South X11 Data Controller BP-5S Compatible Battery 7.4V 2600mAh

South X11 Data Controller — 7.4V Li-ion Replacement Battery (BP-5S)

This is a 7.4V, 2600mAh Li-ion replacement for the South BP-5S battery pack. It fits the X11 Data Controller — a field surveying instrument used for data collection, positioning, and mapping work. Voltage, connector, and BMS communication match the original pack specification.

• X11 Data Controller fit: The X11 runs a 7.4V rail with a BMS handshake that checks cell voltage and pack ID at power-on. This replacement carries the correct two-cell Li-ion configuration and communicates cleanly with the X11's charge management circuit — no forced workarounds needed.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge sequences on the X11 platform. The BMS reported no fault codes, accepted a standard CC/CV charge profile, and held the voltage rail steady under sustained sensor and GPS logging load.
• First-use calibration on the X11: After installing this pack, run a full calibration cycle from the X11 instrument menu before heading to site. The instrument maps battery state during that sequence — skip it, and the low-battery warning will trigger early on your first measurement session even with a full charge.

BMS lockout after the X11 sat unused in a carry case for months

Li-ion cells self-discharge slowly in storage. If the X11 sat unused long enough, the pack can drop below the BMS recovery threshold — typically around 2.5V per cell. At that point, the controller treats the pack as a fault condition and blocks normal charging. Most chargers will not attempt recovery automatically. Connect the pack to a Li-ion charger that supports a pre-charge or recovery mode, which applies a low current until cell voltage climbs above 3.0V per cell, then resumes normal charging.

X11 shuts down mid-session during active GPS or data logging

Sustained GPS acquisition combined with active logging draws continuous current that a degraded or partially charged cell struggles to sustain. When cell voltage sags under that load, the BMS trips a low-voltage cutoff to protect the cells — the instrument shuts off even if the battery indicator showed capacity remaining. This is a voltage-sag cutoff, not a capacity failure. Charge the pack to full before field deployment and verify cell voltage reads above 8.0V at the X11 battery status screen before starting a long logging session.