Charging lithium-ion phone batteries. Using lithium-ion batteries

Permissible temperature ranges for charging and discharging lithium-ion batteries

Testing Features

Tests for the number of cycles were carried out with a discharge current of 1C; for each battery, discharge/charge cycles were carried out until 80% of the capacity was reached. This number was chosen based on the timing of the test and for possible comparison of results later. The number of full equivalent cycles is up to 7500 in some tests.
Life tests were carried out at various charge levels and temperatures, voltage measurements were taken every 40-50 days to monitor discharge, the test duration was 400-500 days.

The main difficulty in the experiments is the discrepancy between the declared capacity and the real one. All batteries have a capacity higher than stated, ranging from 0.1% to 5%, which introduces an additional element of unpredictability.

NCA and NMC batteries were most commonly used, but lithium cobalt and lithium phosphate batteries were also tested.

A few terms:
DoD - Depth of Discharge - depth of discharge.
SoC - State of Charge - charge level.

Using Batteries

The number of cycles

At the moment, there is a theory that the dependence of the number of cycles that a battery can withstand on the degree of discharge of the battery in the cycle has the following form (discharge cycles are indicated in blue, equivalent full cycles are indicated in black):

This curve is called the Wöhler curve. The main idea came from mechanics about the dependence of the number of stretches of a spring on the degree of stretching. The initial value of 3000 cycles at 100% battery discharge is a weighted average at 0.1C discharge. Some batteries show better results, some worse. At a current of 1C, the number of full cycles at 100% discharge drops from 3000 to 1000-1500, depending on the manufacturer.

In general, this relationship, presented in the graphs, was confirmed by the results of experiments, because It is advisable to charge the battery whenever possible.

Calculation of superposition of cycles

When using batteries, it is possible to operate with two cycles simultaneously (for example, regenerative braking in a car):

This results in the following combined cycle:

The question arises, how does this affect the operation of the battery, is the battery life significantly reduced?

According to the results of the experiments, the combined cycle showed results similar to the addition of complete equivalent cycles of two independent cycles. Those. The relative capacity of the battery in the combined cycle fell according to the sum of the discharges in the small and large cycles (the linearized graph is presented below).

The effect of large discharge cycles is more significant, which means that it is better to charge the battery at every opportunity.

Memory effect

The memory effect of lithium-ion batteries was not noted according to the experimental results. Under various modes, its total capacity still did not subsequently change. At the same time, there are a number of studies that confirm the presence of this effect in lithium phosphate and lithium titanium batteries.

Battery storage

Storage temperatures

No unusual discoveries were made here. Temperatures 20-25°C are optimal (in normal life) for battery storage, if not used. When storing a battery at a temperature of 50°C, capacity degradation occurs almost 6 times faster.
Naturally, lower temperatures are better for storage, but in everyday life this means special cooling. Since the air temperature in the apartment is usually 20-25°C, storage will most likely be at this temperature.

Charge level

As tests have shown, the lower the charge, the slower the self-discharge of the battery. The capacity of the battery was measured, what it would be during its further use after long-term storage. The best results were shown by batteries that were stored with a charge close to zero.
In general, good results were shown by batteries that were stored with no more than 60% charge level at the start of storage. The numbers differ from those below for a 100% charge for the worse (i.e. the battery will become unusable earlier than indicated in the figure):

Figure taken from article 5 practical tips for using lithium-ion batteries
At the same time, the figures for small charge are more optimistic (94% after a year at 40°C for storage at 40% SOC).
Since a 10% charge is impractical, since the operating time at this level is very short, It is optimal to store batteries at SOC 60%, which will allow you to use it at any time and will not critically affect its service life.

Main problems of the experimental results

No one has conducted tests that can be considered 100% reliable. The sample, as a rule, does not exceed a couple of thousand batteries out of millions produced. Most researchers are unable to provide reliable comparative analyzes due to insufficient sampling. Also, the results of these experiments are often confidential information. So these recommendations do not necessarily apply to your battery, but can be considered optimal.

Results of the experiments

Optimal charging frequency - at every opportunity.
Optimal storage conditions are 20-25°C with a 60% battery charge.

