How to Check a Used Tesla's Battery Health Before You Buy (2026)

Personal opinion, not affiliated with any dealership.

I've bought and sold hundreds of Teslas. On every one of them, the battery is the question that decides whether the deal makes sense. Here's how I check it, in the order I'd do it on a test drive.

Mileage on its own tells you less than people think. I've charged a 2013 Model S with about 110,000 miles to 100%, and it still showed roughly 180 of the ~200 miles it was rated for new. I've also seen plenty of Model 3s past 100,000 miles with healthy packs. What matters is how the pack has aged, how it was charged, and whether the car reports any faults.

The short version

Put the car in Service Mode (in effect a built-in scan tool) and look for battery, drive unit or electrical faults. Look, don't touch.
Do the real-world test: charge to 100% (ask a private seller to do it before you arrive) and drive 10–20+ miles to see how fast the percentage falls.
Look at Controls > Service > Battery Health on the screen, if the car has it.
Do the range math (below). It works on every Tesla, takes two minutes and needs no tools.
Check the battery warranty that's left, based on the in-service date.
Watch for alerts that block the test. Those are a red flag on their own.

Step 1: Check Service Mode for faults

Every Tesla has a built-in Service Mode, the same back-end screens technicians use to diagnose the car. Anyone can open it, and it's easy. Tesla's service manual gives the steps: tap Controls > Software, press and hold the large "MODEL" name for a couple of seconds, type service in the access-code box, and tap OK. The screen gets a red "SERVICE MODE" border or overlay. [7]

Once you're in, open Service Alerts and then go through the High Voltage, Drive Inverter and Low Voltage sections, looking for any active codes, faults or alerts. Tesla's Service Mode guide uses those names, but the layout changes with software updates, so the screens on a given car may look a little different. [10] A clean car shows nothing alarming there. Anything flagged on the battery or drive units is something I'd want explained, in writing, before going further.

Caution: look, don't touch. Service Mode is meant for technicians. Don't change any settings, run any routines or calibrations, or toggle anything. You can mess up the car. Read the screens, take photos, and exit through Controls > Service Mode > Exit Service Mode. [7] If you're looking at a seller's car, ask before you open it.

Step 2: The real-world test (charge to 100% and drive)

This is the best test I know. Charge the car to 100%, then drive it 10–20 miles or more in normal driving and watch how fast the percentage drops. A healthy pack loses charge at a steady, believable rate for the miles you drove. A pack that falls off quickly, or a percentage that suddenly drops, is a warning sign.

The hard part is getting the car to 100% before you buy it. Many dealers will let you take the car on an overnight test drive, so you can charge it to 100% at home and run your own test. If an overnight test isn't possible, ask for it in writing that you can return the car if the battery turns out to have problems or is more degraded than you were told.

With a private seller, I ask them to charge the car to 100% before I come to look at it. That way I can see the full-charge range on arrival and run the drive test right away.

On a lithium-ion car, charging to 100% for one test is fine. Tesla's daily advice for those packs is a lower limit, and 100% is for road trips. LFP cars are meant to sit at 100% anyway. See "Know which battery you're looking at" below.

Step 3: Tesla's own Battery Health screen

Tesla's owner's manual describes a Battery Health screen at Controls > Service > Battery Health. It compares the pack to what's expected for its type, age and use. There's also an optional Battery Health Test that gives a percentage of energy retained compared with new. [1]

What the test needs, per Tesla [1]:

An AC charger delivering at least 5 kW. A wall connector works; a Supercharger doesn't.
The car in Park, with less than 20% charge and no pending software update.
No active battery (BMS) or thermal (VCFRONT) alerts.
Up to 24 hours. The car runs itself down below 10%, possibly to 0%, and climate control is off during the test.

Two cautions:

Not every car has it. Tesla's manual says your car may not be equipped with the test. [1] A third-party guide reports that software 2025.26 removed it from many newer cars and left some older ones showing only their last result. [2] Treat that as reported, not confirmed by Tesla.
Check the date on the result. A seller can run the test the night before you show up. That's fine, but know when it was run. [2]

Step 4: The range math (works on any Tesla)

Set the range display to miles, not percent.
Note the miles shown and the battery % at the same moment.
Full-charge range = miles ÷ % × 100. For example, 201 mi at 60% works out to 335 mi.
Divide that by the original EPA range for that exact trim and wheel size. Look it up at fueleconomy.gov. [3]

Example from a published guide: a Model Y showing about 334 miles projected against a 357-mile EPA rating comes to about 93.6%. [2]

Get the comparison right:

Use the EPA figure for the wheels the car shipped with. Bigger wheels carry a lower rating. [2]
A cold battery reads low. If you see a blue snowflake by the battery icon, the pack is cold. Drive it for a while or check it after it's been plugged in. [2]
A car that only ever does small top-ups can show a range estimate that has drifted below what the pack really holds. [2]
A Tesla that sits unplugged loses some range every day while it keeps the pack at a safe temperature. A car showing a little less than yesterday isn't automatically a bad battery.

What number is "normal"?

I don't use a fixed walk-away number, because every EV loses some range as the miles go up. Judge the car against its age and mileage:

Newer, lower-mile car: I'd expect the battery to still be above 90% of its original range. Below that on a young car, I'd want to know why.
Most of the loss happens early, in roughly the first year or two or the first 20,000–30,000 miles, and then it levels off. That's what I've seen, and it lines up with Recurrent's fleet data: most EVs lose a small amount of range in the first year, and the rate slows after that. [11]
High-mile cars can still be healthy. Tesla's 2022 Impact Report says Model S and Model X batteries keep about 88% of their capacity on average after 200,000 miles. [8]
My own reference points: my 2019 Model 3 Standard Range Plus was rated about 240 miles and showed about 221 on a full charge after four years. The 2013 Model S above lost under 10% in a decade.

