Most cars are bought used. For the electric transition to complete, a functioning second-hand market has to exist, and it is being held back by a single missing piece of information.
The problem
Battery capacity declines with age and use. A car with eighty percent of original capacity is worth substantially less than one with ninety-five, and there is no standard, trusted way for a buyer to tell which they are looking at.
In the absence of information, buyers assume the worse case and discount accordingly. That penalises well-maintained vehicles and depresses the whole market.
What degradation actually looks like
Better than early fears suggested. Most modern packs lose capacity quickly in the first year or two, then very slowly. Cars with high mileage frequently retain more capacity than expected.
What accelerates it is heat, frequent fast charging, and habitually charging to full and running to empty. A car used gently on home charging degrades remarkably little.
What would fix it
A standardised state-of-health figure, produced by the vehicle, in a comparable format across manufacturers, available to any buyer.
The technical capability exists – the car knows. Manufacturers have been slow to expose it in comparable form, and some regulatory frameworks are beginning to require it.
What a buyer can do now
Independent testing services exist and produce a report. Some manufacturers provide a health figure through their app. Third-party diagnostic tools can read the data on many models.
None of that is as good as a standard, and all of it is better than guessing.
The warranty point
Battery warranties typically run eight years and transfer to subsequent owners, usually guaranteeing capacity above a threshold. Checking the remaining term is the cheapest due diligence available.