Paper B converts the diagnostic-device workload into a battery decision: matching chemistry to device class, sizing capacity from an exam-mode duty cycle rather than a single wattage, protecting the sensitive analogue front-end from supply noise, and building packs that survive dock-based clinical use.
Pocket ultrasound and wearable ECG recorders optimise weight and runtime and therefore use lithium-ion or lithium-polymer, with the mandatory BMS and IEC 62133-2 evidence. Laptop-class portable ultrasound and clinic-based diagnostic carts are different: they are heavier products with room for cells, are docked between shifts, and value intrinsic safety, clean supply rails and low total cost — the territory where NiMH competes strongly. Its flat discharge curve keeps DC/DC inputs steady through a scan-mode burst, its aqueous electrolyte cannot thermally run away inside an expensive imaging system, and simple -ΔV charging suits a shared docking cradle. For handheld ECG devices around the 2 W level, NiMH AA/AAA packs also remain a legitimate rechargeable alternative to primary cells.
Average power is the duty-weighted sum of modes. Take a portable scanner drawing 30 W in B-mode, 40 W in colour/PW, 6 W frozen and 1 W standby, with an exam mix of 40 % B-mode, 15 % colour, 40 % frozen and 5 % standby: average power is about 19 W. For a three-hour shift between docks on a 12 V rail, raw energy is 57 Wh ≈ 4.75 Ah; applying depth-of-discharge (0.85), end-of-life fade (0.8) and a thermal margin (0.85) raises the design target to roughly 8.2 Ah. Sizing on the 30 W scan figure alone over-specifies the pack; sizing on idle under-specifies it — the exam mix is the only defensible basis.
Ultrasound beamformers and ECG amplifiers measure microvolt-level signals, so battery impedance and switching noise matter as much as capacity. Cells are matched for internal resistance to avoid step changes in rail voltage during a scan burst, welded interconnects minimise contact noise, and pack layout separates power return from analogue return. NiMH's low, stable impedance and smooth voltage curve reduce the burden on downstream regulators and help the device meet its diagnostic accuracy and acoustic-output obligations under IEC 60601-2-37.
Imaging systems generate heat beside the battery compartment, which accelerates NiMH aging and lowers charge acceptance above about 45 °C; packs need a thermistor and a thermal path away from the processing board. Dock charging with -ΔV/temperature termination and a maintenance current keeps a clinic fleet perpetually ready without overcharge, and charge time to a clinically useful level should be validated with the device powered in standby, as wards recharge between cases.
Weijiang Power supplies low-impedance matched NiMH cells and custom diagnostic-device packs with welded construction, NTC supervision and IEC 62133-1/UN 38.3 documentation. Send your mode-by-mode power trace, exam mix and shift runtime target and we will size a pack that holds imaging performance to the declared limit.
