# Battery Equivilents?



## fantasymaker (Aug 28, 2005)

What size or weight of battery is equivilent in energy storage to a gallon of fuel?


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## Homesteadwi5 (Mar 16, 2008)

Thats hard to compare but for overall storage,the Trojan L16 6V is pretty much the standard that i sold for use in homes and cabins and the like. If you check out thier website they do offer small less amp hour batteries that are more price friendly.


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## watcher (Sep 4, 2006)

From what I found a gallon of gas has the energy equivlent to about 36 KWh. 

gallon of gasoline 1.3x10^8j or 130,000,000 j
http://www.phy.syr.edu/courses/modules/ENERGY/ENERGY_POLICY/tables.html

130 000 000 joule = 36.111 kilowatt hour
http://www.onlineconversion.com/energy.htm

If I remember correctly w = v X a 
3611 w/12v = 300 amps. 

If my math is correct you'd need a 12 volt battery capable of producing 300 amps per hour to equal one gallon of gasoline. Of course as you raised the voltage you'd lower the needed amps. A 110v system would only need to produce 32 amps/hr; 220v 16.5amps/hr; 440v 8 amps/hr; 1000v 3 amps/hr


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## wy_white_wolf (Oct 14, 2004)

Going by this for lead acid batteries:



> ....Even with a 20% efficient IC engine, a gasoline tank stores 20 times as much energy as a battery of equal weight. As the vehicle is moving it gets rid of some of that weight. Battery powered vehicles must carry the full weight of their energy source....
> http://cleantechnica.com/2008/07/24...utomobile-engineers-chose-choose-fossil-fuel/


That would mean for every pound of gasoline you would need 20 pounds of battery. Gas is ~7.5 pounds per gallon so ~150 pounds of battery. Tells you why it is so hard to design an electric car that has any kind of range.


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## whistler (Apr 20, 2005)

watcher said:


> From what I found a gallon of gas has the energy equivlent to about 36 KWh.
> 
> gallon of gasoline 1.3x10^8j or 130,000,000 j
> http://www.phy.syr.edu/courses/modules/ENERGY/ENERGY_POLICY/tables.html
> ...


You are off by a factor of 10. 36.111 KWh = 36,111 Wh. 

A 6V Trojan T125 can provide 240 Ah and weighs 66 pounds.

36,111Wh/6V = 6018.5 Ah. Divide that by the amount available in each battery (240 Ah) and you will need 25 batteries each weighing 66 pounds. Thus you would need 1,655 pounds of batteries to provide the same amount of energy in a gallon of gasoline.

Of course this is all purely theoretical because there is no way to tap into all the energy contained within a gallon of gasoline.

In practical terms, a generator will produce about 5 KWh per gallon of gasoline. Redoing the math would then lead us to (using the same battery):

5,000 KWh/6V = 833 Ah 
833Ah/240Ah (in the battery) = 4 batteries 
4 batteries X 66 pounds = 264 pounds

So you would need 264 pounds of batteries to capture the energy given off by a gallon of gasoline burned in a generator.

Whistler


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## wy_white_wolf (Oct 14, 2004)

> ...Of course this is all purely theoretical because there is no way to tap into all the energy contained within a gallon of gasoline...


This also applies to batteries. 80% is tha absolute maximun that should be discharged too. 50% if you want anything that respembles a life span for them. Recomended is only 20%.


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## watcher (Sep 4, 2006)

whistler said:


> You are off by a factor of 10. 36.111 KWh = 36,111 Wh.


Thanks for catching it. That's why I always show my work. Its so easy to slip a decimal incorrectly.


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## fantasymaker (Aug 28, 2005)

If I figger about 25 percent efficacy for fuel and 80 for electricity with a 25 percent storage factor Id be in the neighborhood?


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