Every lithium battery datasheet carries a cycle life figure, and almost every procurement conversation treats it as a single comparable number. It is not. A cycle life rating is only meaningful alongside two qualifiers: the depth of discharge it was measured at, and the capacity threshold that counts as end of life.
Quote one without the others and the number means very little.
Reading the full specification
Across our commercial range you will see ratings written like this:
| Rating | Where it appears |
|---|---|
| 3,000+ cycles @ 80% DOD | Most commercial traction and ESS packs |
| 3,500+ cycles @ 80% DOD | Deep-cycle energy storage packs |
| 2,500+ cycles @ 80% DOD | Prismatic LFP two-wheeler packs |
| 2,000+ cycles @ 85% DOD | Certain e-rickshaw traction packs |
| 1,200+ cycles @ 80% DOD | NMC two-wheeler packs |
| 800+ cycles @ 80% DOD | Light cylindrical e-cycle packs |
Note the fourth row. 2,000 cycles at 85% DOD is not obviously worse than 2,500 cycles at 80% DOD — it is a different test. The 85% figure discharges the pack deeper on every cycle, which is harder on the cells, and it delivers more usable energy per cycle.
Comparing those two numbers directly, as if 2,500 beats 2,000, is a mistake.
What depth of discharge means
Depth of discharge is how much of the pack's capacity you use before recharging. An 80% DOD cycle on a 100Ah pack draws 80Ah and leaves 20Ah in reserve.
Lithium cells degrade faster the deeper they are cycled. The relationship is not linear: the last 10 or 15 percent of discharge is disproportionately damaging, because the cell spends that time at low state of charge where internal stresses are highest.
This is why a pack cycled to 80% DOD may last several times longer than the same pack cycled to 100%. It is also why reserve capacity is not wasted capacity — it is the margin that buys pack life.
End of life does not mean dead
The industry convention is that a cell reaches end of life when it retains 80% of its original rated capacity. A 100Ah pack at end of life still delivers about 80Ah.
That matters practically. A traction pack that has reached its rated cycle count has not failed and does not need replacing that day. It has lost roughly a fifth of its range. For many fleet operators the correct response is to reassign that vehicle to shorter routes rather than to buy a new pack.
When someone quotes a cycle life figure, it is worth asking which threshold it refers to. Not everyone uses 80%.
Why your real-world number will be lower
Rated cycle life comes from laboratory testing: controlled temperature, controlled charge rate, consistent discharge profile. Real commercial service is none of those things.
The main things that pull real cycle life below the rated figure:
- Temperature. Sustained operation at high ambient accelerates degradation. Our commercial packs specify a -10°C to 55°C operating range; running persistently at the top of that band costs cycle life.
- Charge rate. Fast charging generates heat and stresses cells more than slow charging. A pack fast-charged twice daily will not match a lab figure measured at a gentler rate.
- Partial cycling patterns. Frequent shallow top-ups are generally gentler than deep cycles, but irregular patterns complicate any simple projection.
- Cell balance. Without active balancing, the weakest cell in a series string determines the usable capacity of the whole pack, and that divergence grows with age.
A realistic planning assumption is that a well-managed pack in Indian commercial service will deliver somewhere below its rated figure, and that the gap widens the harder you run it.
Questions worth asking a supplier
- At what depth of discharge was this cycle life measured?
- What capacity threshold defines end of life?
- At what ambient temperature and charge rate was it tested?
- Does the pack perform active cell balancing, or passive?
A supplier who can answer all four is telling you something real. A supplier who quotes a bare number is telling you less than it appears.
If you want help translating a rated figure into an expected service life for your specific duty cycle, that is exactly the sort of question the application engineering desk exists to answer.