Sources

1. Course “Battery Storage Systems”, RWTH Aachen, Prof. Dr. rer. nat. Dirk Uwe Sauer

Lithium-ion batteries are not as finicky as their nickel-metal hydride counterparts, but they still require some care. Sticking to five simple rules, you can not only extend the life cycle of lithium-ion batteries, but also increase the operating time of mobile devices without recharging.

Do not allow complete discharge. Lithium-ion batteries do not have the so-called memory effect, so they can and, moreover, need to be charged without waiting for them to discharge to zero. Many manufacturers calculate the life of a lithium-ion battery by the number of full discharge cycles (up to 0%). For quality batteries this 400-600 cycles. To extend the life of your lithium-ion battery, charge your phone more often. Optimally, as soon as the battery charge drops below 10-20 percent, you can put the phone on charge. This will increase the number of discharge cycles to 1000-1100 .
Experts describe this process with such an indicator as Depth Of Discharge. If your phone is discharged to 20%, then the Depth of Discharge is 80%. The table below shows the dependence of the number of discharge cycles of a lithium-ion battery on the Depth of Discharge:

Discharge once every 3 months. Fully charging for a long time is just as harmful to lithium-ion batteries as constantly discharging to zero.
Due to the extremely unstable charging process (we often charge the phone as needed, and wherever possible, from USB, from a socket, from an external battery, etc.), experts recommend completely discharging the battery once every 3 months and then charging it to 100% and holding it on charge 8-12 hours. This helps reset the so-called high and low battery flags. You can read more about this.

Store partially charged. The optimal condition for long-term storage of a lithium-ion battery is between 30 and 50 percent charge at 15°C. If you leave the battery fully charged, its capacity will decrease significantly over time. But the battery, which has been collecting dust on a shelf for a long time, discharged to zero, is most likely no longer alive - it’s time to send it for recycling.
The table below shows how much capacity remains in a lithium-ion battery depending on storage temperature and charge level when stored for 1 year.

Use the original charger. Few people know that in most cases the charger is built directly into mobile devices, and the external network adapter only lowers the voltage and rectifies the current of the household electrical network, that is, it does not directly affect the battery. Some gadgets, such as digital cameras, do not have a built-in charger, and therefore their lithium-ion batteries are inserted into an external “charger”. This is where using an external charger of questionable quality instead of the original one can negatively affect the performance of the battery.

Avoid overheating. Well, the worst enemy of lithium-ion batteries is high temperature - they absolutely cannot tolerate overheating. Therefore, do not expose your mobile devices to direct sunlight or place them near heat sources such as electric heaters. Maximum permissible temperatures at which lithium-ion batteries can be used: from –40°C to +50°C

Also, you can look

The first lithium-based battery appeared in 1991. But only against the backdrop of the popularization of mobile phones, Li-ion devices also became widely popular. At the moment, lithium batteries are used wherever autonomous operation of an electronic or technical device is required. Batteries supply energy to household appliances, power tools, gadgets and various equipment. Due to the low self-discharge threshold, the ability to replenish energy without waiting for the power supply to be completely consumed and the rich resource of Li-ion batteries, they are able to support the operation of devices that require high power.

Lithium battery design

According to the design, Li-ion batteries are produced in prismatic and cylindrical designs. Prismatic batteries are made by stacking rectangular plates on top of each other. Such models provide for more dense packaging compared to cylindrical counterparts, but it is necessary to provide more intense compressive forces against the electrodes. The cylindrical device of a lithium battery is a package with electrodes and a separator, rolled up and enclosed in a metal frame connected to the negative electrode. The positive electrode of the battery is connected to the cover via a special insulator. By the way, the roll assembly principle is also used in some versions of prismatic models in the form of an elliptical spiral. This design combines the advantages of both types of lithium batteries.

Why shouldn’t it be brought to “zero”?

Experts do not recommend using batteries until the energy is completely spent. Lithium devices do not have the memory effect that other types of batteries have. In practice, this means that you need to charge the battery before its level drops to zero. By the way, the number of cycles by which lithium batteries are charged is an indicator of the durability of power sources - manufacturers indicate this figure in the labeling.

