The elements are built on the basis of a cathode made of a composition of lithium and manganese and are characterized by increased thermal stability. The anode is made of graphite with additional additives. The batteries have an increased service life and are adapted to use in circuits with low resistance. Output voltage is 3.7V, a bank of 3 cells in series replaces the lead-acid power supply.
Products allow continuous discharge current up to 30 A (peak short-term values reach 50 A). To ensure an increased resource, the battery case must not be heated above 80 ° C. The capacity of a battery based on a lithium-manganese composition is 30% lower than that of a similar-sized nickel-cobalt battery. There are products of the same standard size, differing in capacity and intended for installation in different equipment.
The rate of capacity recovery depends on the strength of the current; when the parameter is exceeded, the release of gases begins, which can rupture the battery casing. The battery is designed for deep discharge (up to 2.5 V). But with constant discharge or long-term storage in this state, degradation of active substances and electrolyte begins, leading to irreversible damage to the battery.
There is a combined cell of lithium-nickel-manganese-cobalt type, which provides an increase in energy intensity while increasing the service life. The products are used to drive vehicles (in hybrid power plants). Due to the combined scheme, it was possible to reduce the likelihood of thermal breakdown (the temperature is more than 250 ° C) and to reduce the fire hazard of the battery.
The device has an increased capacity, but does not allow accelerated charging modes (due to intense gas evolution). The layered cathode is made of an alloy of lithium and cobalt oxide; pressed graphite is used for the anode. Normal voltage is 3.6 V, the use of 4 cells in series to replace acid batteries is not recommended as the products are not intended for use in equipment with high energy consumption.
An increase in the load causes overheating and destruction of the case with the leakage of electrolyte into the cavity of the device. The products are designed to discharge and charge with a current not exceeding the rated capacity. It is not recommended to charge the battery to a voltage higher than the permissible parameter (4.2 V). Also, products are distinguished by a reduced resource and reduced thermal stability (the temperature of thermal breakdown does not exceed 150 ° C). When fully charged, the likelihood of breakdown increases.
To restore the operating parameters, it is recommended to use microprocessor-controlled charging blocks that allow adjusting the charging parameters. An additional disadvantage of the battery is the low environmental friendliness of production, the spent cells must be disposed of. The products are used in cell phones, tablets or laptop batteries, the product life is up to 1000 discharge and charge cycles (depending on operating conditions).
Current output of lithium-ion batteries
Current output is an additional parameter that characterizes the battery, the value is applied to the battery case, measured in A (amperes) or mA (milliamperes). Batteries with a higher parameter are called high-current (High drain marking) and have a reduced capacity. When choosing a battery, it is necessary to take into account the characteristics of the electric drive, an increased load on the battery leads to overheating of the structure and premature failure of the unit.
Old 18650 batteries as battery cells for drill, electric screwdriver
To drive the electric motor of an electric screwdriver, you need to use 3 elements of the 18650 standard, which are combined in a series circuit. To charge cells at the same time, a capacity equalization board is used, which does not provide the stated battery life. For increased durability, it is recommended to use the off-the-shelf 3-channel charger, which is supplied under the designation Imax B3.
In battery banks for screwdrivers, a discharge regulator is used, which may be discarded. Control is carried out visually using a LED located on the side of the tool body.
Since the cells of the 18650 series have reduced dimensions, the charging unit will also fit into the standard battery case. A plug must be provided on the casing for connecting the cable from the AC mains.
Algorithm for making a homemade battery can for an electric screwdriver based on lithium-ion cells of the 18650 series:
- Disassemble the factory battery, install the power supply at the bottom and solder the leads to the connector that is installed in the window on the side of the case. It is recommended to install a knife-type fusible link rated for a current of up to 10 A, the cell is placed in the 18650 power supply circuit.
- Route the control diodes of the charging board into separate holes. The design includes red and green lamps. When the green light turns on, the battery stops charging.
- Modify the charging board by replacing the resistances responsible for the current in the charging circuit with elements with an increased rating. Since the microcircuits of the unit heat up during operation, it is recommended to provide for the installation of an aluminum or copper radiator. The use of a heat sink increases the reliability of the device in conditions of increased temperatures and a closed case of the battery bank.
- Install the 18650 cells into the cover, the connection pins remain unchanged. The batteries are directly connected to the working contact plates of the jar and are soldered with cables to the outputs of the charging unit. Copper stranded wire is used for the connection, ensuring the safe operation of the device.
