Development of compact electrical source based on the synergetic partnership between conventional electrochemical storage batteries and ultracapacitors

Abstract

Nowadays, the need of compact moveable powerful electrical sources is going up. The most well-known applications of these arrangements are needed in automotive and transportation industry, in devices of emergency starting of internal combustion engines, for supplying pulses of high current in special equipment and so on. Most of these implementations may be developed on the base of conventional electrochemical storage batteries (ESB). ESB are representing the suitable kind of rechargeable electrical sources and may be applicable in moveable equipment. But the power parameters of batteries compare to their dimensions leave much to be desired. If the high power (current) is required (together with the small dimensions of the energy system) the employ of ESB only is not really capable. The synergetic combination of ESB together with UC seems to be very promising solution in this case. A conjunction between these two different energy sources links together the outstanding power characteristics of UC with relatively high specific energy of ESB. However, the combination of these devices requires decisions of some technical problems. For example, when the voltages of UC and ESB a priori are different, and this difference is used for special goal, for example to provide high load current when the battery is weak and unable to deliver the needed power. The special inverter has to be included between UC and ESB in this case. Its major function is providing UC charging from ESB. The problem of UC charging is stemming from its very small (sometimes negligible) internal resistance and usual connection between terminals of UC and ESB may cause to the serious difficulties such as a very high equalizing current, small charging efficiency and diminished battery's service life. These problems become expremely smart when UC before charging is fully or partially empty. Additional serious difficulties are associated with electric security needs. This kind of devices are equipped, as a rule, with flexible cables are being ended by special clamps for load connecting. An occasionally shortening of these clamps during a device leading to a load may cause serious troubles. Thus, the preventing of such cases depicts an important technical challenge. The supplementary problem is represented by the need to switch the power supply on at the right moment of time and only after this device will be connected by cables to the load. This problem is issuing in principle from the previous one. If it will be solved this would solve automatically the first problem too because the switching power supply at the needed moment of time means that shortening of clamps before their connection to the load will not cause any damage. Thus, this device has to be equipped with special power circuit and it's control system which algorithm will i) avoid occasionally clamp shortening ii) will define the moment of time when the load has to be connected to the power supply. The presented work is dealing with the research and development of this kind of compact electric source where conventional ESB is used with UC, a special electronic circuit provides the optimal connection between these two electrical devices and makes available the protected functionality of the entire energy system.