It is unfortunately a relatively common experience among many operators of motor vehicles that a well maintained, or even new internal combustion engine can not be started when the battery that supplies the power to the starter is discharged below a minimum power level needed to crank the engine. While in many cases an external power source is employed, internal supplementary power sources find increasing utility to provide auxiliary power to start the engine.
Internal supplementary power sources that operate in addition to a main battery may be broadly grouped into one of two classes. One class of internal power sources comprises capacitor-based systems and employ mostly commonly high capacitance double-layer capacitors. Double-layer capacitors typically combine small size with the ability to be charged in a relatively short time, and are therefore especially advantageous in internal supplementary power sources. For example, in U.S. Pat. No. 5,207,194 to Clerici, and U.S. Pat. No. 5,146,095 to Tsuchiya et al., a double-layer capacitor is employed to provide (boost) current to start an internal combustion engine, wherein a main battery charges the capacitor. However, when the capacitor and main battery are discharged to a level not sufficient to start the engine (e.g. due to prolonged non-operation of the vehicle), the capacitor may disadvantageously turn into an additional drain of the main battery. Moreover, electrical degradation or structural damage of the main battery, which may eventually result in insufficient power to start the engine, may concomitantly prevent the capacitor from being charged, thereby rendering the capacitor useless as a second power source.
To circumvent at least some of the problems associated with a battery charged capacitor, Nagao describes in U.S. Pat. No. 5,818,115 a configuration in which an engine starter has a built-in generator that charges the capacitor. Nagao's main battery is independently charged via an alternator, and supplies electricity to loads other than the starter. Although this arrangement affords independence of the capacitor from the battery as well as from the alternator, a specialized engine starter with a generator is needed, which often requires re-engineering of the existing engine starter. Moreover, the engine cannot normally be started in case of a capacitor failure, since the main battery is not electrically connected to the starter.
A second class of internal supplementary power sources comprises battery-based systems, typically employing customary lead-acid batteries. One of the most common configurations utilizing battery-based internal power sources is found in recreational vehicles (RVs) or boats, wherein the electric circuitry for lighting and utilities are separated from the engine starter, and wherein both circuitries are operated by independent batteries. The use of dedicated circuitries generally prevents even an inexperienced person from accidentally discharging the engine battery, but does not usually allow a second battery to boost or substitute for power of the main battery. Other configurations (see e.g. U.S. Pat. No. 5,555,864 to Miyakawa et al.) include dual battery arrangements wherein a source control device temporarily connects two batteries when an engine is started, but otherwise electrically separates the two batteries into an engine-dedicated battery and a utility-dedicated battery. Although the available battery capacity is temporarily doubled during starting in this configuration, the use of an additional similar size battery generally adds significant weight to the vehicle, and requires considerable space. Furthermore, since both batteries are connected to the same electric circuitry, they may share the same fate in an undesired discharge or short circuit event. In still another configuration, (U.S. Pat. No. 5,563,454 to Araki et al.) a main battery charges a smaller subsidiary battery, which is then used to drive a starter motor. The use of a smaller subsidiary battery generally reduces the space requirements of a second battery, however, an accidentally discharged main battery cannot charge the subsidiary battery, especially after a longer period of non-activity, and the subsidiary battery may therefore be discharged to the same extent as the main battery, and cannot be easily recharged without starting the engine or using suitable high current external power sources.
Despite various internal battery backup and support systems, all, or almost all of them suffer from one or more disadvantages. Therefore, there is still a need to provide methods and apparatus for a reliable auxiliary vehicle power and starter system, particularly one that can also be quickly removed for use in starting other engines or vehicles.