Rover Atom Light 8.4V Ni-MH Replacement Battery Bat-Pack-STC3

Rover Atom Light / HD ProTab Series — 8.4V Ni-MH Replacement Battery (Bat-Pack-STC3)

This is an 8.4V, 4200mAh Ni-MH battery pack built to fit the Rover Atom Light, HD ProTab, HD Pro, HD Touch, and over 25 additional Rover survey and measurement instruments. It replaces OEM part Bat-Pack-STC3 directly. Capacity figures are taken from product data — 4200mAh, 35.28Wh.

• Multi-model fit across Rover survey platforms: The Atom Light, HD ProTab, HD Pro, and HD Touch series share the same 8.4V Ni-MH power rail, battery connector format, and BMS handshake protocol — which is why a single pack covers all of them. Swapping between units in the same fleet does not require a different battery.
• Bench tested on actual hardware: We ran the pack through charge and discharge cycles on Rover survey equipment, monitoring BMS response during sensor initialisation. The pack held voltage through the initial probe power-up spike without tripping the protection circuit.
• Field calibration before first deployment: After installing this pack, run a full calibration cycle through the instrument menu before heading out. The Rover platform maps battery state during that process — skipping it causes the low-battery indicator to trigger early on the first measurement session, even when the pack has substantial charge remaining.

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

Ni-MH packs self-discharge at roughly 1–2% per day. After several months in storage, cell voltage drops below the BMS recovery threshold — typically around 6V on an 8.4V pack. When voltage sags that low, the BMS enters a protective lockout state and the instrument shows no response when powered on. A standard charger will not wake the pack from this state because it expects a voltage handshake before delivering current. Use a charger with a Ni-MH recovery or reconditioning mode, or apply a short trickle charge at 100–200mA until cell voltage climbs above 7V — at that point the BMS re-initialises and normal charging resumes.

Rover instrument shuts down mid-measurement despite showing charge on screen

This is a voltage dropout issue, not a capacity issue. Under sustained sensor load — particularly when GPS, probe modules, or data logging are all active simultaneously — instantaneous current draw spikes above what the pack can deliver cleanly. Voltage dips briefly below the instrument's cutoff threshold, triggering a shutdown even though the battery gauge showed plenty of capacity remaining. The gauge reads resting voltage, not loaded voltage, so the two numbers diverge under sustained draw. Running the full calibration cycle after installation lets the instrument calibrate its threshold mapping to this specific pack, which reduces false cutoffs significantly.