About this replacement
Viavi MTS-5800 / MTS-5802 OTDR — 7.4V Li-ion Replacement Battery (22015374 / 22016374)
This 7.4V 10400mAh Li-ion battery replaces the internal pack in the Viavi JDSU MTS-5800 and MTS-5802 Optical Time Domain Reflectometers. These are professional fiber optic test instruments used in the field for cable fault location and loss measurement. Capacity figures come from the product data — 76.96Wh total energy at rated voltage.
- MTS-5800 and MTS-5802 platform compatibility: Both units share the same battery bay, connector pinout, and BMS handshake protocol — the instrument reads cell voltage and temperature data over the same communication line, so the pack seats and communicates identically in either chassis.
- Bench tested on actual hardware: We cycled this pack through the MTS-5800 power management sequence, including a laser module activation and port scan loop. The BMS held voltage within tolerance under sustained optical module draw, and thermal reporting stayed within the instrument's acceptance window throughout.
- First-deployment calibration step: After fitting the new pack, run a full calibration cycle through the instrument's system menu before heading into the field. The MTS-5800 maps battery state during that routine — skip it and the low-battery indicator will trigger early on the first measurement session, even with a full charge.
BMS cutoff when the OTDR laser module initialises
When the MTS-5800 powers on its optical module, the laser driver circuit pulls a short but sharp current spike as the port comes online. If the replacement pack's BMS protection threshold is set conservatively, this spike can trip the overcurrent cutoff before the instrument reaches its idle state. The instrument then appears to shut off immediately after the boot screen. Reseating the battery and powering on with the module set to standby mode — rather than auto-launch — gives the BMS time to settle before the high-draw event hits.
Pack not charging after the instrument sat unused in a carry case for months
Li-ion cells that drop below approximately 2.5V per cell enter a deep-discharge state where the BMS latches off to prevent damage. The charger sees no load and does not begin a charge cycle. To recover the pack, connect it to the Viavi charger and leave it for 15–20 minutes — most BMS circuits include a trickle pre-charge mode that slowly raises cell voltage back above the recovery threshold before full charging begins. If the charger LED stays dark after 20 minutes, check that the charger output is reaching 8.4V on a meter before assuming the pack is unrecoverable.