Rohde & Schwarz FPH-B29 Compatible Battery 10.8V 5200mAh

Rohde & Schwarz FPH-B29 / FPH-B100 Series — 10.8V Li-ion Replacement Battery

This is a 10.8V, 5200mAh (56.16Wh) lithium-ion battery for the Rohde & Schwarz FPH-B29, FPH-B100, FPH-B100 type N RF, FPH-K7, and related field analyser platforms. It fits instruments used in RF spectrum analysis, cable and antenna testing, and telecommunications field surveys. Voltage and cell count match the OEM specification directly.

• FPH platform compatibility: The FPH-B29, FPH-B100, and FPH-K7 variants share a common 10.8V three-cell architecture and the same physical connector format. The BMS handshake protocol and charge termination threshold are consistent across this family, so one pack covers the full range listed.
• Bench tested on actual hardware: We cycled this pack through the FPH instrument's charge and discharge routine, monitoring BMS communication at probe power-up — the point where current draw spikes sharply. The pack held the rail without triggering a BMS cutoff event across repeated measurement sessions.
• First-use calibration before field deployment: After installing this pack, run a full calibration cycle through the instrument's system menu before heading into the field. The FPH maps battery state during that calibration pass. Skipping it causes the low-battery indicator to fire prematurely on the first active measurement session, even when charge is adequate.

BMS cutoff at probe or module initialisation on the FPH platform

When the FPH-B100 or FPH-K7 powers up an RF probe or test module, inrush current spikes briefly above steady-state draw. Ageing cells with elevated internal resistance can't sustain voltage across that spike, and the BMS interprets the voltage dip as a fault — cutting the pack off. A fresh pack with lower internal resistance holds the rail above the BMS threshold during initialisation. If the instrument cuts out specifically at the moment a module connects or a measurement routine starts, this is the mechanism.

Pack won't charge after the instrument sat in a carry case for months

Lithium-ion cells self-discharge during storage. If the FPH sat unused long enough for cell voltage to drop below roughly 2.5V per cell, the BMS enters a sleep state and blocks standard charge current as a protection measure. Connect the instrument to the OEM charger and leave it for at least 15–20 minutes without interrupting the connection — most FPH chargers apply a low recovery current (trickle mode) before switching to full charge. If the charge indicator still doesn't activate after that hold period, check that cell voltage at the pack terminals reads above 8.0V total before assuming the pack is unrecoverable.