Electric screwdriver battery make lithium ion battery

Electric screwdriver battery make lithium ion battery

If you have read my previous writings, you may remember that after the standard batteries of an electric screwdriver gave out, and I urgently needed to continue working, I soldered together a fairly powerful converter with a rating of 8 A and a short-term load up to 15 A. From 24 volts to 15 volts. Two 7 Ah 12 V batteries connected in series. I have an electric screwdriver for 14.4 В.

After spending the last construction season building the formwork with this clunker, I decided that in the new season I need a normal battery.

After searching on the internet I understood the Bosch marketing ploy for my original batteries. One new battery costs as much as a new electric screwdriver with two batteries in the set. Buying this crap for that kind of money didn’t make sense.

There were no lithium ion batteries for my model electric screwdriver. The new Li-ion screwdrivers were inadequately priced. Some kind of bacchanalia of scamming suckers.

Then it occurred to me to convert my electric screwdriver to lithium. Li-ion cans for 3.7 volts and we need 15-16 volts. Put four batteries in series and you get 16.8V in a fully charged version (4 of each.2v per can).

If you have a 12-volt electric screwdriver you can connect three cans in series.

Banks that is individual batteries from which is going to be our battery in one big battery, I decided to take a type 18650.

That’s the fashionable thing to use in flashlights these days. They are also found in laptop batteries.

It’s a Sony vtc4 type battery. Capable of giving the load (max) as much as 30 amps. Perfect for our purpose.

It would be ok, but lithium is a dangerous thing, you can make a boom if overcharged.

over, our individual batteries are connected in series and over time there will be a large imbalance, t.е. some banks will be overcharged and the other strongly undercharged. The consequence is that the battery will fail very quickly.

To help me again came our friends the Chinese. There is such a thing called a balancer. It monitors the charging voltage of each individual bank and if it is fully charged it shuts down and the others continue to charge and so on until all the individual banks in our series battery chain are fully charged.

This thing costs pennies from the Chinese. But I got a little more serious stuff from them.

Slightly more expensive but well worth it. The fact that these batteries do not have any protection. Anyway, I also ordered a battery controller. This thing includes the balancer mentioned above, as well as a whole set of protections. In particular it includes: short circuit protection, overheat protection, overcurrent protection, etc.д.

  • B: Battery plus;
  • B3: 1st battery.minus and 2nd battery plus;
  • B2-: 2nd battery.minus and 3rd battery plus;
  • B1-: 3rd battery.minus and the 4th battery plus;
  • B: 4th Battery.minus;
  • P: load/charge V (to the screwdriver /or to the charger );
  • P-: load/charge V- (to the screwdriver and/or to the charger).

Putting everything together, I tried the electric screwdriver in business and oops nothing works. What the heck, did the Chinese sold me a fake, but no they were not to blame. The thing turned out that in the process of assembling, I must have something somewhere shorted, in general, it triggered a defense, completely disconnecting the battery from the load.

To remove the protection (you can guess yourself, it’s not in the seller’s manual), you need to apply voltage from the load side, i.e.е. you can simply recharge the battery. Protection is removed in no time.

Tucked everything into the original battery case, previously removing the old nickel-cadmium cans from it. Soldered to the contact pads. I put some hot melt glue on it to keep them from falling out.

The received battery normally charges regular charger, although the voltage is small (recommended 18V), but so far I have not got around to it. No need to worry about overcharging. The controller will disconnect the banks after they are fully charged.

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Home-made Li-ion battery for an electric screwdriver is at 2.1 Ah (2100mAh). Against the regular capacity of 1.2 Ah. The new battery weighs only half as much.

Tested the product on the disassembly of the slab formwork. Just super, very happy with the result. It works perfectly, doesn’t run down for a long time, pulls powerfully.

Then I ran into a little disadvantage. When you forget to set the force on the electric screwdriver (drilling mode), especially when it is under load, when you stop the motor, it triggers protection. I don’t know if it’s good or not. If you’re also going to take not balancer, and a full controller, then take a larger current load, otherwise you’ll be sick of removing protection. Or look for a controller with autodischarge.

