ZiO Dual D1 Compatible Battery 3.7V 900mAh Li-ion

ZiO Dual D1 / Lupus L1 / Premium P1 — 3.7V Li-ion Replacement Battery

This is a 3.7V 900mAh Li-ion cell for the ZiO Dual D1, Lupus L1, and Premium P1 smartphones. It slots into the same battery bay as the original and connects to the same fuel gauge IC and charge controller. Capacity is 900mAh (3.33Wh) — exactly as rated in the product specification.

• Dual D1, Lupus L1, Premium P1 compatibility: These three ZiO handsets share the same battery bay dimensions (53.00 × 34.00 × 4.80mm), the same 3.7V nominal voltage rail, and the same connector pinout — which is why one cell covers all three models without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a test rig, confirmed the BMS reported correct status to the charge IC, and verified the protection circuit tripped correctly on overcurrent — no false lockouts, no thermal events.
• Fuel gauge recalibration on first cycle: After fitting this cell, run one full discharge to shutdown then charge uninterrupted to 100% before re-enabling fast charging. The fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve during that first cycle — skipping it causes erratic percentage readings in early use.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a high current spike and the cell voltage drops sharply below the BMS cutoff threshold — even though the fuel gauge still shows 20–30% remaining. The fuel gauge IC was calibrated to the old cell's discharge curve, so its capacity estimate no longer matches the actual voltage-to-charge relationship of the new cell. One full discharge-to-shutdown followed by a complete charge corrects the coulomb counter. After that cycle, the reported percentage and actual cell voltage track closely again, and the shutdowns stop.

Phone will not power on after sitting in storage with the replacement battery

Li-ion cells self-discharge during storage, and if the cell drops below approximately 2.5V, the BMS enters a lockout state to prevent damage — the phone will not respond to the power button or show a charging indicator. Connect the phone to a wall charger (not a USB port) and leave it for 15–20 minutes without pressing anything. The charge IC trickle-charges the cell at low current until it climbs above the BMS re-enable threshold, typically around 2.9–3.0V. Once that threshold is crossed, the BMS releases, the charge IC switches to normal CC/CV charging, and the phone boots normally.