For example, for high-quality models the number of cycles can be 600. In order to increase the service life of the Li-ion battery, it is worth charging the device regularly. The optimal level at which you should start charging is 15%. This measure can increase the number of cycles to 1,100.

How is charging done?

Lithium batteries are charged according to a mixed scheme, that is, first from a direct current of 1C to an average voltage of 4.2 V, and then at a constant voltage level. The primary stage lasts about 40 minutes, and the second - longer. It is worth noting that only modern lithium batteries can be charged at voltages up to 4.2 V. Industrial and military battery models have a longer service life than standard models, as a result of which the threshold for the end of their charge has been pushed back to 3.90 V.

How long does it take to charge?

The process of charging a lithium cell with a 1C current usually takes 2.5 hours. The Li-ion battery fully replenishes energy when its voltage level corresponds to the same cutoff indicators. At the same time, the current should decrease by approximately 3% relative to the initial charge. There is an opinion that lithium batteries charge faster when the current increases. In reality, this is not the case, however, the increased charging current contributes to an increase in voltage, while recharging from the end of the first stage requires more time.

In some types of devices, charging lithium batteries takes less than 1 hour. The reduction in time is due to the fact that the second stage of the cycle is absent and the battery can be used immediately after the completion of the first stage. But there is one caveat: the battery does not completely replenish its energy reserve - it is only 70%.

It would seem, what is the point of such a charging scheme? This approach is beneficial if multiple fast charging cycles are required. For example, a screwdriver with a lithium battery will require 30 minutes for each operation, after which you can charge the current battery and continue working with a spare one (power tools are usually equipped with two batteries).

Why do you need to overcharge the battery?

It is recommended to start charging before the energy is reduced to zero, however, once a month it is still worth completely discharging. After this, you should use the original charger for lithium batteries in order to replenish the energy 100%. The need for this procedure is due to the characteristics of Li-ion batteries. Experienced users of devices powered by lithium cells may have noticed that the indication of the remaining charge is not always correct. For example, the tablet screen displays that the device is only 50% discharged - in fact, only 10 minutes of active work can drain the battery.

To prevent such inconsistencies, lithium batteries should be completely discharged. As a result, the device will be able to more accurately calculate the capabilities of the power source and reliably display information on the display.

Reducing power consumption during charging

Although powering mobile devices and other gadgets that require lithium batteries in terms of energy consumption is incomparable with powerful household appliances, a few simple tips will help not only save on electricity, but also extend the life of the devices:

Using the capabilities of the device’s software to minimize power consumption.
Disable functions that work unnecessarily. For example, the Internet, various networks and Bluetooth - according to statistics, their combined work can reduce the operating time of the device by 30%.
Optimize the device settings - dimming the backlight, turning off unnecessary notifications and sound effects will extend the operation of the gadget by 10-15 minutes. This is not much, but in critical situations it will not be superfluous.

Rules for preserving lithium batteries

Durability is one of the strengths of Li-ion batteries. Thus, the annual reduction in volume as a result of self-discharge is no more than 10%. Despite this, chemical and structural methods for protecting batteries from overheating should be taken into account during operation. If modern lithium batteries have protection against improper charging, temperature effects still pose a danger to them. Therefore, it is recommended to reduce any unnecessary heating of the batteries. However, manufacturers are also working in this direction. The use of cathode elements, in particular, will increase the thermal safety of lithium power supplies.

A couple of weeks ago I brought 6 Makita devices for repair.

4 screwdrivers, 1 jigsaw and 1 sander.

The whole box. Heavy.

They gave me a price for repairs. It turned out that only one screwdriver made economic sense to restore. The rest went for spare parts.

In general, the time has come to replace the fleet of hand-held cordless tools.

So I immediately purchased new screwdrivers with Li-ion batteries for all the carpenters.

Immediately a problem.

Guys are used to Ni-cd batteries, but Li-ion requires a completely different approach. Just the opposite.

And, of course, we are talking not only about how to charge the Li-ion battery of a screwdriver. If it is not properly discharged and/or stored, it will also do little good.

Therefore, I looked at a couple of dozen sites and a couple of hours of videos.

I threw out all the husks and made the most “dry” squeeze without “water”.

