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Discussion Starter · #21 ·
Not at all -- just my calibration of what one category of cars cost vs the other. A non-destroyed econobox from the 90's (a ford probe) is actually worth decent money due to how rare it is -- a wrecked nissan leaf is 1.) Not hard to find 2.) Not worth anything to anyone, so they really are cheaper. If I can talk my wife into letting me buy one, it'll be hard to explain "Yeah this more recent car was $1000 at auction in the same zip code, but this shitbox from the 90's was $2000 and we had to drive 14 hours to get it"
 

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Not at all -- just my calibration of what one category of cars cost vs the other. A non-destroyed econobox from the 90's (a ford probe) is actually worth decent money due to how rare it is -- a wrecked nissan leaf is 1.) Not hard to find 2.) Not worth anything to anyone, so they really are cheaper. If I can talk my wife into letting me buy one, it'll be hard to explain "Yeah this more recent car was $1000 at auction in the same zip code, but this shitbox from the 90's was $2000 and we had to drive 14 hours to get it"
Was hard to tell from your posting.

You get it...she may not...until she sells your stuff off someday 😂
 

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Discussion Starter · #27 ·
Again, in comes the horsepower and torque confusion by both of you.

As a pimple-faced 12 year old at the time, I can assure you that my 15HP International Super A tractor would pop a wheelie...on tires that, I'm guessing, were 2x the diameter of a car tire.
Isn't that just because the transmission on the tractor was built for very low top speed but absolutely redonkulous torque? Like, yeah HP and Torque absolutely matter, but so does the gear ratio to the final drive.

The reason electric "feels" like more power is because HP ratings for ICE cars are taken from the top of a very narrow RPM range (which is typically kinda high) while electric motors have a very broad power band, right?
 

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My tractor makes 15hp through its gearbox at 5mph, your electric motor makes 10hp at 5mph through its gearbox. I have 50% more torque at 5mph, but with double diameter tires, the acceleration of both vehicles is the same (assume same mass). 👀

I am operating at peak HP. Can't go faster without killing the torque. High gear to get 10mph on a tractor sucks for acceleration.

The electric has a flat torque curve. With its fixed gearing, it made 10HP at 5mph but also can make 100HP at 50MPH. And have a constant pull (ignoring drag) from 0-50mph because the torque is constant.

What is the electric equivalent to? I'd argue it's the same as a 10hp ICE tractor up to walking speed. Same as a 1000hp salt flats ICE racer at 50mph. Or same as a 200hp ICE...in a car geared for 100mph.

It's garage talk to assign a horsepower equivalence between ICE & electric because horsepower is torque at a speed....through a gearbox (and tires).
 

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Oh? 150 was actually on the high side, I really have little to no idea of how to convert the AH ratings if batteries to range,
...
I suppose I may not be understanding the range conversion math (the actual "a car weighs x so it needs y joules to push it z miles math), but 40 AH at a 20 amp max output means 2 hours of runtime, and given I'm splitting the max voltage I'd guess that motor needs, I would imagine 75 mph (thus for two hours at 75 id get 150 miles) is sustainable?
There are some rule of thumb type guesstimators, and then there are some online calculators guesstimators to help with the math.

rule of thumb version is that the energy needed per mile (while driving at moderate speeds) is about 10% of the weight; so if the car weighs 3000 lbs, then it will take 300 W-Hr per mile. For 150 miles that would need a 45kWh pack. If your pack voltage is 450 V, then you would be looking at cells rated 100 A-Hr. If you drive at 75, then this rule doesn't apply.

calculatus eliminatus version is based upon the weight, tire friction, aerodynamic drag coefficient, frontal area of the car. Online calculators will show that at 75 mph you will need much more power that you assumed. i would guess that you would be lucky to get 15 minutes of driving at 75 mph and your 40 Ah pack would be drained. :LOL:
 

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KW is an absolute unit for power. HP is a function of torque and RPM. Yes it's possible to convert between the two but it's not directly comparable.

Also EVs have the benefit of not shifting through gears, in the 1/4 mile that can be over a second of saved time.
 

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This is the first I've seen of someone putting a number to the difference. Most responses are, "HP is HP."
If you want to see some comparisons, look up threads by major or tropes, for example swapping out ICE for Electric in dragster,

#1

In post #2 is an index to posts in that thread with various calculations.
 

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Again, in comes the horsepower and torque confusion by both of you.

As a pimple-faced 12 year old at the time, I can assure you that my 15HP International Super A tractor would pop a wheelie...on tires that, I'm guessing, were 2x the diameter of a car tire.
Yes I am aware of the difference. Just saying how the peak hp value actually feels in ev vs ice for day-to-day driving.
 

