Paper B guides the battery decision for defibrillators and AED trainers: when a primary lithium pack is correct, when rechargeable NiMH is the better engineering and economic choice, how to size a high-pulse pack, and how construction determines whether a defibrillator still reaches 200 J after thousands of shocks.
Three use models drive three different choices. Public-access AEDs (airports, schools, offices) are used almost never but must work instantly after years on a bracket: non-rechargeable LiMnO2 wins on shelf life and zero maintenance, with a dated replacement regime. Hospital crash-cart and transport defibrillator-monitors are daily-tested, frequently used in training and regularly recharged: rechargeable NiMH avoids recurring primary-pack cost and waste while delivering the high pulse current capacitor charging demands. AED trainers and simulators run the same user interface without a high-voltage stage and are a natural NiMH application. This paper concentrates on the two rechargeable cases.
Energy delivered to the patient is not energy drawn from the battery: capacitor-charging efficiency (typically 50–70 %) and converter losses must be included. A 200 J shock at 60 % efficiency draws roughly 330 J ≈ 0.09 Wh from the pack — tiny in energy terms, but delivered at high power over a few seconds, which is a power problem rather than an energy problem. Sizing instead follows three constraints: (1) enough total energy for the declared shock count plus operating time (the familiar "200 shocks or 4 hours" benchmark); (2) a source impedance low enough to meet charge-time limits at every shock; and (3) reserve at end of life so the 2500th rated shock still reaches target energy.
High-rate NiMH cells with low DC internal resistance are selected first; capacity is matched to the required shock/operating budget. Cells are binned by resistance (not merely capacity), because a single high-resistance cell throttles the whole series string during capacitor charging. Heavy welded nickel tabs carry the pulse current without voltage drop or heating, and protection devices are chosen to withstand repeated surge current without nuisance tripping — the worst failure is a protection cut-out during a resuscitation.
Manual defibrillator-monitors typically run 12–14.4 V rails (10–12 NiMH cells), with the capacitor charger designed around the battery's end-of-discharge voltage. Daily-dock charging suits NiMH: constant current with -ΔV or temperature termination and a maintenance current keeps a crash-cart unit perpetually ready without overcharge. A thermistor guards against the heat of repeated rapid recharge after training sessions.
Weijiang Power supplies high-rate, resistance-matched welded NiMH packs for defibrillator-monitor and trainer OEMs, with NTC charge supervision, surge-rated protection and IEC 62133-1/UN 38.3 documentation. Send your energy-per-shock, charge-time and shock-cycle targets and we will engineer a pack that still meets them at end of life.
