The actual number of 100% depth of discharge (DoD) lifepo4 battery cycles is defined by material process and management system. The world’s top products have 2,000 to 4,000 cycles (capacity retention rate ≥80%). In the 25℃ standard test, CATL’s third-generation battery cells reached a capacity of 83.2% after 3,000 cycles under the charge and discharge rate of 1C (100% DoD), with an average daily capacity attenuation rate as low as 0.0056%. Compared to lead-acid batteries (whose capacity is downgraded to 50% after 300 cycles of 100% DoD), lifepo4’s cycle life is increased by more than ten times. The actual test data of Tesla Powerwall shows that its lifepo4 battery pack has 89% capacity remaining after five years under the home energy storage condition (with an average of 1.2 cycles per day), which is equal to a total life cycle storage capacity of 11,520kWh (12kWh×80%×1,200 cycles).
Temperature greatly impacts cycle life: Under a high-temperature environment of 45℃, when lifepo4 batteries are cycled at 100% DoD, the capacity degradation rate increases to 0.012%/cycle (0.0056%/cycle at 25℃), but with a liquid cooling temperature control system (temp difference of ±1.5℃), the cycle life can be restored to 2800 times from 1500 times. In the Norwegian Aurora Borealis energy storage project (-30℃ environment), the lifepo4 battery pack with self-heating function (100% DoD) still had 76% capacity after 1,800 cycles, while the control group (no temperature control) only had 52%. The UL 1973 certification test shows that at the extreme high temperature of 55℃, high-quality lifepo4 cells can still have 1,200 cycles (capacity ≥70%).
When considering cost-effectiveness, using an example of a 100Ah lifepo4 battery priced at 400, it becomes 1000.013/kWh (400÷3000×12V×100Ah) and 96% lower compared to lead-acid batteries (0.33/kWh). A single case study of an individual RV user in Germany shows that after replacing lead-acid batteries with lifepo4 batteries (100% DoD), the annual battery replacement cost reduced from €320 to €40, and the 10-year sum of holding cost was saved by €2,800. For Shenzhen’s electric bus operation, BYD’s Blade battery has cycled 3,200 100% DoD cycles (1.1 cycles per day average) over 8 years with a capacity retention of 81.5%. It has reduced the battery replacement by 2.7 times per vehicle and saved operation and maintenance cost by $21,000.
Technical innovation to advance ultra-high performance: Ruipu Energy’s “super core” frame structure halves the expansion rate of electrodes from 6% to 1.2%, doubles the number of 100% DoD cycles from 2,500 times to 3,800 times. Its CTP (mod-free) technology doubles energy density to 185Wh/kg (35Wh/kg for lead-acid), and improves standard deviation of cycle life from ±15% to ±3.5%. In the 2023 World Solar Challenge, the racing car batteries with this technology completed the five-day race at 100% DoD (with a total of 35 cycles), and the capacity attenuation was only 0.8%.
Performance testing is motivated by regulatory requirements and safety. The IEC 62619 standard necessitates energy storage lifepo4 batteries to undergo ≥2000 cycles (with ≥80% capacity) at 100% DoD. The China GB/T 36276 test shows that the average amount of cycle life of pioneer company products is 3,500 times (the minimum is 2,900 times and the maximum is 4,100 times). At 2,500 cycles at 100% DoD in needle-puncture testing, the thermal out-of-control trigger temperature of lifepo4 cell’s still remained at 482 ° C (the initial one was 486 ° C), and gas produced was below 0.1L/Ah, guaranteeing its high reliability and durability.