HP Jornada 820 Replacement Battery F2937A 3.7V 950mAh

HP Jornada 820 / 928 — 3.7V Li-Polymer Replacement Battery (F2937A)

This 3.7V, 950mAh Li-Polymer cell replaces the original F2937A battery in the HP Jornada 820 and Jornada 928 handheld computers. Both devices share the same battery bay, connector pinout, and BMS handshake protocol. Capacity figure is 950mAh (3.52Wh) — taken from the product specification, not estimated.

• Jornada 820 and 928 compatibility: HP used the same battery compartment and three-pin connector across both Jornada models. The BMS in each unit reads cell voltage and temperature from the same pin arrangement, so one replacement cell covers both handhelds without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Jornada 820 unit. The BMS accepted the cell without fault flags, voltage held steady across the operating range, and the charge controller terminated correctly at capacity.
• Sync before you swap: The Jornada 820 holds open files, calendar data, and application state in volatile SRAM powered directly by the main battery. Pull the battery without syncing to ActiveSync first and that data is gone. Run a full sync to your host PC before removing the old cell.

Why the Jornada 820 won't complete its boot sequence after a battery swap

The Jornada 820 boot ROM checks cell voltage before loading Windows CE. If the replacement battery ships at a low state of charge — common with Li-Polymer cells stored for months — the voltage can sit below the threshold the boot ROM expects. The device powers on briefly, shows the HP splash screen, then cuts out before the OS loads. Charge the new cell fully before the first boot attempt. Connect to the AC adapter, wait until the charge LED clears, then power on.

Jornada 820 showing full charge but losing power faster than the original battery

An original battery that has been through years of shallow cycles can have a recalibrated fuel gauge — the device learned a smaller capacity and reads "full" at a lower actual charge. After fitting the new 950mAh cell, the gauge may under-report for the first few cycles until the Jornada recalibrates. Run two or three full charge-to-low-battery cycles to let the fuel gauge re-learn the cell's actual capacity. After recalibration, the charge indicator should track accurately from 4.2V down to the 3.0V cutoff.