Hybrid Car - Parallel Hybrid or Series Hybrid

All hybrids have in common is the ability to generate electric current, store it in a large battery, and use that current to help drive the car. Hybrids capture electrical energy produced by a regenerative braking system, and their engines can power a generator, too.

A series hybrid is very similar to a parallel hybrid. Both have the advantage of increasing fuel efficiency compared with conventional gasoline-powered vehicles, and giving the driver greater range than an all-electric vehicle. Both types of hybrids are reliant on large battery packs to store energy and both types may use additional technologies like regenerative braking to capture energy that would otherwise go to waste.

However, the mechanisms are quite different:

Parallel Hybrid

With a parallel hybrid electric vehicle, both the engine and the electric motor generate the power that drives the wheels. The addition of computer controls and and a transmission allow these components to work together. Parallel hybrids can use a smaller battery pack and therefore rely mainly on regenerative braking to keep it recharged. However, when power demands are low, parallel hybrids also utilize the drive motor as a generator for supplemental recharging, much like an alternator in conventional cars.

Series Hybrid

This is the simplest hybrid configuration. In a series hybrid, the electric motor is is the only means of providing power to get your wheels turning. The motor receives electric power from either the battery pack or from a generator run by a gasoline engine. A computer determines how much of the power comes from the battery or the engine/generator set. Both the engine/generator and regenerative braking recharge the battery pack. The engine is typically smaller in a series drivetrain because it only has to meet average driving power demands; the battery pack is generally more powerful than the one in parallel hybrids in order to provide remaining peak driving power needs. This larger battery and motor, along with the generator, add to the cost, making series hybrids more expensive than parallel hybrids.

Comparison:

• The series hybrid can be charged off of the power grid, for convenience & much cheaper operation (< 20% of the cost of running on gas) with no loss of performance (except range), otherwise use the onboard generator, The parallel hybrid may be able to run off the power grid if you expand the battery pack, but with reduced performance.

• The series hybrid is much simpler in design & maintenance than the parallel hybrid. It does not need a clutch or transmission, no oil changes, spark plugs, fuel/oil filters except on the separate generator which can be removed or replaced easily. It does not need the complex control / interface between the gas engine & electric motor.

• The series hybrid has better acceleration due to the superiority of the much larger electric motor to the gas motor in this respect.

• The generator engine on the series hybrid can be much smaller, simpler and more efficient than on the parallel hybrid.