Quote:
Originally Posted by euromodder
In this situation, you don't really lose fuel energy or efficiency to braking.
There simply wasn't anything to be gained when you can come down the mountain using engine braking or aerodynamic braking with the engine off.
But you still had to drag the trailer up the mountain first.
There's a limit to that as well - the uphill part would have drained them to as low as the conditioning software will let it, but once the batteries are full, the harvest is over.
And these batteries too, have to be dragged up the mountain first.
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I believe that these engineers look at thermodynamics and BSFC when they do their numbers.If any kinetic energy of a downhill descent is lost to braking,then they enter it as a loss in the energy balance.
The Chrysler engineer who published the paper on the Chrysler De Soto Airflow streamlining based all work on thermodynamics.
The context of what I posted was kinda like this:
*You take a SMART EV with a gasoline equivalency of 40 mpg @ Cd 0.38,then put the 620-lb Battery-Range-Extender Trailer behind it,which drops the drag to Cd 0.15.
*The aerodynamics boosts the efficiency to 52 mpg.
*Allowing for the added rolling-resistance of the BRE trailer,the mpg drops back to 48 mpg,an 8-mpg improvement over 'stock.'
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*On mountain highways,up to 2% gradients,the uphill and downhill basically cancel out according to AASHTO.I'm not in a position to dispute their peer-reviewed science.
*On mountain highway grades in excess of 2%,the EV,with regenerative braking,can provide runaway control via regenerative braking, which I understand will recover 80% of the kinetic energy,partially recharging the batteries on descents.(Mr. Sharkey wrote of such things when he traveled long-distance with his range-extenders).
*The 8-mpg advantage helps offset the climbing penalty of the trailer.
*The regenerative-braking helps recover 80% of the energy lost on the climb.
*And we never had to 'brake.'
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Without the regenerative-braking,the trailer forces me to use my brakes,causing an mpg penalty.
*If the trailer were 200-lbs instead of 620-lbs I think I could shrug it off.That will require a complete redo.And I believe it would be worth it.
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*When USAC tested their CRXs back in 1984,between Clinton,Oklahoma,and Santa Rosa,New Mexico,They lost 24% mpg on the uphill run,and gained only 14% the same stretch downhill.
*When Popular Mechanics tested their Geo Metro LSi from San Francisco,to New York,they saw a 6% drop climbing and only a 5.6% gain going downhill.
*Motor Trend realized similar phenomena with their CRX between Los Angeles and Salt Lake City and back.
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I'm pretty confident that the trailer's extra weight is beating me up in the mountains.
So it's go on a diet, stick to the flat lands,or pay!
