm that’s for sure. But you need a good fast flux. I use TAGS glycerine flux. Half a second and you’re done.
Solder the other ends of the wires to the board according to the schematic.
I always put even thicker 1.5 kV wires on the battery connectors.mm. because the space allows. Before I solder them to the mating pins, I put a piece of heat shrink tubing on the board. This is needed to additionally insulate the board from the battery cells. Otherwise the sharp edges of the solder could easily rub or puncture the thin film of the lithium-ion cell and cause a short. You don’t have to use a heat shrink, but at least something insulating to put between the board and the cells is absolutely necessary.
The contact part can be secured to the battery with a couple of drops of superglue.
It’s nice when the case is screwed, but that’s not my case, so I just glue the halves back together with Mint.
I use the regular charger to charge the battery. However, the algorithm changes.
I have two chargers, a DC9710 and a DC1414 T. And they work differently now, so I will tell you exactly how.
Makita DC9710 charger and lithium-ion battery
Previously, the battery charge was controlled by the device itself. When it reached full, it stopped the process and signaled the end of the charge with a green light. But now the level control and power off is done by the BMS circuit we installed. So when the battery is fully charged, 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 easy. LED on. charging in progress. Off. charging is complete, the battery is fully charged.
The Makita DC1414 T battery charger and the Li-Ion battery
There is a little nuance to be aware of. 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 goes 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 volts) will reach 12 volts (we have Li-Ion cells, which may have a maximum total voltage of 12.6 volts), the charger will blow the roof. Because it doesn’t know if it’s charging a 9.6volt or a 14.4volt battery. And at this point the Makita DC1414 will go into error mode, alternately flashing red and green LEDs.
This is fine! Your new battery will still charge, but not completely. The voltage will be about 12 volts.
That is, some of the capacity you will miss with this charger, but I think that can be survived.
Total battery upgrade cost about 1000. A new Makita Makita PA09 is twice as expensive. We received twice the capacity, and the next repair (in case of end of life) will be only the replacement of li-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.
Electric screwdriver conversion to lithium batteries 12v
What do we have: an old electric screwdriver Interskol DA-12ER-02 quite cheerfully working, but with dead batteries.
Our goal: to replace old Ni-Cd batteries with new li-ion ones
To remodel according to my option we will need:
- – electric screwdriver Interskol Da-12ER-02 )))
- – soldering iron from 60W t.к. You can’t solder with less power
- – multimeter (tester)
- – “solder acid.”. There are many variations of this, take it with a paintbrush
- 18650 lithium batteries, for example take batteries already with tails. Batteries we need high amperage read.
- protection board with balancer 3S 40A 12.6V 40A lithium battery protection board
- Wires short, but thick cross section of 1.5 cm and more
- double sided tape
- 1 thick wide relatively soft pad.5. 2 cm
Charger (you don’t have to remake it):
- – DC-DC converter (XL4015). Article about these converters read
- – breadboard such as. We need a thick board.
- – 4 diodes from 100v 3A or a ready made diode bridge, I used the look. Or it can be taken from the original charger board.
- – Capacitor from 470Mcf 35V. Either this will be taken from the original charging board.
- – Two LEDs of different colors 5mm.
- – hot melt glue
- – Wires of different length and cross section.
- – 2mm drill bits
- – When working with batteries must be extremely careful not to let them short circuit, at the moment of contact in the place of contact appear huge currents, which can lead to burns, eye damage, explosions and fires. As well as the failure of all components.
- – When working with acid, extreme care must be taken.к. it can get in the eyes on the skin, etc.д. the results can be very unfortunate.
- – Perform work only on equipment that is unplugged from the 220v power supply. You should also take into account that the power circuit uses capacitors which accumulate charge and when you disconnected the device from the network, it does not mean that the board is de-energized.
If you don’t have anything from the list above, it’s best not to start the work because.к. You will create more trouble than you make work.
