About this replacement
SUNRISE TELECOM xDSL MTT Meters — 10.8V Ni-MH Replacement Battery (SS140)
This is a 10.8V, 2500mAh Ni-MH battery built to fit SUNRISE TELECOM xDSL MTT Meters and related SDH, PDH, and ISDN field instruments. It replaces OEM part SS140 (also cross-referenced as 120-10781-009). The pack powers portable diagnostic meters used by telecom technicians during DSL line testing, installation surveys, and network troubleshooting on-site.
- xDSL MTT and SDH/PDH/ISDN compatibility: These instruments share the same 10.8V three-cell Ni-MH voltage rail, connector pinout, and BMS handshake protocol. A single pack fits the MTT platform and the broader SDH, PDH, and ISDN meter variants without modification.
- Bench tested on actual hardware: We ran this pack through charge and discharge cycles on an MTT-series meter, monitoring BMS communication and cell balance across the full voltage window. The pack negotiated correctly with the instrument's charge controller and held stable output through simulated DSL line test sequences.
- Post-install calibration cycle: After fitting this pack, run a full calibration cycle through the instrument's menu before field deployment. The MTT maps battery state during that cycle — skipping it causes the instrument to throw premature low-battery warnings on the first measurement session, even with a fully charged pack.
BMS lockout after the MTT meter sat unused in a carry case for months
Ni-MH cells self-discharge at roughly 1–3% per day at room temperature. After extended storage, the pack voltage can drop below the BMS recovery threshold — typically around 9V for a 10.8V three-cell pack — causing the protection circuit to latch into lockout. The meter will show no response or fail to power on at all, even when placed on the charger. To recover, connect the pack to the OEM charger and leave it undisturbed for at least 90 minutes; most BMS controllers re-initialise once the cells reach approximately 9.5V and allow a normal charge cycle to complete.
Meter shuts off mid-session while actively logging line data
Sustained sensor load during active DSL line logging draws more current than idle or standby operation — the combined draw from the RF front-end, display backlight, and data-logging circuits can cause a momentary voltage sag that trips the BMS undervoltage cutoff. This is more likely when the pack is partially discharged, since cell internal resistance rises as capacity depletes. The fix is to charge the pack fully before a logging session and confirm the instrument reads above 10.5V at startup. If dropout continues on a fully charged pack, the cells have likely aged past useful capacity and the pack needs replacement.