- Test battery charging and screwdriver operation.
It is allowed to assemble a battery bank from elements equipped with leads for soldering connecting wires. The elements are welded at the factory, the design allows you to assemble a jar with an increased capacity. To connect the elements, a copper cable or a jumper with a cross section of at least 1.5 mm² is used.
Aging, storage and operating temperature range
When storing lithium-ion batteries, there is a natural deterioration in operating parameters associated with a change in the composition of the anode and cathode. Manufacturers provide a 10% reduction in capacity for each year the item is in the warehouse (subject to storage conditions). If the battery is in inappropriate conditions, then the degradation processes are accelerated. The date of manufacture and expiration date are printed on the cell body, after which the manufacturer does not guarantee the battery’s performance.
It is forbidden to store products in conditions of high or low temperatures, place packaging in direct sunlight or near heating devices. When the case temperature drops below 0 ° C, the lithium-ion battery loses up to 50% of its starting capacity. It is recommended to store partially charged batteries (30-50%) with periodic recharging. When storing discharged cells, the processes of destruction of the cathode and anode are accelerated, the subsequent recovery of the battery is impossible.
Protected and unprotected lithium-ion batteries
Protected batteries are labeled with the Protected prefix. On the negative pole there is a metal shield, under which a round-shaped board with a microprocessor is installed. The protective block is connected to the positive terminal with a separate flat ribbon cable with an insulator that runs along the battery case. The node provides short-circuit protection and prevents excessive current flow during charging. Over-discharge protection is provided, when the voltage drops, the circuit opens.
To reduce the cost of the product, the practice of refusing to install the controller, the batteries are marked Unprotected on the case. Since the protective block is excluded from the circuit, it is recommended to install batteries in devices with reduced power consumption. The user independently controls the level of battery charging, to restore capacity, a microprocessor-controlled charging unit is used.
Types of lithium-ion batteries
The industry produces several varieties of 18650 series batteries:
- Lithium-cobalt cell designed for use in devices with reduced energy consumption.
- Lithium-manganese node featuring increased power and improved stability.
- Lithium-nickel-manganese-cobalt-oxide battery with increased power and energy intensity. To further improve the characteristics, the anode is doped with silicon, but the material negatively affects the durability of the battery. Devices are used to drive electric motors in tools or vehicles.
- Lithium-iron-phosphate battery, resistant to over-discharge and adapted to be installed instead of sulfuric acid batteries in traction drives.
- Lithium-nickel-cobalt-aluminum-oxide cell with increased power and extended service life (compared to lithium-cobalt type products). It is better not to use the device for an electric screwdriver, since the battery retained the main disadvantages of lithium-cobalt batteries.
- Lithium-titanium assembly equipped with a lithium titanate crystal anode. The cathode is made of graphite, the voltage at the terminals is 2.4 V. The device supports accelerated charging modes, allows operation at low temperatures. The drop in capacity during cooling to 30 ° C does not exceed 20%. The product is not susceptible to thermal breakdown, but low energy consumption and increased cost inhibit the proliferation of lithium-titanium cells.
How to find out which 18650 batteries are better in terms of technical characteristics
To determine the optimal 18650 battery, the calculation of parameters in accordance with Ohm’s Law is used. To determine the parameters, you need to know the operating voltage U and the resistance of the device R, which is measured with a test device switched to ohmmeter mode.
The ratio of U and R allows you to determine the current in the power circuit, based on the analysis of the value, a battery is selected that will work without overload. When choosing, the capacity and dimensions of the battery are additionally taken into account, which is located in the body of the tool.
The effect of storing the charge level
This phenomenon is called “memory effect”. If the battery on the instrument was not completely discharged and then put on charge, then the residual charge level begins to be perceived by the battery as zero. Having charged to a full stage, it will function until the energy supply reaches a new level, and after that it will report that it is discharged, although the container will not be completely emptied.
In view of this phenomenon, the master has to make sure that the battery is completely discharged, and only then put it on charge. This is not always convenient if there is still a charge at the end of the day, and tomorrow there is a lot of work ahead. All types of nickel batteries have a memory effect. But lithium-ion models can be charged at any time. they will always use up the accumulated energy to the end, without spontaneous decrease in capacity.