It is possible to use and 6 pieces. 18650, which will increase our battery capacity by twice, but will require a higher charging current, which will require abandoning the original power supply without modification, and our charging will last oooooooooooo long.
I want to draw your attention and this is very important, the batteries in the photo are not suitable for our task, this is my fault, I bought without thinking. Use only high amperage batteries. But since.к. I didn’t have any options, I did with them.
Why we need high amperage batteries. Lithium batteries are designed to be used in certain discharge conditions, the ones in the photo allow them to be cut with 2C currents t.е. In this case it is about 6A.an electric screwdriver at startup draws a current of 15A to 25A and at constant load about 10A. As we can see we have exceeded the manufacturer’s requirements. High amperage batteries are designed for higher discharge currents from 10A, which guarantees us a longer life, as well as fewer surprises in the future from improper use. Read about these batteries
A board with protection and balancing allows us to operate the lithium batteries within the limits recommended by the manufacturers. It will protect our batteries from deep discharge and also from overcharge, which for lithium batteries is very critical and violations of this point will lead to very rapid degradation of the battery t.е. of their capacitance loss. This board also has a balancing circuit that is designed to equalize the charge on each battery cell. Our batteries are connected in series, which during operation will lead to uneven charging.п.1, but this board will eliminate that effect. The circuit board shown here, modernized as requested by the workers and self-repairing when the protection is triggered.
We use batteries with the tails already welded on. The first thing we do is remove the protection from the tails, then we need to tin the ends. You can’t tin without using acid (carefully) so take the acid, soldering iron and solder and tin. Tinning at both ends. Apply only a thin layer of acid, that’s enough otherwise you will get splashes in all directions.
If you bought acid without a brush, you can pour it into a tube of nail polish or you can use a disposable syringe, where you squeeze the drop and immediately retract it back, leaving a thin film. We need to tin the plus side of the first two batteries, in these places we will connect the batteries with each other.
Once you have tinned everything, solder the batteries in series.Figure. The tab on one of the batteries is reversed. Soldering is also done with a powerful soldering iron, just put the tongue and press the tip of the soldering iron. This is what we have.
Now you have to put some electrical tape on them or you can do it before soldering. Glue double sided tape to fix the board.
Disassemble the original battery. Remove the old batteries (Careful).
Bite off the black thing and solder. We need thick wires because.к. We have currents up to 25A and more. that with thin wires can cause them to catch fire, and we will also have a loss in power. The batteries will be neatly put aside.
Now we need to find a thick, wide and relatively soft gasket 1.5. 2 cm. I ripped it off the package of some gadget. We cut it out according to the size of the case and put it on the bottom, put double sided adhesive tape and glue the batteries. Fix the black thing, the protruding end should be long enough to fit into our batteries to close the case with some tension. Make sure you get the polarities right!
In this case, the brown wire is minus, and the black one is plus. The brown one is a lot thicker than the black one.
We cut the wires as short as possible not to lose the current on losses, but we have to take into account that we have to solder them to the board. We solder and assemble the case and the battery is ready.
You can use the ready made battery with the existing charger, but:
- – there are complaints that the case will be very hot, which many people fear. But there is a transformer in the charger and heating is normal for it. In my experiments with 1A it got up to 60C. The design does not include a current limiting system so that the current in the system can be many times higher and the heating higher. At the same time now we need more time to charge the batteries.
- – the charger is designed with a system of charging time limitation and the charge time is one hour. Т.е. we have to jumper the battery to fully charge it.
- – it will be hard to use the native charger if we decide to use 6 18650 cells t.к. the maximum current deliverable according to the manufacturer should be 1.8А. Т.е. prolonged use with currents higher than this value may lead to unknown consequences. For 3 cells of 3000mAh and a recommended charging current of 0.5C.1С (1.5A. 3A) we are within the charger parameters. for 6 cells we need twice the charging current. And yes, as I said before, the charger has no charging current limiting circuit t.е. in a certain period of time we will charge our batteries within the capacity of the charger, which is tolerable for 3, but not for 6 cells.
