About this replacement
Sony Clie PEG-T400 Series — 3.7V Li-Polymer Replacement Battery (UP523048)
This 3.7V, 850mAh Li-Polymer cell replaces the original battery in the Sony Clie PEG-T400, PEG-T410, PEG-T425, and PEG-T600, along with thirteen additional Clie models. It restores power to the device for contacts, calendar, tasks, and document management. Capacity figure is 850mAh / 3.15Wh, matching the original cell specification.
- Clie T-series compatibility: The PEG-T400, T410, T425, and T600 share the same UP523048 cell footprint, connector pinout, and BMS handshake protocol. One battery covers all four core models without modification.
- Bench tested on actual hardware: We ran this cell on a PEG-T400 and confirmed the BMS accepted the charge cycle without triggering overcurrent cutoff. The device booted normally and Palm OS loaded without prompting a hard reset.
- RAM data protection before swap: Perform a full HotSync to your host computer before removing the old battery. The Clie stores open application state and unsaved data in volatile SRAM powered directly by the main cell. Cutting power without syncing first will erase that data permanently.
Why the Clie PEG-T400 loses all data after a battery replacement
The PEG-T400 uses SRAM for active storage, not flash. SRAM is volatile — it requires continuous voltage to retain data. When the old battery is removed and the new one is not yet installed, that voltage drops to zero and the RAM contents are wiped. This is not a fault with the replacement cell; it is a hardware limitation of early 2000s PDA architecture. To avoid data loss, complete a HotSync immediately before the swap so everything is preserved on the host machine.
Clie PEG-T400 stuck on boot screen after new battery installation
A freshly shipped Li-Polymer cell often arrives at a storage charge of around 3.0–3.2V. The PEG-T400 boot sequence requires a minimum voltage threshold to initialise Palm OS; below that, the device stalls on the startup screen or loops. Do not attempt repeated resets — they drain the cell further. Connect to the OEM charger and allow at least 30 minutes of charge before attempting to power on. Once the cell reaches approximately 3.5V, the boot sequence completes normally.