EV defects: battery, charging, and software

What's different about EV defects

State lemon laws were written for internal-combustion vehicles. The drafters in the 1980s and 1990s assumed mechanical defects: transmissions, engines, brakes. The presumption frameworks — "three repair attempts" or "30 days out of service" — translate cleanly to mechanical failures.

EV defects are different. The high-voltage battery pack is a single sealed assembly that can either work or not work; partial battery degradation doesn't fit the traditional "defect" framework cleanly. Charging-system failures involve both hardware (the on-board charger, the charging port) and software (charging-curve management, communication with charging networks). Over-the-air software updates can introduce new defects after vehicle delivery — a scenario that didn't exist when most state lemon laws were drafted.

Battery defects

Three battery-defect patterns generate most of the EV cases we evaluate:

• Capacity degradation beyond expected curve. EV battery packs lose capacity over time as a normal characteristic. But unusual degradation — a 30% capacity loss in the first two years, for example — falls outside normal patterns and may indicate a defective pack.
• Charging restrictions imposed by the manufacturer. Manufacturers sometimes impose over-the-air charging restrictions in response to fire-risk recalls or pack-failure investigations. A vehicle whose charging speed is permanently limited — making it functionally a different vehicle than what was sold — may support a claim.
• Outright battery failures. Complete loss of high-voltage propulsion. These are typically warranty-covered as battery-pack replacements, but the timeline to replacement can stretch months, and during that time the vehicle is undriveable. State "days out of service" presumptions become highly relevant.

Charging-system defects

Charging defects often manifest as intermittent failures that the dealer cannot reproduce. The vehicle won't charge at home, but it charges at the dealer. The vehicle won't fast-charge on the highway, but the diagnostic at the service center shows no error.

This pattern — defect occurs in the wild, defect can't be reproduced in service — is exactly the pattern MMWA was designed to address. Every "could not duplicate" service write-up is documentation that the manufacturer's service network failed to repair. After enough of those, the manufacturer has had a reasonable opportunity and failed to take it.

Software defects

Over-the-air software updates can change vehicle behavior dramatically. An update can extend range, add features, or — rarely — introduce defects that weren't present at delivery. Common software-defect patterns we see: regenerative-braking behavior changes that surprise drivers, ADAS (advanced driver assistance systems) becoming more conservative and triggering false-positive interventions, infotainment systems freezing or crashing after an update.

The legal treatment of software defects is still evolving. Our view: a written warranty that covers the vehicle covers the software that runs the vehicle. If a software defect renders the vehicle non-conforming to the warranty, MMWA applies.

Why most EV cases run through MMWA, not state lemon law

Most state lemon laws have specific procedural requirements that don't map cleanly to EV defects. Florida's 24-month presumption window, for example, predates EVs entirely. The federal MMWA framework is more flexible because it doesn't prescribe a specific number of repair attempts — it requires a "reasonable opportunity to repair," which a court can adapt to the specific facts.

This is why we file most EV cases under MMWA, often with a state lemon-law claim layered in where the facts support it. The federal claim provides the procedural flexibility; the state claim provides additional remedies in jurisdictions where state law is consumer-favorable (Florida, California under Song-Beverly, Vermont).

If you own an EV with documented battery, charging, or software defects that the manufacturer hasn't resolved, take our case quiz. EV cases are part of our core practice.