FSH-Z32 Spectrum Analyzer Replacement Battery 7.2V 3500mAh Ni-MH

Rohde & Schwarz FSH3 / FSH6 / FSH18 Series — 7.2V Ni-MH Replacement Battery (FSH-Z32)

This is a 7.2V 3500mAh Ni-MH replacement battery for the Rohde & Schwarz FSH-Z32 battery module. It fits the FSH3, FSH6, FSH18, and related handheld spectrum analyzers used in field RF measurement and telecommunications maintenance. Voltage and capacity match the original FSH-Z32 specification exactly.

• FSH3, FSH6, FSH18 compatibility: These analyzers share the same FSH-Z32 battery bay, connector pinout, and charge management interface. The instrument reads cell voltage directly — no proprietary authentication chip is involved, so a correctly rated Ni-MH pack is recognised without handshake issues.
• Bench tested on actual hardware: We cycled this pack through the FSH charge circuit and monitored BMS behaviour at full load. The pack accepted the delta-V termination signal correctly and held voltage stable under sustained RF sweep loads without tripping a premature cutoff.
• Pre-deployment calibration on first install: After fitting this battery, run a full instrument calibration cycle through the FSH menu before heading into the field. The analyzer maps battery state during calibration — skipping it causes the low-battery warning to trigger well before actual depletion on the first measurement session.

FSH spectrum analyzer shutting down mid-sweep with no low-battery warning

The FSH series draws a brief current spike each time the RF front-end sweeps a wide span or activates the preamp. An aged or deeply discharged Ni-MH pack sags under that spike, and the instrument interprets the voltage drop as a fault condition rather than a low-battery state. This triggers an abrupt shutdown instead of the normal warning sequence. A fresh pack at full charge recovers quickly from these transient draws and maintains the voltage above the shutdown threshold. If shutdowns continue after a full charge, confirm the pack voltage under load reads above 6.8V with a multimeter before blaming the instrument.

Pack will not charge after the analyzer sat unused in a carry case for months

Ni-MH cells self-discharge steadily during storage — at room temperature, a fully charged FSH-Z32 pack can drop below 5.5V after several months unused. The FSH charge circuit uses delta-V termination and may refuse to initiate a charge cycle if it detects voltage this low, treating the pack as a fault rather than a deeply discharged cell. To recover the pack, apply a low-rate trickle charge externally at 0.1C (350mA) for 30–60 minutes until cell voltage climbs above 6.0V, then reinsert and charge normally through the instrument. If the pack fails to hold above 6.0V after the trickle recovery, the cells have sulphated and the pack should be replaced.