"plug-in mild hybrid" upgrade

[Frank Lee]

I want to add wunna these:

[ConnClark]

I think hauling around the extra weight of the battery will out weigh any real benefits unless your driving an extra heavy car. Even if it did work you still have the same problem of an electric car( your using energy from a power plant instead of gasoline ).

[MetroMPG]

NiHaoMike: this has been done successfully already.

GasSavers member Brock saw a 5-7% increase in fuel efficiency even with this inefficient setup: He put two 6v golf cart batteries in his Jetta (in addition to the OEM battery), plus a DC/AC inverter connected to a 55A charger (to the OEM battery) which would keep system voltage at 14.4v.



He "manually" removed the alternator load from the engine by pulling its main fuse. (That way he could put it back in when his wife drove the car, so she wouldn't have to worry about monitoring the "boost pack" voltage.)

Details here: Plug-in Blackfly: going alternator optional nets +10% mpg - MetroMPG.com ... near the bottom of the page.

The caveat in this approach is that batteries are consumable items. You'll save energy doing this, but without a cheap source of batteries (or unless fuel is far more expensive), you probably won't save money.

Even if it did work you still have the same problem of an electric car( your using energy from a power plant instead of gasoline )

It's not necessarily a problem - power plants (even coal fired ones) generate power more efficiently than gasoline engines, so the net energy use is lower. Also, many people have access to renewable (clean) electricity generation so net pollution is lower too.

[cfg83]

MetroMPG -

Originally Posted by MetroMPG

...

It's not necessarily a problem - power plants (even coal fired ones) generate power more efficiently than gasoline engines, so the net energy use is lower. Also, many people have access to renewable (clean) electricity generation so net pollution is lower too.

If it's a standard 120 volt connection, you could use one of those kill-a-watt gizmos to meter your electricity and then add the "virtual gallons" to your fuel log :

Convert gallon [U.S.] of automotive gasoline to kilowatt-hours - Conversion of Measurement Units



CarloSW2

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[ConnClark]

Originally Posted by MetroMPG

It's not necessarily a problem - power plants (even coal fired ones) generate power more efficiently than gasoline engines, so the net energy use is lower. Also, many people have access to renewable (clean) electricity generation so net pollution is lower too.

Lead acid batteries are about 75 to 85% efficient. ( http://www.sandia.gov/pv/docs/PDF/batpapsteve.pdf )

A 14.4V charger is about 86% efficient. (
stepdown transformer 95% efficient * efficiency due to diode losses = .95 * (1 - (1.4/14.4)) = 86% )

average efficiency of powerplants = 33% Power Plant Efficiency Hasn’t Improved Since 1957 : CleanTechnica


transmission and distribution efficiency = 93.9% http://tinyurl.com/dghtoh


so 100% * .33 * .939 * .86 * .85 = About 23% efficient. Just about the same efficiency as a typical car engine

[modmonster]

nice calculation connclark

[modmonster]

i think in europe we have better power station efficiency. closer to 45%. internal combustion engines are only 20% efficient (diesel is better.)

[Piwoslaw]

Originally Posted by modmonster

i think in europe we have better power station efficiency. closer to 45%. internal combustion engines are only 20% efficient (diesel is better.)

The figures I've seen are 40% for diesel and 30% for gassers, but I can't find that source anymore, so don't listen to me...

[Daox]

Nice calculation ConnClark. However, I once calculated efficiency of an engine using EPA mileage for my Matrix and Paseo. It came out to 13% for each. 23% would be a HUGE increase. Ironically, thats about what it came out to be when I plugged in my summer mileage for the Paseo (which wasn't too far from 100% above EPA). There are pretty huge gains to be had for supplimenting or replacing gasoline for electric power.

[ConnClark]

Originally Posted by Daox

Nice calculation ConnClark. However, I once calculated efficiency of an engine using EPA mileage for my Matrix and Paseo. It came out to 13% for each. 23% would be a HUGE increase. Ironically, thats about what it came out to be when I plugged in my summer mileage for the Paseo (which wasn't too far from 100% above EPA). There are pretty huge gains to be had for supplimenting or replacing gasoline for electric power.

The 23 % efficiency is for the engine alone. Using mpg you have to account for transmission, drive line, aero, rolling friction, etc...

some more efficiency factoids.....

A typical new car engine is more like about 25 to 28% efficient. A diesel is about 30 to 45%.


A modern supercritical Rankine cycle power plant is about 42% at best. (if your power plant is more than 10 years old don't plan on this being the case)

clean energy ( geothermal, solar, wind, hydro electric, and biomass) made up only 7% of US power sources in 2006 and 90% of that was biomass and hydro electric based.