Lithium battery cycle life and capacity fade — what fleets need to plan for

• Table of Contents

1. Cycle life expectations by chemistry
2. Capacity fade trajectory
3. End-of-service-life criteria
4. Replacement interval planning

Lithium auxiliary bank cycle life and capacity fade behaviour directly affects fleet TCO and replacement planning. Quality LFP bank delivers 3000–6000 cycles to 80% capacity with proper care. Understanding the fade trajectory helps fleet managers plan replacement before capacity affects operational reliability.

Cycle life expectations by chemistry

LFP: 3000–6000 cycles to 80% capacity with proper care. NMC: 1500–3000 cycles. Cycle counted as one full discharge from 100% to ~10% SOC; partial cycles count proportionally. Daily parking AC use averages 0.5–1 cycle per night.

Capacity fade trajectory

Early life (0–500 cycles): minimal fade (typically <5%). Mid-life (500–3000 cycles): linear fade to 90% capacity. Late life (3000–5000 cycles): accelerated fade to 80% capacity. End-of-service-life: typically defined as 80% of rated capacity — system still functional but with reduced run-time.

End-of-service-life criteria

80% capacity (default OEM definition). 70% capacity for cost-conscious fleets accepting reduced run-time. Capacity fade tracking via BMS SOH metric — most quality BMS report SOH continuously. Plan replacement when SOH approaches threshold.

Replacement interval planning

Typical commercial LFP auxiliary bank: 6–10 years to 80% capacity in normal parking AC use. Plan capital replacement in TCO model. Reactive replacement after failure costs 30–50% more than planned replacement.

Frequently asked questions

How many years does a lithium auxiliary battery last?

6–10 years to 80% capacity for quality LFP in normal parking AC use. Depends on cycle frequency and thermal exposure.

What defines end of service life?

80% of rated capacity is the conventional definition. System remains functional below this but with reduced run-time.

Can I extend cycle life with better practice?

Yes. Avoid extreme temperature, limit fast-charge use, charge to 90% daily, balance loads. Best-practice operation can extend cycle life by 30–50%.