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Originally Posted by mort
The problem for a car is that the self discharge rate for hydraulic storage is screwy.
But I like the idea and hope they can get these thing on the market.
-mort
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What? You must be talking about the motors efficiency or losses in the plumbing of hydraulic systems...? If I close the valve on a hydraulic accumulator I could come back a year later and the psi(energy) would be nearly the same. Battery pack?... Not even close.
On top of that the reported brake regen for the EPA’s hydraulic hybrids typically capture at least 70 percent of the braking energy otherwise lost to heat. Estimates for electric hybrids capture more like 20 to 25 percent, because their batteries have comparatively poor power density.
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high-pressure hydraulic accumulators usually charged in excess of 3,000 psi. The best of these accumulators have power densities of roughly 500 kW/kg, according to Jim O’Brien, founder and chief technology officer for Hybra Drive Systems, a start-up focusing on the development of hydraulic power trains.
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I do not understand the 500 kW/kg -vs- 300W/kg... Hydraulics can't have almost 2000x the energy density of a typical Li-on battery pack... ?
See
Lithium-ion battery - Wikipedia, the free encyclopedia
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~250-~340 W/kg, Charge/discharge efficiency 80-90%, and Self-discharge rate of 8% at 21 °C -to- 31% at 60 °C. Cycle durability 400-1200 cycles.
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