Part of why Teslas hold up is their liquid thermal management, which actively heats and cools the pack. Older EVs like the Nissan Leaf have packs with no active liquid cooling, and they tend to show more wear. On a Leaf, check the capacity bars beside the charge gauge instead.

Step 5: What about an OBD reader?

I've never used an OBD reader on a Tesla. I don't need one: Service Mode is basically a scan tool built into the car, and it shows the battery, drive-unit and electrical faults I'd be looking for (Step 1). Third-party adapters and apps such as Scan My Tesla do exist and read the battery management system directly [4], but they're not part of how I check a car. Service Mode plus the 100% drive test is what I rely on.

Step 6: Check what's left on the battery warranty

As of October 2026, Tesla's battery and drive unit warranty for a new car runs 8 years / 100,000 miles on the base Model 3 RWD and 8 years / 120,000 miles on the Model 3 Premium and Performance versions, with at least 70% capacity retention. [5] Tesla says the warranty follows the car to the next owner when the ownership transfer goes through Tesla, and once the car is in your app you can see it under Specs & Warranty. [5] Older cars carry whatever warranty came with them, so check that car's warranty document. The clock starts at the original in-service date, not the model year or the day you buy it. [6] Many owners sell before the battery warranty runs out, so a lot of used Teslas still carry a balance.

Know which battery you're looking at

Some Teslas have LFP (lithium iron phosphate) packs, mostly base rear-wheel-drive cars from about 2022 on. Others have lithium-ion (NCA/NMC). Two cars that look identical can have different packs, so check:

Controls > Software > Additional Vehicle Information. LFP cars list "High Voltage Battery type: Lithium Iron Phosphate." Other cars don't list a type. [9]
The charge-limit slider. LFP cars show "50%" and "100%"; lithium-ion cars show "Daily" and "Trip." [9]

They're charged differently. For LFP, Tesla recommends keeping the limit at 100%, even for daily use, and charging fully at least once a week. [9] On a lithium-ion car, the car warns you if you set it to 100%; keep daily charging lower and save 100% for trips. Ask the seller how they charged it. A lithium-ion car that was kept at 100% and Supercharged every day is the pattern I'd be most wary of.

PNW notes

Cold, wet mornings drop the displayed range. Don't panic over a 38°F reading. Check again when the car is warm.
I don't use a fixed buffer percentage for the passes. Put your real route into the car's trip planner before a winter trip over Snoqualmie or White Pass. It accounts for temperature, elevation, wind and tire pressure, and it tells you where to stop and how long. Driving from Tacoma to Spokane, mine routed me through North Bend before the pass and then a stop on the east side.
Leave with a good charge in winter, and precondition: use scheduled departure, or navigate to the Supercharger so the car warms the pack on the way.
The health baseline still applies: on a newer, low-mile car I'd expect 90%+ of original range before you think about buffers at all.

Red flags that should slow you down

Service Mode shows faults or alerts on the battery, drive units or electrical system.
The Battery Health test won't start because of a battery or thermal alert. Ask which alert. [2]
On the 100% test, the percentage drops much faster than the miles you drove.
A newer, low-mile car that's already well under 90% of its original range.
Impact damage underneath. Get down and look under all four corners and along the battery pack for dents or scrapes.
A charging history of 100% every day plus daily Supercharging on a lithium-ion car, especially with very high annual miles.
A seller who won't let you see the Battery Health screen, won't allow a 100% test, and won't put a return option in writing.

Sources

Tesla Model 3 Owner's Manual, High Voltage Battery Health: https://www.tesla.com/ownersmanual/model3/en_us/GUID-B9807218-7291-4F68-9AFF-7C525CF498F3.html
tbx.report, How to check a used Tesla's battery health: https://tbx.report/guides/used-tesla-battery-health
EPA/DOE fuel economy data: https://www.fueleconomy.gov
Scan My Tesla diagnostics guide (zverski.eu): https://tesla.zverski.eu/en/articles/all-scan-my-tesla-diagnostics
Tesla Vehicle Warranty: https://www.tesla.com/support/vehicle-warranty
Tesla New Vehicle Limited Warranty (PDF): https://digitalassets.tesla.com/tesla-contents/image/upload/tesla-new-vehicle-limited-warranty-en-us.pdf
Tesla Service Manual, Service Mode (enable/disable): https://service.tesla.com/docs/Model3/ServiceManual/en-au/air/GUID-1295FB92-F7BD-4CF2-AA5B-C7D23A978AB2.html
InsideEVs, Tesla: battery capacity degradation averages 12% after 200,000 miles (2022 Impact Report): https://insideevs.com/news/664106/tesla-battery-capacity-degradation-average-2022/
InsideEVs, Tesla recommends charging Model 3 RWD's LFP battery to 100% (quotes the owner's manual): https://insideevs.com/news/557527/tesla-model3-lfp-charging-recommendations/
Tesla Service Mode User Guide (PDF): https://service.tesla.com/docs/Public/ServiceMode/service_mode_user_guide.pdf
Recurrent, Is it normal for my EV's battery to lose range after the first year?: https://www.recurrentauto.com/questions/is-it-normal-for-my-evs-battery-to-lose-range-after-the-first-year