The electrical system is split into two main parts:
The 'high voltage' system is derived from the battery and this could be anything from about 100V to 800V. There are a few manufacturers working with 800V systems though (Hyundai and Kia) due to the safety issues. The main reason for using higher voltages is the ability to use more powerful motors. The public charging infrastructure is not really in place with support for these high voltages though.