What is the self-discharge rate of NiMH batteries when not in use?

Nickel Metal Hydride (NiMH) batteries are rechargeable batteries that experience self-discharge when not in use, which is when the battery loses charge naturally without a load. The self-discharge rate is the percentage of charge a battery loses in a certain period of time, and this rate is affected by many factors, including the manufacturing quality of the battery, storage conditions, the age of the battery, and the battery's chemical composition.
Factors affecting the self-discharge rate
1. Battery manufacturing quality: High-quality batteries generally have lower self-discharge rates. Battery manufacturers take various measures to reduce the self-discharge rate during the production process, such as optimizing the internal structure of the battery and using high-quality materials.
2. Storage conditions: Temperature is an important factor affecting the self-discharge rate. At higher temperatures, the chemical reactions of the battery are more active, resulting in an increase in the self-discharge rate. Therefore, storing the battery in a cooler environment can slow down the self-discharge process.
3. Battery age: As the battery grows in use, its internal structure may change, causing the self-discharge rate to gradually increase. The aging of the battery affects its ability to hold a charge.
4. Battery chemistry: Different battery formulations and manufacturing processes affect the self-discharge rate. Some specially designed batteries, such as low self-discharge (LSD) batteries, can provide lower self-discharge rates.
Self-discharge rate of NiMH batteries
The self-discharge rate of NiMH batteries is usually between 20% and 30% per month, which means that if the battery is fully charged and left unused for a month, its charge may decrease by 20% to 30%. However, this value is not absolute, because the actual self-discharge rate will be affected by the above factors.
Ways to reduce self-discharge rate
1. Low temperature storage: Storing batteries in a lower temperature environment can significantly reduce the self-discharge rate.
2. Partially charged storage: Batteries stored in a partially charged state will have a lower self-discharge rate than fully charged batteries.
3. Regular charging: Regularly charging the battery can reduce the loss of power caused by self-discharge.
4. Use low self-discharge batteries: Choose batteries designed for low self-discharge, such as some brands of low self-discharge NiMH batteries, which can provide better power retention.
Conclusion
The self-discharge rate of NiMH batteries is an important indicator of its performance, which directly affects the battery's ability to retain power when not in use. Understanding the self-discharge rate and its influencing factors can help users better manage batteries, extend the battery life, and ensure that the battery can provide sufficient power when needed. By taking appropriate storage and maintenance measures, the self-discharge rate can be effectively reduced and the battery power can be maintained.