# can 900w & 7.5 amps A/C do 55mph?



## major (Apr 4, 2008)

Yeah, that sounds about right for the air conditioner.


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## zeroemission (Sep 14, 2010)

i'll take that as a no then. the guy with the serial hybrid opel GT is getting 50mph with a 5hp generator i was guessing is less efficient than the modern honda & yamaha units.

if more people were doing this, it would be easier to research.

since posting this question, i found a volts/amps/watts converter that lets you calculate one with two of the other and saw that the generator puts out 120v. i know amps = "pressure" & volts = "current flow" and watts = "current amount", but wonder how one car can roll with, say 36v and the 1st version of white zombie could go 125mph with just 168v. 120v is a lot.

after just looking a briggs & stratton 5hp motor up, i see that it has 206cc. i guess a 50cc motor, even an efficient one just can't generate the same amount of power as a 5hp. i thought the 2 were roughly =.

i could have sworn i saw some stat claiming you could cruise at 55mph with a ridiculously low amperage like .8 or something somewhere.

anything less than 150mpg isn't even worth attempting as far as i'm concerned. i guess i'll remain stranded in my little city then.

thanks for raining on my parade. not being sarcastic. i prefer the truth. if nothing else, i won't waste any more time on this impossible dream either then. electric cars just don't offer me anything useful. if i ever want to go cross country again, i'll have to rent a car i guess as i'm sure as heck not doing cramped busses again or flying.

i'm trying to figure out how the opel guy could get 100 amps out of a 5hp generator. when i look at larger honda generators, one that's pretty close rated at 2300 watts & 120v (4x voltage) is still only rated almost 20 amps. i can't find ANY 100 amp generators except for huge enclosed home units. this is the kind of switch around crap that makes this stuff impossible to research. if this were enough to push a car 55mph, then, in theory, a car with this honda generator could get 146mpg at load & 219mpg at 1/4 load. my understanding has been that once you get to cruising speed, it takes much less power to maintain it.

a generator weighs much less than batteries and an A/C one driving an A/C motor should be more efficient and powerful than D/C from what i've gathered.


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## Overlander23 (Jun 15, 2009)

It's quite simple. You can't get something for nothing. In this case, you're essentially wondering whether 900 watts can power a car 55mph. One horsepower is roughly equivalent to 750 watts, so can 1.2 hp (900/750) propel a full-sized vehicle 55 mph. Errr, no. And that's assuming 100% efficiency between the generator and the wheels. 

In the end, volts, amps, it doesn't matter. Watts is power. You can use volts and amps to derive watts; amps * volts = watts... If you heard that someone can power a vehicle down the road on just 0.8 amps, and let's assume 15 hp for something like a Civic @ 55 mph:

15hp * 750 = 11250 watts

watts = amps * volts, so: 11250 watts / 0.8 amps = 14062 volts

14062 volts, not very realistic. But something more realistic would be:

11250 watts / *80* amps = 140.6 volts. So in this case, 140 volts is needed to power a Civic at 55 mph (15 hp), while pulling 80 amps. Much more in-line with a conventional EV conversion.

The relationship is simple. Look at it another way. What about a 36 volt system? That's 11250 watts / 36 volts = 312 amps. A lot of amps, but it can be done if the batteries can handle it.

A 300 volt system? 11250 watts / 300 volts = 37.5 amps.

So there you go, the higher the voltage, the less amps are needed to create an amount of power. The lower the voltage, the more amps you need to create the same amount of power.

At 55 mph aero drag is a big concern. Some vehicles will consume more than 15 hp maintaining it, while more aerodynamic, lighter vehicles will consume less. But 1.2 hp? Nope... Very light, aero-sheathed, recumbent bicycle maybe...

Let's look at your second posting.

Open Guy is claiming 100 amps out of a 5 hp generator. That's 5 hp * 750 = 3750 watts. 3750 watts / 100 amps = 37.50 volts. There's your "36v" system. But it's still only 5 hp.

You researched a 2300 watt generator @ 120v. That's 2300 / 120 = 19.17 amps. Sounds like almost 20 amps (which is what its rating was). But it's only 2300 watts / 750 = 3 hp.

Most consumer generators are 120v, because they're designed for household appliance use. A 100 amp generator @ 120v would be producing, 100 amps * 120 volts = 12000 watts. That's a big generator. And 12000 watts is, 16hp. So yes, a 100 amp, 120 volt generator could probably get most of the way to powering continuously @ 55 mph. And I'll bet that generator will be using a 16+ horsepower engine. Probably closer to 20hp due to efficiency losses. See how much fuel that burns in an hour.

Keep in mind that 15 hp is generally what you will need to maintain 55 hp. To get there requires either a bit more, or a lot of patience.


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## zeroemission (Sep 14, 2010)

as to hp conversion, everything i've read says it's almost meaningless applied to electric motors as they're all about torque.

then, just as someone claimed in a comment about the alleged 5hp Opel, the claim is a flat out lie. there is no such thing as a 100amp 5hp generator. as the old saying goes... if something sounds too good to be true, it probably is.

do you know of any graphs that show equivalent volts to amps substitutions eg. as volts go down, amps must go up "this much" to compensate? if i could SEE the relationship, i could better understand it.

if you're not familiar with the opel GT, it looks like a baby corvette & weighs 2,100 in a system with batteries. it could be made lighter with stripping & fiberglass, is very aerodynamic (smaller than a honda civic hatchback from what i remember) and even cooler has a lightning bolt in a circle badge.

besides needing a car to get out of town, i could use one for hauling gear i use for work. a typical 40/40 pure electric wouldn't be much help there either.

i need to go back and read your reply a few times to see if i can get the math in my head. when i read mathmatic formulas, they tend to go in one ear and out the other until i can visualize them. i'm guessing the 15hp you're referring to is the minimum needed for highway speeds as i recall reading a typical car needs 20hp. if that's the case, then THAT makes sense. all of the different formulas you're quoting are just variations on the same 15hp at the wheels power. with that & the interchange calculator, i can convert info on any system or piece of gear to an equivalent. 

if 750 watts = 1hp, what about volts & amps? the rating has to include those too as 750 watts alone can be puny or astronomical. i'll look that up online. there has to be a horespower to watts converter or graph somewhere.

thanks for your help.

