How to charge the lithium battery of an electric screwdriver. How to charge a lithium ion battery
How to Charge and Store an Electric Screwdriver Battery
Electric screwdriver. this is one of the most in-demand in home and professional activities electric tools. It not only makes it possible to tighten and loosen different types of fasteners, but also to drill holes. The devices are divided into mains-powered and battery-powered according to the power supply method. The battery-powered models are almost as good as the 220 V-powered ones in terms of performance. With their help it is possible to perform working operations in autonomous mode. It is also advantageous that the power cord does not restrict movement. But the battery of an electric screwdriver should be properly charged and stored so that it will last a long time. Many problems with the battery pack can be corrected by yourself, using a multimeter to find the cause of the problem.
The battery is the power source for cordless screwdriver models. Through physical and chemical processes (electrolysis), this cell stores electrical energy, and then outputs a DC voltage of the desired value at the corresponding outputs. Voltage and capacity are the main parameters of any storage device. the first indicates the potential difference between the cathode and the anode of the battery. The voltage is measured in volts. Capacity determines the amount of current produced per 1 hour by the battery, so this parameter is measured in ampere hours.
In different models, the battery pack (battery) looks and is designed in a similar way. It is made up of the following components:
- housing with the contacts located on it;
- of the power elements (batteries);
- Temperature sensor (thermistor) circuit, which performs the function of block protection against overheating (the range is from 50 to 600 degrees).
Not all models have thermistors. The housing is usually a two-piece plastic box. It mainly has about 10 batteries inside, but sometimes their number is more. In this case, the batteries are connected to each other in a chain. the free terminals of the outermost cans are connected to the terminals located on the housing for powering the tool motor and connecting to the charging equipment. The output voltage of the battery is determined by summing up this parameter of all batteries connected in a single circuit.
- two power (“, “-“) contacts for charging and discharging;
- one upper control contact connected with a thermistor;
- One contact used for charging from special stations, which are able to equalize the value of the charge of all the batteries present in the unit.
According to the type of batteries, battery storage units are divided into the following types:
- Ni-MH batteries (referred to as NiMh) with an output voltage of 1.2 V;
- Nickel-cadmium (labeled NiCd) at the output also give 1.2 V;
- Li-Ion batteries (designated with the Li-Ion symbol), whose voltage depends on the number of power cells in the battery and can be in the range of 1.2 to 3.6 V.
Li-ion batteries have a control board. At the same time, a special controller monitors the operation of the batteries.
A separate battery consists of the following structural elements:
- positive and negative contacts;
- of the positive charge electrode;
- the external coating of the casing;
- negative electrode.
Nickel-cadmium energy storage batteries are the most common because of their affordable price, compact size, and high capacity. They can be recharged more than 1 thousand times.
Peculiarities of charging with Chinese modules
standard buy 20 pcs charge and protection module for a lithium battery (link on aliexpress) is positioned by the seller as a module for one 18650 cell. Can and will charge any lithium battery regardless of shape, size, or capacity to the correct voltage of 4.2 volts (voltage of a fully charged battery, topped up). Even if it’s a huge 8000mah lithium pack (of course we are talking about one cell at 3.6-3.7v). The module gives 1Amp charging current, it means that they can safely charge any battery with a capacity of 2000mah and above (2Ah means charging current is half of the capacity, 1A) and charging time in hours will be equal to the battery capacity in amperes (actually a little more, 1.5-2 hours for every 1000mah). By the way the battery can be connected to the load during the charge.
Important! If you want to charge a smaller capacity battery (e.g. one old 900mah can or a tiny 230mah lithium sachet), the charging current of 1A is too high, it should be reduced. You can do it by changing the R3 resistor on the module according to the attached table. The resistor does not need to be smd, the most common one will do. Recall that the charging current should be half the capacity of the battery (or less, no big deal).
But if the seller says that this module is for one 18650 battery, can it charge two?? Or three? What if you need to build a high-capacity powerbank of multiple batteries? POSSIBLE! All lithium batteries can be connected in parallel (all pluses to pluses, all minuses to minuses) IN ACCORDANCE WITHOUT THE CAPACITY. Batteries soldered in parallel maintain a working voltage of 4.2v and their capacity adds up. Even if you take one 3400mah and the other 900mah you get 4300. Batteries will work as one unit and will discharge proportionally to their capacity.
voltage in a parallel assembly is ALWAYS the same on all the accumulators! And no one battery physically can be discharged in the assembly before the others, here works the principle of communicating vessels. Those who claim otherwise and say lower capacity batteries will discharge faster and die are confused with the LAST assembly, spit in their face.
