Alteration of a screwdriver battery using lithium batteries may be necessary for professional craftsmen who use the tool on a daily basis and need powerful power sources. Of course, with a strong desire, you can re-solder the battery to lithium, but whether it is advisable is up to you. Read more about which batteries are better for a screwdriver →
Thus, you can not only disassemble the battery of any screwdriver, but also solder one of two bundles, which will last as long as possible, and you will not have to buy a new battery in the near future.
The work of a converted battery, provided that the cells are correctly soldered, will be no worse. The main thing is to treat the process with patience and maximum care, so that at the first experience, you will finish the job with minimal losses and solder everything correctly. If you manage to collect everything, this will become an additional incentive to continue your experiments in the field of electronics. Assemble the battery yourself once - and you can save money in the future on buying new batteries for the screwdriver.
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The use of screwdrivers has become part of the construction business. Cordless drills allow you to perform tasks in places where there is no external power source or it is difficult to feed an extension cord. But over time, the batteries fail. Some found it possible and easy for themselves to repair a screwdriver battery with their own hands. What is needed for this and can existing elements be restored? To answer this question, you need to understand the varieties of existing batteries.
Screwdriver manufacturers use batteries in their models that are not compatible with competitors' products. But this applies to the external structure, the internal components are the same and can be of several different types. Among them are:
lithium-ion;
nickel-cadmium;
nickel metal hydride.
Each of these options has advantages and disadvantages. Most often, the inscription Ni-Cd can be found on the battery case. She says that inside there are elements that have a nickel-cadmium composition. Previously, these batteries were also used in mobile phones. This is due to the low cost of cells for such batteries. In terms of service life, they are inferior to the other two groups. This is due to the small number of discharge / charge cycles. Typically, the voltage per cell is 1.2 volts. To reach a voltage of 12 volts, you would need to use 12 cans for one battery.
This negatively affects the weight and dimensions of the battery. An 18 volt battery requires 18 cells. Positive properties are deep discharge endurance. They can also be stored uncharged without affecting their recoil. If you leave a charged battery for a long time, then after a while it will lose its charge.The production of such elements is not environmentally friendly, therefore it is not allowed in every country.
Nickel-metal hydride batteries were developed as a replacement for the previous type. They have become more widely used in the domestic sphere. Conventional pen-type rechargeable batteries are based on the principle of nickel-metal hydride batteries. Such products have practically no memory effect. This means that you can charge them until they are completely discharged. But there are some limitations, which consist in the period of stay in a partially discharged state. If the battery has been in it for more than a month, then it will need to be completely discharged before charging. Their production does not harm the environment as much as nickel-cadmium.
Products are capable of holding a charge longer, but their cost is two or more times higher than that of the first option. Batteries that contain nickel-metal hydride cells can withstand up to 300 charge / discharge cycles. In addition, the self-discharge rate of this type of battery is also several times higher. Not so long ago, elements were developed that are subject to less self-discharge. The voltage of one cell is also 1.2 volts. Manufacturers advise charging standard cells with a low current for a long time.
Recently, lithium-ion batteries have become widespread. They are used not only in screwdrivers, but also in most equipment and electronics, which are powered from a portable source. Such elements are identified by the inscription on the packaging or the Li-Ion case. One such element has a voltage three times higher than that of one can of the previous two, it is 3.6 volts. Elements can be of very different capacities. At the same time, their dimensions remain small, which reduces weight and allows you to make the screwdriver more compact. The number of cycles has been increased to 500. The element has no memory effect, so it can be charged at any time when it is needed. The production of such batteries is more expensive, so technology with them also has a high price tag.
To correctly identify a malfunction, it is worthwhile to understand that the energy source consists of separate cans, which are connected in series with each other. For nickel-cadmium and nickel-metal hydride, the charge controller is installed in the charger, and in lithium-ion, it is most often located in the batteries themselves. If the battery does not charge from the charger, then you need to check what voltage the device produces. For this, a voltmeter is connected to it and measurements are taken. If everything is in order, then the reason lies in the elements themselves. Usually, the components do not fail together. One or more cans have lost their capacity.
