[ausev] Fwd: Good sources to get started?

[Sarah & Erik]

Yes, except you missed the conversion from the 20 hour rate to the 1
hour rate, which makes the batteries act smaller than they are.

A little background - batteries are rated for a certain number of amps
for a certain amount of time. The energy stored in the battery is then
Amps X Time. The faster you discharge the batteries, the less capacity
they appear to have. EVs tend to discharge their batteries at a rate
that averages out to about emptying them in an hour, or a 1 hour rate.
A rough conversion factor to account for this is to multiply the total
capacity at the 20 Hour rate by .57 to get the 1 hour rate. (I think
this number is right! but I might be off)

I think this tends to be conservative, but a good first guess.

Erik

On Nov 27, 2007 10:28 PM, Josh Handel <jhandel at ktomics.net> wrote:
> I think I understand BUT I as much as I think I get it, I think I don't
> :-P... So let me perpose an "example" of what I am hearning, and someone can
> correct (sumorized example below word example) :-P
>
> Lets say I start with 12, 12v Batterys all rated for 40ah (at 20 hours to
> make the math easy) running in serial.
>
> If I understand you correctly, what I have is 144v rated at 40 amp hours. OR
> 5.76kWh's of battery. (stop me here if I am totally wrong here)..
>
> Now continuing on, I make a "perfect" car and it gets 28.8 wh/m at 60mph..
> so if everything above is "correct" and I understand what you are saying
> then I have would have a 200 mile range (5760 watt hours / 28.8 watts
> hours).
>
> 12 - 12volt/40Ah batteries in serial = 144volts at 40Ahs = 5760 Wh
>
> 5760 wh (from above) / 28.8 wh (consumption per mile) = 200 miles
>
> (yes these are totally bogus numbers, but I wanted to get the
> forumla/concept right first :-)..)
>
> So did I "get it" or am I completely wrong?
>
> Thanks
> Josh "Not an EE" Handel
>
>
>
> On 11/27/07, Sarah & Erik <electricbasset at gmail.com> wrote:
> > A well built EV will take less than 250 WH/mile, a more common number
> > is probably higher than that, say 300-350. This is probably
> > appropriate numbers for around town use. Depending on aerodynamics
> > your highway energy consumption could be much higher, maybe twice that
> > at 60 mph.
> >
> > To take a stab at whether lead acid batteries will work, look at the
> > total capacity which will be given at the 20 Hour rate, and multiply
> > by .57 to get how much energy you can count on at the 1 Hour rate.
> > Generally with Lead acid, aim for 50-60 % discharge on your normal
> > run. Sorry for the short email, feel free to ask questions if this
> > doesn't make sense.
> >
> > Please feel free to pipe up if you think my numbers are bogus.
> >
> > Erik
> >
> > On Nov 27, 2007 9:28 AM, Josh Handel <jhandel at ktomics.net> wrote:
> > >
> > > (Sorry for the duplicate if this shows up twice, I sent the first one
> from
> > > the wrong address, and I figure MailMan will probably bounce it so I am
> > > sending it again, this time from the right address)
> > >
> > >
> > > Howdy all,
> > >
> > >    I'm just starting the "investigation" stage of making an ev roadster.
> The
> > > goal would be to have something I could commute with (currently its a 50
> > > mile round trip from lake travis into town (so Hill country + highway)..
> The
> > > idea I am playing with is building roadster based on a locost design.
> If
> > > you want to know what a locost sports car is just google locost :-P but
> the
> > > short description is its a lotus 7 clone that is home grown.
> > >
> > >  Anyways before I can go to far I need to find out more about using an
> EV
> > > power plant (transmission concerns, power needs, battery capacity,
> etc..)
> > > and while I can read lots of different websites (and have been for the
> last
> > > few weeks). I figured I would be better off dropping a line and seeing
> what
> > > "starter" sources you guys suggest.. (yes I have read austinEV's getting
> > > started and EV America's getting started and a few others as well.. What
> Im
> > > am looking for is more detail about calculating performance, range, and
> > > power, motor requirements, etc...
> > >
> > > Thanks
> > > Josh
> > > _______________________________________________
> > > AusEV mailing list
> > > AusEV at austinev.org
> > > http://www.austinev.org/mailman/listinfo/ausev
> > >
> > >
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> >
>
>
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