How to extend the life (life) of a lithium-ion battery

I thought for a long time how to present the material, and, in the end, decided that it should be presented as separate facts concerning the life of real lithium-ion batteries. So let's start ...

Lithium-ion batteries suffer more from the aging process (degradation over time) than from cycling. This means that most batteries cannot last for more than 5 years under normal operating conditions (optimistic outlook). The moral is - if you buy a lithium-ion battery, be careful about the date of manufacture - if you are six months old, you will lose 10% of the stated resource.

Aging of batteries is accelerated when working or storing in hot conditions - see the table for lithium-cobalt batteries (for lithium-manganese and lithium-iron batteries, the results are slightly better)

Taking into account that the standard for determining the end of battery life by a manufacturer is to reduce its capacity to 80% of the nominal, it’s clear where 5 years of life came from (when the battery is operating at a temperature not higher than 25 ° C and most of the time is in a semi-discharged state). Therefore, it is necessary to properly arrange the cooling of the batteries during operation and charge the battery immediately before use, achieving an average charge level during operation close to 40% (tested in practice - when charging my mobile battery every 3-4 days up to 80-90% capacity and wearing it is in the outer pocket of clothes - the life has already reached more than 4 years with the safety of the container).

The temperature factor should also be taken into account when using lithium-ion batteries - discharge can be carried out at low temperatures (depending on the battery chemistry from -25 ° C to -10 ° C), but the charge should be made only at positive temperature of the battery.

The number of charge-discharge cycles does not affect the life of the lithium-ion battery as much as age and temperature factor — with a short cycling time (continuous charge / discharge cycles of 0.5C) and good cooling, the lithium-ion battery can withstand over 1000 cycles ( for lithium-cobalt) up to 2000-3000 cycles (for lithium-manganese).

Exceeding the final voltage after charging from 4.2V to 4.35V increases the battery capacity by 10-15% while reducing the life time by 4-6 times.

BMS (Battery Manegement System) - battery management system - an electronic device that is necessarily placed on each battery bank in the battery to monitor the charge-discharge process of the battery, advanced BMS also have logic to determine the temperature, number of charges / discharges, estimate the probability of failure battery Basically, the BMS task is to monitor the battery voltage and shunt the currents when the boundary limits are reached, and the element temperature can also be monitored. To avoid failure of the lithium-ion battery when it is fully discharged, you must immediately charge it, otherwise the BMS will not allow the charge to start when the voltage on the cell drops below a certain threshold due to self-discharge of the battery for safety reasons (tested in practice - I left my handheld for 3 weeks in an almost discharged state and then, despite the late resuscitation, the soul of the battery safely moved into a better world (I sincerely hope so :)).

Existing advanced battery status monitors most likely use Peukert’s equations in their calculations. However, everything is not so simple: usually consumed current varies over time, there are long battery interruptions, as well as the constant values ​​of Pekert's capacitance and exponent change during battery operation (and they have to be recalculated from time to time to get real monitor readings). This is especially vividly seen in the example of a “digital memory effect” in lithium-ion batteries for laptops - when operating under partial charge / discharge conditions, a gradual decrease in battery life is observed due to a mismatch between the remaining capacity calculated by the battery management system and the real one. The effect of “digital memory” is leveled by battery calibration: a full charge followed by a full battery discharge every 30-50 cycles (laptops without a calibration system built in BIOS Setup, need to be discharged when entering the BIOS settings, charge immediately after switching off the battery ).

Lithium-ion batteries do not tolerate low charge currents and high discharge currents (note about high discharge currents not related to LiFePO ₄ batteries, which can carry large discharge currents, and to a lesser extent for LiMnO ₂ and LiMn ₂ O ₄ ). To achieve maximum life expectancy, it is necessary to use currents of 0.5C (half the nominal capacity) to charge and discharge the battery. For LiCoO ₂ batteries, it is undesirable to pass the limit of 1C for charge and discharge currents (discharge at 2C reduces life by 2 times, at 3C - 4 times).

Observance of all specified precautions will allow to reach the big term of life (resource) of your lithium-ion battery and it will long please you with its capacity and low level of internal resistance. Also, lithium-ion batteries based on other chemical compounds and the internal structure appear every 6-12 months - they will have a little (or a lot) other characteristics. Manufacturers' statements about new batteries should be treated with a certain degree of skepticism, since only long-term operating experience can answer the questions of the compliance of the declared parameters with real ones and check the decisions on the correct operation of lithium-ion batteries.

This article marks a subjective view on the problem of extending the life of lithium-ion batteries. Digital data is taken from trusted sources ( batteryuniversity.com - lithium-ion (lithium-ion) batteries , from sites of lithium-ion battery manufacturers - Valence, ThunderSky, Everspring), but during the compilation of the information, some overly optimistic statements by battery manufacturers had to be omitted or a few fix, if you notice errors - write.

More information about the different types of batteries you can find on the author's website: http://sdisle.com/battery/

PS I was very surprised that there is no support for text indexes (sub ... / sub tag) on ​​the desktop - due to this some chemical formulas in the article are depicted incorrectly :(.