To check this, you will also need a multimeter, which is switched to voltmeter mode to measure DC current. It is also necessary to disassemble the battery to gain access to individual banks. But before that, it is necessary to plug the discharged product into the charger and wait until the end of the cycle. When it is signaled that a full charge has been reached, then you can proceed to disassembly. Most often, the body is made non-separable. This means that you have to use your imagination and observation to open it without damaging the internal components. Often the halves can be glued together, so you can use "Galosha" gasoline and a syringe with a needle. It is necessary to apply a small amount to the joint and wait until the degreaser dissolves the adhesive.
Now, using a multimeter, it is necessary to measure the voltage at each element. It is important not to mix up the probes, as the readings may be incorrect. In a charged state, lithium-ion batteries can have a voltage of up to 4.2 volts, if it is below 3.5, then we can assume that there are problems with the cell.In the other two types of cells, the voltage of a charged cell is in the range from 1.2 and higher. After taking measurements, you can put a "+" sign on good banks, and "-" on those that have lost capacity. You can choose any convenient designation. After checking, you can collect the source. You should not glue the halves of the case. You can rewind them with electrical tape, since one more disassembly will be required.
The battery must be put into operation until it becomes clear that it has lost capacity or is discharged. After that, the source body can be dismantled again and measurements can be made on individual elements that have been marked as out of order. If the voltage across them sank by 0.5 volts from the nominal lower threshold, then the elements were identified correctly and their further maintenance or replacement will be required. After disassembling the battery, it is necessary to carefully inspect all connection and soldering nodes. If there is bad contact on any of the elements, then it may be the fault of everything, and the bank will be in order.
Recovering items that have lost capacity is challenging and not always successful. In most cases, the procedure can slightly extend the life of the can, but later it will need to be replaced. Lithium-ion batteries cannot be repaired, so you shouldn't even try. Most often, when they fail, they swell, deforming the internal components, and nothing can be done about it. The first method that can be applied is the selection of a different control system. You can rearrange the banks from a non-working battery to a working one and see if anything changes. If that helps, then the issue is resolved. But the donor battery must be of a similar model. For nickel-cadmium cans, you can try recovery with multiple charge and discharge cycles. If after this there is a normal set of capacity, then you can use it for some time.
To repair a screwdriver battery, you will need to have similar or the same cans as in your own battery. You need a soldering iron, a flux that does not have a corrosive effect on the material, tin and a wash that will remove the remaining flux.
The soldering iron for work must be of sufficient power to warm up the plates well. Spoiled items are removed and discarded. It is better to hand them over to recycling centers so as not to harm the environment. According to the existing scheme, new cans are substituted and connected with native plates. It is worth working quickly so as not to overheat the battery cells too much, from which they can fail. It is important to look carefully at the markings of the elements so as not to reverse the polarity. Flux is applied first, followed by tin. After assembling the battery, it is necessary to allow the new banks to gain the required capacity. For these purposes, it is necessary to carry out several cycles of complete discharge and charge of the battery. For more information on battery repair, see the video.
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Repairing a battery for a screwdriver is not a difficult task if you know about the nuances that were described in the article. The main problem can be the selection of suitable cans, which would correspond to the parameters of the current and would be suitable in size for a specific battery.
The cost of a new screwdriver is about 70% of the cost of the battery for it. Therefore, it is not surprising when, faced with a battery failure, we ask ourselves the question - what's next? Buy a new battery or a screwdriver, or maybe there is an opportunity to repair a screwdriver battery with your own hands and continue working with an already familiar tool?
In this article, which we conditionally divide into three parts, we will consider: the types of batteries that are used in screwdrivers (part 1), their possible causes of failure (part 2) and available repair methods (part 3).
It should be noted that, regardless of the brand of the screwdriver and the country of the manufacturer, the batteries have an identical structure.The assembled battery pack looks like this.
If we disassemble it, we will see that it is assembled from small elements that are assembled sequentially. And from the school physics course, we know that elements that have a serial connection harmonize their potentials.
Note. The sum of each battery gives us the total voltage at the contacts of the battery.
