Quote:
Originally Posted by CobraBall
bennelson
Will you post your formula to obtain MPG for your electric bike?
How many minutes/volts/amps to fully charge a dead battery.
Maximum miles for one charge?
CB
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Maximum miles is easy. I did an endurance run for that great efficiency. It was 33.5 miles. At that point the voltage told me I was discharged down to 40%. I was still able to drive pretty fast and all, but knew that performance would drop pretty fast after that.
[QUOTEHow many minutes/volts/amps to fully charge a dead battery. CB[/QUOTE]
Well, for starters, you don't charge a dead battery. You charge a partially discharged battery. Running your batteries down really far, and often is a great way to kill them.
My batteries hold 55 amp-hours. If I run them down half way, that's 27.5 amp hours I have to put back in to fully recharge them.
My charger charges at a rate of just over 100 watts. I know from calculations that the cycle uses very close to 100 watt-hours per mile. That means I have to run the charger for one hour for every mile I go.
A gasoline equivelent can be figured out by using a common energy measurement between a gallon of gasoline and a KWh (kilowatt-hour) of energy. 1 KWh of electricity is how much energy you use when you leave a 100 watt lightbulb on for ten hours.
I can do a big long calculation of energy conversion based on that there are 125,000 BTUs in a gallon of gasoline and 3400 BTUs in a KWh of electricity, or I can round ever so slightly and say that there 37 Kwhs in a gallon of gasoline.
I have a killawatt plugged into my garage which measures how much energy I use to recharge the cycle. Once the cycle is charged, the green light on the charger goes on. Then I look at the
Killawatt and see how much energy was used. Lets say it was 1.5 kilowatt-hours. Divide 1.5 by 37 to see what part of a gallon of gasoline was used. You get .0405 of a gallon. a very small amount. Now divide your miles by your gallons to get Miles-Per-Gallon. Lets say the trip odometer read 13.5 miles. Divide 13.5 by .0405 to get 333 and a third miles.
Writing this all down and explaining it is way longer and more complicated than actually doing it.
Divide Killawatt measurement by 37, then divide your trip odometer by the amount you got. That's your eMPG.
Of course, there are other things that really aren't fair to compare. You can't make gasoline from solar or wind for example. I am also measuring electricity at the wall, so how efficient or not the charger is is important.
No, I am not calculating how much electricity is lost in transmission lines, but I am also not measuring how much diesel fuel is burned to move a tanker ship of petroleum across the ocean. Just trying to measure the energy used by the vehicle.
Pardon any simple math or rounding errors. Just trying to use easy numbers for simplicity's sake. I use the full BTU numbers when doing the calculations for the cycles fuel economy.
A good source of info for converting forms of energy into each is
Peak Oil: Life After the Oil Crash
I also have an energy conversion widget running on my Mac. It's pretty slick, but it doesn't do gasoline into KWhs of electricity. Gotta do that myself.