About this replacement
YUT SF620 / SF650 / SF760 Series — 10.8V Li-ion Replacement Battery (DC-19)
This 10.8V Li-ion battery replaces the OEM DC-19 pack across YUT's SF620, SF650, SF760, and CTS-22A surveying and measurement instruments. It delivers 5200mAh (56.16Wh) of capacity to keep instruments running through full site sessions. The cell format and connector match the original pack exactly.
- SF620 / SF650 / SF760 / CTS-22A platform compatibility: These models share the same 10.8V three-cell battery bay, connector pinout, and BMS handshake protocol — one pack covers all of them without any modification.
- Bench tested on actual hardware: We ran this pack through the SF620's probe initialisation sequence and sustained logging load. The BMS held stable through the current spike at sensor power-up and maintained consistent voltage under extended measurement cycles.
- First-deployment calibration step: After installing, run a full calibration cycle through the instrument menu before field deployment. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings during your first measurement session on site.
BMS cutoff at probe or sensor initialisation on the SF620
When the SF620 powers up its probe module, it draws a short, sharp current spike to initialise the sensor circuitry. On a degraded or deeply discharged pack, that spike can push the BMS over its instantaneous discharge threshold, triggering a protective cutoff before the instrument finishes booting. A fresh pack with healthy internal resistance absorbs the spike without tripping. If the instrument shuts off at the splash screen, charge the battery to full before retrying — a partial charge is not enough to clear the cutoff margin.
Pack will not charge after months unused in carry case
Li-ion cells left in a carry case for several months can self-discharge below the BMS recovery threshold — typically around 2.5V per cell. When voltage drops that low, the BMS enters sleep mode and blocks charge current, so the charger shows no activity and the instrument shows no sign of life. Place the pack on the charger and leave it for at least 30 minutes — most BMS circuits include a low-voltage recovery pathway that trickle-charges the cells back above the wake threshold. If the charger light does not change after 45 minutes, cell voltage has likely fallen below 2.0V per cell and recovery is not possible.