Battery protection circuit board or how to rebuild an electric screwdriver battery

Since I quite often made reviews of batteries, and also mentioned the redesign of cordless tools, I often get asked in my PM about these or those nuances of the redesign.Different people ask and the questions are often about the same, so I decided to do a short review and at the same time answer some general questions about the choice of accessories and modification of batteries.

Maybe someone might find this review incomplete because only the battery itself was reworked, but don’t worry, I plan to do a second part of the review where I will try to answer questions about recharger rework. And at the same time I wanted to know what people think is better. universal board with PSU, board by itself, DC-DC boards or other options.

Screwdrivers, and just any other cordless tool, have been produced for quite a few years now. Therefore, users have accumulated on their hands quite a lot of old batteries, and lying sometimes dead weight tools.There are several ways of solving this problem:1. Just repairing the battery, t.е. Replacing old cells with new ones.2. Conversion from battery power to mains power, right up to installing the PSU in the battery compartment.3. Replacing Nickel-Cadmium and Nickel-Metal hydride batteries with Lithium.

As a small digression, sometimes there is no sense to remake / repair. For example if you have a really cheap electric screwdriver, bought at a mega sale for 5 bucks, you might be a bit surprised that the cost of rework will be as much as several of those screwdrivers (I’m exaggerating). That is why it is necessary to evaluate for yourself firstly the pros/cons of alterations and its usefulness, sometimes it is easier to buy a second tool.

The first option many have probably already passed, as well as me. It gives a result, though in case of a branded tool it is often worse than it was originally. In terms of price comes out a bit cheaper, the labor intensity is easier and much easier.

The second option also has the right to life, especially if you work at home and do not want to spend money to replace batteries.

The third option is the most labor-intensive, but allows you to significantly improve the performance of the tool. This increase in battery capacity and the absence of “memory effect”, and sometimes even an increase in power. But in addition to labor intensity, there is a side effect, lithium batteries are slightly worse in frost. Although, provided that many companies produce such tools without any problems, I think that sometimes the problem is exaggerated, although fair.

Batteries have different design, although in general they have a lot in common, so I will tell you about it and show you by the example of one of the representatives of this category, an electric screwdriver Bosch PSR 12 VE-2. This electric screwdriver of my friend, he also was a “sponsor” of the review, providing for the alteration of the electric screwdriver, batteries, protection board and consumables.Electric screwdriver is pretty good, has a spindle lock, two speeds, so remake makes sense.

Battery protection card or how to remake a battery electric screwdriver

Battery protection circuit board or how to rebuild an electric screwdriver battery

It so happened that the battery pack was even three, but will remake one, another one left for another review 🙂

Battery protection card or how to rebuild the battery of an electric screwdriver

By the way, the batteries are different, but both are 12 volt, capacity 1.2Ah, respectively 14.4Wh.

Battery protection plate or how to remake an electric screwdriver battery

Disassemble the battery packs in different ways, but most often the case is twisted with a few self-tapping screws. Although I have seen variants both on the latches and glued.

Battery protection card or how to rebuild an electric screwdriver battery

Either way, you’ll see something like this inside. In this case it is an assembly of 10 NiCd batteries, usually using the same size, but the battery packing might be different. Pictured here is one of the common variants, 9 pieces at the bottom and one in the vertical part.

Battery protection circuit board or how to rebuild an electric screwdriver battery

The first thing to do is to choose replacement batteries.

Power tools use batteries that are designed for high discharge current.Not too long ago I did a review of different batteries, at the end of which I gave a table that can help in this matter, but if you are not sure, just find the documentation for the batteries you plan to buy. But brand name batteries don’t usually have this problem.

Battery protection circuit board or how to rebuild the battery of an electric screwdriver

For example, I recommend these types:For powerful power tool. Samsung INR18650-25R, US18650VTC4, Liitokala INR26650-50AFor medium power tool. LGDBHG21865, LGDBHE41865, Samsung INR18650-30Q

Peculiarities of rework

Most models, at least “Interskol”, “Makita”, “Hitachi” have universal mechanisms. This means that the charger is designed to power Ni-Mh and Li-Ion type batteries.

Features are connected with the power of batteries. New and replacement products must match each other. Otherwise there will be a failure or break in the circuit, which is signaled by the indicator. If overloaded or broken, red and green lights flash simultaneously.

In a situation where the charger is not universal, it will need to be converted, as well as the power supply. The process depends on the type of charger and the manufacturer, involving almost complete unsoldering of the board elements, install a capacitor, resistors and their subsequent adjustment.

