Battery SOH Meaning
Description
Battery SOH refers to the State of Health, which is an important indicator used to evaluate the performance and life status of the battery,here is a detailed description:
1.Definition and meaning
1.1 Definition
It reflects the current health of the battery and is usually expressed as a percentage. 100% indicates that the battery is in a brand new state, and the SOH value will gradually decrease with use and aging,when the SOH drops to a certain extent, such as less than 80%, it is generally believed that the performance of the battery has been significantly reduced and may not meet the normal use requirements of the device.
1.2 Significance
For users, knowing the SOH of the battery can help them determine whether the battery needs to be replaced and estimate how long the battery will continue to use,for the battery management system, SOH is an important basis for formulating a reasonable charge and discharge strategy, which helps to extend the service life of the battery and ensure the safe operation of the equipment.
2.Influencing factor
2.1 Cycle Life
The charge and discharge cycle of battery is one of the main factors leading to its aging,each cycle will cause a chemical reaction inside the battery, and with the increase of the number of cycles, the electrode material of the battery will gradually lose, and the battery capacity will gradually decrease, resulting in a decrease in SOH,different types of batteries can withstand different cycles, for example, general lithium-ion batteries after hundreds to thousands of cycles, SOH will be significantly reduced.
2.2 Operating ambient temperature
Temperature has a significant effect on the aging process of batteries,the high temperature environment will accelerate the chemical reaction inside the battery, resulting in increased corrosion and loss of the electrode material, thereby reducing the SOH of the battery,the low temperature environment will reduce the charge and discharge efficiency of the battery, and long-term use in a low temperature environment will also cause irreversible damage to the battery,for example, in the hot summer, if the battery of an electric vehicle is exposed to high temperatures for a long time, its SOH will decline much faster than in a normal temperature environment.
2.3 Depth of charge and discharge
Deep charging and discharging (that is, charging the battery to close to 100% or to close to 0%) is more damaging to the battery, which will accelerate the aging of the battery and reduce the SOH. Shallow charging and shallow discharge (for example, keeping the battery power between 20% and 80%) helps to extend the battery life and maintain a high SOH.
3.Evaluation method
3.1 Battery capacity test
By fully charging and discharging the battery, the actual amount of electricity it can release is measured, and the initial capacity of the battery is compared to calculate the SOH. For example, a new battery has a capacity of 100Ah, and after a period of use, its actual capacity is measured to be 80Ah, then the SOH of the battery is 80%. This method is more direct and accurate, but requires special test equipment, and the test process takes a long time.
3.2 Internal resistance measurement method
The internal resistance of the battery increases with aging, and it can be indirectly assessed by measuring the internal resistance of the battery and comparing it with the internal resistance of the new battery,in general, the greater the increase in internal resistance, the lower the SOH,however, the measurement of internal resistance is affected by many factors, such as temperature, charge and discharge state, and requires accurate calibration and compensation to obtain more accurate results.
3.3 Model estimation method
Based on the electrochemical model and historical data of the battery, a mathematical model is established to estimate the effect of various factors on the aging of the battery,this method can comprehensively consider the influence of various factors on the aging of the battery, and has high accuracy and real-time performance,however, a large amount of experimental data is required to train the model, and the accuracy and applicability of the model are limited by factors such as battery type and use conditions.