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Oh hey wow, I've been looking for a not wrecked 30 year old car for this, wrecked ten year old cars are cheap
It's all about relative rarity - there were lots of second-generation Ford Probes made, but only for five years, and not as many as more common models, and very few would still be "not wrecked" (or rusted). I haven't seen more than a handful in past few years.
 

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This is the first I've seen of someone putting a number to the difference. Most responses are, "HP is HP."
The first, because it has no validity. There is way too much variability in the performance (available power versus speed, response time, etc) between engines and between motor/controller/battery systems to make such a simplistic comparison. Also, "feel" (which is largely about response time and noise) has little to do with objective performance (time to accelerate between two speeds).
 

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KW is an absolute unit for power. HP is a function of torque and RPM. Yes it's possible to convert between the two but it's not directly comparable.
Watts (or the multiple kilowatts) are the measure of power in the international system of units. Horsepower is a measure of power (defined as 746 watts, or 735.49875 watts for the European "metric horsepower"), originating from attempts by steam engine inventors to describe the output of their machines. They are just different (new and old) units for the same thing, and completely comparable.

Both watts and horsepower are defined in more basic units of work per unit time, or force at a velocity (since work is force through distance):
  • watts = joules per second, or newton metres per second
  • horsepower (traditionally) = 550 foot-pounds per second (or the rate of work done by a horse pulling a rope to lift a 550 pound weight at one foot per second)

Rotationally, the combination is torque (instead of linear force) and rotational speed (instead of linear speed)
  • 1 watt = 1 newton-metre radian per second (so Power (kW) = Torque (N·m) x Speed (RPM) / 9548.8)
  • 1 horsepower = 5252 pound-foot rotation per minute (so Power (HP) = Torque (lb-ft) x Speed (RPM) / 5252)
Shaft power is always a function of torque and speed, regardless of the units.

Watts and horsepower are completely interchangeable, using the appropriate conversion factor (746 W = 1 HP). The proper SI units (watt, etc) are convenient because they also work with electrical units, so power (W) = voltage (V) x current (A); one could do the same with horsepower, but with a conversion factor.

Internal combustion engines are now routinely rated in kW, because that's the modern unit... although for the general public this is still commonly converted to horsepower.
 

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It's all about relative rarity - there were lots of second-generation Ford Probes made, but only for five years, and not as many as more common models, and very few would still be "not wrecked" (or rusted). I haven't seen more than a handful in past few years.
As has been the case with many "classic" cars - during their day, common, unremarkable, boring, taken for granted. Sent to the scrap yard without a second thought.

The reason for the "highly desirable" 55-57 Chevy was lost over time...they were sought after by car builders, so "collectors" fell into the fray, also creating that desirability and demand for a run of the mill sedan. The reason they were popular, despite crap engines at the time and being death traps?...flat sheet metal that was tolerant of backyard bodywork.
 

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Watts (or the multiple kilowatts) are the measure of power in the international system of units. Horsepower is a measure of power (defined as 746 watts, or 735.49875 watts for the European "metric horsepower"), originating from attempts by steam engine inventors to describe the output of their machines. They are just different (new and old) units for the same thing, and completely comparable.

Both watts and horsepower are defined in more basic units of work per unit time, or force at a velocity (since work is force through distance):
  • watts = joules per second, or newton metres per second
  • horsepower (traditionally) = 550 foot-pounds per second (or the rate of work done by a horse pulling a rope to lift a 550 pound weight at one foot per second)

Rotationally, the combination is torque (instead of linear force) and rotational speed (instead of linear speed)
  • 1 watt = 1 newton-metre radian per second (so Power (kW) = Torque (N·m) x Speed (RPM) / 9548.8)
  • 1 horsepower = 5252 pound-foot rotation per minute (so Power (HP) = Torque (lb-ft) x Speed (RPM) / 5252)
Shaft power is always a function of torque and speed, regardless of the units.

Watts and horsepower are completely interchangeable, using the appropriate conversion factor (746 W = 1 HP). The proper SI units (watt, etc) are convenient because they also work with electrical units, so power (W) = voltage (V) x current (A); one could do the same with horsepower, but with a conversion factor.

Internal combustion engines are now routinely rated in kW, because that's the modern unit... although for the general public this is still commonly converted to horsepower.
Right, but they are still not directly comparable.

A horse lifting a weight is not the same measurement of an engine's horsepower. An electric Watt is not comparable to an engine spinning up on the dyno.

For instance let's say an electric motor can pull 100KW at 1 RPM from the battery. That is 100 KW but in order for that same motor to make the equivalent 134HP at 1 RPM, it would have to produce over 703,000 ft-lbs. Clearly not possible.
 
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