Focus of this thesis is to evaluate the possibilities of using the energy from hybrid battery of Toyota or Lexus vehicles to pre-heat the gasoline engines of the vehicles. Object is to design a prototype system that can be turned into the system that would use power from the hybrid battery to pre-heat the engine and could be fitted as an aftermarket option to new vehicles. The system should be easy to use by consumer, parts and installation should be relatively cheap and the entire system needs to be very reliable. The prototype system is installed into my own 2004 NHW20 Prius. Even though the vehicle is already old its nickel metal hydrate battery with 201,6V of nominal voltage is still basically the same as most of new Toyota hybrid vehicles. Focus of the thesis is to evaluate the effectiveness of the heater, possible problems that it had, and to come up with fixes to those problems.

The prototype system that uses power from the hybrid battery to pre-heat he engine is made to use power from hybrid battery directly to power the contact heater already installed onto the vehicles engine to pre-heat the engine. System is designed to be very reliable, easy to use, and simple to install. When testing the system it was discovered to be working satisfactory. But it was also discovered that system caused a problem in controlling charge level of the hybrid battery. After finding the problems, focus of the work was to find solutions to those problems. But after extensive testing it was ruled that system cannot be designed to satisfy all the design goals without reprogramming some control unit which is unfortunately not possible within this project.