About this replacement
Microsoft Xbox Elite Series 2 (Model 1797) — 3.7V Li-Polymer Replacement Battery (DYND01)
This 3.7V, 1800mAh Li-Polymer battery replaces the DYND01 cell inside the Xbox Elite Series 2 wireless controller (Model 1797). It fits the original battery bay and connects to the same charge management circuit Microsoft uses on the stock cell. Dimensions are 51.80 × 30.00 × 12.10mm — measure your existing cell before ordering if you are unsure.
- Model 1797 fitment: The Elite Series 2 uses a single Li-Polymer pouch cell running a 3.7V nominal rail. The BMS on the controller board reads cell voltage directly, so the replacement must match that voltage or the charge IC will fault before the cell is full.
- Bench tested on actual hardware: We ran this cell through the Elite Series 2 charge circuit and confirmed the BMS accepted the cell without fault codes. Charge current ramped normally through CC and CV phases with no thermal flag.
- First-cycle calibration on the Elite Series 2: After installing, run one complete wireless play session — with rumble active — until the controller powers off automatically. This lets the fuel gauge IC lock in the empty reference point against the new cell's discharge curve. Skip this step and the battery indicator will read inaccurately for several sessions.
Why the Elite Series 2 fuel gauge jumps around after a cell swap
The Elite Series 2 uses a coulomb-counting fuel gauge that builds its capacity model against the original cell's discharge curve over time. Fit a new cell and that stored model no longer matches the actual chemistry, so the percentage reading can jump — often showing full, then dropping sharply mid-session. The gauge recalibrates automatically over three to five full discharge-to-charge cycles. Running the controller wirelessly with rumble on accelerates this process because it draws heavier current, giving the gauge IC more data to work with per cycle.
Controller drops wireless connection before the battery indicator hits empty
This happens when the cell voltage sags below the controller's cutoff threshold under combined wireless radio and rumble load — even though the resting voltage looked fine a moment before. A degraded or unconditioned cell has higher internal resistance, which causes a larger voltage drop the instant high current is drawn. The BMS reads that sag as a low-voltage event and shuts the controller down to protect the cell. After two or three full conditioning cycles, internal resistance drops and the sag under load narrows — confirm by checking that the controller now holds a steady connection through heavy rumble sequences.