What is the best way to extend the life of rechargeable batteries? 

When using the rechargeable batteries

In order to maximize the performance of rechargeable batteries, it is vital to use cells of equal condition. Use batteries of the same specifications such as: 

• same product code
• batteries that were purchased together
• same (dis)charge time

When charging the rechargeable batteries

• Do not use batteries in high temperatures as this increases internal pressure within the cell, which induces leakage and a shorter service life.
• Recharge the batteries with the same brand charger. 

 When storing the rechargeable batteries

• Make sure you separate the batteries by age and make. Batteries from different manufacturers cause damage, start leaking or can react with each other.
• The recommendation says batteries need to be stored around 15°C. Keep your batteries away from the sun and choose any cool and dry room for storage.  A battery loses charge capacity when temperatures are extreme.