OK volts times amps = watts. then, in theory, you don't really need amps or volts if you have watts, and you can figure out watts by mutliplying volts & amps or dividing watt's by one or the other. right? is it that simple? to get a desired 20hp, i'd need 15,000 watts, or 125 amps at 120v and 62.5 amps at 240v. 

it would seem there's not much benefit at all then to serial hybrids as they chug a gallon an hour when you start getting up to 10kw. the 5hp opel claim is bogus. looking at a 15kw generator, it needs 1.6gph with a 1 liter motor. my 3 cylinder daihatsu had a 1 liter motor and could hit 80mph with a tailwind maybe, but got 42mpg highway.

my heads starting to hurt. it looks like electric is less efficient when i was under the impression it's much more so.

if that's the case, how could a 1,500 pound kit car with a 750cc motorcycle perform like a super car eg. 0-60 in 4 seconds and 120mph+ top speed?


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## Overlander23 (Jun 15, 2009)

Amps x Volts = Watts... It's all there. 

Watts and HP are the same thing, more or less, just different units (750 watts per HP) of power. Power is the motivating force.

100 volts x 100 amps = 10000 watts = 13.3333 hp

10 volts x 1000 amps = 10000 watts = 13.3333 hp

1000 volts x 10 amps = 10000 watts = 13.3333 hp

Get it?

Solve for 1 hp; 750 watts...

750 watts = 100 volts x 7.5 amps

750 watts = 10 volts x 75 amps

750 watts = 1 volts x 750 amps

Random one; 750 watts = 34 volts x 22.05 amps : 750/34 = 22.05 : 750/22.05 = 34... take your pick.

Each of those voltage/amperage combination produce the same amount of power.

Put it this way. It's impossible to have a situation where 750 watts of power is created from 12 volts and 100 amps, because 100 amps x 12 volts = 1200 watts.

Generally higher voltage (and therefore lower amperage) setups are more efficient than lower voltage (and therefore higher amperage) setups.

Doesn't matter if an electric motor or an ICE is providing it as far as power/constant speed is concerned. Power is power. A watt (over time) is what gets you down the road regardless of how it is generated. Acceleration is where you'll see a difference in characteristics between a motor and an engine.


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## zeroemission (Sep 14, 2010)

for a given amount of power though, electric IS much more efficient too, up to 90% vs. something like 20% for typical ICE (don't like that term as ICE is also a term for high efficiency class D amplifiers which might have use in electric cars) and maybe 40% for a turbocharged motor.

i'm quite familiar with newton's conservation of energy laws and the impossibility of a perpetual motion machine, but simply not the math for electronics.

750 watts = 1hp
&
volts x amps = watts
are very simple concepts to understand. with that formula, i can compare the capabilities of a 1,000 watt moped with a 300hp electric dragster now. that simple formula is the missing link that lets one compare apples & oranges.

your note about voltage being more efficient than amps helps a lot too and helps me jump to the conclusion that i bet amps are better for brute force eg. drag racing.

once i can visualize the problem, i can even make logical deductions. i bet a nickel i'm right about amps. the problem wasn't really everyone is "speaking a different language" although watts vs HP is, they're just picking different parts of the same V x A = W puzzle.

thank you for clearing a lot of cobwebs up and the valuable efficiency tip. now i know that voltage is the goal for practicality.

with a lot of applying the formula to different conversions now, i'll be able to figure out how many watts are being used in each system to get to it's capabilities. it's frustrating when you don't know the formula or even to right question to ask to get to it. it will get memorized right next to Pi x R squared.


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## Duncan (Dec 8, 2008)

Hi Zero

You can get a "car" to do 55mph on 900 watts BUT it will need to be a bit special!

This is Solar Racer territory!

It would need to be very light and "streamlined" - which does not mean "looks fast"

It would need to have the air flow over it without separation

This means it needs a loooong gently sloping tail 


When we talk about electric motors being more efficient or more "powerful"

Energy out (useful power) / Energy In
an IC engine is about 30% - (absolute max)
An Electric motor is about 90%

A 100Hp (75Kw) IC engine only produces that at about 5000rpm - at 2000rpm it probably has 20 Hp (15Kw)

An electric motor with 100Hp has 100Hp at 1000 rpm and at 5000rpm

A car engine is not expected to run at full power for more than a few minutes

The DC motors from forklift we use are rated as continuous power


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## zeroemission (Sep 14, 2010)

i'm VERY familiar with aerodynamics and drag coefficients. the most efficient vehicle shape is something like a bug. heck, i can remember "inventing" a NASA duct at about 3 years old when i told my grandfather that his giant "aerodynamic" hood scoop on his stock cars (a teardrop shaped deal with holes drilled in it) caused drag and that it would be better to remove it and instead use a recessed slot after he explained that the reason for it was aerodynamics. i understood the concept when he said air is like water flowing over surfaces. as soon as i had that VISUAL, i knew water would mostly pass over a sunken slot, but some would get sucked in. in my liimted vocabulary, i used the term "fall in", but i was picturing the car vertical with water falling down & his "aero" design was splashing like crazy. i also understand how the expanding air in a true ground effects system creates a vacuum, but still can't quite visualize how the air moving over the top of a wing's increased velocity generates negative pressure, but can at least parrot the concept. 

i have a high functioning mechanical intellect, but suffer from name & number dyslexia which makes math & ABSTRACT concepts a nightmare. i despise computers. i need to be able to create a concrete visual of any problem in my head in order to understand it. i can totally understand how golfball dimples make a surface more aerodynamic than a smooth surface because i can picture air dragging on the surface where the turbulence of dimples makes a slippery "air to air" surface. if a problem can be explained in plain english and not math, it's a piece of cake for me. i'm more of a *faraday* (i think... the INTUITIVE thermodynamics scientist... there goes that name & number dyslexia again) than a mathmatics bound *newton*.

i can deal with V x A = amps & 1hp = 746w, but not the insane math that made me walk out of physics theory 101 after 10 minutes. they weren't speaking english. THAT is what theory is to me... a description of processes in action, the idea, the underlying form, not a bunch of meaningless numbers. when i see a pool ball transferring it's energy to another, i don't see numbers & equations, i see concepts in action. i see an efficient transfer of energy as the two hard surfaces don't compress & convert the inertia into heat although some energy is lost as sound waves.

