Two Stores, One Power Pack: The Physics of Battery–Supercapacitor Hybridisation, the Patented Hybrid Power Pack Architecture, and the Applications Where It Delivers Most

Background. Electrification is asking a single battery to do two different jobs at once: to hold energy for hours and to deliver or absorb bursts of power in seconds. Electric car sales exceeded 17 million worldwide in 2024, and every one of those vehicles, like every start–stop engine, telecom site and solar-plus-storage installation, presents its battery with a load that is part steady and part rapidly fluctuating. The fluctuating part is what heats a battery, sags its voltage and accelerates its ageing. Approach. This paper sets out, from first principles and the peer-reviewed literature, why a battery and an electrochemical double-layer capacitor (supercapacitor) are complementary rather than competing stores; derives a compact, testable relation for the benefit of combining them; describes the patented Hybrid Power Pack (HPP) circuit architecture of which the author is the inventor; and ranks applications by the physics rather than by assertion. Numerical results are computed from the published WLTC Class 3b regulatory drive cycle and from engine-cranking events, with every model parameter stated. Results. When the supercapacitor carries the varying part of the load, the battery's Joule heating falls by 1 − 1/FF², where FF is the form factor (rms ÷ mean) of the load current. On the WLTC drive cycle FF is 1.46–2.98 by phase, giving an ideal reduction of 53–89 %. On engine cranking FF is 5.5–8.7, giving 96.7–98.7 %, and the supercapacitor needed is only 1.40–2.06 Wh of usable energy. For cranking the benefit survives a full system energy balance: the break-even battery resistance is 0.85–5.12 mΩ, several times below the 12.8 mΩ assumed for an illustrative 12.8 V pack. Conclusions. The battery–supercapacitor combination is most valuable where the duty cycle is peaky and the pack is small — engine cranking, start–stop, pulse power and fuel-cell buffering — and it is exactly this class of application for which the patented HPP architecture, with its separate battery charge and discharge paths, bidirectional capacitor path and supervising controller, is laid out. Independent peer-reviewed studies of supercapacitor storage, alone or with a battery, across ten sectors — starting and start–stop, cold starting, mild hybrids, electric vehicles, pulsed power, rail, port cranes, fuel-cell systems, renewable microgrids and backup power — report benefits including an almost fivefold extension of starter-battery life, a 7 % fuel-economy gain over battery-only storage in a hybrid vehicle and a 74 % cut in power loss under pulsed load. A defined comparative test programme is proposed to convert the derived HPP results into measured ones. Inventor and patents. The Hybrid Power Pack architecture is protected by granted patents naming Hemant K. Rohera as inventor, including IN 301517, US 10,523,019 B2, JP 6644883 B2, EP 3 320 595 B1 and CA 2,991,527 C (status per family register, 22 September 2026; see Section 8 of the paper). Preprint, not peer reviewed. Author hub: https://hemant-rohera.vercel.app/