Basically these are the main nuances of using the native charger.
About the native charger.
At idle speed charger gives us 19-20V and short circuit current not measured. Manufacturer says the operating current is 1.8A.
SD-C804S charger schematic found on the net.
Scheme has, in my opinion, a number of incorrect designations, but not the point. The circuit has no nodes that would monitor and limit the charging current. But there is a circuit for monitoring the execution voltage on the chip U1 (not a fact, to confirm the performance of this node did not work), as well as a node to limit the time of the charge made on the chip U2.
What bothers us: it is the charging time limitation circuit which bothers us, but it can be simply disabled, otherwise everything suits us fine. But, I could not get the charger to show the end of charge. Turning on the native battery to charge, the charge indicator light came on, but breaking the circuit on the battery t.е. we got the output supply voltage, the LED did not turn off, and should have, if the end of the charge is regulated by the battery voltage (I’m not a specialist in electronics and to understand how it works completely can not). And for us this is a critical point t.к. The protection circuit board of our molded batteries simply breaks the circuit at the end of the charge.
There were a lot of ideas how to make the charge. from upgrading the current scheme, with automatic choice which battery is inserted the old or new with simple elements, to front everything on the Arduino with control of everything. But all this takes a lot of time and effort It was decided not to re-invent the wheel and go the same way as everyone else.
I chose a DC-DC converter with charge current control on XL4015 chip to control the charge read
Redesigning the native charger (horrible kolhoz):
We will remake it in order to be able to charge the old type of batteries.
Take our Chinese board, connect it to the lab PSU set up 19v, or disassemble the battery charger and connect to the outputs of diodes.
We turn the voltage trimmer and set the output voltage 15V t.к. typical Ni-Cd batteries have full charge voltage 1,4V-1.5V, and we have 10. For the new battery assembly this parameter doesn’t matter, the main thing is more than 12.6в.
UPD: protection board with balancer disconnects the battery itself when battery voltage exceeds 12.6V, so 15V is not important for us. This is important for charging the old batteries t.к. there is no protection board.
Switch the multimeter to the current measurement mode. Turn out the current trimmer resistor counterclockwise (I think it goes this way) to the end t.е. set the minimum output current. Connect the ends of the multimeter to the output, close the circuit, set the current to 1A. The higher the current, the faster our battery will be charged, but it will also heat up more. Do not set more than 1.5A to be on the safe side. This completes the board setup.
Disassemble our charger. To build the new board we need to unsolder the original board, remove everything but the two LEDs, diode bridge, and smoothing capacitor, as well as the battery connector itself. This is because we can’t put in a new board.к. The board’s encirclement is in the way. I decided to keep the original board intact and make a kolhoz.
We take the breadboard, diode bridge, capacitor, two LEDs, or solder everything from the original board. We also solder out the connectors
Next, we need to assemble on a breadboard. Figure. (as best I could) what is circled with a black line.
And solder our LEDs as in the figure. The brown one is a minus, and the orange one is a plus. To keep the wires from breaking off at the soldering point, we put some hot melt glue on them. We solder everything according to the diagram. Do not mix up the polarity of the capacitor and all connections. LEDs in the case, fixing them with hot melt glue.
As a result we have such a kohlrabi.
Now all check, assemble and use. My protection with this board does not work by pushing, but by hand, it is possible to make it work. Charge lamp will turn off when the charging current is less than 10% of the set value t.е. less than 0.1А
Addendum of 15.09.20:
I don’t use the screwdriver very often and it worked three times after the modification. So today I put the battery pack on charge and after a couple of hours I heard a pop. When I opened the case I found leakage of one of the battery banks, all the batteries were discharged to zero and when you try to charge them from an external source, they did not take a charge. BMC board has no external damage and short circuits in the main points.