without any mathematics, i TRIED to argue that the hydro powered water pump generator scam bought by a casino owner was an impossibility because energy is lost in a closed system with some idiotic co workers who couldn't understand that simple plain english description of conservation of energy. even if the system WERE 100% efficient, you still couldn't draw electricity from it as the energy would me needed to maintain equilibrium. their minds still pictured magic fairies that dole out unlimited energy to those "who truly believe" LOL the college student co worker who argued most strongly never got back to me on what a physics or even general science teacher said.

as long as the subject isn't math, you don't have to talk down to me. my conceptual intellect clocks in at 157 on tests that aren't time based while my mathmatical abilities end at 9th grade level forgotten algebra & geometry. i'm mathematically challenged, that's all. i'm not ashamed of that limitation, but it can be frustrating when looking at numerical babble.

right now, i'm testing hydrogen serial hybrids in my head... convert motorcycle engines? multiple cylinders increase efficiency. that's how an indy car can produce 1khp with just 1 liter... no math needed. LOL i often find too that i'm very good at explaining concepts to others that they've struggled with before because the info wasn't explained in plain english. it took me 1 minute to explain 1/2 down to 1/16th inch marks on a ruler to a home depot worker (who cut wood... scary!) who never understood it. each smaller mark is 1/2 of the next larger one & every time you halve something, you double it's notation. 1/2 = 1 of 2. cut each half in half again and you get 1/4. i can't imagine how whoever tried to teach him that could mess it up. that's the most recent example i can think of. as soon as i learned the metric system in 4th grade, i couldn't understand why it isn't universal... just move the decimal point! what could be easier?

i just found a pair of kinetic energy in joules formulas and now that i have that, am sure i can find a joules to watts formula. that should cover all of the basic math needed for how to move a given weight at a given velocity or calculate what velocity a given system is capable of excluding efficiency losses due to friction etc. great... the conversion throws time into the equation. *sigh* should i be converting to watts per hour?


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## Overlander23 (Jun 15, 2009)

A watt is an instantaneous measure of power. A joule is a unit of energy, or the amount of power produced over time.

One watt delivered for one second equals one joule. Or 1 Watt-s = 1 Joule. Going further, you can see that by adding time you can get watts per hour (watt-hrs) as a unit of energy. One Watt-hr = 3600 joules (since there are 3600 seconds in an hour).

Take a 100W lightbulb. It takes 100W to illuminate it. Apply that amount of power for an hour and the lightbulb consumes 100W-hrs of energy, or 360,000 joules.

Notice that this is how you derive the energy capacity of a battery pack. A battery pack made up of 10 cells, each at 1.5v and 100 amp-hours of capacity yields a battery pack that is capable of storing 1500 watt-hrs of energy (10 x 1.5 x 100 = 1500 watt-hrs). That's equivalent to 5,400,000 joules of energy (1500 watt/hrs x 3600 = 5400000 joules).

If wired in series, the battery pack will be a 15v pack with 100 amp-hrs of storage.

If wired in parallel the battery pack will be a 1.5v pack with 1000 amp-hrs of storage.

Notice, though, that both packs contain the same amount of energy, 1500 watt-hrs.

Typically, you'll read about the amount of energy required to power an average EV quoted in watt-hours per mile. It can range from about 100 to 600 watt-hrs/mile depending on the weight, aerodynamic efficiency, and average speed. Using this info, and the aforementioned 1500 W-hr battery pack, you can see that a car with an average efficiency of, say, 250 watt-hrs can travel 6 miles before depleting its energy reserves.


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## zeroemission (Sep 14, 2010)

so, how does one convert the 300kj needed to push a 1 ton car just over 55mph into watts needed then? by seconds?

how about this?

a natural gas burning 100-150cc generator followed by a stirling engine "turbo generator" to recycle some of the energy lost as heat? any promise of noticeably higher efficiency than a standard ICE there? turbochargers nearly double ICE efficiency. i'd bet a stirling engine is more efficient than a turbo charger if one can be run off the temperature difference between one's hand and ambient air. the heat difference from an exhaust compared to to fresh air is much greater and if propane expands from it's liquid state into a gaseous one for combustion, that could form an air conditioner style "intercooler" for even greater efficiency. i first thought of it in a steam engine configuration until i saw how inefficient steam power is. 

my research dead ended with a pure alcohol burnining ICE which would run cheaper than anything if you distilled your own fuel, but natural gas is the emissions champ for easy conversions.

you just can't find much info on hydrogen conversions. virtually any link for it is for a conversion kit of which i've heard rumors many are bogus and a lot of dead links.

there just have to be answers to questions no one has asked yet. i guess this is another dead end though as a puny 5hp stirling running off combustion is HUGE. the returns from an already 5hp engine's exhaust would be minimal, even with it's 40% efficiency.


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## Duncan (Dec 8, 2008)

Hi Zero

You will have to bite the bullet and get your head around mathematics - if you can't use the numbers you are just going -WhaWhaWha

Go back to school - get a tutor - do what it takes but if you can't do the maths you can't do engineering

If you cant handle simple maths you cannot do engineering! - full STOP'

_*turbochargers nearly double ICE efficiency*_ - *COBBLERS!!*
You can get double or triple the POWER - but not increased efficiency

For all of your - use the exhaust stream .... 
you need to know the heat engine equation

(Temp In - Temp Out) / Temp In = Maximum Possible efficiency 
(Temp in degrees Kelvin)

Temp in - 100C, 373K - Temp out 50C -323K - max efficiency 50/373 = 13%
And that is theoretical maximum with no losses of friction!!