Important! All batteries should have approximately the same voltage before they are connected to each other so that equalizing currents do not flow between them at the moment of soldering, which can be very high. Therefore it is best to simply charge each battery individually before assembly. Of course the charging time of the whole assembly will increase if you use the same 1A module. But it is possible to parallel two modules, getting a charging current up to 2A (if your charger can give this much). To do this you need to connect jumpers to all similar terminals of the modules (except Out- and B, they are duplicated on the boards by other pins, already will be connected). Or you can buy a module with integrated circuits in parallel. This module is capable of charging at 3 amps.
Sorry for the completely obvious stuff, but people still get confused, so we’ll have to discuss the difference between parallel and series connection.
A parallel connection (all pluses to pluses, all minuses to minuses) maintains the battery voltage of 4.2 volts but increases the capacity by adding all the capacities together. All power banks use parallel connection of multiple batteries. Such an assembly can still be charged via USB and the voltage is raised to 5v by the step-up converter.
The SECOND connection (each plus to the minus of the following battery) gives a multiple of 4.2v of voltage per bank charged (2s. 8.4v, 3s. 12.6v and so on), but the capacity remains the same. If three 2000mah batteries are used, then the capacity of the assembly is 2000mah.
Important! It is considered sacred to use only batteries of the same capacity for a series assembly. It really isn’t. You can use different ones, but then the capacity of the battery will be determined by the LOWEST capacity in the assembly. If you add up 30003000800 you get an 800mah assembly. Then the experts start cuckooing that then the lower capacity battery will discharge faster and die. It doesn’t matter! The main and truly sacred rule is to always and obligatorily use a BMS protection board for the right number of cells. It will determine the voltage of each cell and disconnect the whole assembly if one of them discharges first. In the case of the bank at 800, and it will discharge, BMC will disconnect the load from the battery, the discharge will stop and the remaining charge of 2200mah on the other banks will not matter. you need to charge.
The BMS board, unlike the single cell charger, is NOT a “series-assembled” charger. You need a proper voltage and current source for charging. Guyver made a video about it, so don’t waste time, watch it, it is as thorough as possible.
What is the optimum amount of time to charge?
The time it takes to fully charge a battery is usually given in the instruction manual for the electric screwdriver. We recommend that you follow these guidelines. Often, the charger has indicators that tell you when it is done and when it is over. They will help you understand how long to keep the battery charging. Remove the battery from the charger after completing the procedure to avoid damaging it.
An electric screwdriver battery typically takes anywhere from a half hour to 7 hours to charge. So, a 1.2 Ah NiCad battery will take about 7 hours to fully charge it with 250mA.
There are two types of battery chargers. standard and pulse. The first are designed for household screwdrivers and charge the battery for 3-7 hours. The latter are used in professional equipment and are able to restore the capacity within 1 hour.
Peculiarities of recharging batteries of different types
The differences in the charging of batteries are associated with the properties of the materials from which the batteries are made. Reservoir rechargers are pulse rechargers and regular rechargers. The former are used with professional electric tools, while the latter are used with home screwdrivers.
There are three types of batteries in total:
- Nickel-cadmium. They have a distinctive memory effect. After purchase they must be charged and discharged 3 times. Only in this way will the highest battery capacity be achieved. The following charging must be done only after the charge is finished.
- Nickel-metal hydride batteries. Also have a memory effect. It is recommended to perform the same procedure 4 times. Further recharging is performed arbitrarily.
- Lithium-ion. These batteries are the most unpretentious. They are capable of maintaining their original capacity for a long time. You can charge them at will.
Correctly charging new power sources
With nickel cadmium and nickel metal hydride batteries, the fundamental factor is the initial charging cycle, which allows the full available capacity to be used later.
Note! There are no special rules for charging lithium-ion batteries, whether it’s how long to charge an electric screwdriver or other points, because they have no “memory effect”.
A training cycle is mandatory for all nickel batteries. The manufacturers recommend that this be carried out at least three times. It is very important that the battery is first fully discharged and then charged again to 100%. Ni-MH batteries should undergo at least 4 or 5 cycles of full discharge and charging. Subsequently, batteries can be recharged as needed without having to wait for them to be fully discharged.
For new lithium batteries, it is sufficient to charge them fully and then replenish the charge as it is lost. However, a training cycle will also be useful for these batteries, which is not critical.
Unfortunately, no manufacturing company (not even the world-famous Bosch or Bosch) describes how to perform this procedure. And this is important, because it affects the technical condition of the battery and in particular has a strong influence on the capacity.
The actual training cycle should be performed as follows:
- Charge the battery at 10% of its capacity or let the tool run without load, alternating between cycles of 3 minutes.
- Charge the battery until the charger is disconnected.
- Wait 20 to 30 minutes.
- Re-position the battery and again until the charger is disconnected.
- Once again wait for a pause (20-30 minutes).
