EV Battery Degradation Projection Calculator

Studies show EV batteries degrade about 1.5-2.5% per year on average. After 100,000 miles, a typical EV battery retains 85-90% of its original capacity. After 200,000 miles, 70-80% remains. Chemistry matters: LFP (Lithium Iron Phosphate) batteries degrade slower (1-1.5%/year) but have lower energy density. NMC (Nickel Manganese Cobalt) degrades at 1.5-2%/year but offers higher density. The Tesla Model S battery degrades about 5% in the first 20,000 miles then ~1% per 20,000 miles thereafter. Most manufacturers warrant batteries to retain at least 70% capacity for 8 years or 100,000 miles.

Key factors: (1) Fast charging (DCFC) above 80% regularly increases degradation by 1.5-2× compared to Level 2 charging. (2) High state of charge: keeping at 100% for extended periods accelerates calendar aging. (3) Extreme temperatures: sustained operation above 40°C (104°F) or charging below 0°C (32°F). (4) High discharge rates: frequent hard acceleration. (5) Number of full charge cycles: LFP batteries handle 3,000-5,000 cycles vs 1,000-2,000 for NMC. (6) Age: calendar aging continues even without use. Best practices: keep SoC 20-80% daily, limit DC fast charging, park in shade, and use scheduled charging to avoid high-SoC dwell.

Remaining useful life is projected based on degradation curve. First 20,000 miles: ~5% loss (initial break-in). Miles 20,000-100,000: linear ~1% per 10,000 miles. Beyond 100,000: slight acceleration. Formula: Capacity at mileage M = C0 - D0 - (M - M0) × D_rate, where C0 = initial capacity (100%), D0 = initial drop (5% at 20K mi), M0 = initial drop mileage, D_rate = ~1% per 10K mi. For time-based: Capacity at year Y = 100% - 2% × Y. For accurate projection, combine both: use the worse of mileage-based and time-based degradation. Thermal management (active liquid cooling) reduces degradation by ~50% vs passive cooling.

DC fast charging degrades the battery primarily during the last 20% (80-100%). Charging 10-80% on a 350 kW charger causes similar degradation to Level 2 charging due to the constant-current phase. The main stress occurs during the constant-voltage phase above 80%, where high voltage pushes lithium plating. Strategy: charge to 80% on fast chargers, then use Level 2 for the final 20% when practical. Battery preconditioning (heating the battery before charging, standard on Tesla, Hyundai, etc.) reduces degradation significantly. Occasional DC fast charging (1-2×/week) has minimal impact. Daily DC fast charging can reduce battery life by 10-15% over 8 years.