*i can totally understand how golfball dimples make a surface more aerodynamic than a smooth surface because i can picture air dragging on the surface where the turbulence of dimples makes a slippery "air to air" surface.*

*NO NO NO*
the reason it works is because the turbulent air (which has more drag not less than laminar flow) stays attached to the surface longer reducing the form drag (the pocket of low pressure behind the ball)

You can do engineering with a small number of simple equations BUT you need to handle things in numbers -
Engineering = Quantitative

Art = Qualitative and works with people - but it doesn't work on "things" - they need engineering


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## zeroemission (Sep 14, 2010)

i can handle simple equations like V x A = W and even more complicated ones like the 2 used to calculate joules, but when i doon't know the bridge between one formula like watts to joules, then it drives me nuts.

i have ZERO interest in learning math or computer programming etc. even if they'd help me do things like program a chess opening tutor that actually works. i'll just do without.

in the long run, this entire line of research is going to dead end for me as i just don't have $5k lying around or a machine shop, even a garage. i'm just toying with CONCEPTS.

i totally disagree with you about math too. if anything, being too mathematical is an IMPEDENCE to creativity as one can never think outside the box. when i was a kid, i knew a super genius with a photographic memory. he could name a formula for anything, who made juilius ceasar's sandals and so on, but when it came to making non-linear connections and creating things, i could run circles around him. ONLY when given the ideas he never could make the leap to, could he fill in the blanks with math.

i see my non-linear thinking as an asset. in many ways, i see "calculatus eliminatus" as an entirely backwards way of thinking unless you're an engineer who needs to know the load bearing capabilities of a bridge or how to design a circuit etc. rigid thinking is quick to dismiss ideas. it's just like a study done by scientific american or discover magazines. in some ways, children are actually more brilliant than adults as they haven't yet acquired the intellectual baggage that stifles their creativity. when one scientist was puzzled by the question of how to make a needle float on water without touching it. his 3 or 4 year old daughter instantly came up with the elegantly simple solution of simply freezing the water and dropping the needle on it. realistically, as everything came up to temperature, the needle would probably melt into the ice & break the surface tension, but he had to admit that she out did him in trying to find a solution.

in another instance, i was reading omni or discover, i think, and couldn't believe that the "high minded scientist" couldn't figure out why his shower curtain blew in against the force of water when he was totally overlooking CONVECTION. the hot air rising created a vacuum that let the denser cold air push in. i'm positive that "genius" knew math better than me, but in a practical situation, he was a complete idiot, hampered by a closed mathematical mind. either that, or he was making a scientific joke.

whoever replied about the golf ball, you're saying the EXACT same thing i did, but with different words. did i not say that the layer of air that clings to the dimples is more slippery than a smooth surface? maybe turbulence is the wrong technical word, but the dimples absolutely DO disturb the flow of air at the surface creating a sort of film over which the air that keeps flowing slides much more easily just like teflon does with surfaces, only in a gaseous form. the air in contact with the dimples is NOT static, hence the term turbulence, just like an air hockey puck sliding effortlessly.


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## Duncan (Dec 8, 2008)

Hi Zero

_*whoever replied about the golf ball, you're saying the EXACT same thing i did, but with different words. did i not say that the layer of air that clings to the dimples is more slippery than a smooth surface? maybe turbulence is the wrong technical word, but the dimples absolutely DO disturb the flow of air at the surface creating a sort of film over which the air that keeps flowing slides much more easily just like teflon does with surfaces, only in a gaseous form. the air in contact with the dimples is NOT static, hence the term turbulence, just like an air hockey puck sliding effortlessly.*_
*NO NO NO NO NO*

*Read what I said* ! There is MORE surface drag in turbulent air - MORE 
There is also LESS Form drag which more than balances for the increased surface drag

Until you can handle numbers you can't tell diddly

If you are too lazy to do the maths you are just playing with yourself


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## zeroemission (Sep 14, 2010)

stress... they make prozac for that.

i'm just testing ideas. as i have much less than $1,000 savings to work with, the point on building an actual system is moot. 

i'm also trying to think outside the box with ideas that no one else is using and have seen a lot of my solutions being used or proposed by others elsewhere. i imagined a range extending generator trailer before i saw it proposed in another EC conversion forum a few days ago. 

most recently, i started designing a modified single seat tubular dunebuggy frame with open wheels for a light, cheap and aerodynamic ride only to see a couple designs extremely similar to what i imagined at the X cup. math is for techies and engineers where artists, like me see the POETRY in a flowing aerodynamic shape. you CAN come to the very same conclusions and solution as mathematicians without using math whether you'll admit it or not. i can intuit the underlying form of the math without being hobbled by a straightjacket of formulas. yes... if i ever had a REAL concept, i WOULD test the math before attempting to build. i have tried to understand the math too, but only get muddled answers. no one ever did answer my question about how amps correlate to amp HOURS or that other time based roadblock to using the watts per velocity & mass formula. you can't do the math if you can't get all of the measures on the same poage can you.

back to aerodynamics, AGAIN you're taking my words out of context. the SECOND time, i did not use the word turbulence, did i? i will bet you $1 right here and now that the air layer that clings to a dimpled surface is NOT static like you're saying but that flows at a slower rate. the air film IS moving! you want to put a $1 on it and prove me wrong because your mathematical superiority complex is really testing my patience and i'd really like to prove you wrong and give you a dose of humility. the air on a dimpled surface flows & eddies (to me, turbulence = motion, not "disruption" or "chaos" or whatever definition you're going by). i only wish i could remember where i read about that phenomenon... discover? scientific american? popular science? mechanics? the MOTION of the air is what creates the slippery air boundary.

it didn't take long to find the evidence to prove YOU wrong and guess what, TURBULENCE IS the reason exactly as i said



> On Zipp's smooth discs this was much higher than for the dimpled wheels and, suggesting the Recr is reduced by the presence of the dimples. It also suggests that the dimples make the flow turbulent at an earlier point so the *more energetic turbulent flow* may stay attached to the surface for longer.


http://www.racecar-engineering.com/allarticles/166403/dimpled-aerodynamic-surfaces.html

now it's MY TURN, before you go around flaunting your alleged intellectual superiority and telling everyone how wrong THEY are, maybe, just maybe you should try something essential in mathematics... PROOFS otherwise known as CHECKING YOUR FACTS. i am NOT the idiot you think i am.

methinks YOU were confused by turbulence being a side effect of BAD AERODYNAMICS, but on the small scale, eg. dimples, the effect is opposite. feeling a bit more humble now mr. newton?


