How long does the Tesla battery health test take?

Up to 18 hours, depending on battery size and charging power: the car first discharges the battery almost completely, then recharges it in a controlled way. Plan for a night on the wallbox and expect the car to be unusable in the meantime.

Why does the test not start, or say the battery is not discharging?

Usually one of the documented preconditions is not met: the state of charge must be at most 20%, the car must be plugged into AC charging with at least 5 kW, parked and online, and there must be no active alerts or pending updates. Start the test with a half-full battery and you will first wait hours for the discharge, or the start is refused.

Has the battery health test disappeared from my Tesla?

Possibly. With software 2025.26, Tesla removed the test from many cars without announcement or limited it to showing earlier results; it has also disappeared from the user-accessible service mode. There is no official explanation; observers note that Tesla is reworking the tool.

Does the test harm the battery?

The procedure (one deep discharge, then a full charge) is designed by the manufacturer and is unproblematic as an occasional calibration. It is still not a routine tool: Tesla itself limits it to once every six months.

Tesla

Tesla's Built-In Battery Health Test: Steps, Duration, Limits (2026)

Updated: 22 August 2026 · 3 min read

Tesla is one of the few manufacturers with a battery test built right into the car: free, no garage, a percentage as the result. It sounds like the perfect solution and is still the feature people trip over most in the forums: the test refuses to start, seems to take forever, or has vanished after an update.

What the test does — and where to find it

The battery health test sits under Controls → Service → Battery Health. It measures how much energy the battery stores today compared with when it was new and returns the result as a percentage, Tesla's take on the SoH. Technically, the car discharges the battery almost completely and then recharges it in a controlled way. A side effect: the battery management system is recalibrated in the process, which is why the range display often looks more plausible again after the test.

The preconditions — and why the test so often refuses to start

The test only runs when all of this is true at once:

State of charge at most 20% — with a half-full battery you wait, or the start is refused
Plugged into AC charging with at least 5 kW (wallbox or mobile connector, not the rapid charger)
Parked and connected to the internet
No active alerts, no pending software update

This is where the typical frustration comes from: start at 60% and you watch nothing happen for hours while the car discharges first. And a single active alert, however harmless, blocks the start entirely.

How long the test takes

Up to 18 hours, depending on battery size and charging power. In practice: start the test in the evening, leave the car on the wallbox overnight and possibly half the next day. The car is unusable in the meantime. Tesla also limits the test to once every six months — a tool for the occasion, not for routine.

Since 2025.26: the test is disappearing — partially

With software update 2025.26, Tesla removed the test from many cars without announcement: newer models lost the menu item entirely, older ones sometimes only show earlier results, and the test has also vanished from the user-accessible service mode, while individual cars still have it. There is no official explanation; observers note that Tesla is reworking the tool.

For you this means: do not rely on the test being available when you need it — say, shortly before a sale.

What the result is worth when selling

The built-in test is the best free single measurement a Tesla offers. Two things it still cannot do:

It is the manufacturer's self-report. For you as the owner the number is a good reference — to a buyer it remains a value the product reports about itself, with no independent methodology behind it.
It is a snapshot. Whether the battery is stable or currently degrading fast is something no single measurement shows; only a history does.

That is why the tools complement each other: the built-in test calibrates and gives you a reference for today; for a documented and checkable record at the point of sale Akkubrief builds a battery history. Connect once, the history builds itself while you drive as usual, and the signed document is verifiable by any buyer in the browser. The difference from a test is the lead time: a test can be done at any point, a history has to have started earlier. For an overview of every method, from service mode to owner apps, see checking Tesla battery health.