Typesetting parts or "cans", as a rule, have a standard size and voltage, they differ only in capacity. Battery capacity is measured in Ah and is indicated on the cell (shown below).
For the arrangement of screwdriver batteries, the following types of elements are used:
nickel - cadmium (Ni - Cd) batteries, with a nominal voltage on the "banks" of 1.2V;
nickel-metal hydride (Ni-MH), voltage across elements - 1.2V;
lithium-ion (Li-Ion), with a voltage of 3.6V.
Let's consider in more detail the advantages and disadvantages of each type.
The most common type due to its low cost;
Low temperatures, such as Li-Ion batteries, are not scary;
It is stored in a discharged state, while retaining its characteristics.
Produced only in third world countries, due to toxicity during production;
Memory effect;
Self-discharge;
Small capacity;
A small number of charge / discharge cycles, which means that they do not "live" for a long time with intensive use.
Environmentally friendly production, there is an opportunity to purchase a high-quality branded battery;
Low memory effect;
Low self-discharge;
High capacity compared to Ni - Cd;
More charge / discharge cycles.
Price;
Loses some of its characteristics during long-term storage in a discharged state;
It does not "live" for a long time at low temperatures.
No memory effect;
Self-discharge is almost absent;
High battery capacity;
The number of charge / discharge cycles is several times greater than that of previous types of batteries;
To set the required voltage, a smaller number of "cans" are required, which significantly reduces the weight and dimensions of the battery.
High price, almost 3 times in comparison with nickel - cadmium;
After three years, there is a significant loss of capacity, because Li decomposes.
We got acquainted with the elements, let's move on to the rest of the elements of the screwdriver's battery pack. Disassembling the unit, for example, for repairing the battery of a Hitachi screwdriver (pictured below), is very simple - we unscrew the screws around the perimeter and disconnect the case.
The housing has four contacts:
Two power ones, "+" and "-", for charge / discharge;
Upper control, it is switched on through a thermal sensor (thermistor). A thermistor is necessary to protect batteries, it cuts off or limits the charge current when a certain temperature of the cells is exceeded (usually in the range of 50 - 600C). Heating occurs due to high currents during forced charging, the so-called "fast" charging;
The so-called "service" contact, which is connected through a 9K ohm resistance. It is used for complex charging stations that equalize the charge on all battery cells. In everyday life, such stations are useless, due to their high cost.
That's actually the whole design of the battery. Below is a video on how to disassemble a block.
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We figured out the purpose of the battery structure elements, now we will consider how to determine the malfunction, this is part 2 of the screwdriver battery repair. Immediately, we note that all the elements cannot fail at once, and since our circuit is sequential, when one element fails, the whole circuit does not work. Hence, our task is to determine where we have the weakest link in the chain.
For this, we will need a multimeter, and for the second method of troubleshooting a 12V lamp, if your battery for a screwdriver is also 12 volt. The procedure is as follows:
- We put the battery on charge, wait for the signal of a full charge.
- We disassemble the case and measure it on each battery bank. For Ni - Cd, we should have 1.2 - 1.4V, in lithium - 3.6 / 3.8V.
- Check all "banks" in which the voltage is less than the nominal one. For example, most Ni - Cd cells have a voltage of 1.3V, and one or more - 1.2 / 1.1V.
- We collect the battery and work until a noticeable loss of power.
- We remove, disassemble and measure the voltage drop across the "banks" of the battery. On the marked elements, the voltage "sag" will be greater than on others. For example, they are no longer 1.2V, but 1.0V or even lower.
Note. The difference between the cells in the battery of 0.5 - 0.7V is considered significant, which means that the cell becomes unusable.
Thus, we have found candidates for "resuscitation" or "amputation" and replacement with new elements.
If your screwdriver operates on a voltage of 12 or 13V, you can search with a simpler method. We disassemble the fully charged battery and connect a 12 volt lamp to the contacts "+" and "-". The lamp will be a load and will drain the battery. Next, we take measurements on the battery cells, where the voltage drop is strongest, there is also a weak link.
There are other ways, instead of a lamp, you can choose a resistance, but for this you already need the basics of electrical engineering, and it is doubtful that a resistor with the necessary resistance would be at hand.
