About this replacement
Sony Clie PEG-J25 / PEG-TJ35 — 3.7V Li-Polymer Replacement Battery (PL-383450)
This 3.7V, 1350mAh Li-Polymer cell replaces the original PL-383450 battery in the Sony Clie PEG-J25 and PEG-TJ35 handheld PDAs. Both devices run Palm OS and store contacts, calendar data, and application state in RAM that depends on continuous battery power. Swapping this cell restores full PDA operation when the original battery no longer holds a charge.
- PEG-J25 and PEG-TJ35 compatibility: Both models use the same PL-383450 cell with identical voltage rail, connector pinout, and physical footprint at 61.20 × 34.69 × 3.92mm. The BMS on each device communicates charge state the same way, so one cell covers both units without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on PEG-series hardware. The BMS accepted the cell without fault codes, balanced to full charge correctly, and held voltage within the expected range across load cycles.
- RAM data sync before removal: Perform a full HotSync to your PC before removing the old battery. The Clie stores open application state, unsaved memos, and contacts in volatile RAM powered directly by this cell. Cutting power without syncing first can wipe that data permanently.
Why the Clie PEG-J25 loses saved data after a battery swap
Palm OS devices keep a portion of working data in SRAM, which requires continuous battery voltage to retain its contents. When the main cell drops below roughly 3.0V or is removed entirely, that SRAM loses power and the data it holds is gone. This is not a fault with the new battery — it is how the architecture works. The fix is a HotSync before any battery work, so the host PC holds a full backup ready to restore.
Clie not booting after new battery installed
A freshly shipped Li-Polymer cell can arrive at a storage charge of around 3.6–3.7V, which is below the minimum threshold some Palm OS boot sequences require. The device may power on briefly then shut down, or show nothing at all. Charge the new cell fully before attempting the first boot — connect to the Clie cradle or USB cable and allow a complete charge cycle to 4.2V. After that, boot proceeds normally.