Our budget ev's fail because they are too heavy. If you converted or built a
small light vehicle using a kit as are available you will find that you will
gain in every area with a small pack and light vehicle. Look at Stella Lux.
Pushing a 700 mile range with 15kw pack. Look at what the Tesla could do with
a light vehicle. Because of the 85 to 90kw pack the car must be much heavier
to carry the weight. Carrying more weight hurts range so it is a vicious cycle
of over engineering. 375 miles on 16kw or 300 miles on 85kw. I will take the
lighter alternative...add solar and you never need plugging in as solar makes
sense on light vehicles....not heavy ones like we convert. Lawrence Rhodes
From: Jukka Järvinen <[email protected]>
To: Peri Hartman <[email protected]>; Electric Vehicle Discussion List
<[email protected]>
Cc: Lawrence Rhodes <[email protected]>; "[email protected]"
<[email protected]>
Sent: Monday, September 28, 2015 2:00 PM
Subject: Re: [EVDL] EVLN: The Big EV Debate> Go for Small or Big Battery Pack?
I think it's more important to think how the user benefits from the battery
sizing.
While it might sound irrational to have 150kWh onboard it would enable
stressless driving with longer useful lifetime. The vehicle it self will have
better resale value as it remains more usable even after 10 or 15 years. Also
people need to charge their cars only as much as they use. It has nothing to do
with the battery size.
But... 1C charging with 20kWh pack is 333Wh/minute. 1C charging for 150kWh pack
is 2.500Wh/minute. If it takes 250Wh/km (400Wh/mi) you either gain
0,83mi/minute or 6,25mi/minute. A DC-dumping with 300kW will stress less the
larger pack as it has more mass to absorb the losses and there's less
temperature rise during use. Also the discharge side has to be considered. You
might not need more than 20kW to move one econobox but see how Model S P85D
puts the EV's on the map. Our budget conversions could not do that. We need to
admit that. Sorry.
What makes all the difference for the business is how much does the battery
cost. We will see less than $100/kWh before 2020. Or at least it is possible
but if demand is high it sets the price level. On the other hand Tesla may
provide Model 3 as a service and they will own the cars always. Then it does
not matter how much the cells cost. You just pay that 10c/mi and nothing else.
So it does not matter if it weights 2, 3 or 5 tons. Even less if the car drives
itself. :)
-Jukka
http://www.google.com/profiles/jarviju#about
2015-09-28 23:39 GMT+03:00 Peri Hartman via EV <[email protected]>:
I think the key factor is the Cd of .16. While I think lighter vehicles are
better for many reasons, it doesn't seem to make that much difference in
efficiency unless you are spending most of your time on slow speed city streets.
For example, my Leaf gets about 1.5 - 2.5 miles per kWh (depending on
accessories and temperature) on city streets where I live. But if I go 60mph
on the freeway, I can sometimes get 4 miles per kWh.
Peri
------ Original Message ------
From: "Lawrence Rhodes via EV" <[email protected]>
To: "[email protected]" <[email protected]>; "[email protected]"
<[email protected]>
Sent: 28-Sep-15 1:31:45 PM
Subject: [EVDL] EVLN: The Big EV Debate> Go for Small or Big Battery Pack?
The debate should be about light or heavy vehicles and efficiency. If you
have an efficient vehicle that is light you might draw 55wh per mile. The
typical heavy conversion like the I3 , Leaf, Rav4, IMEV, or any other of the
currently available EV's are just too heavy to give good range with a small
pack. They all draw 200 or more wh per mile. The I3 is going in the right
direction. It has a relatively small pack and is more efficient than all the
other competitors. If however you have a light vehicle around a thousand
pounds your range will be close to 350 miles with a 16kw battery pack. The
vehicle needs to have a CD of about .16. With these specifications you don't
have to have a big pack. It will charge in 2.5 hours with a 6.6kw charger.
Efficiency and charging time should be the goal. Smaller the pack the quicker
the charge. Also the packs will last longer as they are not stressed as much
by carrying large weights. Engineering the right combination is what is
needed. Not 85kw packs in 5000 pound cars...however they are very comfortable
and useful as is and better than the ICE alternative. Lawrence Rhodes
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