What happened I did not understand and do not want to find out. I ordered a new Interskol DA-10/14.4Л3, 1.5Ah [383.0.2.00]
As a variant, I think, in the future BMC boards to take not from obscure Chinese, and take clones of BMC from real existing shureks.
Converting EB1414S battery of DS14DVF3 electric screwdriver to Li-Ion and lowering current in Hitachi UC18YG battery charger
Battery conversion EB1414S of electric Hitachi DS14DVF3 screwdriver to Li-Ion lithium batteries and, respectively, conversion to Li-Ion and current reduction in the charger Hitachi UC18YG.
Remove the dead Ni-Cd batteries from EB-1414S box and solder some 18650 Li-Ion batteries inside (5 pcs x 4.2V = 21V).
Why 21V and not like Ni-Cd 12pcs x 1.44V=17.28V and you need to put about 4pcs Li-Ion x 4.2V = 16.8V max? Because the quality of the circuit and the screwdriver motor is high, and it keeps perfectly well the voltage raised by 21% and power respectively by 47%, moreover, the starting current is limited by the circuit and the rpm controller (the button gives a slow rpm when lightly pressing it, and a strong high one).
In the charger change the ZD2 regulator for BZX55C20 (20V), and change the variable resistor VR1 (there is one with a yellow cross bar) for constant 300 kOhm, the result will be charging the battery current of 400mA, showing a red LED charging to 21V (up to 21V recharges the battery droplet, reduced current, as it should Li-Ion).
After conversion check the voltage at the terminals of the charger without battery, it is 20.6 21.0 V (jumps once per second). If the voltage is higher than 21V it is better to use ZD2 regulator with little bit lower voltage. Check charging current on R15 resistor 0 when installing a dead battery.1 Ohm (measuring for current), with a charging current of 0.4A voltage on it will be 40 millivolts (0.04V).
- Li-Ion battery is twice as light as Ni-Cd and has more torque, at 47%.
- Capacity. If you usually have Ni-Cd 1500mAh for one day, then the same Li-Ion 2200mAh will last a day and a half.
- Charge with a small current of 0.4A Li-Ion battery life will be 4-5 years, which is twice as long as it was on the former’s native 2.6A accelerated charge Ni-Cd (2-3 years) overheat cutoff! of aces at every charge.
- The red LED at the end of the charge does not go out and the charger itself is warm enough from the bottom, even without the battery (in the standby mode it is better not to leave it switched on, not to eat the power).
- Longer charging time of 2200mAh Li-Ion battery, current 0.4A for about 6 hours.
- Of course, in freezing temperatures, Li-Ion batteries lose their ability to work much faster and harder than Ni-Cd batteries, but the cost of new Ni-Cd 1500mAh batteries is higher than the price of battery rebuild.
- The battery circuit does not have a balancer for lithium batteries so there is no overcharge above 4.2V, so you need to put the same capacity batteries in the ac.
Not recommended: Even a little overdischarge Li-Ion batteries (that is, when you lose power electric screwdriver (discharge) is strictly prohibited to kill the converted Li-Ion battery to shit (to finish the job), but in reality because of his laziness or race to drain the battery to zero. If you are pressed for time, it is more important to charge the battery at least a little and finish the construction issue without killing the battery. After all Li-Ion battery is more prone to loss of capacity on strong discharges (Below 3.6V per ac, but here x 5 pcs = 18V).
It is important to sign everything converted bright marker, 21V Li-Ion, for example 2200mAh, also it is strictly forbidden to SAVE IN HOLE, so do not stick in other chargers and did not burn anything.
It is also important to take the principle: work with a screwdriver, and be sure to put the battery on the charger.
Where to get 5 pcs of Li-Ion batteries 4.2V ?
- A dead neighbor’s battery from an old, broken laptop.
