JDSU VIAVI MTS-2000 Replacement Battery 7.4V 5000mAh

JDSU VIAVI MTS-2000 / Smart OTDR — 7.4V Li-Polymer Replacement Battery (4-JS001P)

This is a 7.4V 5000mAh Li-Polymer replacement battery for the JDSU VIAVI MTS-2000 portable optical test platform and Smart OTDR series, including the 100AS and E100AS. It replaces OEM part numbers 4-JS001P and 636395. Capacity is 37Wh — matching the original pack specification.

• MTS-2000 and Smart OTDR compatibility: These models share the same 7.4V two-cell Li-Polymer architecture, physical footprint, and BMS handshake protocol. The same pack covers fibre and copper test configurations without modification.
• Bench tested on actual hardware: We ran this pack through probe initialisation sequences on the MTS-2000. The BMS held stable through the current spike at OTDR port power-up — a point where degraded cells often trip the protection circuit and kill the session.
• First-use calibration on MTS-2000: After installing, run a full calibration cycle through the instrument menu before field deployment. The MTS-2000 maps battery state during calibration. Skipping this step causes premature low-battery warnings during the first measurement session, even with a fully charged pack.

BMS lockout after the MTS-2000 sat unused in a carry case for months

Li-Polymer cells self-discharge slowly over time. If the instrument sat unused long enough, the pack voltage may have dropped below the BMS recovery threshold — typically around 2.5V per cell for a 7.4V two-cell pack. At that point the BMS enters a protection lockout state and the charger sees no load, so charging appears to fail entirely. The fix is a slow pre-charge using a compatible charger that supports recovery mode, or connecting the battery and leaving the instrument on the dock for 30–60 minutes at low current until the BMS re-initialises above 6.0V total.

MTS-2000 shuts down mid-measurement with no low-battery warning

This is a voltage sag issue, not a capacity issue. Under sustained OTDR laser firing combined with display and processing load, a degraded or cold cell pack can momentarily drop below the BMS cutoff threshold even when the indicator shows 40–60% remaining. The instrument loses power instantly because the BMS trips on undervoltage, not on capacity. Check cell health by watching the voltage reading in the instrument's diagnostic menu — if voltage under load drops below 6.8V, the pack needs replacing regardless of what the charge indicator shows.