Keysight N9330B Replacement Battery 10.8V 4000mAh

Keysight N9330B / N9340B Series — 10.8V Ni-MH Replacement Battery

This is a 10.8V, 4000mAh (43.2Wh) Ni-MH battery for the Keysight N9330B and N9340B handheld spectrum analyzers. It fits both the standard N9330B and the N9340B variants, including the Antennentester and Spektrumanalyzer configurations. Swap this in when the original pack can no longer hold a full charge through a field session.

• N9330B and N9340B platform fit: Both instruments share the same battery bay geometry, connector pinout, and BMS handshake protocol. The 10.8V rail is common across the series, so one pack covers all four fit models without modification.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the N9330B platform and confirmed the BMS communicates state-of-charge correctly to the instrument's power management circuit. No false low-battery flags or premature cutoffs during sustained RF signal capture.
• First-use calibration step: After installing this pack, run a full calibration cycle through the instrument menu before field deployment. The N9330B maps battery state during that calibration pass — skipping it causes the low-battery warning to trigger early on the first measurement session, even with a fully charged pack.

BMS lockout after the N9330B sat unused in a carry case for months

Ni-MH cells self-discharge over storage. If this pack sat discharged for an extended period, the BMS may enter a sleep state and block normal charge acceptance. The charger will show no activity even with a good connection. To recover, apply a slow trickle charge at a low rate for 30–60 minutes to bring the cell voltage above the BMS wake threshold — most chargers with a reconditioning mode handle this automatically. Once the BMS wakes, normal charging resumes and the pack cycles correctly.

N9340B shuts down mid-sweep during active signal logging

The N9340B draws a sustained higher current during continuous sweep and logging operations compared to idle display use. A degraded or partially charged Ni-MH cell sags under that load — the voltage drops below the instrument's cutoff threshold and triggers an immediate shutdown. This is not a firmware fault; it is the BMS protecting the cell. Charge the pack to full before a logging session and verify the instrument reads above 11.5V at startup before beginning a sweep sequence.