Xiaomi Air 2 Charger Box Compatible Battery 3.7V 250mAh

Xiaomi Air 2 Charger Box — 3.7V Li-Polymer Replacement Battery (AEC482030)

This is a 3.7V, 250mAh Li-Polymer cell that replaces the original AEC482030 battery inside the Xiaomi Air 2 charging case. It powers the case's internal charging circuits that store and top up the Air 2 earbuds between uses. When the original cell degrades, the case can no longer complete full earbud charging cycles — this cell restores that function.

• Air 2 Charger Box compatibility: The Air 2 case runs a low-voltage charging management circuit matched to a 3.7V nominal cell at this exact physical footprint — 31.40 x 20.00 x 5.00mm. The AEC482030 cell connects via a BMS that monitors cell state before passing current to the earbud charging contacts. A mismatched cell voltage or oversized cell body will prevent the lid from closing or disrupt BMS communication entirely.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge passes on the bench. The BMS accepted the cell without error flags, charging current tapered correctly at top-of-charge, and the case passed current to the earbud contacts at expected voltage throughout.
• Case conditioning on first use: After fitting, charge the case via USB-C until the indicator shows full before placing the earbuds inside. The case BMS logs cell capacity on that first full cycle — skipping it causes the charge indicator to report inaccurately for the first several uses.

Why the Air 2 case stops charging earbuds before the indicator shows empty

The case BMS uses a stored capacity map to decide when to release current to the earbud contacts. As the original cell ages, its actual capacity drops well below what the BMS map expects — the circuit cuts output current early to protect the cell, even though the indicator still shows remaining charge. A fresh 250mAh cell resets this mismatch. After one full conditioning cycle through USB-C, the BMS re-maps to the new cell and resumes normal charge handoff to the earbuds.

Case indicator showing full charge but earbuds cut off after one use

This happens when a replacement cell is installed at storage voltage — typically around 3.6V — rather than being fully charged first. The BMS reads the resting voltage as near-full and reports accordingly, but the available capacity under load is minimal. Charge the case uninterrupted via USB-C to 4.2V on the cell before first earbud use. After that single full cycle, the indicator and actual available capacity will align correctly.