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## major (Apr 4, 2008)

Hey zeroe,

You seem like a pretty angry guy there. I think you might find what you seek if you kept your post less on the confrontational side, less wordy and keep to simple questions. Like I never saw you ask: 


zeroemission said:


> no one ever did answer my question about how amps correlate to amp HOURS or that other time based roadblock to using the watts per velocity & mass formula.


Which is quite simple.

Ampere hours (Ah) is a unit of charge. Ampere (A) is a unit of current or defined as a rate of charge. Therefore, charge equals current times time. Or Ah = A × h. So if you have 2 A flowing for 3 hours, it equals 6 Ah of charge. 6Ah = 2A × 3h.



> time based roadblock to using the watts per velocity & mass formula


This is a little difficult for me to understand what you are looking for. But velocity (v) and mass (M) relate to energy in the form of kinetic energy (KE) or energy associated with motion, by the formula KE = ½Mv².

Watts (W) are the units for power. We all know what time is and the units are seconds (s). Any type of energy has the units of joules (j) which are defined as watt seconds (Ws). So KE = Ws. 

Therefore your quest to find "watts per velocity & mass" is W / (½Mv²) = W / Ws = 1/s. So you are correct that time (or the inverse) is watts per velocity and mass, which for some reason you call a roadblock. But I guess time is the roadblock of the universe.

Regards,

major


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## TigerNut (Dec 18, 2009)

zeroemission said:


> so, how does one convert the 300kj needed to push a 1 ton car just over 55mph into watts needed then? by seconds?
> 
> how about this?
> 
> ...


One Watt of power is equivalent to one Joule of energy expenditure per second. It may require 300 kJ of energy to accelerate a car to 55 mph but that would generally depend on the amount of time taken to do the acceleration. Once you're moving, maintaining a given speed is dependent on your friction and drag losses, and requires a certain rate of energy expenditure - i.e. a certain amount of power.

Turbochargers do improve energy efficiency of an engine but not by 100 percent. They can double the power output but only at a substantially greater fuel consumption compared to the naturally aspirated engine. 
As a rule of thumb, a contemporary gasoline engine will typically convert 1/3 of the chemical energy in the fuel to mechanical work at the crankshaft, 1/3 into cooling system heat, and 1/3 into exhaust heat. The turbocharger recovers some of the exhaust heat and effectively turns it into available work at the crankshaft. The end effect is that the exhaust gas temperature of a turbocharged engine is lower than a naturally aspirated engine, for a given gas flow rate. Assuming that equal combustion temperatures are reached, this implies that the turbocharged engine is more efficient.

Stirling engines are interesting in many regards, but their thermodynamic efficiency is determined by the same equation as for any other heat engine, and the hard thing with Stirling engines is to design one that will tolerate very high temperatures at one end and near-room temperature at the other, while also having minimal 'dead' space for the working gas (which ideally is kept at as high a pressure as possible). And you still need a near-frictionless sliding seal for the pistons and a reciprocating-to-rotary motion conversion system. In contrast, the turbocharger can extract the same energy from the exhaust with one moving part.


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## Overlander23 (Jun 15, 2009)

zeroemission said:


> so, how does one convert the 300kj needed to push a 1 ton car just over 55mph into watts needed then? by seconds?



As mentioned previously, 1 watt-s = 1 joule. Also previously stated, a watt is instantaneous work. Add the time factor and it becomes an amount of energy.

300,000 joules = 300,000 watt-s, or 5000 watt-minutes, or 83 watt-hours.

If you were to provide 83 watts of power over the period of an hour, you'd be using the energy equivalent of 300,000 joules.

If you used a more useful period, say the acceleration time of a car going from 0-55 mph over 10 seconds, you'd have 50,000 watts over 10 seconds. That's 50,000 watts delivered for 10 seconds equaling the energy of 300,000 joules... ~65hp for 10 seconds. Reasonable for a 2000lb car.

It's all there. People haven't given you the specific answer to your numerical problem, but they've given you the tools to figure it out.

The best problem solvers are those that can be artists and understand the numerical reasons why. The artistry is good for problem solving. The math makes the problem-solving practical. Thankfully, humans aren't either-or. It's not like you give up artistry the more math you know, and vice-versa.


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## Duncan (Dec 8, 2008)

Hi Zero

You are still wrong
You said - the turbulent air 
*the surface creating a sort of film over which the air that keeps flowing slides much more easily just like teflon does with surfaces*

which is plain wrong


I said the effect is to keep the flow attached longer

On Zipp's smooth discs this was much higher than for the dimpled wheels and, suggesting the Recr is reduced by the presence of the dimples. It also suggests that the dimples make the flow turbulent at an earlier point so the *more energetic turbulent flow* may _*stay attached to the surface for longer*_

*Stop getting annoyed and read other peoples posts before you fly off the handle*


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## zeroemission (Sep 14, 2010)

turbulence AS I SAID FROM THE BEGINNING... CORRECTLY is why dimpled surfaces are aerodynamic to which you immediately, and incorrectly told me how wrong i was with a snide & condescending tone i will not tolerate, especially after proving you wrong. i'm just going to mute you. now go talk to someone else as i'm done indulging your superiority complex. tell it to someone you can convince you're smarter than.

i'm right, you were wrong and now you have no vocal cords in my world... buh bye mute.

so, i can't mute you? well that sucks. just don't bother talking to me duncan. you have NOTHING to say that i want to hear and i'm making a mental note to ignore you the old fashioned way.


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## Duncan (Dec 8, 2008)

Zero
Forget what I said about learning some maths 
Learn to READ!