Other faults are very rare. For example, loss of contact at the soldering points of the batteries or the power contacts of the unit, failure of the thermistor. This problem is more inherent in fakes. Due to the rarity, we will not focus on the battery elements.
With the "problem" elements sorted out, it is necessary to repair. How to repair a screwdriver battery? In general, 2 methods are available for repair, so to speak. This is the restoration and replacement of elements that have become unusable.
Let's proceed to part 3 of repairing a screwdriver battery and immediately make a reservation that the concept of "resuscitation" for lithium - ion batteries is not applicable. There is no memory effect in them, most likely, lithium decomposition has occurred, and nothing can be done about it. In such batteries, it is necessary to find out what the cause of the malfunction is: the element itself or the control circuit. There are two options here:
we change the control scheme from another, but similar to ours, battery, if it helps, we find a replacement and change it;
apply 4V to a cell with a current of about 200mA, this requires an adjustable charger. If the voltage on the element rises to 3.6V, the element is working properly, the problem is in other elements, or in the control circuit.
Screwdriver battery refurbishment is available primarily for Ni - Cd batteries, but these are usually the most common in household screwdrivers.
So how to reanimate a screwdriver battery? There are two types of "resuscitation" for these types of batteries:
The method of compaction or compression (it will work in cases where the electrolyte is still present, but the volume is lost);
"Firmware" voltage and current greater than the nominal. This method allows you to eliminate the memory effect, and although not completely, but restore the lost capacity.
This method is shown below in the video.
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Note. As a rule, in a nickel - cadmium battery, the main reason for the loss of capacity is the boiling off of the electrolyte, and if it is critically small, no "firmware" will help.
This method, if its result is positive, will not solve the problem of failure of elements. Rather, it will only postpone the replacement of those that have become unusable and in the future you will still need to repair the battery of the Makit screwdriver or any other.
A more effective way to repair batteries for a screwdriver is to replace elements that we have identified as faulty.
To carry out repairs, we need either a "donor" battery, in which some of the elements are in good order, or new "banks". It will not be difficult to purchase them, even on the Internet you can easily find a dozen stores that are ready to send these items by mail.The price does not bite too much, for example, a nickel-cadmium cell with a capacity of 2000 mAh costs around 100 rubles.
Note. When purchasing a new element, make sure that its capacity and dimensions coincide with the native elements.
We also need a soldering iron, a low-corrosion flux (preferably an alcohol flux for rosin) and tin. We are not talking about spot welding, since there is hardly a need to purchase or assemble it for a one-time battery repair ...
There is nothing complicated in the replacement itself, especially if you have at least some experience in soldering. In the photographs, everything is shown in sufficient detail, we cut off the faulty element, instead of it we solder a new one.
Several nuances should be noted:
when soldering with a soldering iron, try to solder quickly, so that the battery does not heat up, because risk spoiling it;
if possible, implement the connection using native plates, or use the same copper plates, this is important because the charging currents are large and if the cross-section of the connecting wires is incorrect, they will heat up, respectively, the thermistor protection will be triggered;
in any case, do not confuse the plus of the battery with the minus - the connection is sequential, which means that the minus of the previous can goes to the plus of the new can, and the minus of the new one goes to the plus of the next one.
After the new elements have been soldered, it is necessary to equalize the potentials on the "banks", since they are different. We carry out a charge / discharge cycle: we set it to charge overnight, give it a day to cool down and measure the voltage on the elements. If we did everything correctly, the picture will be something like this: on all elements the same indicator of the multimeter, within 1.3V.
Next, we proceed to discharge the battery, insert the battery into the screwdriver and load it "in full". The main thing is to spare the screwdriver itself, otherwise you will have to repair it too. We bring it to full discharge. We repeat this procedure two more times, i.e. charge and discharge completely.
It should be noted that the procedure for erasing the "memory effect" should be carried out every three months. It is carried out by analogy with the above-described training.
Such a not very tricky procedure will prolong the work of your screwdriver, at least until you have to replace it with a new one.
Video (click to play).
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