Paper C maps the validation programme for a wearable infusion battery: IEC 60601-2-24 basal and bolus accuracy, ingress and body-worn safety, IEC 62133 cell cases, UN 38.3 transport, and the aging evidence that guarantees weeks of therapy without surprise failure.

The Standards Stack

• IEC 60601-2-24 — infusion pumps and controllers, including pumps for ambulatory use; its basal (clause 50.104) and bolus (50.106) test methodology is the reference used even in independent academic insulin-pump accuracy studies.
• IEC 60601-1 / -1-8 — general safety and staged low-battery alarms that must give the user time to replace or recharge before any basal dose is missed.
• IEC 62304 — medical device software lifecycle, governing the dose-control and battery-management firmware.
• Ingress and biocompatibility — modern wearables cite IP28 (continuous immersion, e.g. to 3.7 m for one hour) and ISO 10993 biocompatibility for skin-contact materials.
• IEC 62133-1/-2 and UN 38.3 — cell safety by chemistry and transport evidence.

Dose-Accuracy and Runtime Matrix

For a wearable pump the battery test is coupled to delivery accuracy. Runs follow the IEC 60601-2-24 basal and bolus protocols at battery states from full charge to the low-battery threshold, at skin temperature and cool ambient, with radio duty at minimum and at continuous closed-loop operation. Each run records delivered-volume accuracy (the standard's flow-error and trumpet-curve analysis), the voltage behaviour during each bolus pulse (no brown-out reset), time to low-battery alarm, and residual therapy time after alarm. An aged cell at 80 % capacity repeats the worst-case day — frequent boluses plus maximum wireless duty — because the guarantee is weeks of accurate therapy, not a new-cell bench number.

Body-Worn Safety and Cell Cases

IP28 immersion testing verifies the enclosure protects the cell compartment; drop, crush and clothing-snag abuse reproduce real wear. IEC 62133 adds external short (ambient and elevated temperature), overcharge, forced discharge, mechanical and thermal cycling for the cells themselves. NiMH's aqueous chemistry and controlled-vent failure mode are valuable against the skin: there is no flammable organic electrolyte and no thermal-runaway pathway, which materially simplifies the risk file for a device worn 24 hours a day. UN 38.3 covers shipment of cells and replacement packs.

Aging and Replacement Planning

Rechargeable wearables cycle shallowly but constantly at body warmth, which accelerates both fade and self-discharge. Development combines real-profile cycling and elevated-temperature storage to project when wear time between charges drops below the user's longest interval between docking opportunities — the meaningful end of life. NiMH fades gradually and internal resistance rises predictably, so the device can estimate remaining wear time from pulse-voltage response and prompt replacement before accuracy is affected.

Failure Modes to Design Out

• Mid-bolus reset — pulse sag; prevented by low-impedance cells and end-of-life bolus testing.
• Short wear time — high sleep current or self-discharge; prevented by nanoamp housekeeping and low-self-discharge cells.
• Sudden therapy stop — prevented by IEC 60601-1-8 staged alarms with real residual-time validation.
• Body-contact hazard — addressed by IP28 sealing, IEC 62133 evidence and intrinsically safe chemistry choice.

Weijiang Power

Weijiang Power supplies low-self-discharge, low-impedance NiMH AAA/AA cells and miniature custom packs for wearable medical OEMs, with IEC 62133-1 and UN 38.3 evidence and support for IEC 60601-2-24 dose-accuracy validation across battery life. Send your basal/bolus trace, wear-time target and enclosure constraints and we will engineer a cell strategy that protects every dose.