Estimated service life
The time that the battery will last on an electric screwdriver depends on the frequency of use and correct use. To some extent, the number of charge cycles is indicative of how long the battery will “live”. Based on this, you might think that lithium-ion batteries have the shortest lifespan.
In fact, these batteries do not have a number of disadvantages inherent in other types, due to which, in most cases, these batteries serve a longer period.
|Number of charge and discharge cycles||1000||300-500||600|
|The ability to charge quickly||4-8 hours||4-8 hours||30 minutes. 2 hours|
|The cost||cheap||cheap||cost up to 50% of the tool itself|
|Response to tool operation at full power||good performance||good performance||low rates|
|The effect of storing the charge level||there is||there is||not|
|Self-discharge||10% per month||7-10% per month||3-5% per month|
|Working in the cold||can work||can work||poorly tolerate low temperatures|
|Full discharge ratio||tolerate well||tolerate well||must be charged in advance|
It happens that the tool has not been used for some time and it is unexpectedly needed. At such a moment, it may turn out that the battery is self-discharged, and in order to perform the operation, you must first put it in the charger and wait a few hours. It is inconvenient for occasional use.
Unfortunately, nickel-cadmium batteries, as well as nickel-metal hydride batteries, have such a “disease”. For the first, the self-discharge rate reaches 10% per month, and for the second 7-10%. Lithium-ion is much better in this regard. left to lie without use, they will lose only 3-5% after four weeks.
Nickel Metal Hydride (NiMh)
This type is most often used in AA batteries. They began to be developed in the late 1970s. The main substances for the accumulation of charge and its return are nickel-lanthanum, which serves as the anode, and nickel oxide, which is the counterpart, the cathode. Ion transfer is provided by potassium hydroxide.
Nickel Cadmium (NiCd)
This type of battery appeared in the middle of the twentieth century. Nickel hydroxide supplemented with graphite powder acts as a cathode in it. To create the movement of ions from the cathode, an electrolyte is used. potassium hydroxide. The last key element is the anode, which here is made of cadmium oxide hydrate. The second version is metallic cadmium used in powder form.
The ability to charge quickly
If there is a lot of work ahead, then one battery may not be enough, so the craftsmen use two batteries: while one is functioning in an electric screwdriver, the second is being charged. The performance of work depends on how quickly it happens.
Nickel-cadmium and nickel-metal hydride batteries are charged within 4-8 hours, depending on capacity. The latter, although they quickly accumulate energy, need constant recharging during storage.
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The leaders in this category are lithium-ion batteries, which can be fully charged within 30 minutes to 2 hours, depending on capacity. Thanks to this, the battery installed on the electric screwdriver will not have time to discharge, and the second one, located at the charging station, will already be ready for use.
For home use
To quickly disassemble household appliances, a unit in the car or screw a couple of sheets of drywall at home, a small capacity of 1.5-2.0 Ah and a voltage of 12 V is sufficient.Li-Ion is suitable for the type of battery for household use, which holds a charge better and is always ready to work ? even after long-term storage. It is optimal to have two batteries and alternately install them on an electric screwdriver, this will increase the autonomy time.
- b) It is advisable to take Chinese KEEPPOWER batteries. Samsung does not release models with protection.
- a) The correct output readings are 5 Volts and a current from 0.5 to 1 of the nominal capacity of the battery itself.
- a) 10. 25 are ideal indicators. Do not place the battery in any other environment.
- a) Two stages. first with a voltage of 0.2-1A, and then with a high constant.
- a) Only one. A high voltage is immediately applied to the element. The rest of the stages are missing.
The problem with a nickel-cadmium battery installed in an electric screwdriver is that it needs to be used constantly. If the battery is completely discharged or is not used for a long time, then the crystallization process will begin in it, and the battery will soon fail altogether.
It costs a lot of money to replace the battery as batteries that fit an electric screwdriver are not cheap.
For these reasons, the owners of screwdrivers slightly alter the battery in order to connect lithium cells to it. But before starting to carry out such work, you need to think about whether it is necessary to make such an alteration and whether it is advisable at all.
Definition: An 18650 battery is a 3.7V battery.
8650 battery. why it is
Repairing power tool batteries usually involves restoring the electrolyte of the nickel-cadmium “cans” or replacing them altogether. The idea of changing one type of energy element to a more perfect one is quite sensible. This eliminates a wide range of battery-powered tool problems, including high weight, low capacity, memory effect and low cold hold capacity.