How to charge a Li-ion screwdriver battery and other important rules for its operation

Remember -Li— ion to the opposite differ fromNi— Cd !
Place Li-ion on charge when there is residual charge 20-50% .
Important! Li-ion discharge should not be allowed below 10-20% . This is a critical value. The lower the discharge, the longer Li-ion will work -

Li-ion works optimally in the range from -10 to +45°C. Charge at temperatures from +10 to +30°C.
Once every 4 months, carry out a full discharge-charge cycle to calibrate the charge level sensor in the battery controllers. That is, discharge to almost 100% and charge for 12 hours.
Li-ion must be stored on charge 40-60% .
It is impossible to store 100% charged Li-ion, since in this case it will permanently lose 20% of its capacity in 3 months.
If stored correctly - with a charge of 40-60% - Li-ion will irreversibly lose only 1% of its capacity over the same 3 months.
If the screwdriver is equipped with two Li-ion, then charge one to 40-60% and store it as a backup. Once a month, use it as a worker - charge it to 100%, discharge it to 40-60% and leave it for storage again.
The second Li-ion is the main worker. Once you've worked, charge it at the end of each day, even if it's less than 10% discharged.

Use a backup Li-ion if the main working Li-ion is discharged as a result of intensive work and there is no time to wait for it to charge.

That's all. Now you know how to charge a Li-ion battery for a screwdriver.

I gave one to each carpenter, and even hung it on the notice board in the shop.

And here’s another question: why did I switch from Ni-cd to Li-ion cordless screwdrivers?

Here are the advantages of Li-ion batteries over Ni-cd:

at least 2 times higher specific capacity;
self-discharge is several times less;
no memory effect, which makes it possible to recharge at any time;
withstands on average twice as many charge-discharge cycles, that is, it will live twice as long.

Are there any disadvantages?

I don't know anyone like that.

They write that:

Li-ion is subject to aging.
Well, are Ni-cds eternal? They also get old.
Li-ion has low stability when operating at low temperatures.
All this is in the past. Now Li-ion is made in such a way that it works even at -10°C. And some sources indicate that I can work even at -30°C;
Li-ion chargers require the use of only the original charger.
Well, what's wrong with that? All screwdrivers are sold with their original charger included.
Li-ion has a high cost.
Well, I wouldn’t say that anymore. I recently went to the store. Ni-cd batteries below 1 t.r. did not see. And on AliExpress you can buy an entire screwdriver with Li-ion for 3 thousand rubles.

And finally, if you work with a screwdriver professionally - don’t doubt it too much - it will crumble at the same time as the Li-ion battery. So you most likely won’t have to buy a Li-ion battery separately.

Just with reasonable, non-vandal use, a screwdriver should be enough for a couple of years.

And, yes, one more important rule. Don't skimp on screwdriver power. It corresponds to the battery voltage. Take a Li-ion battery of at least 20 volts. It will spin like a beast.

But buy a weak one - it will be of little use, and there will be no joy from saving a penny either.

In general, I collected screwdrivers with 25 volt Li-ion batteries. The carpenters couldn't be happier. Especially after Ni-cd at 14 volts.

Look like that's it. If you have any questions or disagree with something, write in the comments.

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Owners of various devices sometimes experience certain difficulties when finding information about the proper use of batteries. This short FAQ is devoted to this issue.
All modern phones, smartphones and PDAs are equipped with lithium-based batteries - lithium-ion or lithium-polymer, so in the future we will talk about them. These batteries have excellent capacity and service life, but require very strict adherence to certain operating rules.

The fundamental rules for charging and discharging batteries, which are controlled by a device (controller) built into the battery, and sometimes by an additional controller located outside the battery, in the PDA itself.

The battery must remain in a condition throughout its entire life in which its voltage does not exceed 4.2 volts and does not fall below 2.7 volts. These voltages are indicators of the maximum (100%) and minimum (0%) charge, respectively.

The amount of energy supplied by a battery when its charge changes from 100% to 0% is its capacity. Some manufacturers limit the maximum voltage to 4.1 volts, while the battery lasts longer, but its capacity is reduced by about 10%. Also, sometimes the lower threshold rises to 3.0 volts with the same consequences.

