The real health of your Tesla battery.
T4U reads your battery's health straight from your Tesla's BMS: real capacity in kWh, health score with an A–E grade, cell balance. Not an estimate — a measurement.
Health score included in the free version. Read-only: the app never wakes your car.
Your battery, measured — not guessed.
Most apps deduce battery health from displayed range. T4U connects to Tesla's official interface and reads what the car's battery management system actually reports.
- ✓Health score and real capacity — free
- Your SOH as a percentage, your usable kWh, and a clear verdict on your pack's balance.
- ✓A grade you can share
- An A–E grade, positioned against comparable Teslas — useful when selling or buying.
- ✓Always up to date, even asleep
- Measurements arrive on their own, without opening the app and without waking the car. A home-screen widget keeps the latest reading in view.
Everything the car knows about its battery
Each indicator answers one question. Here is what each one measures.
Health score (SOH)
How much of its original capacity your battery retains, with its A–E grade.
Real capacity
Your usable kWh today, versus the pack's capacity when new.
Cell balance
The voltage spread between your pack's weakest and strongest cell groups — an early warning sign.
PremiumThermal spread
Temperature differences across the pack's sensors — a healthy pack heats evenly.
PremiumCharging sessions
Energy delivered, charging efficiency, and your fast-charging peak over the last 12 months.
Cycles and history
Real charge cycles, total energy, and your health curve month after month.
PremiumGroup voltages
4 mV spread96 cell groups, under continuous watch.
The heart of the new version. T4U maps your pack's actual layout and watches the voltage of every cell group and the temperature of every sensor — while you drive, while you charge, while the car sleeps.
- ✓Your pack's real map
- The modules as they are laid out in your car, with the weakest and strongest groups pinpointed by number.
- ✓An early warning, before capacity loss
- A spread that widens month after month, or the same group always lowest, points to a weakening cell — often before any measurable capacity loss.
- ✓Thermal balance
- Every temperature sensor in the pack, side by side: a healthy pack heats evenly.
- ✓A clear verdict
- Balanced, or worth watching — the app tells you plainly, and keeps the history to prove it.
Your pack, live, on your Tesla's own screen.
Open my.tesla-4u.com in the car's browser and enter the code shown in the app: your battery diagnostics appear full screen and update as you drive.
- ✓Cells, live
- The highest and lowest cell groups, with their number and the spread in millivolts.
- ✓Pack and motor temperatures
- Module temperatures, plus front and rear stators and inverters.
- ✓Charging and driving
- Live charging power at the Supercharger, trip consumption, battery preheating.
- ✓Nothing to install, read-only
- A web page paired to your car with a single-use code, revocable at any time from the app.
In the car's browser: my.tesla-4u.com
Your home charging, ready for your expense report.
Charging a company car at home? T4U detects every session charged at home, prices it at your own electricity rate and produces a monthly PDF statement to hand to your employer.
- ✓Detected on its own
- When you plug in, T4U checks whether the car is at home. Nothing to enter, nothing to start.
- ✓At your own rate
- Flat rate, peak/off-peak or EDF Tempo: each session is priced to the minute, following your own time slots.
- ✓Superchargers included
- Your Supercharger sessions are added to the statement, at the amounts billed by Tesla.
- ✓A signed, verifiable PDF
- Monthly or yearly statement, signed and verifiable by QR code. Emailed to you every month if you wish.
📍The car's position is only read when it is plugged in, and only if you turn the statement on. No trips are tracked.
Your battery is your Tesla's most valuable component. Know its condition, prove it when you sell.
Designed to be trusted
Your car, your data. T4U observes — it never acts.
Read-only, by design
The app requests no command permissions: it cannot unlock, act on, or wake your Tesla. No phantom drain caused by T4U.
No trip tracking
T4U records neither your trips nor your movements. Only the charging statement, if you turn it on, reads the car's position when it is plugged in, to recognise your home.
Official Tesla sign-in
You sign in on Tesla's own page (OAuth). Your Tesla password never passes through our servers.
Hosted in France
Your measurements are stored on servers in France, under GDPR.
Free to know. Premium to dig deeper.
The essentials are free, for every Tesla. Premium unlocks the pack's fine-grained measurements, the in-car screen and the charging statement.
- ✓Health score (SOH) measured by the BMS
- ✓Real capacity in kWh
- ✓A–E grade and pack verdict
- ✓Pack diagram and charging sessions
- ✓Shareable health card
- ✓Everything in Free, plus:
- ✓Cell imbalance, group by group
- ✓Thermal spread across the pack
- ✓Internal resistance and open-circuit voltage
- ✓Real cycles and total energy
- ✓Cell map with sensor detail
- ✓Live screen in the car (my.tesla-4u.com)
- ✓Home charging statement as a PDF, for your expense report
Also available in the app: the full MyBatteryHealth report — official PDF certificate, one-time purchase (€24.99).
Tesla battery: your questions
What Tesla owners ask most about their battery's health.
How do I check my Tesla battery's health?
The car itself does not display a health score. T4U signs in to your Tesla account through Tesla's official interface and reads the battery data reported by the car's own battery management system (BMS): health score (SOH), real capacity in kWh, and an A–E grade. The health score is free.
What is a normal degradation for a Tesla battery?
Most Tesla batteries lose the most in their first years, then the curve flattens. What matters is your position against comparable vehicles — same model, similar mileage. T4U grades your battery from A to E and situates it against comparable Teslas.
Is the range displayed by the car a good health indicator?
It is an estimate, sensitive to settings, temperature, and calibration. A measurement taken at the source — what the battery management system itself reports — is more reliable. That is what T4U displays.
Can T4U drain my battery or wake my car?
No. T4U is read-only by design: it requests no command permissions and never wakes the vehicle. It causes no phantom drain.
Why watch the cells, not just the overall score?
Because a weakening cell often shows up in the voltage spread between groups before any measurable capacity loss. T4U watches the 96 cell groups and the pack's temperature sensors continuously, and tells you if the pack stays balanced.
Is a battery health report useful when selling a Tesla?
Yes: the battery is the vehicle's most valuable component, and a documented health status reassures the buyer. T4U offers a shareable health card, and the full MyBatteryHealth report as an official PDF certificate.
Can T4U be displayed on my Tesla's screen?
Yes, with Premium: open my.tesla-4u.com in the car's browser and enter the code shown in the app. Cells, temperatures, motors and charging appear live on the Tesla's screen, read-only, with nothing to install.
How do I justify home charging to my employer?
With T4U Premium's charging statement: every home charging session is detected when you plug in and priced at your own electricity rate (flat, peak/off-peak or EDF Tempo). Every month, a signed PDF statement, verifiable by QR code, lists sessions, energy and cost, Superchargers included. The car's position is only read when it is plugged in, and only if you turn the statement on.
Backed by MyBatteryHealth
T4U is built by the team behind MyBatteryHealth, the EV battery diagnostics platform used by fleet operators and automotive professionals across Europe.
Discover MyBatteryHealthYour Tesla battery has things to tell you.
Download T4U for Tesla and get your first measured health score.
Download on theApp Store