However, why should it be exactly 18650 batteries, and not some others? The answer is simple: this is the most common type of battery, except perhaps for batteries for mobile phones or other gadgets. The latter can be used, but most of them carry a built-in charge controller on board, and this is an extra waste of money.
In addition, the batteries must be high-current, that is, capable of supporting a load of 70-100 W. Batteries for electronic cigarettes made by Samsung or LG are optimal. You should not take products from an unknown manufacturer: after all, Li-ion is a rather powerful thing and the low quality of the power cell case can provoke a loss of tightness from overheating with all the consequences. And if there are half a dozen more batteries in the neighborhood, the consequences can be very dire.
How to avoid 4 mistakes when assembling 18650 charging
To properly connect lithium cells to the battery, you will need to follow the instructions exactly:
We disassemble the battery case. The 14.4 Volt model contains 12 1.2 Volt nickel cadmium batteries. We immediately get rid of this coupling. we bite off with pliers. As a result, you will get only a connector with “plus” and “minus”.
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Chargers for 18650 batteries
The 18650 battery will have to use the correct charger. At the output, it will give out 5 volts and a current from 0.5 to 1 of the nominal capacity of the battery itself. If the lithium cells support 2600 mAh, then a current of 1.3-2.6 amperes should be used to charge it.
The lithium battery charger charges the battery in several stages:
- First, a voltage of 0.2-1A is applied to the battery.
- Further, charging already takes place at a constant voltage.
If the charger has a pulse mode, it will significantly speed up the charging time.
In the event that the battery contains graphite, then the voltage should not exceed 4.3 Volts per cell. If this figure is exceeded, then the energy density will increase, and the oxidative process will go.
There are lithium batteries that take less than an hour to charge. The second stage is not provided for them. the current is immediately supplied to 80% and after that it is put into operation. It is normal for a lithium type battery.
The inevitable has come. the batteries in my old Hitachi DS 12DVF3 are completely dead. They have become disgusting to hold a charge for a very long time, but the available capacity was enough for small household needs, so I never thought about solving this problem. Until the moment when I needed to drill a hole in a stainless steel kitchen sink, which took me forty minutes! One hole! One battery could not be swung at all, while the other did not work, twists for twenty seconds, charges for about ten minutes. It was then that I realized that it was time to give a new life to my favorite instrument. It is clear that first it was necessary to familiarize myself with the theory a little in order to understand what in general I have to do. Of course, this topic is not at all new and everyone who is not lazy is engaged in the translation of screwdrivers into lithium. But each does it in his own way, depending on his education, the amount of laziness and the concept of beauty. I needed everything to be done absolutely correctly from the technical point of view, so that it did not look scary from the outside and that the batteries could be conveniently used. After re-reading and reviewing a huge amount of material, I took a project from AlexGyver as a basis.
Here you need to carefully break off the upper contact pad, it will be needed later. You will also need nickel jumpers to solder the second unit to the batteries, so I move this stuff aside for now. Next, I try on new components in order to understand the front of the upcoming work.
The rapid degradation of cordless tool batteries is a real scourge. Almost always, the life of the screwdriver itself exceeds the service life of Ni-Cd cells and you either have to buy spare batteries or say goodbye to the tool. Today we will talk about the main way to extend the life of the battery.
Current output of lithium-ion batteries
Current return. this is an additional parameter that characterizes the battery. On the battery case, the current output is marked with amperage (A). The more amperes are not easy, the harder it will “fry” the battery. Batteries with the highest amperes are considered High drain. Specifically, the number of amperes determines which high-current 18650 battery is best. However, these batteries have a relatively small capacity. The lower the resistance with which the battery must work, the more current it will have to deliver. And the limit of this return depends on the described value. The capacity of the battery determines the current strength in the context of time, and the current output shows this limit. Based on these two parameters, you can calculate the maximum battery life with the maximum power possible for it. It is important to understand that if the current required for a particular device is greater than the maximum current output of the battery with which this device works, then this will be an overload for the battery. The working life of the battery when constantly working under heavy load is greatly reduced.
Lithium ion 18650 batteries for electric screwdriver
Many screwdriver owners want to convert their batteries to lithium battery cells. Many articles have been written on this topic and in this material I would like to summarize information on this issue. First of all, consider the arguments in favor of converting a screwdriver to lithium batteries and against it. And also consider some moments of the process of replacing batteries.
