About this replacement
Sony Clie PEG-TJ27 / PEG-TJ37 — 3.7V Li-Polymer Replacement Battery (UP553048-A6H)
This is a 3.7V, 750mAh lithium-polymer battery replacing part number UP553048-A6H in the Sony Clie PEG-TJ27 and PEG-TJ37 handheld PDAs. Both devices use the same cell format, connector, and BMS handshake. Dimensions are 48.79 × 29.00 × 4.95mm — measure your original before fitting.
- PEG-TJ27 and PEG-TJ37 compatibility: Both models share the same battery bay geometry, 3.7V supply rail, and UP553048-A6H part number. The BMS protection thresholds are identical, so one cell fits both without modification.
- Bench tested on actual hardware: We cycled this cell through charge, idle, and active-display draws on a TJ-series unit. The BMS held low-voltage cutoff correctly and recovered from a depleted state without tripping the protection circuit.
- Sync before you swap: The Clie PEG-TJ27 stores open application data and user state in SRAM powered directly by the main battery. Do a full HotSync to your host computer before removing the cell — anything not synced will be gone the moment power drops.
Why the Clie PEG-TJ27 won't boot after a fresh battery install
Li-polymer cells ship in storage state, typically around 3.0–3.2V. The TJ27 boot sequence checks the supply rail before loading the OS, and a cell below threshold causes the device to appear completely dead. This is not a fault with the battery or the PDA. Connect the device to its charger for at least 30 minutes before pressing the power button, then attempt the boot with the charger still attached.
Calendar and contacts wiped after battery replacement
The TJ27 keeps its PIM data — contacts, calendar, memos — in volatile SRAM, not flash. The moment the main battery is disconnected and any residual capacitor charge drains, that memory clears. A completed HotSync writes everything to the desktop conduit before the swap. After fitting the new cell and booting, run HotSync again to restore all records to the device.