Battery life is best at approximately 45 percent charge, and as the charge level increases or decreases, battery life decreases. If the charge is within the limits provided by the battery controller (see above), the change in durability is not very significant, but is still present.

If, due to circumstances, the voltage on the battery exceeds the limits specified above, even for a short time, its life is dramatically reduced. Such conditions are called undercharge and overdischarge and are very dangerous for the battery.

Battery controllers designed for different devices, if they are made with proper quality, never allow the battery voltage to exceed 4.2 volts during charging, but, depending on the purpose of the battery, may limit the minimum voltage during discharge in different ways. So, in a battery intended for, say, a screwdriver or a car model motor, the minimum voltage will most likely be truly the minimum permissible, but for a PDA or smartphone it will be higher, because the minimum voltage of 2.7 volts may simply not be enough to operate the electronics of the device. That is why in complex devices such as phones, PDAs, etc. The operation of the controller built into the battery itself is complemented by the controller in the device itself.

Operating rules that you and I can influence, thereby significantly increasing or decreasing the battery life.

you need to try not to bring the battery to a minimum charge, and even more so to a state where the machine turns itself off, but if this happens, charge the battery as soon as possible.
There is no need to be afraid of frequent recharges, including partial ones, when a full charge is not achieved. This does not harm the battery. In this case, I am guided by common sense: if during normal use of a PDA I always put it on charge before going to bed, then in the case of very intensive use (WiFi always on, listening to music, etc.), when the charge approaches the minimum, I do not disdain directly At work, connect the PDA to any available USB. If you don’t have a normal charger and use a special USB charger instead, it is important not to wait until the charger is completely discharged, because in this case the current from the USB port may not be enough to start the charging process.
Contrary to the opinion of many users, overcharging harms lithium batteries no less, and even more, than deep discharging. The controller, of course, controls the maximum charge level, but there is one subtlety. It is well known that battery capacity depends on temperature. So, if, for example, we charged the battery at room temperature and received a 100% charge, then when we go out into the cold and the machine cools down, the battery’s charge level may drop to 80% or lower. But the opposite situation may also be true. A battery charged at room temperature to 100%, when slightly heated, will become charged to, say, 105%, and this is very, very unfavorable for it. Such situations occur when operating a machine that has been in the cradle for a long time. During operation, the temperature of the device and along with it the battery rises, but the charge is already full... In this regard, the rule says: if you need to work in the cradle, first disconnect the machine from the charger, work on it, and when it goes to " combat" mode - connect the charger. By the way, this rule also applies to owners of laptops and other gadgets.
Ideal conditions for long-term battery storage are to be outside the device with a charge of approximately 50%. A working battery does not require care for months (about six months).

And finally, some more information.

Contrary to popular belief, lithium batteries, unlike nickel ones, have almost no “memory effect”, so the so-called “training” of a new lithium battery makes virtually no sense. For your own peace of mind, it is enough to fully charge and discharge the new battery once or twice, mainly to calibrate the additional controller.
Device owners know that you can charge the battery both from a charger and from USB. At the same time, the impossibility of charging from USB often causes bewilderment. The fact is that, according to the “law,” a USB controller must supply a current of about 500 mA to peripheral devices connected to it. However, there are situations when either the controller itself cannot provide such a current, or the device is connected to a USB controller on which some kind of peripheral is already hanging, consuming some of the power. So there is not enough current for charging, especially if the battery is too discharged.
Lithium-containing batteries REALLY DO NOT LIKE FREEZING. Always try to avoid using the machine in severe cold - if you get carried away, the battery will have to be changed. Well, of course, if you took the machine out of the warm inner pocket of your jacket and made a couple of notes or calls, and then put the little animal back, there will be no problems.
Practice shows that lithium batteries (not just batteries) reduce their capacity when atmospheric pressure decreases (at high altitudes, on an airplane). This does not harm the batteries, you just need to take this fact into account.
It happens that after purchasing a battery with a higher capacity (say, 2200 mAh instead of the standard 1100 mAh), after a couple of days of using the new battery, the machine begins to behave strangely: it hangs, turns off, the battery seems to be charging, but somehow strange, etc. P. It is possible that your charger, which works successfully on a “native” battery, is simply not able to provide sufficient charging current for a high-capacity battery. The solution is to purchase a charger with a higher current output (say 2 amperes instead of the previous 1 ampere).