Disassembling the case
The first step is to disassemble the battery case into two halves. The easiest way to do this is if the battery pack is tightened with 4-5 screws: just unscrew them and pull out the top.
If the battery case is glued together (Makita, AEG), then the hassle will significantly increase. We put the battery on its side and carefully tap the glue seam with a rubber mallet. The blows are accurate, not strong, and frequent. We beat off the joint evenly around the perimeter and try to stretch the halves every 50–100 strokes. Even the most stubborn corps surrender in 10-15 minutes of such “execution”.
Next, we throw away the unnecessary parts of the content. The terminal block must be carefully torn off the two upper cans so that two nickel tongues remain on it. Looking ahead, we say that usually, when reworking, a new package of batteries is welded together by contact welding in the manner of factory ones. This is a cool solution, but not everyone wants to build a welding machine. Therefore, leave the length of the strips so that you can fix the wires to it with two small bolts, and the rest of the elements will be connected by soldering.
In any convenient part of the case, you also need to make a hole for the JST-XH balancing connector. On the outside with an awl we mark a rectangle 6 mm high and 15 mm wide for a battery voltage of 12 V or 20 mm for a voltage of 18 V. Insert the connector into the hole made and secure with hot glue or epoxy.
Well, then the assembly process itself goes. Disassemble the battery case first. If this is a 14.4 volt model, then there will be 12 nickel-cadmium batteries with a nominal value of 1.2 volts inside.
After that, you need to solder the purchased items into an assembly with a serial connection. Next, the controller is soldered to it in accordance with its circuit. In this case, balancing points are connected. The board has a special connector for them, and often wires with a connector are supplied in the kit.
After assembling the battery, the terminals for plus and minus are soldered, and the whole structure is placed in the case. In principle, this is the end of the process. Problems can only arise with the charger. But in most cases, standard screwdriver chargers charge lithium cells without problems. In this case, the charge of the cans goes through the controller, so nothing terrible will happen to the elements themselves.
On the network, you can find recommendations for saving on the controller board. That is, a cheaper model is bought, designed for a lower current. And so that it does not limit the work of the screwdriver, the discharge is done not through the controller, but directly from the cans. And their charging, as expected, goes through the controller.
Our client is left with batteries of size (form factor) 18650 have their pros and cons. Therefore, it is difficult to say which 18650 batteries are better. This, faster, is a matter of personal preference, not the requirements that you place on the battery. The technical properties are not the characteristics of the battery depend on the type of chemistry used (electrolyte).
How to place items
Unlike Ni-Cd or Ni-MH cells, lithium batteries have a higher capacity and voltage, so fewer of them will be included in the battery. The dimensions of the 18650 cell are 65mm height and 18mm diameter. Initially, check how many of them will fit in an empty case, and determine the layout, if necessary, cut off the interfering stiffeners.
If the battery pack has a protruding top, a pair of cells will fit into it. Another one is convenient to put on its side right under the two vertical ones. The remaining space can hold 5 to 7 more batteries. If the battery has a charging slide connector, stack the cells across the case in two stacks.
The voltage of the Li-ion battery is 3.7 V, but under load there is a drawdown of about 10-12%. This means that for a 12 V screwdriver you need at least 4 batteries, and for an 18 V. at least 5 pieces, although it is better to use 6, because a lot is not a little. Do not worry that the engine will be “frightened” by the high voltage and will order it to live long. With a drawdown under load, the overvoltage will be minimal and well within the operational limits. You need to decide on the number of batteries before you embed a balancing connector into the case, because there should be one more contacts in it than there are elements in a serial connection.
Now about the capacity. For lithium cells, it ranges from 2.5 to 3 A / h, which is not bad in itself. To double the capacity, you will need to double the number of batteries, but it’s definitely worth it. The only thing that can stop you in this venture is the size of the battery pack. In any case, remember that the number of elements must be strictly a multiple of 4, 5 or 6, depending on the voltage.
When you put the batteries in the right order, fasten them together with electrical tape and achieve complete immobility of the elements inside the case by filling the remaining space with pieces of expanded polystyrene or polyurethane foam. There is no need to leave space for the wires; in extreme cases, during the final assembly, you will need to perform a couple of additional cuts.