About this replacement
ROSE EPG-0244-2 — 9.6V Ni-MH Replacement Battery (161-0025)
This is a 9.6V, 4000mAh Ni-MH replacement battery for the ROSE EPG-0244-2 GoTo telescope. It powers the motorised mount, handset controller, and onboard digital systems. Part number 161-0025 matches the OEM battery specification for this model.
- EPG-0244-2 mount compatibility: The EPG-0244-2 uses a 9.6V Ni-MH cell pack to drive both the RA and DEC slew motors. The connector pinout and BMS discharge curve on this replacement match the OEM pack. The mount controller reads voltage state-of-charge continuously — a mismatch here causes false low-battery warnings or premature motor cutoff during slew.
- Bench tested on actual hardware: We ran this pack through full charge-discharge cycles and verified BMS cutoff behaviour under simulated slew load. Peak current draw during a fast slew engaged the protection circuit at the expected threshold, then recovered cleanly. Tracking load at sidereal rate held steady voltage throughout.
- GoTo alignment after every battery swap: The EPG-0244-2 stores star alignment data in volatile RAM. Every time the battery is removed — even briefly — that alignment is gone. After fitting this replacement, run a fresh two-star or three-star alignment before attempting any GoTo slew. Skipping this step will send the mount to the wrong coordinates.
Motor stalling mid-slew on the EPG-0244-2
Slew motors on the EPG-0244-2 pull significantly more current at startup than during steady tracking. A battery with degraded capacity or high internal resistance will sag below the mount controller's voltage floor during that startup surge. The controller reads this as a fault and cuts motor power mid-move. If the replacement battery is fresh off a full charge and the stall still occurs, check that the battery terminals are fully seated — a loose connection adds resistance and mimics a weak cell. A healthy pack at full charge should hold above 9.0V under slew load.
RA tracking drifts during long exposures
Sustained RA tracking puts a continuous low-level load on the battery across an entire imaging session. As the pack discharges past the midpoint, voltage sag causes the RA motor to run fractionally slower than the commanded sidereal rate. The result is gradual star trailing in long exposures — not a mount alignment issue, even though it looks like one. Check battery voltage before a session. If the pack reads below 8.8V at rest, charge it fully before imaging to keep motor speed consistent across the session.