About this replacement
HP iPAQ 3600 Series — 3.7V Li-Polymer Replacement Battery (253514-B21)
This is a 3.7V, 1300mAh Li-Polymer replacement battery for the HP iPAQ 3600 series Pocket PC. It fits the iPAQ 3630, 3635, and 3641, among other models in the same line. The OEM part numbers covered include 253514-B21, PE2030A, PE2030, PE2031, and PE2031A.
- iPAQ 3600 series fit: These models share the same 3.7V voltage rail, Li-Polymer cell format, and BMS handshake protocol. Swapping between them uses the same connector and charge circuit — the battery works across the range without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the iPAQ platform. The BMS held stable cutoff at the correct low-voltage threshold and accepted a full charge from the cradle without fault flags or thermal events.
- Pre-removal sync requirement: Perform a full ActiveSync data sync to your host PC before removing the old battery. The iPAQ 3600 holds open files, contacts, and application state in SRAM powered directly by the main cell — pulling the battery without syncing first will wipe unsaved data.
Why the iPAQ 3600 loses RAM data during a battery swap
The iPAQ 3600 uses SRAM for active storage — unlike flash memory, SRAM loses its contents the moment power drops to zero. There is no internal backup cell on this platform to bridge the gap during a swap. Even a two-second power interruption is enough to clear the RAM entirely. Sync everything to ActiveSync before you remove the battery, then install the new cell and restore from the sync record.
iPAQ 3600 won't boot after new battery installed
A fresh Li-Polymer cell ships at a partial state of charge — sometimes as low as 3.0V — which falls below the minimum voltage the iPAQ boot sequence requires. The device will appear dead even though the battery is functional. Place it in the charging cradle for at least 30 minutes before attempting a boot. Once the cell reaches approximately 3.6V, the device will power on and complete the boot sequence normally.