Observed arrival · 2026-10-25

NineWatt reads the IONIQ 9 battery cell by cell

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Editorial interest 77/100 Selection signal · not a rating of the site

NineWatt is a phone app for Hyundai IONIQ 9 owners that reads high-voltage battery data through an OBDLink MX+ adapter.

Landing page captured for the 2026-10-25 issue.

For: Hyundai IONIQ 9 owners with an OBDLink MX+
Worth noticing: The page says the app goes quiet after the high-voltage system has been off for a few minutes, to avoid draining the 12 V battery.

Field notes

The described setup relies on a Bluetooth OBDLink MX+ adapter, paired with an iPhone or Android phone. NineWatt says it can display each cell’s voltage and data from 16 temperature sensors, alongside battery-health checks. The site also says readings stay on the phone and the app stops querying the car after its high-voltage system has been off for a few minutes.

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