Viavi 120 DSP Compatible Battery 3.7V 2600mAh Li-ion

Viavi 120 DSP / Seeker Series — 3.7V Li-ion Replacement Battery (0090048000)

This 3.7V 2600mAh Li-ion cell replaces OEM part 0090048000 in the Viavi 120 DSP and Seeker family of fiber optic leakage detectors. It fits the Seeker, Seeker D, and Seeker D Lite alongside the 120 DSP. Capacity is 9.62Wh — matching the original pack's energy rating.

• 120 DSP and Seeker platform fit: These models share the same 3.7V single-cell architecture, connector pinout, and BMS handshake protocol — one pack covers all variants listed. The battery communicates state-of-charge to the instrument's firmware, so the cell must match the original voltage curve exactly.
• Bench tested on actual hardware: We cycled this pack through charge and full optical-scan load sequences on a 120 DSP. The BMS held cutoff voltage cleanly at the low-cell threshold and accepted a full charge cycle without triggering protection flags.
• First-use calibration on the 120 DSP: After installing, run a full calibration cycle through the instrument menu before field deployment. The 120 DSP maps battery state during calibration — skipping this step causes premature low-battery warnings on your first measurement session.

BMS lockout after a Viavi 120 DSP sat unused in a carry case for months

Li-ion cells self-discharge during storage. If the 120 DSP sat idle long enough, the pack voltage can drop below the BMS recovery threshold — typically around 2.5V per cell — and the protection circuit locks out the charge path entirely. The instrument shows no charging activity and may not power on at all. Connecting to a charger that supports trickle or pre-charge mode at low current can nudge the cell voltage back above the recovery threshold and re-enable normal charging. If the cell has dropped below 2.0V, recovery is not always possible and a replacement pack is the correct fix.

120 DSP shuts down during USB data transfer to a PC

USB data transfer pulls current from the same power rail as the optical circuitry. When both loads run simultaneously, total draw can spike past what a partially discharged or degraded cell will sustain — the BMS trips on undervoltage and the unit cuts off mid-transfer. This is not a firmware fault. Charge the pack to at least 3.9V before initiating any USB export session. If shutdowns continue on a fully charged pack, the cell's internal resistance has risen enough that it can no longer hold voltage under combined load — replace the battery.