About this replacement
Viavi JDSU MTS-5800 / MTS-5802 — 7.4V Li-ion Replacement Battery (22015374)
This 7.4V, 13500mAh Li-ion battery replaces the OEM pack in the Viavi JDSU MTS-5800 and MTS-5802 Optical Time Domain Reflectometers. It also fits the broader JDSU OTDR platform sharing part number 22015374 or 22016374. At 99.9Wh, it supports extended field sessions where recharging is not an option.
- MTS-5800 and MTS-5802 platform fit: Both instruments share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The pack communicates state-of-charge data directly to the OTDR firmware — the instrument reads cell voltage and reports it through the on-screen battery indicator without any additional configuration.
- Bench tested on actual hardware: We cycled this pack through OTDR power-up, optical port initialisation, and sustained trace acquisition. The BMS held stable under the current spike at laser module power-up and did not trip during back-to-back measurement sessions.
- First-deployment calibration: After installing the pack, run a full calibration cycle through the MTS-5800 instrument menu before heading into the field. The OTDR maps battery state during calibration — skipping this step causes the low-battery warning to fire early on the first measurement session, even with a fully charged pack.
BMS cutoff at OTDR optical port initialisation
When the MTS-5800 powers up its laser module, there is a brief inrush current as the optical port initialises. On a degraded or recently stored pack, the BMS can read this spike as an overload condition and cut the output. The result looks like a spontaneous shutdown at the exact moment the port comes online. A pack with healthy cells and a correctly initialised BMS absorbs this spike without tripping — voltage recovery takes under 200ms and the instrument never sees a dropout.
OTDR not recognising pack after storage
If this battery has sat unused for several months, the BMS protection circuit may enter sleep mode once cell voltage drops below approximately 2.5V per cell. In that state, the MTS-5800 powers on briefly or shows no battery indicator at all — the pack is not dead, the BMS is locked out. Connect the battery to its charger for 15–30 minutes before inserting it into the instrument. Most chargers will push a recovery charge below the normal threshold, which wakes the BMS and returns cell voltage above 3.0V per cell before the OTDR attempts communication.