When you have finished primary school - successfully I hope! you will be able to read other peoples posts and UNDERSTAND (a big word) them


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## zeroemission (Sep 14, 2010)

that's it duncan... keep sticking your idiotic foot deeper in your stupid butt mouth after you've been PROVEN wrong and keep talking down to make yourself look even stupider than you are you effing MORON! it's hilarious when idiots and liars stick to their stories even when you beat them over the head with facts. me? when i don't know something, i have the smarts to keep my mouth shut and work on learning. the first sign of intelligence is the ability to say "i don't know". anyone that goes out of their way to try and twist your words around to try and make someone look stupid is just begging for a lobotomy. i can't believe i let an effing MORON like you convince me that i didn't KNOW that dimples cause turbulence which creates a layer of air that's slipperier than a smooth surface it wants to cling to was actually wrong when i knew and have since PROVEN is EXACTLY correct. i do feel embarrassed to have been duped by an absolute moron who has zero ability to admit they're wrong. i knew what i was talking about all along. don't question authority... ignore it!

trying to get the math down but that darn apples & oranges crap as well as bogus info even within a formula is holding me back. i have this INCORRECT kinetic energy formula to start with, 



> Using "engineering" units, convert mph to fps, multiplying by 22/15: 55 mph = 80 . Divide weight (in pounds) by 32.174 to get mass in slugs. Substitute these values in formula above; you should get 215.9 × 10³ *(10,000???!!!)* ft lb. *(215900???? formula calls for 215.9 x 1 to get 292.72 result!)* Finally, convert to J, multiplying this by 1.356 J/ft lb. I get 292.72 kJ.


that's OK though, the 10 CUBED can just be ignored and just multiply 215.9 by 1.356 to get the proper 292.72 instead of 292720. 
215.9 x 1.356 = 292.7604kj actually. they didn't even multiply their own numbers correctly DESPITE the erroneous cubing.

so, after wading through the nonsense to get to the allegedly CORRECT formula for how many kj are needed to push 2135 lb @ 55mph, the math becomes USELESS anyways because another online conversion utility says that 300kj (rounded up from 292) = just 83w!!! there's no way that can be right. even if the three erroneous 0s you get from cubing 10 are added back to the mix to get 300,000kj, the conversion becomes 83,000w which can't be right either. the math is seriously busted in one or both places.


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## Duncan (Dec 8, 2008)

*Beautiful!*  

After you have stopped gibbering try - LEARNING TO READ!


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## major (Apr 4, 2008)

major said:


> Hey zero,
> 
> Do you ever read replies to your posts?
> 
> major





zeroemission said:


> after wading through the nonsense to get to the allegedly CORRECT formula for how many kj are needed to push 2135 lb @ 55mph, the math becomes USELESS anyways because another online conversion utility says that 300kj (rounded up from 292) = just 83w!!! there's no way that can be right.





major said:


> velocity (v) and mass (M) relate to energy in the form of kinetic energy (KE) or energy associated with motion, by the formula KE = ½Mv².
> 
> Watts (W) are the units for power. We all know what time is and the units are seconds (s). Any type of energy has the units of joules (j) which are defined as watt seconds (Ws). So KE = Ws.





TigerNut said:


> One Watt of power is equivalent to one Joule of energy expenditure per second. It may require 300 kJ of energy to accelerate a car to 55 mph but that would generally depend on the amount of time taken to do the acceleration. Once you're moving, maintaining a given speed is dependent on your friction and drag losses, and requires a certain rate of energy expenditure - i.e. a certain amount of power.





Overlander23 said:


> 1 watt-s = 1 joule. Also previously stated, a watt is instantaneous work. Add the time factor and it becomes an amount of energy.
> 
> 300,000 joules = 300,000 watt-s, or 5000 watt-minutes, or 83 watt-hours.
> 
> ...


---------------------------------


> another online conversion utility says that 300kj (rounded up from 292) = just 83w!!! there's no way that can be right


You are correct. This is incorrect. kj cannot equal w. Energy and power are different quantities. I suggest you brush up on some basic physics fundamentals and then it will become easier to correctly apply the math.

Regards,

major


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## Overlander23 (Jun 15, 2009)

> _Using "engineering" units, convert mph to fps, multiplying by 22/15: 55 mph = 80 . Divide weight (in pounds) by 32.174 to get mass in slugs. Substitute these values in formula above; you should get 215.9 × 10³ *(10,000???!!!)* ft lb. *(215900???? formula calls for 215.9 x 1 to get 292.72 result!)* Finally, convert to J, multiplying this by 1.356 J/ft lb. I get 292.72 kJ. _


I mean no offense by this, but you seem to have a serious problem with units. It's either self-imposed, because you make assumptions, or you're not careful with your reading/comprehension.

Let's look at what you found... 215.9 x 10³. First off, 10³ = 1000, not 10,000. So you end up with 215,900. Then the equation says, multiply by 1.356 J/ft to get Joules (note: not kilojoules). The result is 292760.4 joules, which is close to the stated 292.72 kJ. The cubing was fine.

See Major's post for the rest. But you're probably not reading this anyway... 



zeroemission said:


> trying to get the math down but that darn apples & oranges crap as well as bogus info even within a formula is holding me back. i have this INCORRECT kinetic energy formula to start with,
> 
> 
> 
> ...


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## zeroemission (Sep 14, 2010)

if no one pointed it out yet, 10 cubed is 1,000 and not 10k as 10 to the first is 10. i ran that in my head before i went to sleep and it bothered me all night.

the formula was shoddy talking about kj one second then plain old joules the next.

why on earth should i have to study physics when all i want is a simple formula (or group thereof) that converts mass & velocity into watts? that's ALL i'm looking for eg. mass x velocity x .1234 = ergs, ergs divided by 4.321 = horsepower & horsepower x 9.876 = watts. that's all i'm trying to get to, but can't find the COMPLETE formulas. if KJ can't be converted to watts, then that's the wrong formula.

why does EVERYONE in this forum have to be so difficult?

and everyone joining in to attack me about reading needs to go back and read what i said. dimples lower drag by creating slippery turbulence. you can try to quibble with semantics and say that's not true when it is because i didn't put it in the words YOU WANT but too freakin' bad! that is exactly how it works! i learned that by FREAKIN' READING by the way.

just as all of the formulas etc. i find compare apples and oranges, so do you all compare mathematical dyslexia with illiteracy which have nothing to do with each other at all. i can deal with formulas that use up to basic algerbra, but not sine, cosine & tangents etc. as long as the formulas are systematically broken down one step at a time. when 10x formulas are listed at once though, it becomes an overwhelming blur to me and it becomes hard to ingest no matter how much i stare at it.

anyways... thanks for nothing everyone. it's become clear that no one is ever going to answer any question i say and everyone is simply here to pat themselves on the back because math comes easier to them than someone else who unfortunately struggles with it. thanks for all of your comments about how stupid i am. they really helped clear everything up.

so... the formula is:
people with name & number dyslexia shouldn't be allowed to drive electric no matter what their ACTUAL IQ is cars because they're too stupid. OK... got it. i tell you, i'd love to take an IQ drag race with everyone at the site that measures high IQs with a test that isn't time based and see how well you can visualize unseen sides of a cube & other real world type problems as well as SOME math because i scored a 157, dyslexia and all.