19.10.2010 10:53

Original taken from kolochkov in Rules for the use of lithium-ion batteries

We are already tired of writing and speaking the same misconceptions about lithium-ion batteries.
To stop this madness, I quote from the “Rules for the Use of Lithium-Ion Batteries” by one respected source:

Proper use of cell phone batteries

The electrodes of lithium-ion batteries are already half charged due to the manufacturing process, but it is not advisable to immediately test a fresh battery under load. Initially, the lithium-ion battery needs to be fully charged. Using a battery without an initial charge can dramatically reduce the capacity available to the user.
After initially charging the battery, it is advisable to completely discharge it to calibrate the battery management system. Recharge the battery immediately after discharge. Calibration cycles for cell phones with lithium-ion batteries should not be performed frequently (usually one full charge-discharge cycle every 3 months is enough). The calibration cycles themselves are needed only to correctly display the forecast of the remaining battery capacity. The three to four deep charge-discharge cycles recommended by some users and sellers can be fatal for a not new lithium-ion battery.
It is advisable to use original batteries from the mobile phone manufacturer. Since the functions of the battery management system for mobile phones are greatly reduced, and the charge is managed by the cell phone charging system, a battery from a third-party manufacturer will last less, since the charging system does not know the features of non-original batteries.
Due to the fact that the “aging” effect of lithium-ion batteries increases sharply at high temperatures, it is advisable to keep the cell phone away from heat sources (human body, direct sunlight, heating radiator).
It is advisable not to fully charge the cell phone battery often, and also to charge the battery before the charge level reaches the red level of the charge indicator (approximately 20% of the remaining capacity).
The aging of lithium-cobalt batteries (the most common batteries for cell phones directly depends on the load level). Talk less and less often on your mobile phone - this will keep not only your battery healthy, but also you.
Do not charge a battery that has been in the cold until it warms up to a positive (Celsius) temperature - this is an important requirement for the safe operation of lithium-ion batteries.

Correct use of laptop batteries

The laptop battery contains a complete management system, which often allows the user to forget whether he is using the battery correctly. However, there are a few things to keep in mind when working with a laptop.
When connecting for the first time, the laptop battery should be fully charged, and then calibrate the control system. Calibration is carried out by completely discharging the battery under constant load (you need to enter the BIOS settings and leave the laptop running when unplugged until turned off; many BIOS adjusters have a special Calibration item designed to perform this task). Make sure to charge your laptop battery immediately after it is completely drained.
Calibration of a laptop battery is usually carried out once every 1-3 months, to eliminate the effect of “digital memory” - during operation on battery power, errors in determining the residual capacity gradually accumulate, which reduces the battery life of the laptop.
For some laptop models, there are manufacturer utilities for setting the level of battery discharge at which charging begins. If the laptop battery serves as an uninterruptible power supply (work is carried out stationary with mains power), then setting the permissible discharge level to 40% and maintaining the battery in a half-discharged state will double the battery life.
Some laptops come with an extra battery. If you do not use it for a long time, it makes sense to discharge the additional battery to 40%, pack it in a plastic bag with a vacuum seal and leave the bag in the refrigerator compartment at a temperature of 3-4°C.

Correct use of Power Tools batteries and video cameras

The rules for using Power Tools batteries (mainly screwdriver batteries) and video cameras differ little from the rules for using cell phone batteries.
The difference is that the use of these devices in everyday life is quite rare, and the cost of batteries is high and these batteries become less accessible over time. To ensure a long life of such batteries, they should be stored in a semi-discharged state in the refrigerator at a temperature of 3-4°C, pre-packed in a plastic bag with a vacuum seal. Before use, the battery must be fully charged using a standard charger, and during operation, the battery must not be completely discharged (at the first opportunity, recharge the battery during operation).
In conclusion of the article, I would like to say that although the operating rules allow you to maintain battery parameters for a long time, life dictates its own operating conditions, which are often incompatible with the concept of proper operation of such a high-tech thing as a lithium-ion battery.