Along with this there is a universal way of transforming the charger. It involves using a BMS board that stabilizes the input voltage and current. On the market it is labeled DC-DC StepDown, and there are tweaking resistors directly on the board. The module is soldered into the charger circuit, using the P and P- connections on the board and the old charging terminals.

Conversion to 12 volt lithium batteries

The above method applies to all batteries. Voltage is determined by the parameters of the power supply. Differences are related to the number of batteries. The bulk of the manuals for the transformation refers to 14 volt units, where 4 lithium batteries 18650 are used for replacement. For a 12 volt unit this number is a bit much. Here 3 18650 batteries will be enough.

Conversion to 18 volt lithium batteries

A similar approach applies to 18 volt products. Here the differences are also related to the number of batteries. The battery consists of 5 18650s, which makes it super efficient. If the work process is too intensive, the electric screwdriver even gives off a burnt. So later the 5th battery is often removed.

The screwdriver battery conversion to lithium. A practical example of high energy.

Happy Old New Year! Please don’t throw any hoops, but this is another example of screwdriver battery modification. Nothing new or revolutionary here, just an example of how the highest battery capacity can be achieved. In my particular case just a demo example.

A few compatible things happened, so I thought, why not combine them? All the more reason to be curious about what will come out of it. So, there is a LiitoKala Lii-500, used batteries from laptops, a screwdriver with old and native batteries, and two old batteries from a screwdriver brand unknown to me. But, with a similar connector and a deeper dimension. A quick check showed that in the enlarged battery can easily accommodate up to 16 batteries 18650. That is, to make 3S5P or 4S4P. My screwdriver needs 12 volts, so I need five batteries in parallel, in series with two more similar batteries. After testing the batteries, I ended up with three 7 Ah batteries each. Of course, there is a full galvanic separation of the batteries with the connection of their terminals to the connector installed for this purpose. A jumper is necessary to connect the screwdriver battery to the battery charger as LiitoKala Lii-500. When the charge is complete, a mating plug(dad) with jumpers that connect all three batteries is inserted into the connector. I will not go into details, if it’s not clear to anyone, I’ll explain in more detail. One unpleasant thing is that the batteries are so precisely matched to the depth of the body that it was possible to solder the conductive strip only to the plus contact, and the minus is soldered to the sides of the batteries. But you can see everything in the photo. Of course, no electronic gimmicks to put it was not possible, and they are not needed. High-current batteries are not needed in my case, because the output of five parallel batteries is already very high. However, if this design put the new modern batteries, the power reserve will be unprecedented. The screwdriver came with its own charger. In principle it is not necessary, however, may be useful for small-time recharging in case of need, and already at home to add LiitoKala Lii-500. By the way, the case is not native, too, I had to cut the plastic to fit. However, everything is clear on the photo.

I added the photo of the plug (papa) with the fuses:

I add a modified battery with a voltage meter on the tip of alex323

P.S.: Some commenters wrote that there is no separate charger. In fact, there is a very simple solution with charger. The fact that each battery section is galvanically isolated and connected in series only by the remote and detachable connector (papa). But, it is also possible to connect all three battery sections in parallel with another connector (papa). And connect it to a specially made charger. Made, for example, on the basis of this converter. Set the battery to turn off when the voltage reaches 4.2 volts. As a power supply it is enough to use a common switching power supply, for example, 12 volt and 1 amp. You do not need to balance anything, everything is done automatically and of the utmost quality. Since all the batteries are connected in parallel.

DeWALT electric screwdriver conversion to lithium

Good afternoon Muskie readers! Today I will tell you how to convert your DeWALT electric screwdriver to lithium. Who is interested, please let me cut: So we have a DeWALT 12V electric screwdriver with a dead ni-cd battery. I had already remade this model so I asked the customer to look for a power supply. The customer had a charger from Interskol it fits perfectly. electric screwdriver was used professionally the case is dirty. That’s why before modification the carcass was disassembled and the body washed.

Three cans of high current 18650 with real capacity 2200mAh were bought here: All Bought for my Extra LED and diode and wires from stock.