- For the third time connect the battery and wait until the charger is disconnected.
- Allow about a half hour for the voltage to stabilize.
- Now discharge it as described in point 1.
- Repeat this entire cycle at least 3 times (points 1 to 8).
A practice cycle should be performed once every six months, but it is still recommended that you do it every three months. In this case the capacity of the batteries will not decrease.
How to check the charge level
unlike 6 or 12 volt lead-acid batteries, you will not be able to determine the level of charge (SOC) of a lithium ion battery using the instantaneous output voltage correspondence table. For example, the graph above shows that under different conditions the same output voltage (3.8 volts) can correspond to a charge level of either 50% or 2%. Naturally, no user can be satisfied with such an error.
Also, the extremely non-linear relationship between terminal voltage and load, and power supply temperature is not conducive to proper battery state-of-charge determination. In budget-priced gadgets this method is sometimes used, but it cannot be completely trusted.
There are more accurate methods of determining the capacity, for example, by steady-state voltage, but its measurement requires several hours of stable load (or better. open circuit), which in reality almost never happens. But there are mathematical methods that can calculate the remaining charge from a short time voltage.
This method also does not give absolute accuracy, but for practical purposes is quite applicable. There are other, more reliable methods of measuring the residual charge:
The disadvantage of all these methods is the complexity of implementation in conditions of mass-designed gadgets. So there is no precise, unambiguous and simple way to determine the remaining energy reserve of lithium batteries.
Types of batteries
In order to ensure that the battery lasts “like clockwork” for a long time, you must first read the instructions that come with the device. It should be noted that the screwdrivers differ not only in price, power, manufacturer, but also are divided into professional and semi-professional. Accordingly, the batteries will also have different prices, quality, and charge capacity. Professional types are equipped with higher-capacity power sources, which will cost a level more expensive, but will also work longer than conventional ones. Manufacturers use different batteries in the manufacture of their devices, each of which is endowed with certain parameters and features that should be taken into account during recharging. Batteries for screwdrivers can be classified into such types:
Considered to be the most powerful batteries. They recharge quickly enough, and they have no memory effect. To recharge this kind of battery is easy. There is no need to recharge it after a complete discharge, it is allowed to recharge as needed. High cost and intolerance to low temperatures discourage many people from buying them, so they are not in high demand. Batteries should be charged at temperatures between 10 and 40°C. If the battery gets hot during charging, it must be cooled to avoid further damage.
The nickel cadmium battery is endowed with compact dimensions and great capacity. Following the enclosed instruction, it can be recharged more than 1000 times. It has a memory effect, if charged before it is fully discharged, it can reduce the capacity. Charge and discharge the battery pack at least three times before first use. It is also recommended that the device be fully discharged and charged later, this will allow you to bring the capacity to the desired operating condition. The same rule applies during storage of the tool.
Nickel-metal hydride Ni-MH
They belong to the newest generation of batteries, for this reason, the memory effect is somewhat weaker than the previous variety, which is a definite plus. The disadvantage of the NGB is the high self-discharge current. In order to keep the battery functioning for a long time, it is necessary to keep it charged. If the electric screwdriver is not used for a long time (about a month), it should be fully recharged.
Charging Lithium Batteries: The Charge Cycle
As you can see, each battery has its own specific characteristics, which will allow you to charge your electric screwdriver correctly.
Safety and Precautions
Before you charge something, it is necessary to be familiar with safety precautions. It helps to prevent possible problems that may occur while recharging the battery of the tool.
The following recommendations should be followed:
- The process must be monitored at all times. Once you are finished charging the battery, you must stop the process completely. The fact is that lithium components can boil as a result of overcharging. Their temperature readings increase dramatically, which can lead to an explosion.
- It is necessary to make sure that all cells are properly turned on. Pay special attention to the polarity and specifications of the battery used.
- If the characteristics of the modules differ from each other, the battery should not be charged for too long.
Additional Information! The length of time required to recharge depends greatly on the type of battery. On average, the procedure takes about 3-4 hours. However, some batteries can only be recharged after 7 hours.
How to charge the battery properly
If you buy a new tool with a nickel-cadmium or nickel-metal hydride battery, fully discharge and charge the battery three times before use (pumping). When using an electric screwdriver, do not charge the battery until it is fully discharged. Then pumping should be repeated periodically as a preventive measure.
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Important! To avoid downtime, it is a good idea to have a spare battery.
When Ni-Mh and Ni-Cd batteries are fully charged, they are disconnected from the network (in case of lithium-ion batteries, this is done by the controller). If the battery is not used for an extended period of time, remove it and store it separately from the electric screwdriver.
With careful handling, following the manufacturer’s instructions, the battery will last a long time and will not require early replacement. And minor repairs can be done with your own hands.