About this replacement
Palm M130 / M135 — 3.7V Li-ion Replacement Battery (F21918595)
This 3.7V, 750mAh Li-ion cell replaces the original battery in the Palm M130 and M135 handheld PDAs. These devices store calendar, contacts, and application data in RAM powered directly by the main battery — so a dead or degraded cell means lost data, not just a dark screen. The F21918595 is the correct OEM part number for both models.
- M130 and M135 compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V power rail. The BMS handshake is identical across both, so one cell covers either unit without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Palm M130. The BMS accepted the charge without flagging an incompatible cell, and voltage held stable at 3.7V nominal across the test load.
- Sync before you swap: Perform a full HotSync to your host computer before removing the old battery. The M130 and M135 hold open application state and unsaved records in volatile RAM — cutting main battery power without syncing first will wipe that data permanently.
Why the Palm M130 loses all data when the battery goes flat
The M130 has no internal flash storage for active application data. Everything in RAM — open memos, unsaved calendar entries, installed apps — is kept alive by a continuous trickle from the main battery. The moment the cell drops below the BMS cutoff voltage, that RAM loses power and clears completely. This is not a firmware bug; it is how the hardware was built. A working, charged battery is the only thing standing between your data and a full reset.
Palm M130 shows the charging screen but never reaches full charge
A replacement Li-ion cell shipped in storage state can arrive at a resting voltage too low for the M130's charger to enter its normal CC phase. The device may display the charging animation while the charger sits in trickle pre-charge mode and never advances. Connect the PDA to its cradle or cable and leave it undisturbed for at least two hours before checking status. If the battery reaches approximately 3.7V resting voltage after that session, the charge circuit has recovered and subsequent charges will complete normally.