First of all the power supply and the charger. I will immediately answer the question why I did not start to poke the native source. I already rebuilt this DeWALT model and the output is over 50v at idle. Nickel batteries do not care, but most of the national ponizhayek to 35v And since the customer had his own unnecessary power supply, it is the easiest method. Interskol Charger. The goal is to turn a smart charger into a stupid power source. I open, leave the transformer, the bridge. I change the capacitor 330uf to 1000uf plus I put 0.1uf ceramic. I put all the other parts in the.т.h and pins (foolproof). Soldering the wire. I drill a hole in the case, put the wire out. Assembling the case. DeWALT charger. I remove all the parts from the board except for the contacts, LED. Putting a diode on the board. I drill a hole in the panel and put another LED. Desolder the smd leds from the lowering board. Wiring the LEDs to the step-down circuit board. I drill a hole in the case, put a wire through. The lowering input from the power supply, output through the diode to the contacts. Next adjustment set the voltage 12.6V current of 1.2A (power supply 1.5A for these batteries 1.2A standard charger). I close. Charge ready.

The battery: I open it, remove the ni-cd jar, unsolder the contact. Soldering two wires to the contact. The contact in the leg then absorbent cotton with epoxy. I usually assemble the battery on the holder type “jigsaw puzzle” (this is correct, I’ve been working on it).к. banks do not touch the chassis and a better cooling), but in this case, such a design simply does not fit in the case. The only option is to connect the banks closely. And then had to file a little plastic housing. I assemble the battery 3s1p connect by contact welding. On the side of the board where there are no parts soldered copper bars. I switch bms to 3s mode by setting two jumpers. Then I connect all wires by soldering. Connecting an electric screwdriver works. Check the charge. Charges, balances. I close the case with insulation.

About the components. dc-dc at charging current more than 1.5-2A makes sense to take another board (which has heat sinks). Do not believe the Chinese, who write about 5A. 2A for this board is max. BMS I think that at the moment for the redesign of power tools is one of the best boards. Don’t get the 450 boards.5-2 if you don’t want to have sex with the board first and end up replacing it anyway electric screwdriver works. The customer is satisfied. Thank you all for your time and effort!

Rebuilding an electric screwdriver for lithium, part two, charging properly

Last time I told you how to properly rebuild a battery for a cordless tool. Also I wrote that I will describe the charging peculiarities and the subject of the review this time is the DC-DC converter board.Anyone interested, please visit.

I originally planned to limit myself to two parts, the rework of the battery and the charger. But while I was preparing this review I got an idea for the third, more complicated part.And in this part I will tell you how you can rebuild a native transformer charger if it still works, or if the power transformer is still alive.

The converter board was ordered some time ago as a spare. It was ordered especially for this rework because it has some special features.

For starters I will divide chargers into three main types:1. The simplest. a transformer, a diode bridge and a few parts. Such chargers are used to equip ultra budget instruments.2. Branded. Essentially the same, but it already includes simple “brains” which automatically turn off the charge at the end.3. “Advanced”. pulsed power supply, charge controller, sometimes charging multiple batteries simultaneously.

The tool from the first category rarely falls under remaking, as it is often easier (and cheaper) to buy a new one, and the third category usually has its own difficulties in remaking. Basically it’s possible to re-do the devices of the third group but not in the frame of article as there are many types of such chargers and each needs individual approach.

This time, I’ll be remaking a charger from the second group, a brand name, albeit simple. But this modification has a lot in common with the first group, so it will be useful for more readers.

In order to charge the battery you need not just connect it to a power adapter, such an experiment usually ends not very well. You have to plug it into a charger. And here comes a little misunderstanding, because quite a lot of people are used to calling chargers small power supply from which they charge their smartphones, tablets and laptops. They’re not chargers, they’re power supplies.

What is the difference between a battery charger and a power supply.The power supply is designed to deliver a stabilized voltage within the range of the stated load currents.A battery charger is usually more complicated because its output voltage depends on the load current, which in turn is limited. A battery charger has a node that stops the charge at the end, and sometimes also protects against connecting the battery in the wrong polarity.

The simplest charger is just a power supply and a resistor (sometimes a light bulb is even better) in series with the battery. Such a scheme limits the charging current, but as you know it can not do more.

It’s a little bit more complicated, when you add a timer that turns off the charge after a certain amount of time, but this principle quickly “kills” the battery.For example this is how one of the inexpensive cordless screwdriver chargers works (not my photo).

The next class is more “smart” chargers but in fact they are not much better.For example here is a photo of brand new Bosch battery charger for charging of NiCd batteries.

Rebuilding an electric screwdriver for lithium, part two, charge it right

But all of these chargers seem very simple after looking at today’s options for charging lithium batteries.

