For example, he also built a keyless entry system with an arduino board and an iPod. This kid is pretty amazing.
144Vx500A = 72KW or 96.5HP. He's assuming 85% efficiency, which would give 82HP, not 34. Furthermore, if the motor were to deliver 100 ft-lbs of torque as stated at its stated maximum speed of 5800 RPM, that would be 110HP. This would obviously require more than 72KW of electrical power input.
Taking the ratio between the motor's stated performance and the electrical numbers given on the datasheet, and multiplying by the electrical power he intends to supply, we get 34/96x920 = 326HP. This too seems a bit off, as 35% efficiency is quite low for an electric motor. My guess is that the motor is actually incapable of producing its full torque at higher RPM.
My guess is he will actually produce something resembling the amount of power he's hoping for, but only briefly, after which they will deliver no power at all, ever.
The actual graphs are at http://www.go-ev.com/images/003_09_01_WarP_9A_Graph.jpg and http://www.go-ev.com/images/003_09_02_WarP_9_SpreadSheet.jpg
My guess is that the motor is actually incapable of producing its full torque at higher RPM.
Correct. At 100 ft/lbs the speed drops to just over 2000 rpm.
I would guess these motors have a thermal fuse wound into the stator coil (source: spent a summer in a rewinding shop), and if he tries to drive them much outside the design limits, they'll simply cut out, perhaps permanently.
EDIT: the datasheet mentions a temperature snap switch, so it sounds like they have a non-permanent cut-out on thermal overload.
When he realizes his error, he'll be able to reason much better about electrical and mechanical engineering than many of his peers in school (if he decides to go to college) due to having actual experiences of failing in the real world (rather than just on paper). Good for him.
http://electriccarinternational.com/media/img-prod/WarP_9_Sa... mentions 5.800 RPM (min. 2.000, max. 5.800 RPM). Thats too much to drive the wheels directly. Does anyone see a gearbox in the forum?
If he get´s this thing working, it would be really great! I can´t wait to call a electric car my own. :D
If you interested in such kind of work, you should search on Youtube for "electric VW Golf II", "electric VW Polo" or "electric VW Käfer". ;o)
Juan's project is impressive, no doubt, but his analysis of the superiority of electric cars is suspect. He writes:
The average car uses about 20% of the potential energy of the fuel in useful motion while wasting the other energy as heat, noise and pollution. Electric cars use upwards of 80% of their 'fuel', a percentage which can be increased relatively easily as most of its losses are electrical.
The biggest problem is that he's treating the electricity in the battery as raw fuel. He does acknowledge that most electricity in the US comes from sources like coal, but ignores various losses between that coal and his car flying down the road. Let's add those in.
The best we can do from a coal plant is about 49%. It may be possible to use the waste heat from such a plant for other purposes; I am not including such uses in this calculation as they do not have anything to do with powering the electric car.
The US power grid is around 93-94% efficient.
Electric cars don't get all the power from the grid in to the batteries as chemical energy. Charging batteries generates quite a bit of heat. The EPA estimates that the best electric cars are 62% efficient at converting power from the grid in to kinetic energy.
So we have 49% * 94% * 62% = 28.6% efficient at converting the chemical energy in coal to propelling the car. This is not a dramatic improvement over internal combustion. There is, of course the advantage of using power sources other than coal and oil, but the claimed efficiency is not quite what electric vehicle proponents would like it to be.
How much energy is used for the extraction, refinery, transport, and distribution of gasoline/diesel fuel? I suspect 26% efficiency for gasoline would also be extremely high compared to reality if those costs were factored in.
PS: If you compare solar cells with Bio fuels it's vary one sided with electric cars far out in the lead.
Electric might well win by a significant margin, but it isn't nearly the 85% to 20% claimed.
Does anyone know the efficiency of the average refinery? Or distribution costs? My suspicion is that they are actually just as bad as the overhead of burning coal.
Anyway, the whole thing is moot. The article may as well say "High School Student crams stuff under hood of car, claims it will kick butt if he can get it to work". I predict we'll never know.
It looks like the best case with natural gas is 60%, or 35% total system efficiency. Yes, that's a significant gain over 26%, but it's a best-case scenario. The real-world efficiency of the most efficient internal combustion cars is fairly similar to that of electric cars.
You can measure the efficiency of a nuclear plant by comparing the total amount of energy released in the reaction to the amount of electric output. Such measurements are commonly used to compare different reactor designs to each other.
I'm going to assume he comes from a fairly well off family.
It's a complex undertaking and he will definitely learn more than his classes in high school!
These battery pricing must've came down a lot over the past couple years because this would've cost something like $40k couple years ago, but a quick google for pricing looks like the battery pack he is using can be bought for around $13k
pricing source: http://www.a123rc.com/goods-468-Excitingly+Powerful+A+123+20...
I had an '05 S2000. I wish I still had it, wonderful car.
~500g each (1.1 lb) based on a quick google [tbc]
Just the drivetrain loss on muscle cars is around 30% approximately.
Also most muscle cars are slushboxes and the torque converter ruins efficiency.