[EMAIL PROTECTED] wrote: > > Ok, I've pondered the previous emails, and pulled some info off > http://www.baaction.org/ev_project/batteries_1.html which seems to make > sense, though there is one "mystery" number I'd like you to ponder. > > First, here are some amp hour specs for Trojan 6 volt batteries: > > T-105 217 (20-amp hour rating) > T-125 235 (20-amp hour rating) > T-145 244 (20-amp hour rating) > > And here's the amp hour conversion factor provided by Trojan for a one-hour > rating, which should be used because of the faster draw of current when the > batteries are used in an EV: > > X hr Conversion rate factor > 1 hour rate is multiplied by .57 > 2 .67 > 3 .74 > 4 .77 > 5 .82 > 6 .84 > 7 .86 > 8 .87 > 9 .89 > 10 .91 > 20 hour rate is multipled by 1.00 > > So, a T-105, rated at 217 amps is really able to produce .57x217=124 amps at > an EV one-hour rate.
Amp-hours, not amps. A 217 Ah battery is acting as only a 124Ah one when discharged in one hour. THe battery can give out far more than 217 amps (not for long though), but never store more than 217 Amp-hours. There is big difference: A and Ah. > So, if I have a 120 volt battery pack of T-105s, I multiple 120x124 and get > 15,500 watts, or 15.5kW (VxA=W) of power on a fully charged battery pack. Again, watt-hours. Ah*V=Wh. > Now comes the mystery formula. According to the website, a Geo Metro using a > DC motor will use about 200 Watt hours per mile at 60mph. This number > supposedly came from a series of tests. Can anyone confirm/challenge? Will assume for the moment it's correct (or not too far from reality). > Anyway, if I divide 15,500 watts by 200 watts/mile, I get a range of 77.5 > miles at 60 mph -- I assume this means the batteries are completly drained at > the end. I know that isn't a good idea, so I'll by .80, to allow .20 left in > the batteries, and get 62.24 miles on a full charge at 60mph, which seems to > be in the ballpark for EVs. > > So, does this math look right? Sure, 15,500 Wh / 200 = 77.5 miles (100% DOD), that's correct. > Now for the final question for tonight -- does all this mean that the vehicle > will be using energy at the rate of 200 watts per mile at 60mph? Is that an > appropriate way to look at the "fuel consumption"? In other words, once the > car reaches 60mph, it theoretically takes 200 watts per hour to keep it > going, assuming a flat road and no other external variables entering the > picture. Is that right? No, don't confuse 200 Wh per mile and 200 W per hour. Watts is instantaneous value for power. Power over time is always Watt-hour (amount of energy). So spending 200 Wh/mile and spending 200 Wh (not W) in an hour is saying that you're moving 1 MPH. at 60 MPH you move 1 mile per minute. So this is how much energy you will spend per minute (for this speed) - 200 Wh. You got almost everything right! Excellent knowledge for a newbie! Victor > As always, thanks for the help. > > Bruce > Chapel Hill, NC > > "Dead fish go with the flow..." Anon.
