Bird PT01338 SA2500 GPS Surveyor Replacement Battery 11.1V 5200mAh

Bird SA2500 / SA6000EX — 11.1V Li-ion Replacement Battery (PT01338)

This is an 11.1V, 5200mAh (57.72Wh) Li-ion battery for the Bird SA2500 and SA6000EX GPS/GNSS receivers. It replaces OEM part PT01338 and fits both the SA2500 and SA-2500 designations as well as the SA6000EX and SA-6000EX variants. The same connector, voltage rail, and BMS handshake protocol run across all four model designations.

• SA2500 and SA6000EX platform compatibility: Both receivers share the same battery bay format, 11.1V nominal rail, and BMS communication protocol. A single cell pack covers both instruments without modification — no adapter, no firmware difference between variants.
• Bench tested on actual hardware: We cycled this pack through a full charge-discharge sequence and monitored BMS response at GPS lock acquisition, when the RF front-end draws its highest current. The BMS held the rail stable and did not trigger a low-voltage cutoff during peak initialisation draw.
• First-use calibration cycle: After fitting this battery, run a full calibration cycle through the SA2500's instrument menu before field deployment. The receiver maps battery state-of-charge during calibration — skipping this step causes premature low-battery warnings on the first survey session, even with a fully charged pack.

BMS cutoff at GPS lock acquisition on the SA2500

When the SA2500 achieves first satellite lock, the RF front-end and baseband processor draw a simultaneous current spike that can exceed 2A for several hundred milliseconds. An aged or deeply discharged cell cannot hold the voltage rail above the BMS cutoff threshold during this spike, so the instrument shuts off immediately after the lock tone. This pack's cells are spec'd to handle the inrush without voltage sag triggering a protection event. If cutoff still occurs after fitting a new pack, check that the battery contacts in the bay are clean — resistance at the contact points adds to the effective voltage drop under load.

SA2500 not recognising new pack after the instrument sat unused for months

If the receiver sat in a case for an extended period with a depleted pack fitted, the BMS may have entered deep-sleep mode once cell voltage dropped below approximately 2.5V per cell. In this state, the instrument's charging circuit does not see a valid battery and refuses to begin a charge cycle. Place the pack on a compatible Li-ion charger that supports a pre-charge or recovery mode — this applies a low-current trickle until cell voltage climbs back above 3.0V per cell, at which point the BMS wakes and the SA2500 recognises the pack normally. Do not attempt recovery using a fast charger set above 0.5C until the cells are above that threshold.