- You can go to any laptop shop and ask the master dead laptop batteries: (there are usually 6 pcs 18650, new ones are about 2200mAh, and for 5 years, usually a couple of 18650 dies, and 4 pcs of them do not lose capacity below 1300 mAh). Test the batteries with the BT-C3100 V2.2 according to the capacity and internal resistance, the higher the capacity and the lower the resistance, the better the battery. It is more important to pick the same capacity lithium batteries in the screwdriver battery. If the internal resistance of the Li-Ion battery is above 500 milliOhms, and 5 units above 2500 milliOhms (2.5 ohms), then they won’t pull the screwdriver.
- Buy on aliexpress from China (but not the Chinese trash 4200mAh-6000mAh, actually 800mAh).) you can real branded Panasonic NCR18650B 3400mAh with cashback at http://epngo.bz/cashback_index/uzlpel. They will really pull more than twice as long as the original EB1414S. 1500 mAh.
Feel free to leave your Комментарии и мнения владельцев and see what you got.
A guide for converting a screwdriver and charging to Li-Ion. Easy current reduction in MT3608 to charge converted Ni-Cd to Li-Ion batteries for screwdriver
If you have (or friends lying around) an old screwdriver for Ni-Cd and all batteries are dead, and even the charger broke (burned out), order at ali board MT3608 for 40 rubles, look for an old charger from a cell phone (all in bulk) and old batteries from a laptop (of which we need batteries Li-Ion 18650).
Today we are going to convert an old screwdriver from nickel-cadmium batteries to lithium-ion batteries, and modify its charger accordingly.
It can be easily remodeled. Let’s start with the batteries.
If you have a 12 volt screwdriver, we need 4 pcs 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 large, and we could use more power.
First, we test the batteries 18650 Li-Ion, if there is something to choose from, we select the batteries with the same capacity. This can be done inexpensively and accurately with the 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 label of the battery. The runtime 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 and it must also be the same.
Without accurate instrumentation, it is sufficient to charge the Li-Ion 18650 batteries to 4.2V in any suitable voltage-limited charger, give them the same load and after the same time, measure the voltage on them. If it has dropped to the same values, normal. For example, load a fully charged 18650 with 3-5 ohms of current (current from 1 ohm to 3 ohms).5 to 0.8 A), and after the same amount of time (for example, three minutes), measure how much is left of 4.2V with and without load. If the final voltage under load and without load is the same, the batteries are suitable. This indicates the same loading capacity and the same internal resistance.
From the case of the removable battery throw out the old Ni-Cd batteries, and solder instead Li-Ion batteries at the voltage we want. The Li-Ion batteries themselves are better to leave the flat connectors from the laptop, but if you still solder to the Li-Ion wires, cool the soldering point with air, solder quickly with flux or acid, to reduce the heating time of the battery surfaces, to avoid failure. Take wires for soldering from an old computer power supply, or thicker.
It will be better if you solder the batteries through a balancer board: 4S or 6S balance protection board, it will not allow the batteries to overcharge above 4.2V. Also with this board will be better to charge variable capacity 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 of 2.8V, while higher capacity batteries will still have voltage reserve. Screwdriver still cranks, but the weaker batteries are already degrading.
Then we check how the screwdriver rotates on the Li-Ion batteries, usually it is an increase in power by 20-40% and reduce the weight of the replacement battery.
Now on to rewiring the battery charger, especially if it’s burned out or nonexistent. They are different from firm to firm, Bosch, Shturm, Hitachi, everything is different. You can take all the stuffing out of the battery charger case, except the terminal block. Generally speaking, we only need a terminal block to connect the removable battery. Of course, everything would be better in an enclosure. 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).
Solder the cell phone charger output to the MT3608 board on the VIn pins, plus, minus. We turn it on and you twist the resistor to the desired output voltage, it’s 16.8, 21 or 25.2V respectively what kind of battery you have Li-Ion.
