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Originally Posted by Old Mechanic
While I understand the dynamics of gyroscopes to a point, it was one of the factors that changed my direction in favor of hydraulic accumulators.
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And hydraulic accumulators have the advantage of being less expensive and simpler.
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The real question is how much capacitive storage do you really need beyond a single high speed stop or start?
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Probably, the energy of two stops from 60 is a reasonable lower limit. This allows for a small amount of assist on long hills, permitting the engine to be smaller than it otherwise would be. The Prius shows that this is not always enough, with a Corolla easily beating a Prius up a long hill.
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Some like to compare this to battery capacity, but that is not really the point.
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Although energy density can be a concern. The UPS hydraulic hybrid had, per Eaton, 2000 hp-seconds (.4kWh) capacity. The accumulators and fluid weighed about 900 lbs. The Prius battery weighs about 100 lbs and has more than three times the energy capacity. (The Li batteries in my POC also weight about 100 lbs, and have 8 times the energy capacity of the Eaton accumulators.)
I hope you will sign up for Doug's "Git er done" challenge. Perfect can be the enemy of the good, and these challenges can help you prioritize what really needs to be done.
Regards, Ken