Tesla battery health: SoH, degradation and inspection results

What is Battery Health and SoH?

In the context of capacitance testing, SoH (State of Health) usually refers to an estimate of stored energy relative to the initial state. Please specify the definition and calculation method for each report. This is not a direct measurement of each cell or a diagnosis of all nodes in a high-voltage system. One percent is useful only along with the method, date, vehicle configuration and test conditions.

Tesla describes the built-in Battery Health score as a calculation based on battery management system data, comparing expected energy storage for a given battery type, age and operation. In test mode, the screen shows the percentage of energy saved compared to the new battery. Evaluation and full search for faults answer different questions.

Wear over time and use is expected, but abrupt change, active warning, sudden power limitation, or repeated charging failure require verification. A low or high percentage alone does not establish the cause and does not confirm the safety of a high-voltage system.

Where to look for built-in assessment

On supported vehicles, open Control → Service → Battery Health. The name and location of the menu depend on the version of the software. In the Model 3 and Model Y manuals, Tesla separately warns that the Battery Health Test feature is not available on every car. So ask the seller to open a menu on a particular car, rather than sending an instruction or screenshot from another Tesla.

If the car only shows an assessment, check if a separate check has been started. The Tesla Battery Health Test requires a suitable AC charge and can take up to 24 hours. In guidelines checked on October 2, 2026, the launch conditions include AC power of at least 5 kW, charge below 20%, Park mode, no pending upgrade and active battery or thermosystem alerts; the car also requires a network connection. These requirements may change along with the manual and the software, so check the procedure for a specific VIN and do not try to bypass locks.

The test discharges the battery during the procedure, can temporarily turn off functions and climate, and the screen after it can recalculate the estimate of the driving range. Follow the vehicle's directions and instructions; do not leave people unattended in the cabin during the test. If you need to disconnect the cable, first cancel the test in a regular way. If the launch is unavailable due to a warning, Tesla recommends contacting the service.

Do not mix the three types of driving range

WLTP is a certification indicator for comparing specific versions in the European test cycle. Verify the exact version, drive and wheels. This is not the promise of such mileage on any trip, nor is it a direct measurement of the remaining capacity of an old car.

The number of kilometers on the screen when parking is an estimate of the remaining energy at a standardised energy-consumption rate. The European Model 3 and Model Y guidelines indicate that the displayed range is based on EPA-rated consumption and does not take into account entirely personal style and external conditions; Tesla notes that the EPA differs from tests in other regions. Therefore, do not compare screen kilometers with European WLTP as the same values.

The Energy app or itinerary forecast uses a recent expense, selected travel period, route, and conditions. In fact, the kilometers traveled only apply to this trip. For a practical estimate, look at the Wh/km consumption and repetitive trips in similar conditions, rather than a single episode or 100% reading.

Why mileage changes without battery failure

Cold can temporarily make some energy unavailable, limit recovery and charging speed; a snowflake may appear on the screen. Cold interior, heating of the battery, heat and air conditioning increase consumption. Once the temperature changes, the available energy and calculation may change. This effect of operating conditions does not in itself prove permanent degradation.

Speed, acceleration, headwind, lifts, short trips, cargo weight, tire pressure and condition, road gradient, wheel size and external trunks also change energy consumption. Security, climate and other parking functions consume energy. These factors reduce the distance on a single charge, but are not equal to the SoH measurement.

Illustration: A conditional 90% as a result of the Battery Health Test means approximately 90% energy conservation relative to the baseline state using this test method. This does not mean that the car has 90% of its lifespan, that the mileage will always be exactly 90% of the WLTP, or that the battery is good in every way. This is a hypothetical example of a percentage reading, not a residual lifespan forecast.

How to Read an Independent Service Report

Before paying, ask for the method: Tesla car evaluation, code reading, external tester, or diagnosis of a specific symptom. Find out the year, software and configuration compatibility of this Model 3/Y, what values it measures, launch conditions, limitations and error. The word SoH or certificate on the form does not reveal accuracy in itself.

The report must include the date, VIN or clear identification of the car, mileage, software version, charge level, temperature or other relevant conditions, equipment and method, source data, result and agreed limitations. Finding a defect requires active and stored errors, proven systems, and an explanation to confirm the alleged cause. Ask to separate the measured fact, the error code and the master hypothesis.

Repeated values are comparable only if the method and conditions are known. Do not apply the universal SoH threshold for purchase and do not decide on a difference of several percent without considering the method. There is no single number that divides all Model 3/Y into good and bad.

Guarantee and Purchase Decision

Tesla’s limited battery and drive warranty may specify minimal capacity retention, but the timing, mileage, threshold, exclusions, and evaluation procedure depends on the vehicle version, market, and document valid for a particular VIN. Find the car’s warranty document and ask Tesla to confirm the remaining coverage in writing. Do not consider the minimum warranty as the recommended level for purchase: the warranty describes the conditions of handling, not the desired condition of the used car.

Before the transaction, ask the seller questions:

• Are there active notifications from the battery or thermosystem?
• Was the Battery Health Test conducted and when?
• Can I see the result screen and the full report?
• Have there been repairs to the battery, drive or charger and have the documents been preserved?
• What is the rest of the warranty for a particular car?
• Can I have an independent diagnosis before payment?

Practical order: check the VIN, the exact version and the wheels; check the notifications in the car menu; request Battery Health and test conditions; compare with the written report and history; evaluate the usual route and availability of charging by consumption, not just by WLTP; check the warranty and cost of further diagnosis. In case of active warning, conflicting data or refusal to show the car, lay the check by a specialist or postpone the decision until the cause is clarified.

Safety

Work with a high-voltage battery is performed only by a trained specialist. Do not open the case, do not disconnect high-voltage connectors and do not measure the elements yourself. When warning, follow the vehicle's instructions and contact Tesla via the app; if the car requires a stop, follow this instruction.