About this replacement
Motorola Droid Razr HD / Razr MAXX HD (XT926) — 3.8V Li-Polymer Replacement Battery (EV40 / SNN5913A)
This is a 3.8V, 3200mAh Li-Polymer replacement battery for the Motorola Droid Razr HD, Droid Razr MAXX HD, and XT926 smartphones. It replaces OEM part numbers EV40 and SNN5913A. The cell fits the stock battery bay without modification and connects via the original flex-ribbon clip.
- Razr HD and MAXX HD platform fit: Both the Razr HD and Razr MAXX HD share the same 3.8V battery architecture, connector pinout, and BMS handshake protocol — which is why a single cell covers both models. The EV40 part number spans the full XT926 platform.
- Bench tested on actual hardware: We ran this cell in an XT926 unit and confirmed the BMS handshake completed on first boot. The charge IC accepted the cell without a fault flag, and voltage held stable across screen-on and modem-active load cycles.
- Fuel gauge recalibration on first use: After installing this cell, disable fast charging and run one full discharge-to-charge cycle before relying on the battery percentage indicator. The fuel gauge IC on the Razr HD calibrates its coulomb counter against the cell's actual discharge curve — skipping this step can cause the percentage readout to drift by 10–15% until the IC resets its baseline.
Sudden shutdown at 20–30% on the Razr HD after a cell swap
The Razr HD's fuel gauge IC was calibrated to the discharge curve of the original cell. A new cell has a slightly different voltage-versus-capacity curve, so the IC underestimates remaining charge and triggers a low-voltage shutdown before the display reaches 0%. This is not a faulty battery — it is a mismatch between the stored discharge map and the new cell. Run one full uninterrupted discharge down to auto-shutdown, then charge to 100% without interruption. After that cycle, the coulomb counter re-anchors to the new curve and shutdowns at low percentage stop.
USB charging not recognised on first plug-in after replacement
On the first connection after a cell swap, the Razr HD's charge IC sometimes fails to negotiate the charging handshake because the new cell presents a higher impedance than the depleted original. The phone may show no charging animation or report "charging paused." Disconnect the cable, wait 30 seconds, and reconnect — this resets the charge IC negotiation cycle. If the issue persists, connect to a 5V 1A charger rather than a fast charger for the first cycle; the lower current demand lets the IC complete the handshake against the uncalibrated cell. After one full cycle, normal charging resumes.