Recharging an electric screwdriver with lithium, part two, charge it right

Reverting an electric screwdriver to lithium, part two, charging properly

Of course the last option does not fit exactly into our conversion concept because it is desirable that our charger not only charges properly but also costs very little money.

chargers Chinese screwdrivers look certainly not an example easier, but then again, to do from scratch such a device is unlikely who wants, although that is what I plan to do in the third part, though more correctly.

part two: to charge the electric screwdriver with lithium

And so, to begin with let’s assume that we have on hand a battery charger which simply does not fit the new type of batteries, but is serviceable. Or at least he has a functioning transformer.As I wrote above, you can even use a simple resistor or a light bulb, but it’s “not our way”.

A typical low-cost charger schematic looks like this:Transformer, diode bridge, thyristor and control circuit. But sometimes you can use relay instead of thyristor, current is not limited and there could be thermal control circuit to prevent overheating (but it doesn’t always save you from overheating).

But we need only transformer and diode bridge from this circuit. But we should add another capacitor and that way we’ll get some basic constant part which is marked in red and won’t change further.

Battery protection and battery controller conversion.

With the batteries sorted out, we continue our conversion of the electric screwdriver battery to Li-ion.

Lithium needs a protection controller. Which will protect the battery banks from over-current, over-discharge, over-discharge, as well as balance the banks when charging.

From those that I tried in terms of price and quality, I like this controller.

Works great. With the load can handle the load. But there are some disadvantages. The protection is not automatically removed. To remove it, you need to apply voltage to the battery or just put it on charge for a couple of seconds.

The second flaw in some grinders can trigger protection when the trigger is pressed sharply electric grinder, and in general it is not configured for our banks (which can easily handle currents and larger), but based on the datasheet on the key transistors (which are also designed for a larger current) battery protection controller can overload it.

Both defects I have corrected as follows.

Reworking the lithium battery controller. On the picture of the board you can see two smd resistors marked R010. Their value is 0.01 Ohm each. They set how much load current the protection will trigger.

I added another resistor of the same 0.01 Ohm to my battery controller cm. Scheme. You can also add a film capacitor to it, just useful to keep the protection from triggering when the trigger is pulled sharply.

The upper part of the circuit is responsible for the “Power” mode. In the on position the transistor switches don’t work at all and there is no load on them. But also the protection. That’s why it’s better not to use this mode.

The 15 Amp fuse in this mode protects by current. Set them to your taste. Take a diode with more power. I have two pulse diodes in parallel for 6A each (12A together), whatever I could find.

You can connect a small digital voltmeter, such as this, to monitor the discharge control.

I have connected instead of a voltmeter home-made discharge indicator tuned to 12V. Its triggering coincides with the triggering of the protection board when it works in normal mode.

For visualization I connected a LED diode with 2Khm resistor in parallel to the discharge indicator (on the schematic it is a voltmeter), to see immediately, when the “Power” mode is on.

I really don’t use the “Power” mode with my electric screwdriver, but I need it to reset the protection that has tripped. Just switch it on and off and you’re good to go.

This is how I got the switch to “Power” mode. It is also used to reset the protection.

On the back there are two indicators. A red light-emitting diode shows when the “Power” mode is on. The yellow one lights up when the battery is down to 12 volts in “Power” mode.

Also added a socket. USB with battery voltage. The main thing that no one by mistake did not put the phone to recharge:) I use at the construction site to listen to the adapted receiver and LED lamp.

Been testing the new lithium battery conversion for a month now, now I like it. The battery doesn’t run out for a long time. The screwdriver can easily handle heavy loads.

There’s just one more thing. Fast charging, like the top-of-the-line models:)

Hitachi 12 volt electric screwdriver converted to lithium

If you’ve read my previous writings, you may remember that when the standard batteries of my electric screwdriver gave out, and I had to continue working, I soldered up rather powerful converter with 8A rating and up to 15A short-term load. From 24 volt to 15 volt. Two 7 Ah 12 V batteries connected in series. I have a 14 amp electric screwdriver.4 В.

After exhausting and getting tired of the last construction season building the formwork with this thing, I decided that in the new season I need normal batteries.

I searched the internet and understood the Bosch marketing ploy for my home-built batteries. One new battery costs as much as a new electric screwdriver with two batteries in the set. It didn’t make sense to buy that crap for that kind of money.

There were no lithium ion batteries for my model electric screwdriver. The newer Li-ion screwdrivers were not affordable. Some kind of bacchanalia of scamming suckers.

