About this replacement
Motorola CD920 / CD928 / CD930 — 3.7V Li-ion Replacement Battery (SNN5360)
This is a 3.7V, 1150mAh Li-ion cell built to the SNN5360 specification. It fits the Motorola CD920, CD928, CD930, MR602, and several related models from the same early-2000s candybar family. Swap it in when the original cell no longer holds a usable charge between calls.
- CD920 / CD928 / CD930 / MR602 family: These models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. One cell fits all of them without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS held the charge cutoff at the correct 4.2V ceiling and triggered the low-voltage protection at the expected floor — no runaway charge events observed.
- Fuel gauge recalibration on first use: After installation, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before normal use. The phone's fuel gauge IC was calibrated to the old cell's discharge curve — this single full cycle resets it to the new cell so percentage readings stay accurate.
Why the CD920 reports wrong battery percentage after a cell swap
The CD920 tracks charge state using a fuel gauge IC that builds a model of the cell's discharge curve over time. When you swap in a new cell, that stored model still reflects the old degraded battery. The gauge reads voltage points on the old curve and maps them to incorrect percentages on the new cell. One full discharge-to-shutdown followed by an uninterrupted charge to 100% forces the IC to rebuild its model against the new cell's actual curve.
Sudden shutdown at 20–30% remaining on the new cell
This happens when the cell hits a voltage cliff — a point where voltage drops sharply under the load of an active call or backlight. The fuel gauge shows 20–30% because it is reading the resting voltage, not the loaded voltage. Under GSM transmit bursts, current draw spikes and the cell voltage collapses below the BMS cutoff threshold. If this occurs repeatedly, charge to 100%, let the phone sit idle for five minutes, then check if the resting voltage reads above 4.1V — if it does, the gauge just needs another full calibration cycle.