About this replacement
Rohde & Schwarz FSH4 / FSH8 Series — 7.2V Li-ion Replacement Battery (HA-Z204)
This 7.2V 10200mAh Li-ion pack replaces the HA-Z204, 1309.6130.00, and HA-Z206 batteries in the Rohde & Schwarz FSH4, FSH8, FSH13, and FSH20 handheld spectrum analyzers. These instruments are used for field-based RF measurements, cable and antenna analysis, and spectrum surveying — work that happens away from mains power for extended periods. At 73.44Wh, this pack keeps the instrument running through full measurement sessions without a recharge stop.
- FSH4 / FSH8 / FSH13 / FSH20 platform fit: All four models in the FSH series share the same battery bay dimensions, connector pinout, and BMS handshake protocol. A single pack format covers the full series because Rohde & Schwarz standardised the power rail across these handheld analyzers from the FSH4 onward.
- Bench tested on actual hardware: We ran this pack through the FSH4 power-on sequence, signal sweep, and tracking generator activation. The BMS passed the instrument's handshake without error flags, and the cell voltage held steady under the combined processor and RF front-end load during sustained sweeps.
- Post-install calibration cycle: After fitting this pack, run a full calibration cycle through the FSH instrument menu before field deployment. The FSH maps battery state during calibration — skipping this step causes the instrument to report premature low-battery warnings during the first active measurement session because it is still referencing the old cell's discharge curve.
BMS cutoff when the FSH tracking generator or pre-amplifier activates
The FSH4 and FSH8 draw a brief but sharp current spike when the tracking generator or internal pre-amplifier first powers up — these subsystems pull from the same battery rail as the main processor. A pack with degraded cells or an overly conservative BMS threshold will read that spike as an overcurrent event and cut the output before the measurement begins. This replacement pack uses cells rated for the peak current the FSH's RF subsystems demand at activation. If the instrument still shuts off at that moment, confirm the battery contacts are clean and that the pack is seated fully — partial contact increases resistance and amplifies the apparent current spike.
FSH won't power on after the pack sat unused in the carry case for months
Li-ion cells self-discharge slowly in storage, and a pack left unused for several months can drop below the BMS recovery threshold — typically around 2.5V per cell. When that happens, the BMS enters a protection lockout and the instrument shows no response at the power button, which looks identical to a dead pack but is not the same failure. Connect the battery to the FSH charger and leave it for at least 30 minutes without interruption — most BMS circuits begin a trickle pre-charge recovery below 3.0V per cell before resuming normal charge current. If the charge indicator does not activate within 45 minutes, check charger output voltage at the connector: it should read between 8.2V and 8.4V under no-load.