As the number of electrical components increase, vehicles require increasing amounts of available electricity. Vehicles have traditionally used 12-volt batteries and a 14-volt charging system, but to meet the increased demand from such high usage systems as electric drives, higher voltage batteries and packs with an appropriately high voltage charging system are necessary.
The advantages of using higher voltage systems include: more power for systems and accessories, fewer concerns about voltage drop across the system, and the use of smaller diameter wires for higher power draw, which also reduces the overall weight of the vehicle.
If we apply Ohm's law we can see how the differences work.
Take, for example, a vehicle with a conventional 14-volt system with a charging current of 200 amps. Using Ohms law, we find that 14 Volts times 200 Amps equals 2800 Watts.
In a higher voltage system, less current is needed to deliver the same amount of power.
By comparison, using Ohms law again, but this time with a 42-volt system, we find that 2800 Watts over 42 Volts equals 66.6 Amps.
For the same amount of “power” the current has decreased by 2 thirds. This means that for any given current flow the cable diameter on a 42-volt system can be reduced in size.
Different types of generation systems can produce this high power output. One method is to combine the vehicle starter motor and charging system into a single unit. A number of “Hybrid” gasoline-electric vehicles use this system and mount the starter/generator on the flywheel between the engine and transmission.
