Taiwan's first independent EV battery certification

Before you buy a used EV,see the battery's real health.

Measured by an independent third party. Not the dashboard number. Not the seller's own readout.

Book a test Verify

Sample

How the test worksThree steps, finished on site

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Step 1
Connect the equipment
The tester comes to your home or another agreed place and connects to the car's diagnostic port.
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Step 2
Measure
We run a charge or discharge measurement suited to the model. We do not just read what the battery management system displays.
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Step 3
Get the report and sticker
You get the Cellproof report on the spot. A sticker goes on the window, and anyone can scan it to verify.

CELLPROOFCertificateSample

Valid until 2027/03/18

Model / year: Tesla Model 3 · 2021LFP 60kWh
VIN: *****ABC123
Test date: 2026/09/18
Mileage: 48,200 km
Service tier: Cellproof Verified
State of health (SoH): 94.0 %
Measured usable capacity: 56.4 kWhFactory nominal 60.0 kWhValue shown by the car 57.1 kWh
Cell voltage spread (at rest): 12 mV
Battery temperature spread: 1.5 °C
DC fast-charge share: 18.5 %86 sessions in total
Pack exterior: Pass
Test method: Charge method
Tester: C.L.

This report reflects the state of the battery as measured with the Cellproof test method on the test date. It is not a guarantee of future battery performance, range or lifespan. Battery state changes with use, environment and time. This report is not advice to buy or sell. Cellproof takes no part in vehicle sales and receives no commission on them. While valid, it can be verified by VIN on the cellproof website.

What is this? How Cellproof tests

What you getOne certificate, one sticker

Each car gets one Cellproof report and one certification sticker for the window.

Scanning the QR code on the sticker opens a page like this one. The VIN, the test date and the measured capacity are all on it, so anyone can check them.

This is a sample. The values are not from a real car.

Why test independentlyBecause the seller's number is the seller's

The range on the dashboard is an estimate. It moves with driving habits. The health figure inside the battery management system can be reset or tampered with. A number the seller reads out with their own tool is the seller's number.

Cellproof's number is one we measured ourselves. It is bound to the VIN, and it can be verified online at any time while the certificate is valid.

Why not just usethe car's built-in test?

Built-in testTesla in-car battery health test

Cellproof testIndependent third-party measurement

Who can run it

Only the owner. A buyer cannot run it before handover.

A buyer can ask us to test before handover.

Time needed

Up to 24 hours, with the car on AC power the whole time.

One on-site visit, 2 to 4 hours.

Can the result be verified

A screenshot. No way to confirm which car or which day.

Bound to the VIN. Scan the QR code to verify online.

What you see

One percentage.

Measured kWh, cell voltage spread, DC fast-charge share, photos of the pack exterior.

Whose side

The carmaker.

An independent third party with no part in the sale.

The built-in test is a good tool. The problem is that a buyer cannot get it before handover, and cannot confirm it.

Measured vs the car's built-in test

Validation data is being collected

Cars compared so far: 0

We will publish the data once there are enough cars. Until then we will not claim any accuracy figure.

How accurate are our numbersEvery certificate shows the raw measurement

How we calculate

During a controlled charge or discharge we record the energy going into or out of the battery. We compare it with the nominal capacity from the factory to get the state of health. Every certificate prints both the measured kWh and the nominal kWh, so anyone can redo the math.

How we check ourselves

Whenever the owner agrees, we also run the car's built-in battery health test on the same car and record both results. Once we have enough cars, we will publish the comparison.

Service areasThe tester comes to you

We currently test on site in these areas.

Taipei
New Taipei
Taoyuan
Hsinchu
Taichung

Outside these areas? Ask us on LINE first.

Common questionsWorth knowing before the test

How is Cellproof different from a dealer reading SoH with a scan tool?

We measure the energy going into or out of the battery during a controlled charge or discharge and compare it with the nominal capacity. We also record the cell voltage spread and the fast-charge history. The result is bound to the VIN and can be verified online. A scan tool shows whatever the car's own system claims.

How do I know a sticker or certificate is real?

Scan the QR code on the sticker, or enter the VIN on the verify page. If the VIN on the page does not match the car, it is not our certificate.

Go to verify

How long is a certificate valid?

6 months. A battery changes with use. After that, test again.

Which vehicles do you cover?

Mainly the Tesla Model 3 and Model Y for now. Other models are being added.

See covered vehicles

Buying or selling a car?Check the battery first.

Three tiers, from NT$1,300. The tester comes to you.

Book a test