My controller for a load current of 8A.

At first I took the second battery with me, connecting to it removes the protection. Then I made a button which switches the circuit to run directly without controller and at the same time removes protection with the same battery voltage.

If you want you can buy cans with higher capacity, but be careful in this regard solid fakes. The seller that I bought and constantly buy from has already been tested and his stated capacity corresponds to the real one.

Disassembly and Reassembly

Rebuilding an electric screwdriver for lithium batteries

  • You open the old battery by removing the 5 self-tapping screws.
  • Remove the Ni-Mh battery from the housing. It will be noticed that the contact pad, meshing with the contact group of an electric screwdriver, is welded to the minus terminal of one of the Ni-Mh cells. The welding points are to be cut using a tool with the DREMEL cut-off stone 4000.
  • Wires with a cross section of at least 2 mm are soldered to the terminals.4 mm 3.5 for the power leads and 0,4 mm 2.7 for the thermistor. The contact pad is glued into the battery case with hot melt glue.
  • Four cells are selected according to the internal resistance value on the meter. The value is the same for all 4 devices.
  • Lithium cells are glued with hot melt adhesive so that they fit into the housing compactly.
  • The cells are welded on the contact welding machine by means of a welding tape made of nickel (its cross-section is 2X10 mm).

Components needed for rework

Beforehand, it is necessary to select the components that will help transform the electric screwdriver. The composition is determined by the specifics 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 plate or module that ensures uniform loading during charging;
  • contact welding machine. It is preferable to soldering because lithium batteries are sensitive to heat and can fail;
  • Wire gauge 0.75mm², 1.5mm², 2.5mm²;
  • heat shrink;
  • screwdriver;
  • circular knife.

The battery must match the power of the old components in the proportion of 1/3. Т.е. 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. You can install 4 batteries, but this will reduce the life of the motor.

The key is the current value listed in the data sheet of the electric screwdriver. It ranges from 15-40A, respectively, selected elements with similar parameters of the output. This applies to both batteries and protection boards. Universal variant BMS module for 25 A or 30 A. It is undesirable to use batteries from an old laptop, because they are not designed for high loads.

Instructions on how to set up a charger

Everything fits the snaggy description)). Works great. I will use it to charge the converted electric screwdriver. Reached Samara in 25 days. For those who can not figure out how the LEDs work, found a great description:

the upper one is lit while the converter is able to supply the load with the current (in the case of using it as a charger it is a CC phase indicator, as soon as it goes out. The middle LED lights up until the current in the load sinks to 0.1 set, is off. charge complete.

value 0.1 is set by default, if you want it can be adjusted as more (charging faster, capacity less) or less (charging time increases, the battery is charged more fully) with the middle potentiometer. But the charge continues even after it is turned off, this is just an indicator that the battery is in principle charged and ready for use. lower LED. simple inverter operation indicator.

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charge. this LED lights up as long as the current in the output circuit is above the set value. This value is set in relation to the maximum current. When setting a high maximum current (units of ampere) it may not be possible to set the display to a small current (units and tens of milliampere).

Conversion of the screwdriver to lithium 18650 batteries

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

Components needed for conversion

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

Also for the modification you need two BMS boards 12.6V 40A, I bought them here:

electric, screwdriver, battery, make, lithium

Battery Conversion

The first step is to carefully disassemble the battery compartment and discard the old, discharged nickel-cadmium batteries.

Then you need to disconnect the battery terminal.

Two wires should be soldered, preferably with a large cross section, in this case we used 4 mm² and a length of about 100 mm. In the photo above you see the red wire, it is left so as not to mix up the polarity, the red wire should preferably be soldered to this wire, to avoid trouble and you will know exactly what it is

Solder the negative wire to the shiny contact:

Then it is necessary to insert the terminal with soldered on wires into the case in its place, making sure that the polarity is correct!

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

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

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 battery face each other.

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

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

Also solder a short wire to pin B2, the other end of which we solder to the battery junction from the opposite side!

And finally we weld the last positive contact.