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## Overlander23 (Jun 15, 2009)

I find this all terribly amusing. Terribly... amusing...

I'm pretty sure I don't have to worry about the OP reading this and taking offense either, since not only have several people given the answers to his questions from a theoretical standpoint... and from a literal standpoint.

Duncan seems to be the only person he reads.

Maybe I'm in his "ignore" list and he's just not getting the posts. In which case, I suppose this post is just as pointless.

Why else would someone post


> _"if no one pointed it out yet, 10 cubed is 1,000 and not 10k as 10 to the first is 10." _


at 1:37 pm PST when at 10:16am PST I wrote,


> _"Let's look at what you found... 215.9 x 10³. First off, 10³ = 1000, not 10,000."_


It's also hard to point out the difference between a Joule and Kilojoule when the answer makes the OP feel stupid. But how much simpler can the explanation get? It was not my intention to make you feel stupid. It was my intention to point out that 1000 joules = 1kJ... and countless other relationships.

OP... ARE YOU READING THIS?!?!


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## major (Apr 4, 2008)

zeroemission said:


> why does EVERYONE in this forum have to be so difficult?


We're not being difficult. Do you read the replies to your posts?



zeroemission said:


> why on earth should i have to study physics when all i want is a simple formula (or group thereof) that converts mass & velocity into watts? that's ALL i'm looking for eg. mass x velocity x .1234 = ergs, ergs divided by 4.321 = horsepower & horsepower x 9.876 = watts. that's all i'm trying to get to, but can't find the COMPLETE formulas. if KJ can't be converted to watts, then that's the wrong formula.


We have posted regarding this several times. I will put it as simple as I can. MASS times VELOCITY equals NOTHING !!!!!!!!!!! Meaning that the product of mass and velocity does not result in any useful quantity in any known system of physics or units in this universe, as far as I am aware.*

Furthermore, an erg = 100 nanojoules, which is a unit of energy. ENERGY is not POWER. So you can NOT convert units of energy to units of power.

No simple factor (number) can be used to make a KJ into a watt.

Got that?

major

* edit. Mass times velocity equals momentum. I missed that. Not a quantity used much in the EV study, but nevertheless, a useful quantity in this universe afterall.


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## Bowser330 (Jun 15, 2008)

This is by far the most bizarre (yet entertaining) thread I have EVER read on ANY forum period...


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## Crash (Oct 20, 2009)

Bowser330 said:


> This is by far the most bizarre (yet entertaining) thread I have EVER read on ANY forum period...


Yep... It's like watching someone try to fit a square peg in the round hole.


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## TigerNut (Dec 18, 2009)

major said:


> We're not being difficult. Do you read the replies to your posts?
> 
> 
> 
> ...


Hey Major, 
I'm not trying to quibble here but Mass times velocity equals momentum. 
_p = mv_​Take the velocity integral of that and you get the energy required or recovered due to the speed change.
_E = 1/2 m(v2^2 - v1^2)_

​To zeroemission: The above concepts are probably over your head but I didn't intend them for you. I'm sorry that we're not getting the basic idea, that power and energy are not the same, across in a way that you can relate to.

As simply as possible: 
Energy divided by time equals power.

It takes a great deal of power to deliver a lot of energy in a short amount of time. A funny car goes from zero to 300 mph in 4 seconds, but it requires about 7000 horsepower to do so.

On the other hand, a tiny solar cell could still deliver megajoules of energy, but it would take years. The solar cell puts out very little power, but the total amount of energy it could deliver is nearly unlimited if you don't care how long it takes.


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## major (Apr 4, 2008)

TigerNut said:


> Hey Major,
> I'm not trying to quibble here but Mass times velocity equals momentum.
> _p = mv_​


Good point. I stand corrected. Momentum. Not something I use much. I double checked several places before posting that and could not see where the unit of kg*m/s was listed anywhere. Also did not see N*s. Oh well 

But I do read replies to my posts


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## zeroemission (Sep 14, 2010)

i APPRECIATE anyone's help as long as they're not snide and condescending (especially when i'm right & they're wrong) about it. if someone gets an attitude with me, they are an enemy for life. i don't believe in second chances in that regard.

i have no problems with admitting my limitations or ignorance on any issue. to do so only makes one look stupider under the light of scrutiny. i am not a know it all and never will be nor will anyone else.

the round peg in a square hole analogy is very appropriate for this thread. that's my entire point. everything that i try to combined into a grand "unified theory" of ergs only frustrates me further because of all of the gaps that make the equations i DO have useless.

i KNOW there are formulas that will allow me to convert watts into velocity for a given mass and am relying on those that know them to share them because no keyword search i've tried, and i have, will lead me to them.

i'd love to bridge the ergs to time void but don't know how. the way i see it, there should just be a simple bar graph that has watts on the X axis and velocity on the Y for a given mass. even if no one has ever thought to make that info so user friendly (AND THEY SHOULD!!!!!!!), there has to be formulas that produce said non-existent bar graph. that the information seems hidden & shrouded in mystery no matter how hard i TRY to find it is frustrating. no, i never read that obscure book you did and in fact, there are absolutely ZERO books on EV conversions in my library that would contain that info COMPLETELY.

back to the square peg & round hole analogy, i'd like to modify it to _"i'm trying to build a puzzle with just 3 pieces"_. where are the pieces? why are they IMPOSSIBLE to find no matter how many times one says _"pretty pretty please with sugar & cream on top"_ to both search engines and human beings who either can't understand or refuse to answer what seems like a very simple question.

regardless, i would NEVER condescend to anyone seeking knowledge i have about something that they don't and would simply try to find the simplest & most direct route to them understanding the issue in plain english. those that condescend are the most worthless sort of people short of liars & thieves or worse in my eyes. they deserve no respect and will never get it from me. _"turn the other cheek"_ is the mantra of suckers & masochists. i live by _"nip it in the bud at all costs"_ and will bite my nose to spite my face at the drop of a hat rather than sacrifice an iota of integrity no matter how many _"you gotta play the game"_ sheep i have to offend. i have a knack for making enemies, but my self respect is an immovable object. now if only i could find the formulas for moving that object at 55mph in relation to planet earth i'd use the word progress.


