About this replacement
Amazon Kindle Fire HDX 8.9 — 3.8V Li-Polymer Replacement Battery (26S1004)
This 3.8V, 6000mAh Li-Polymer battery replaces the original cell in the Amazon Kindle Fire HDX 8.9 tablet, including the 3rd-generation variant (GPZ45RW, GU045RW). It matches OEM part numbers 26S1004, 58-000065, and 58-000059, covering both single and dual-cell configurations listed under those part numbers.
- HDX 8.9 generation fit: The 2nd and 3rd-generation HDX 8.9 tablets share the same battery bay dimensions and connector pinout. Both use a fuel gauge IC that communicates cell state to the OS — the replacement must match the original's voltage profile so that handshake stays intact.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an HDX 8.9 unit. The BMS accepted the charge controller handshake without fault flags, and the fuel gauge IC tracked state-of-charge without dropping into protective cutoff.
- Post-swap fuel gauge reset: After installing this battery, run the tablet down to automatic shutoff, then charge uninterrupted to 100% before use. The HDX 8.9's fuel gauge IC calibrates against the cell it sees — skipping this step causes the OS to display percentages based on the old cell's degraded profile.
Kindle Fire HDX 8.9 shutting down between 15% and 25% remaining
The HDX 8.9 draws hard on the battery when the display is at full brightness and WiFi is actively syncing. Under that combined load, cell voltage drops faster than the fuel gauge IC expects, and the BMS triggers a low-voltage cutoff before the displayed percentage reaches zero. This is a calibration issue, not a faulty cell. Run one full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% — this gives the fuel gauge a real voltage curve to work from and resolves the early cutoff.
Fast charging not available after battery replacement on HDX 8.9
The HDX 8.9 uses Amazon's proprietary charging protocol to enable higher charge rates — the charge controller negotiates this with the connected adapter, not with the battery itself. After a battery swap, the charge controller sometimes defaults to standard rate until it completes one full accepted charge cycle. Plug in the original Amazon 9W adapter, let the tablet charge from near-zero to 100% without interruption, and the fast charge handshake re-establishes on the next session. If you are using a third-party charger, fast charge will not engage regardless of the battery fitted.