Obd

Your Tesla Battery Health Test Says 78%. OBD Says 73%. Which Is Right?

Here’s a question that comes up constantly in Tesla owner forums, almost word for word:

“Coming up on 200k km. Tesla’s battery health test says 78%, but the OBD data works out to about 73%. Where does the difference come from — and which one is right?”

It’s a good question, and the answer matters, because a five-point gap sounds like the difference between a healthy pack and one heading for trouble. So people panic. They shouldn’t — and the reason why is a nice illustration of the difference between a number and a measurement.

Tesla OBD-II Port: What It Is, Where to Find It, and What You Can Do With It

Every Tesla has an OBD-II port. Most owners don’t know it exists, what it does, or why it matters. Here’s the complete guide.

What Is OBD-II?

OBD-II (On-Board Diagnostics, version 2) is a standardized diagnostic interface required on all vehicles sold in the US since 1996. It provides access to the vehicle’s electronic control systems for emissions testing, diagnostics, and real-time data monitoring.

On traditional gas cars, OBD-II is primarily used for emissions-related data. On Teslas — which have no emissions system — the port provides access to the CAN bus (Controller Area Network), the internal communication backbone that connects every electronic module in the car.