About this replacement
HP iPAQ h4100 Series — 3.7V Li-ion Replacement Battery (343110-001)
This is a 3.7V, 1200mAh Li-ion battery for the HP iPAQ h4100, h4135, h4150, and h4155 Pocket PC handhelds. It replaces OEM part number 343110-001 and fits the original battery bay without modification. Capacity is 1200mAh (4.44Wh), matching the factory specification.
- h4100 and h4150 series compatibility: All four models — h4100, h4135, h4150, and h4155 — share the same battery bay dimensions, connector pinout, and 3.7V power rail, which is why a single cell covers the full range.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an h4150 unit. The BMS accepted the charge handshake immediately, reached full voltage without interruption, and held steady under Bluetooth radio load.
- RAM and data state before battery removal: Sync all open files and application data to your host PC before pulling the old battery. The iPAQ stores active RAM contents — including open documents and application state — entirely in battery-backed SRAM. Power removal without syncing first wipes that data instantly.
Why the iPAQ h4100 won't boot after a new battery is installed
A fresh replacement cell ships at partial charge — typically between 30% and 50% of capacity. The iPAQ h4100 boot sequence demands a minimum voltage threshold before the processor initialises. If the cell voltage sits below that threshold, the unit either shows a blank screen or loops back to the boot splash immediately. Connect the device to its charger for at least 30 minutes before attempting the first power-on. Once the cell reaches approximately 3.6V, the boot sequence completes normally.
Bluetooth sync dropping or failing after a battery swap
The h4150 and h4155 Bluetooth radio is voltage-sensitive — at anything below a full charge, the radio transmit power drops and connections become unstable or fail to establish entirely. This is not a pairing issue and re-pairing will not fix it. Charge the device to 4.1V or above before running a wireless sync. A wired ActiveSync connection is the fastest path if you need to transfer data before the battery is fully charged.