MT3608 is a Step Up (boost) converter with pulse width modulation, on the ordinary boards, the output capacitor needs to be soldered to the large contact output VOut and respectively stripped the ground next to it for soldering capacitor. This is a fault of the Chinese, the board has been working poorly since the factory.
Make a current limiter, for this we need a resistor 5-15 Ohm and the simplest and smallest diode. We solder the wire of VOut plus directly to the terminal block to the battery plus. And VOut- through the resistor in the minus wire. From the measuring point of the resistor we solder the diode (with the anode) to the FB signal of the chip, it’s the 3rd pin of the MT3608, it’s small, but it is tested on the potentiometer on the other side of the board, which is easier to solder.
connect the battery to charge and check the charging current, it will be from 50 mA (15 Ohm) to 200 mA (5 Ohm). Respectively, the current from the cellular charger will be, for example, 50mA(21V/5V/KPD) =300mA, and for 200mA(21V/5V/KPD)=1200mA (may be too much, not every cellular charger can handle it). Check the battery, 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 high charging currents close to 1.0C (C-capacity of the Li-Ion battery), charging time is about an hour, the battery is sure to die after 1-2 years of such atrocities. Second, even old Li-Ion batteries tends to recover at low charging currents (unless of course the chemistry is lost or blown), and low current charging will prolong battery life. See https://www.YouTube.com/watch?v=ep8o8DVPz_0 to explore.
Pros: higher capacity of Li-Ion batteries, higher screwdriver power, lighter weight, longer life. Minimal remodeling, easily accessible parts. If the transformer in the battery charger works, this is a bonus (for a lab PSU).
Нестандартная переделка Hitachi на литий-ион!
Cons: long time to fully charge (10-20 hours). It is highly undesirable to put Li-Ion accumulators below 3V on a cell, i.e. to do a full discharge (when screwdriver twists much weaker), Li-Ion accumulators much earlier lose capacity in cold, already at 0 degrees the screwdriver will work little (it is possible to put a glove or scarf or only on battery screwdriver for short-term work in cold, or to heat only a battery in a room on a heating battery).
I strongly advise against buying cheap bright Chinese batteries in stores, their capacity is much less than stated! I would rather take the Panasonic NCR18650B Li-Ion 3400 mAh (4pcs 1100r) on Ali, they are real.
Instead of cell phone charger you can take 5V or 12V from a computer PSU or router/modem PSU.
Somehow I got a very weak Chinese cell phone charger. It says 5V, 450mA. Even at 21V 50mA, the MT3608 would overcharge and the output voltage would drop to 2V, the charger would boil. What I had to redo:
First I limited the starting voltage of the MT3608 Uin conversion (to prevent the converter from switching the charger PSU to 2V 2A, when everything 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 (optimal 10k and R1 10k then). This allowed the StepUp converter to drive only from the higher input voltage, the maximum current for the Chinese charger was at voltage 4.If I wanted to raise it a little bit with the tweeter, converter stopped working and voltage jumped up to 5 volt.
Also I wanted to increase charging current, 21V 80mA was not enough.
The higher the secondary voltage of the high-frequency converter transformer PSU charging, the more power you can remove at the same current (and the maximum current depends on the cross section of the wire), but you can get to oversaturation or overheating of the transformer and the circuit PSU can go into protection or burn out.
The output of the charger PSU has a feedback optocoupler and a 3 to 4 volt resistor or resistors to stabilize the 5.2В. I was lucky enough to get a charger with a protective regulator at 7V.I soldered in place of the metering regulator and got 9V at the charging output. Above 10V it’s better not to overclock the charger for cell phones, usually at 11-12 volt there is a loss of stabilization.
I ended up cranking the input voltage restriction to 8.The power output of the 2 volt converter was 21v, 140mA, so I got 13 hours of charging for my 2000mAh 18650 batteries normally.
Tags: from handheld parts, can be found everywhere, easy to find, easy to remake, simplicity, easier when there is nothing.
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