A system for supplying electrical power for use when the vehicle engine is shut down and configurations of long-haul trucks employing the system are disclosed. The power system is a battery bank contained within an insulated enclosure. The batteries are heated when the truck is in operation with the insulated enclosure maintaining battery temperature sufficient to provide high battery power capacity for an extended period after the vehicle is shut down. A large capacitor, rather than the batteries, provides current for starting the vehicle engine. A dc-to-dc converter controls the fully charged capacitor voltage and provides capacitor charging current even when the batteries have been discharged to a low-voltage condition. The disclosed long-haul truck configurations include a storage cooler that employs a phase-change medium that is thermally charged to a low temperature while the truck is in operation and is used to provide sleeper unit cooling air. Additional provision is made for heating the sleeper unit and for powering a coolant heater that can warm the truck engine block and truck fuel when the engine is shut down during cold weather.