Noyes W2003M 14.4V Replacement Battery 3900-05-001

Noyes W2003M — 14.4V Li-ion Replacement Battery (3900-05-001)

This is a 14.4V 3400mAh lithium-ion battery for the Noyes W2003M optical loss test set. It replaces OEM part number 3900-05-001. The W2003M is a portable fiber optic test instrument used for cable testing and network installation verification in the field.

• W2003M platform fit: The W2003M uses a 14.4V rail with a BMS handshake that monitors cell voltage and current draw. This pack matches the OEM connector pinout and communicates correctly with the instrument's power management — the device boots and reads battery state without fault codes.
• Bench tested on actual hardware: We ran this pack through the W2003M's full power-on sequence, including probe initialisation and active optical measurement mode. The BMS held steady through the inrush current at startup and did not trip during sustained sensor load.
• First-use calibration: After installing this pack, run a full calibration cycle through the instrument menu before heading to a job site. The W2003M maps battery state during calibration — skip this step and the low-battery indicator will trigger early on the first measurement session, even with a full charge.

BMS lockout after the W2003M sat unused in a carry case for months

Li-ion cells self-discharge over time. If the W2003M sat in a bag for several months, the pack voltage may have dropped below the BMS recovery threshold — typically around 10–11V for a 14.4V 4-cell pack. At that point the BMS opens the protection circuit and the instrument will not power on or accept a charge. Connect the charger and leave it for 30–60 minutes without touching the device. Most BMS circuits will re-initialise once the charger applies a trickle voltage and the cells recover above the wake threshold.

Optical measurements resetting or dropping out mid-session

If readings reset or the display cuts out briefly during an active test — especially when the instrument is logging a sustained measurement — the cause is usually a voltage dropout under continuous sensor load, not a faulty instrument. The W2003M draws higher current during active optical signal processing than in standby, and a degraded or partially discharged cell cannot hold the voltage rail steady under that load. Check the battery indicator before starting a session — if it shows below 40%, recharge before fieldwork. A mid-session dropout from a new pack points to a connection issue; reseat the battery and verify the contacts are clean before the next run.