Best OBD-II Adapters for Checking a Used EV's Battery Health

A used EV's battery state of health is the biggest number in the deal, and you can measure it yourself. Most EVs report pack data over the OBD-II port under the dash: usable capacity, cell voltages and sometimes a calculated state of health. A small wireless adapter plugged into that port, plus an app on your phone, is enough to read it during a test drive.

The adapter doesn't read anything by itself. A generic code reader won't show battery health, because the parameters are specific to each manufacturer. The app that understands your model is what interprets the data, and each app supports only certain adapters. So pick the app first (for example, LeafSpy for a Nissan Leaf or Scan My Tesla for a Tesla), then buy an adapter on that app's published supported list. Every adapter here is on at least two app developers' lists.

Your phone narrows the choice further. An iPhone can't use a classic-Bluetooth adapter unless the adapter is Apple MFi-certified. It needs a Bluetooth LE, MFi or Wi-Fi adapter, and many cheap dongles are classic-Bluetooth only. Android works with all of them. Teslas need a separate adapter cable as well as the adapter.

Ask the seller before plugging anything in, and unplug the adapter when you're done. Automatic sleep can't be assumed on an EV: Vgate states that its iCar Pro's auto-sleep doesn't work on electric vehicles. Read state of health alongside the car's own display and a range check. The guide on checking used-EV battery health explains how to judge the result.

How we picked

• On the supported-adapter list of the app that reads your EV's battery data
• Works with your phone: Bluetooth LE, MFi or Wi-Fi for iPhone; any type for Android
• Low-power sleep stated by the manufacturer, and unplugged after use on an EV
• Firmware the manufacturer still updates

We do not accept payment for placement and we do not publish star ratings we did not measure. Specifications come from each manufacturer's published spec sheet.

Side by side

The picks

#1 · Bluetooth Classic adapter (works with iPhone)

OBDLink MX+

Check price on Amazon — OBDLink MX+ (opens in a new tab)(paid link)

A Bluetooth OBD-II adapter that works with iPhone, Android and Windows and appears on more of OBDLink's published third-party app lists than any other OBDLink adapter.

Best for: Covering the most EV battery apps on iPhone or Android (Tesla needs an extra cable)

Connection

Bluetooth 3.0 (Class 2), 128-bit encryption

Platforms

iOS, Android, Windows

Protocols

All legislated OBD-II protocols, plus Ford MS-CAN and GM SW-CAN

Operating current

62 mA

Low-power mode

2 mA (BatterySaver), automatic sleep and wake-up

Operating voltage

12 V systems (8–18 V range)

Size / weight

1.97 × 1.77 × 0.91 in, 3 oz

Warranty

3 years, plus 180-day money-back guarantee

• Works with iPhone even though it's classic Bluetooth. Car Scanner's developer names it as one of the few MFi adapters that iOS allows
• OBDLink lists it as the only one of its adapters that works with Scan My Tesla on iPhone. Scan My Tesla's own adapter page lists it for both iOS and Android
• LeafSpy's tested-adapter list includes it (Nissan Leaf)
• Pairing needs a press of the button on the adapter, so nobody else can connect to it

• Teslas need a separate adapter cable as well. The MX+ alone does not plug into the car
• LeafSpy lists it under its iOS-only Apple Bluetooth category. Android Leaf owners should check LeafSpy's list before buying
• More adapter than a one-off pre-purchase check needs, if the app you need also supports the CX

Read the full write-up →

#2 · Bluetooth LE adapter

OBDLink CX

Check price on Amazon — OBDLink CX (opens in a new tab)(paid link)

A compact Bluetooth Low Energy OBD-II adapter that pairs inside the app on iPhone and Android, built for modern CAN-bus vehicles.

Best for: A Nissan Leaf or other CAN-bus EV, read from an iPhone or Android phone

Connection

Bluetooth 5.1 Low Energy (BLE)

Platforms

iOS, Android (no Windows)

Protocols

ISO 15765 (CAN), SAE J1939, ISO 11898, ISO 9141, ISO 14230. No J1850, MS-CAN or SW-CAN

Operating current

55 mA

Low-power mode

Under 1 mA (BatterySaver)

Operating voltage

12 V systems (8–18 V range)

Size / weight

1.8 × 0.9 × 1.3 in, 0.7 oz

Warranty

3 years, plus 180-day money-back guarantee

• LeafSpy lists it in its "Android & iOS" BLE category and names it as a recognized adapter. No phone pairing step needed
• Car Scanner's developer recommends it for iOS and Android
• Bluetooth LE works with any recent iPhone without needing MFi
• Small and light enough to stay out of the way under the dash during a test drive

• OBDLink says it won't work on GM, Ford and some FCA vehicles built before model year 2008. That's not a problem for most used EVs, but it limits the adapter on an older gas car
• Not on OBDLink's or Scan My Tesla's supported lists for Scan My Tesla
• Sold as a BMW coding adapter ("Made for BimmerCode"), so the box doesn't mention EVs

Read the full write-up →

#3 · Dual-mode Bluetooth adapter

Vgate iCar Pro Bluetooth 4.0 (BLE)

Check price on Amazon — Vgate iCar Pro Bluetooth 4.0 (BLE) (opens in a new tab)(paid link)

A low-cost ELM327-compatible adapter that connects over Bluetooth LE on iPhone and over classic Bluetooth on Android.

Best for: A low-cost adapter for a one-time battery check

Connection

Bluetooth 4.0 LE (iOS) and classic Bluetooth (Android). Shows as IOS-VLINK and ANDROID-VLINK

Platforms

iOS, Android

Protocols

All OBD-II protocols: SAE J1850 PWM/VPW, ISO 9141-2, ISO 14230-4, ISO 15765-4 CAN, SAE J1939

Sleep

Sleeps 30 min after engine stop. Vgate says auto start/sleep does not work on electric vehicles

Firmware

Updatable (Vgate download center)

• LeafSpy's tested list includes it (BT3 on Android, BLE on iOS), and Car Scanner's developer recommends it
• Works with both iPhone and Android. On iPhone you connect inside the app, not in Bluetooth settings
• Covers every legislated OBD-II protocol, so it also works on older gas cars

• Vgate says its automatic sleep doesn't work on electric vehicles. Unplug it after the check or it can keep drawing from the EV's 12 V battery
• Car Scanner warns that firmware older than v4.1.02 mishandles the CAN extended addressing Toyota and BMW use. Update it before testing one of those
• Vgate's site gives no warranty term, only a return window

Read the full write-up →

Working out what you need before you buy? Read the ev finance & ownership guides.