Here I had the idea to myself to convert the electric screwdriver to lithium. Li-ion battery banks for 3.7 volts and we need 15-16 volts. We connect four batteries in series and you get 16.8 volt fully charged version (4 of each).2 volts per bank.).

If you have a 12 volt electric screwdriver, you can connect three banks in series.

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

That’s what they use in flashlights these days. They are also found in laptop batteries.

This is a Sony vtc4 type battery. Capable of supplying as much as 30 amps to the load (max). Perfect for our purpose.

That’s fine, but lithium is dangerous, you can make a boom if you overcharge.

Also, our individual batteries are connected in series and there will be a big imbalance over time, t.е. some banks will be overcharged and some will be undercharged. And the consequence of that is that the battery will fail very quickly.

Once again, our friends the Chinese have come to my rescue. There’s a thing called a balancer. It monitors voltage in the process of charging each individual bank and if it is fully charged it shuts down and the rest continue to charge and so on until all the individual banks in our chain of batteries will be fully charged.

It’s a penny apiece from the Chinese. But I got a little bit more than that from them.

It’s a little bit more expensive, but it’s worth it. The thing is that these batteries do not have any protection. So I also ordered the battery controller. This thing includes the balancer I talked about above, as well as a whole set of protections. In particular contains: short-circuit protection, overheat protection, overcurrent protection, etc.д.

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

Putting everything together, I tried the electric screwdriver in action and oops nothing works. What the heck, did the Chinese sold me a fake, but no they were not to blame. The thing was that during assembly, I must have something somewhere shorted, in general, it triggered protection, completely disconnected the battery from the load.

To remove the protection (guess what, it’s not in the seller’s manual) you have to apply voltage from the load side, i.e.е. Can simply place the battery on charge. The protection is off in a jiffy.

And put it all in the standard battery case, taking out old nickel-cadmium batteries. Soldered to the contact pads. To keep them from falling out, filled the case with hot melt glue.

The battery is normally charged regular charger, although the voltage is small (recommended 18V), but my hands have not reached it yet. No need to worry about recharging. The controller will disconnect the cans itself once they are fully charged.

Homemade Li-ion battery for electric screwdriver turned out to 2.1 Ah (2100mAh). Versus regular capacity 1.2 Ah. The new battery weighs three times less.

Tested the product on the disassembly of the slab formwork. It’s great, I’m very happy with the result. Works great, does not sit down for a long time, powerfully pulls.

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

My controller is for a load current of 8A.

At first I used to take the second battery with me and I would unprotect it by plugging it in. Then I made a button which switches the circuit to run directly without controller and removes protection by battery voltage.

If you want you can buy more capacity, but be careful about the whole bunch of fakes. The seller that I bought and constantly buy from has already checked and its declared capacity corresponds to the real one.


The project implies a quick removal of batteries (so that at the end of work, you can easily put them on a stationary charger, such as the NITECORE I4 (At https://sdelaysam-svoimirukami.There are also articles on how to build a budget charger for these batteries)), so we used holders 2 x 18650.

To achieve the desired voltage it is necessary to connect the batteries in series (In this connection, the plus of the battery is connected to the minus of the next). As I used two holders, they need to be connected to each other for the current exchange

The original holders were too thin, so they could lose some heat, to avoid this they were soldered to a larger diameter wire, taking into account the new location of the batteries.

For approximate indication of the batteries charge level a 12v LED was used, connected in series with a 1k ohm current limiting resistor.

Power to the LED should be brought out in parallel with the power supply of an electric screwdriver. To do this, solder wires with a smaller cross-section to the thicker plus and minus wires of the battery pack.

Wires with a larger cross section should be soldered to the battery terminals of the electric screwdriver, in my case, they are made on a separate plate, and then, the plate is returned to its normal position, if desired, fixing the glue.

It is necessary to make a hole in the body of the battery compartment to observe the LED (a heated nail will do nicely).

Since the LED is an indicator and not a lighting device, you can fix it in the hole by applying thermo glue (this will make the glow softer). Photo of the electric screwdriver after recycling.

Note that for the correct operation of the batteries in series connection, they must be “married”, in other words, must be taken from the same batch, the same capacity and model. If this rule is observed, they will discharge simultaneously. To check the batteries and prevent overdischarging, use a LED light (the lower the charge, the dimmer the light that it emits). Without proper training, it is not easy to do this, so be sure to check the voltage on the batteries with a voltmeter).

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