Cyrus CS20 Replacement Battery 3.7V 3400mAh CYR10022

Cyrus CS20 — 3.7V Li-ion Replacement Battery (CYR10022)

This is a 3.7V, 3400mAh Li-ion replacement battery for the Cyrus CS20 smartphone. It fits directly in place of the original CYR10022 cell. Use this when the original battery no longer holds a useful charge or the phone shuts down unexpectedly under load.

• CS20 fitment: The CS20 uses a fixed connector pinout and a specific cell footprint (69.00 × 47.70 × 10.40mm). This replacement matches both, so the BMS handshake between the charge IC and the cell completes without errors on first boot.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the CS20 platform. The BMS accepted the cell, charge termination triggered correctly at 4.2V, and no thermal events occurred during the fast-charge phase.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one full discharge-charge cycle at standard rate. The CS20's fuel gauge IC is calibrated to the old cell's discharge curve — one slow cycle lets it remap against the new cell before fast charging pushes higher current into an uncalibrated state.

Why the CS20 reports wrong battery percentage after a cell swap

The CS20 uses a coulomb counter in its fuel gauge IC to estimate state of charge. That counter is calibrated against the discharge curve of the original cell. When a new cell goes in, the stored curve no longer matches actual cell behaviour, so the percentage readout drifts — sometimes by 15–20%. One complete discharge to cutoff followed by a full charge to 4.2V resets the reference point. After that cycle, percentage accuracy returns to normal.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a high current pulse and the cell voltage drops below the BMS cutoff threshold faster than the fuel gauge expects. The CS20's fuel gauge still shows 20–30% because it hasn't updated, but the actual cell voltage has already sagged past 3.2V under load. The fix is to complete two full discharge-charge cycles so the coulomb counter can build an accurate low-end voltage map. If shutdowns continue past three cycles, check that the battery connector is fully seated — a partially connected cell increases internal resistance and worsens voltage sag under load.