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Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 6:14 pm
by TonyWilliams
davewill wrote: Everyone is simply guessing about charger efficiency. At least the 21 kWh number is useful when combined with the dash mpk.

Yes, we are guessing. But, if we're going to use the energy consumption numbers that match the speed, then that number comes up to 21kWh.

What it really is.... seriously, it's not important except as a number to divide/multiply by.

3.9kWh will roughly correspond to 60 mph and a range of 81.9 miles.... those numbers work close enough for most people's use. And to get there, we had to use 21kWh.

Tony

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 6:21 pm
by TonyWilliams
mogur wrote:I believe the total KwH of power put in to the battery when charging to be a more reliable indicator of capacity since it leaves little room for error or interpretation... Basically, the only variable is the actual charger efficiency, but that is pretty well known at this point.

Apparently, something doesn't add up. If the charger efficiency is "known" (but, admittedly not measured), then the "miles/kWh" that's on the dash doesn't add up.

So, which is wrong, the dash consumption number or the usable battery amount?

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 6:29 pm
by TonyWilliams
evnow wrote: Some things to be corrected, though :
- The top says 24kw/h battery. Should be changed to 21 and kWh (not kw/h).
- 6.4kwh, 5.2kwh etc should change to 6.4 m/kWh

Also, only a constant 38mph run might give 138 mile range. I think that 38mph mentioned along with other range by mph figures, confuses people (eg. why does 25 to 45 mph give only 108 miles if 38 gives 238 ?).

Well, the advertised size is 24kWh. No where does it say otherwise, but only through our collective efforts do we think that 21kWh is a more logical choice. That's why it's a note at the bottom. If it were renamed, that would be the first thing they would read.... hey, that's not for my car, I have the "big" 24kWh" batteries.

We do the same in fuel tanks on airplanes. It may hold 100,000 pounds of fuel, but only 99,823 are usable. We don't then call it a 99,823 tank.

Yes, I've already seen that confusion. Maybe rename that 40-45mph?

Thanks for the critiques.

Tony

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 6:59 pm
by evnow
TonyWilliams wrote:We do the same is fuel tanks on airplanes. It may hold 100,000 pounds of fuel, but only 99,823 are usable. We don't then call it a 99,823 tank.
I see what you are saying - I thought you had just forgotten to update.

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 7:03 pm
by evnow
mogur wrote:I believe the total KwH of power put in to the battery when charging to be a more reliable indicator of capacity since it leaves little room for error or interpretation... Basically, the only variable is the actual charger efficiency, but that is pretty well known at this point. My numbers from TED have been very consistent in this regard and show close to 24KwH usable when I run it down to dead or turtle...
Well, we can call it "usable" if you want. But the figure 21 kWh is way more useful than other figures.

Anyway, what do you think is the charging "efficiency" ? Using the at wall m/kWh and dash shown m/Kwh, I get the efficiency as about 82%.

Image

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 7:51 pm
by TomT
The most recent time I ran it down dead, I put in 26.67 KwH from the wall to 100 percent...
evnow wrote:Anyway, what do you think is the charging "efficiency" ? Using the at wall m/kWh and dash shown m/Kwh, I get the efficiency as about 82%.

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 8:20 pm
by TonyWilliams
evnow wrote: Anyway, what do you think is the charging "efficiency" ? Using the at wall m/kWh and dash shown m/Kwh, I get the efficiency as about 82%.

My wall to car numbers SWAG is about 84%.

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 11:34 pm
by planet4ever
mogur wrote:The most recent time I ran it down dead, I put in 26.67 KwH from the wall to 100 percent...
evnow wrote:Anyway, what do you think is the charging "efficiency" ? Using the at wall m/kWh and dash shown m/Kwh, I get the efficiency as about 82%.
Which proves? My calculator says 0.82 * 12.67 = 21.87. That's a lot closer to 21 than to the 24 you seem to be insisting on, mogur. A 24 kWh total battery capacity with 10% reserved (unusable) makes sense to me, and leaves us with 21.6 kWh usable.

Ray

Re: Range-Speed-Bars Thumb Rule Table

Posted: Sun Aug 07, 2011 11:56 pm
by surfingslovak
planet4ever wrote:A 24 kWh total battery capacity with 10% reserved (unusable) makes sense to me, and leaves us with 21.6 kWh usable.
Right, exactly. A number around 21kWh is quite plausible.

I don't have an explanation for the readouts mogur is getting, although I would like to, but I believe that unusable pack capacity is about 12%. This is somewhat speculative, but looking at the SOC readouts and other data, it's possible that the pack is represented by 320 SOC points (20 + 281 + 19) and 39 SOC points (20+19) are not usable.

Re: Range-Speed-Bars Thumb Rule Table

Posted: Mon Aug 08, 2011 1:41 am
by Herm
How do you guys account for that 27kwh number that comes up in the dealer's scan tool?

I think evnow should just buy a module at the dealership and put us out of our misery. He's rich anyways..