Motorola EU40 Droid Ultra XT1080 Replacement Battery 3.8V 3050mAh

Motorola Droid Ultra XT1080 / Droid Maxx — 3.8V Li-Polymer Replacement Battery (EU40 / SNN5925A)

This is a 3.8V, 3050mAh (11.59Wh) Li-Polymer cell for the Motorola Droid Ultra XT1080, Droid Maxx, XT1080M, and Droid XT1080 MAXX. It replaces OEM part numbers EU40 and SNN5925A. If your original cell has swollen, drains fast, or the phone shuts down unexpectedly, this cell addresses those symptoms at the hardware level.

• XT1080 and Droid Maxx platform fit: Both the standard Droid Ultra XT1080 and the Maxx variant share the same battery bay dimensions, 3.8V nominal rail, and connector pinout — EU40 covers the full platform without modification.
• Bench tested on actual hardware: We cycled this cell through full discharge and charge sequences on the XT1080 platform. The BMS handshake with the charge IC completed correctly, and the fuel gauge IC accepted the cell without throwing a battery health warning.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — prevents erratic percentage readings from day one.

Sudden shutdown at 20–30% on the Droid Ultra XT1080

This is the most common symptom when the original EU40 cell ages. As internal resistance climbs, the cell can no longer sustain voltage under the combined load of the modem radio and display — the voltage drops below the BMS cutoff threshold even though the fuel gauge still reads a percentage. The phone interprets this as a brownout and shuts down hard. A fresh cell with lower internal resistance eliminates the voltage cliff, and the BMS cutoff returns to its factory threshold near 3.0V.

OS reporting wrong battery percentage after cell swap

The fuel gauge IC on the XT1080 uses a coulomb counter calibrated to the discharge curve of the original cell. When you install a replacement, that stored curve no longer matches the new cell's actual behaviour — the result is percentage jumps, early "low battery" warnings, or a charge reading that stalls. Run one full discharge down to automatic shutdown, then charge uninterrupted to 100% with fast charging off. After that single cycle, the coulomb counter re-anchors to the new cell's curve and percentage accuracy returns.