How EV Batteries Work
Electric vehicle batteries store energy in lithium-ion cells. During charging, lithium ions move from the cathode to the anode. During discharge (driving), they move back. Over thousands of charge-discharge cycles, this movement causes gradual changes to the cell chemistry and structure — reducing the battery's capacity to hold charge. This process is called degradation.
What Is Battery Degradation?
Battery degradation refers to the gradual reduction in a battery's usable capacity over time. A battery that originally provided 60 kWh of usable energy may provide 54 kWh after several years of use — a 10% reduction. This reduces the vehicle's range proportionally. Degradation is measured as a percentage of original capacity retained.
- New battery: 100% capacity (baseline)
- After 3–5 years typical use: approximately 85–95% capacity retained
- After 8–10 years typical use: approximately 75–85% capacity retained
- Most manufacturers warrant batteries to retain at least 70% capacity for 8 years or 160,000 km
Factors That Affect Battery Longevity
Several factors influence how quickly an EV battery degrades. Understanding these helps operators extend battery life and reduce total cost of ownership.
- Charging frequency and depth: frequent charging to 100% and discharging to 0% accelerates degradation
- Fast charging: regular use of DC fast charging generates more heat and causes more stress than AC charging
- Temperature: extreme heat and cold both accelerate degradation; optimal operating temperature is 15–35°C
- Charge rate: charging at lower rates (AC home charging) is gentler on cells than high-rate DC charging
- Parking in extreme temperatures: leaving a vehicle in very hot or cold conditions without thermal management active
- Calendar ageing: batteries degrade over time even when not in use, particularly at high state of charge
Battery Chemistry and Longevity
Different battery chemistries have different degradation characteristics. Lithium Iron Phosphate (LFP) batteries — used in several WOX vehicles — are known for their superior cycle life and thermal stability compared to NMC (Nickel Manganese Cobalt) chemistries. LFP batteries can typically sustain more charge-discharge cycles before reaching the same degradation level, making them well-suited to fleet applications with high daily utilisation.
| Chemistry | Energy Density | Cycle Life | Thermal Stability | Typical Use |
|---|---|---|---|---|
| LFP (LiFePO₄) | Lower | Very high (3,000–6,000+) | Excellent | Commercial, fleet, city vehicles |
| NMC | Higher | Moderate (1,000–2,000) | Good | Premium passenger vehicles |
| NCA | Highest | Moderate (500–1,500) | Lower | High-performance vehicles |
Battery Management Systems
Modern EVs use a Battery Management System (BMS) to monitor and protect the battery. The BMS tracks cell voltage, temperature and state of charge, and actively manages charging and discharging to stay within safe operating limits. It also provides thermal management — heating or cooling the battery to maintain optimal temperature. A well-designed BMS significantly extends battery life by preventing the conditions that accelerate degradation.
End of Vehicle Life: Second Life and Recycling
When an EV battery reaches the end of its useful life in a vehicle (typically defined as below 70–80% capacity), it is not necessarily at the end of its useful life entirely. Batteries with reduced capacity are increasingly being repurposed for stationary energy storage applications — where the lower energy density is acceptable. At the end of their second life, batteries are recycled to recover lithium, cobalt, nickel and other materials.
Key Takeaways
- 1EV batteries degrade gradually — most retain 80–90% capacity after 8–10 years
- 2LFP chemistry offers superior cycle life for high-utilisation fleet applications
- 3Avoiding 100% charges, 0% discharges and frequent fast charging extends battery life
- 4Battery Management Systems actively protect battery health
- 5End-of-vehicle-life batteries can be repurposed for stationary energy storage
Summary
EV battery degradation is a normal, manageable process. Most batteries retain 80–90% capacity after 8–10 years of typical use. LFP chemistry — used in several WOX vehicles — offers superior cycle life for fleet applications. Avoiding frequent deep discharges, minimising regular fast charging and maintaining moderate temperatures all extend battery life. At end of vehicle life, batteries can be repurposed for stationary storage before final recycling.