Keim says 42 volts is the threshold\ufffdanything higher presents safety concerns. Because 50 volts can stop a human heart, anything higher than that requires special safety systems to prevent contact with wiring. In addition, any voltage above 60 needs more heavily insulated wires and connectors that would add weight.

The ability to add technologies, such as start-stop with an ISA, brake regeneration and torque boost, will improve fuel economy 10 percent to 15 percent.