The Hydraulic Plug-in Hybrid and Other Strategies for Reducing Plug-in Battery Costs 2008-01-2765

The hydraulic plug-in is a gas/electric plug-in hybrid with the addition of hydraulic regenerative braking.

Prohibitive battery costs and weight are preventing plug-in hybrid vehicles from realizing their potential to improve global fuel economy in the near term. An efficient, low-cost hydro-mechanical transmission allows hydraulic regenerative braking to be added to the gas-electric plug-in hybrid at a reduction in vehicle component cost and results in greatly reduced battery costs and size. Since the hydraulic system absorbs the braking and initial acceleration power surges normally handled by the electric motor/generator and battery in a gas electric hybrid vehicle, the electric motor/generator can be reduced in size and cost and the battery capacity requirement can be reduced and the battery design shifted to favor storage capacity over power delivery.

Based on cost and weight models from EPRI and EPA, a plug-in vehicle design is described that results in a 10 mile all-electric range with a 60% lower cost battery than gas/electric plug-in with a 10 mile all-electric range. This vehicle will have essentially the same component cost and weight as a charge-sustaining electric hybrid of the same size.

It is also shown that by using the proposed transmission, a hydraulic hybrid (non electric) can be built with a 22% lower component cost and 15% to 100% better mileage than a conventional mid-sized vehicle using an automatic transmission, and a 50% lower component cost and 10% better mileage than a charge-sustaining gas/electric hybrid.

Other regimes to further reduce battery costs are: essentially full time operation of the internal combustion engine; customizing the battery size to driver's needs and; reducing the battery warranty period.

The proposed design is applicable to vehicles of all sizes including buses and trucks.