Now it remains to connect the terminals of the case 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 gets confused, here’s the wiring diagram for the BMS depending on the number of batteries (power supply 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 battery charger or buy a current and voltage stabilization module (also known as a DC-DC) and use it to modify your own charge for the voltage and current we need.

This completes the transformation of the battery! It remains to repair the fabricated battery and put in place the second part of the housing. After the tests, the electric screwdriver worked no worse than 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 an off-the-shelf 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.

Battery selection

Batteries with a voltage of 12 V are often used for electric screwdrivers. Factors to consider when choosing a Li-Ion battery for an electric screwdriver:

  • Cells with high discharge current values are used in such tools;
  • In many cases, the capacity of the cell is inversely related to the discharge current, so you can’t select it only by capacity. The main indicator is the current. The operating current value of an electric screwdriver can be found in the tool’s data sheet. It’s usually 15 to 30-40 amps;
  • It is not recommended to use cells with different capacity values when replacing an electric screwdriver battery with a Li-Ion 18650;
  • Sometimes there is advice to use a lithium battery from an old laptop computer. This is totally unacceptable. They are designed for a much lower discharge current and have unsuitable specifications;
  • The number of cells is based on the approximate ratio of 1 Li-Ion for 3 Ni-Cd. For 12-volt batteries, 10 old batteries can be replaced with 3 new ones. The voltage level will be slightly reduced, but if you install 4 cells, the higher voltage will shorten the life of the motor.
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Important! Before assembling it is necessary to fully charge all cells to equalize.

Choose a battery assembly diagram by capacity, voltage and available space

Depending on the voltage required for power, determine how many batteries 18650 for an electric screwdriver should be connected in series. Dependence of the number of batteries on the voltage:

If space permits, you can connect an equal number of batteries in parallel to increase the capacity by a factor of two.

Laptop power supply

(220 V mains with 18 V DC output). The old battery charger won’t do. it’s low current.

Why do I need such a power supply:. I need to form voltage of about 18 volts with current of about 2 A, it is just a power supply from a laptop.

Can be purchased separately or rummaged through spare parts stash from old laptops.

I found in the stash (from friends). Connector (dash) had to buy in a radio shop.

Lower voltage is not suitable, since there are input voltage limitations for the stabilization board.

Nickel-cadmium and metal hydride batteries why replace them

One of the very first batteries to be used in power tools were nickel-hybrid sources. The advantages of these devices include the optimal reserve capacity and low heat of the batteries, if compared to hydride batteries. In addition, such sources are inexpensive, and yet effectively cope with their main task if they are used correctly.

Cordless Drill Lithium Battery Conversion using 18650 Cells

The advantages of nickel cadmium devices include:

electric, screwdriver, battery, make, lithium
  • Low risk of overheating compared to hydride ones
  • Nickel-cadmium sources are contained within a metal housing, which provides a high level of stability and tightness
  • If properly operated, the nickel hydride will last at least 3-5 years, but precisely because the device has to be used frequently in extreme conditions, the life of the battery decreases sharply from the first day of purchase
  • Low cost, which makes these devices popular
  • Not afraid of deep discharge

To extend the service life of the battery, not to ask yourself how to convert the battery of an electric screwdriver to lithium, it is necessary to follow the simple instructions for the use of Ni-Cd batteries:

  • The tool can and should be operated until the battery is fully discharged
  • It is necessary to charge the source until the capacity is completely replenished
  • Unlike lithium batteries, it is better to store cadmium batteries in a discharged state
  • The presence of a memory effect is a drawback, but it can easily be eliminated by repeating three charge-discharge cycles

Hydride batteries appeared after the cadmium ones, but they are not very popular because they run out quickly and are not suitable for powerful screwdriver models. Hydride batteries have no memory effect and are less harmful to the environment than cadmium batteries. If your battery, which consists of cadmium or hydride sources, sooner or later it will be necessary to replace it. Buying a new battery for an electric screwdriver of a little-known brand or outdated model is almost impossible, so it becomes necessary to upgrade the old one. From an old cadmium battery you can make an even better one, but to do this you will need to figure out how to remake the battery of an electric screwdriver.

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