The best and brightest engineers and technicians at Honda were brought together, (many from the F1 program), to design the Insight over a period of years. Each one understanding in depth their own area of expertise and enough related areas technology to interface with them. To understand the scope of the question, know that Hyundai is currently emplying 10,000 engineers to develop their first hybrid.
Phrased globally, the answer to your question is: God only knows, and if He were to explain it to me, I would understand precious little.
If however you need help troubleshooting or gaining a rudimentary understanding of the electrical system, the electrical suppliment to the shop manual is essential reading.