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Old 07-01-2010, 10:46 AM   #100 (permalink)
KamperBob
Recreation Engineer
 
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Join Date: Dec 2009
Location: Somewhere USA
Posts: 525

Black Stallion - '02 Toyota Tundra 4WD xCab

Half Pint - '06 Yamaha XT225
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Quote:
Originally Posted by NeilBlanchard View Post
Dave uses amp meter(s) in the car, while driving, I believe. These numbers are for the first 170 miles or so, IIRC. The voltage changes nearer the end of the run, so making the exact number a little harder to ascertain. I will ask about using a meter on the charger, which would be an average for the whole trip, but less approximate?
Yeah, dropping from 12.6 to 12.0 is only 5% difference in battery voltage. Even with a 3rd decimal place the curve is nonlinear. Amplified across six in series it's still 5% (75.6 to 72). Unless the batteries have settled (cooled and equalized) terminal numbers can be iffy. Whereas a $20 Kill-A-Watt is easy. It read kW-hr directly and simple math gives utility cost per mile. Most folks probably recharge at home so it seems like a fair real-world benchmark.

Thanks again
KB
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