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## major (Apr 4, 2008)

zeroemission said:


> the round peg in a square hole analogy is very appropriate for this thread.


My God. I think you have read a reply  In that case maybe the following will help.



> now if only i could find the formulas for moving that object at 55mph in relation to planet earth i'd use the word progress.


Please read the EV Information section of this site. http://www.diyelectriccar.com/forums/showthread.php?t=669 

There, under this sub topic, you will find http://www.diyelectriccar.com/forums/showthread.php?t=15508 

And in that you can read this:



> *1. The POWER requirements of your car at a particular speed is:*
> *Power in Watts = ((Mass in kg) (9.8m/s²) (Velocity in m/s) (Rolling Resistance)) + ((0.6465) (Coefficient of Drag) (Area in m²) (Velocity^3))*
> 
> *The 9.8m/s is acceleration due to gravity, the 0.6465 is 0.5 times the density of air in kg/m^3. If you enter the required numbers it will give you your power consumption in watts.*


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## zeroemission (Sep 14, 2010)

my entire purpose in asking questions is to read replies, but not when they take on a condescending tone. i just cannot get along with that personality type at all.

too bad i don't know either the Cd or rolling resistance of my design. i will take a look at it and see if it's possible to ignore those 2 varables and get results.

rough draft of my "cheap, light & efficient" design
http://i188.photobucket.com/albums/z157/zeroemission/electrobug.png

if serial hybrids didn't guzzle pretty much the same amount of gas as a standard ICE car, it would be possible to turn a design like that into an under 500 pound vehicle with a very low Cd profile.

i'm not looking for Nth degree accuracy, just a ballpark estimate to design around. the best i've been able to do is imagine a space in between motorcycle conversions and typical EV conversions, moreso motorcyles as my nylon skinned tube chassis concept is closer to them in weight and drag coefficient.

if one can get better performance than a typical EV conversion building from scratch, but for the same price or less, unless you're given a donor car, it makes more sense to build an "electric skateboard" from scratch to me. i'm not a fan of imitating the look of ICE either unless one gets EV vanity plates to advertise the fact.


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## TigerNut (Dec 18, 2009)

zeroemission said:


> my entire purpose in asking questions is to read replies, but not when they take on a condescending tone. i just cannot get along with that personality type at all.
> 
> too bad i don't know either the Cd or rolling resistance of my design. i will take a look at it and see if it's possible to ignore those 2 varables and get results.
> 
> ...


If you want to get range with your design then figure out a way to put fenders on it (open wheels are very bad for air resistance), and find some narrow, smoother tires. Big knobbies are very bad for rolling resistance.

As a ballpark: Open wheels and square profile front and back, which you have, will probably give you a drag coefficient in the range of 0.7.
For rolling resistance you'll just have to do some Googling and put in numbers that are in a reasonable range.

For the frontal area, you should include everything between the pavement and the highest part of the car.


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## zeroemission (Sep 14, 2010)

those aren't the actual tires, or even scale i'd use IF i saved up enough to actually build the vehicle. i just used that one because it was from an ATV and i planned the design around salvaging stock ATV A arms & using a chain drive in back and because the angle was about right for a 30/60/90 draft.

i think i'd go with even smaller wheels than that.

i had pictured creating aero wedges like grand prix cars use in front of the wheels with lighting & turn signals inside them, but putting them in front of the back wheel would interfere with getting in and out which would already be a challenge without the added intrusion. i have symmetry issues and wouldn't like the look of just wedges in front of the vehicle only. cars should be narrower in the front than the back. i can't stand the look of reverse trikes.

i also imagined a full fairing that stretches the length of the car with one or both sides swinging down to be stepped over, but that just adds weight & complexity as does a front fairing.

i know i could get lower weight, inertia, rolling resistance & Cd using narrower tires, but i want the ride to have some "cool factor" to it too. aesthetics are very important to me. a cool looking car will win people over more than an efficient one. besides looking cooler, ATV slicks would offer better cornering. more than drag racing, i'd like to be able to dust corvettes in slaloms pulling 2g. part of the vehicles intended use would be to haul DJ gear to gigs and a sportier looking design projects a better image. i dread the idea of showing up to gigs in hideous orange U-hauls.

i'm not looking to set records, just to get 55mph & 50 mile range and 30 mile range for hauling as simply as possible. i like the KISS principle. any high performance on top of that is icing on the cake.

also, to keep costs down, the batteries i planned for the ride were 7-8 x 12v @ 155aH (US Batteries US 12V XC) in a T formation with 3 wide forming the seat area with the other 4-5 forming a channel between my legs for a low center of gravity and close to 50:50 weight distribution if that were enough juice to get the magic 55/50 numbers. if necessary, i have allowed for the possibility of mounting a pair of batteries sideways behind the 3 wides. i planned on using those US batteries as all of their higher capacity models are too tall & would add to the Cd. 

one EV conversion site suggested 6v & 8v batteries, but when you do the math, you pay more and weigh more for a given wattage.

i guestimated a total cost of maybe $4000. $1000 for batteries, $1000 for having the frame built, $400 or so for suspension salvage, $1000 for electronics & $600 for miscellaneous fabrication i don't have the tools to do myself. that's in the range of "doable" for me.

from what i've gathered researching motorcycle conversions, if they can get 55/50 out of 4 deep cycle batteries, so 7 or 8 of them should offer better range & performance in a minimalist design like the electrobuggy. if i ever wanted to go cross country, i'd slap whatever size generator i'd need for highway speeds on a trailer for a serial hybrid. it would have been cool if i could just yank the batteries and throw a 30 pound generator in back as i first intended with this thread. that would save a lot of weight if only the juice were sufficient. it looks like those claims of a 5hp @ 75mpg opel GT serial hybrid are pure lies.


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