# is 500 amps overboard??



## Guest (Jul 20, 2010)

First off I'd not go with 48 volts at all. I did a VW Ghia with 72 Volts and it was just OK. If used for an in town car then 72 volts will do OK. My controller I used was a 550 amp controller with a good thick fined heat sink with cooling fan attached. With such low volts you will be needing high amps so the higher the amp capacity of the controller the better. It will be mandatory to use a real good heat sink on the controller and a heavy block of aluminum won't do. You will need a good finned heat sink with fan. My 72 volt controller pushed my Ghia to 65 mph tops in 4th gear. Your car may work OK with 72 volts but more than likely not. Your car is heavier than the old VW Ghia. You won't have much distance either but it will be fun as all get out. I'd say get a controller that will do 500 amps or more to allow the controller to operate within a good safe range with out the fear of destroying the controller. 500 amps minimum for 96 volts or less. Does not give you much choice either. 



Pete


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## JimDanielson (Oct 19, 2008)

depends what type of batteries you are using and the resistance of your motor. 

I have a 750amp controller and the batteries cannot provide over 350amps for more then 5 sec (they are 140Ah (20hr rate) marine deep cycle).

Use ohms law to find out the max current your motor would pull at 48v. V=IR


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## Guest (Jul 20, 2010)

True but your 750 amp controller will live at 350 amps with out fear of destroying your controller. Don't just use a controller that is always living on the edge of its rated max capacity.


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## OMT (May 10, 2010)

thanks for the help. what i origionally wanted to do is try it at 48v ( i have a few friends with a 48-96v controller, then try it at 72. im using 

12v -12X 75A DC24 batteries for a total of 11800 W i beleive, think its enough or not??. at 72V every 2 batteries will be in parallel its hard to explain but it works well.


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## Guest (Jul 20, 2010)

The 48-96 volt controller should do you just fine at 72 volts. Kinda small batteries but they will work. Not sure for how long. What is the amp rating for the controller? Do not do 48 volts. You won't like the performance and it will be a waste of money. Go at least 72 volts and 500 amps. If your controller is not up to snuff on 500 amps then just be sure you have a gauge to monitor the amp draw during acceleration and keep the amps at or below the max. I frequently pulled more than 450 amps accelerating but only for a few seconds. It was below the max and my controller lived. If you pull even once above that max limit you could blow your controller. Be careful. 

Pete


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## TX_Dj (Jul 25, 2008)

500 is the least I would consider for a golf cart, let alone a road car.

At 48v, you're going to still need torque, even if you don't want speed.

I wouldn't even built a 300v car with less than 500A (and probably not even 500A).

Remember, the controller current rating is what it provides to the motor. Current makes torque. Torque is what does the work of moving the vehicle. More is better. More torque at lower RPM = higher RPM than less torque at the same RPM.


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## ewdysar (Jun 15, 2010)

OMT said:


> thanks for the help. what i origionally wanted to do is try it at 48v ( i have a few friends with a 48-96v controller, then try it at 72. im using
> 
> 12v -12X 75A DC24 batteries for a total of 11800 W i beleive, think its enough or not??. at 72V every 2 batteries will be in parallel its hard to explain but it works well.


A 12V 75Ah battery has a rated capacity of 1875Wh (V x Ah). If you're running 6 in series to get 72V, your pack rating is 11,250Wh to 100% depth of dicharge (DoD). If you're running 12 in 6S2P (series x 6, parallel x 2)configuration, you're up to 22,500Wh. 

Figuring only 70% DoD, you're down to 15,750Wh of usable capacity for the 6S2P pack. Throwing in Peukert effect, using a Peukert exponent of 1.25 for flooded cells, that usable 15,750Wh will last one hour at 129A or an efffective capacity of 9,300Wh (129A at 72V for 1 hour). 

I don't know how fast your car will go at 129A. Higher average loads will decrease the effective capacity even further. Conversely, lower average loads will increase your effective capacity a little, for example 100A average load increases the effective capacity to 9850Wh (100A x 72V x 83 minutes).

All these calcs work for the assumptions listed here, different battery types work out differently and can deliver more effective capacity for the same size pack rating.

Eric


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## dtbaker (Jan 5, 2008)

OMT said:


> thanks for the help. what i origionally wanted to do is try it at 48v ( i have a few friends with a 48-96v controller, then try it at 72. im using
> 
> 12v -12X 75A DC24 batteries for a total of 11800 W i beleive, think its enough or not??. at 72V every 2 batteries will be in parallel its hard to explain but it works well.


don't even bother with less than 96v, you won't be happy. 96v and 400amp controller will be fine, 120v would be substantially better and result in far lower peak amp requirements.


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## 9852 (Jan 17, 2010)

OMT said:


> hey I'm buildign a light aurodynamic 99 accent, and me and my dad are having some arguments on what amps to choose. it will be a 48V pack with a 119lbs forklift advanced motor. should we go with 350A 400A or 500A? i want enough torque in 5th to get decent speed though.
> 
> so what amps would you guys suggest for a slightly larger than a metro conversion?


 
go with 500amps, i built my car at 48v to start out with, and everyone is right you wont be happy with that, but "go for it" at 48v have fun building it, then after it is built, when you are not happy and want more speed or performance, then up grade, It will be a fun experience.


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## TX_Dj (Jul 25, 2008)

Simply put, are you building a golf cart, or a car?

A golf cart runs on 36-48v and 300-500A.

A car (much heavier than a golf cart) built on the same specs will perform comparably, even with bigger tires or higher gear ratios "for speed".


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## DavidDymaxion (Dec 1, 2008)

48 V with 500 Amps will only be about 20 horsepower at the wheels. I have run my car (aerodynamic and ~2000 lbs) at 48 V. I would use it in the city on level ground, but it's not up to highway speeds or hill climbing at just 48V. Also, the high current draws needed at low voltages (Power = Amps * Volts, so you need more amps with lower voltages to get the same power) make the motor and controller run hotter.

If you were determined to make 48 V work (like going for a 48 V racing record), then you could do multiple 48 V packs, multiple motors, and multiple controllers -- but that would then be probably more money than just running higher voltage in the first place.



OMT said:


> hey im buildign a light aurodynamic 99 accent, and me and my dad are having some arguments on what amps to choose. it will be a 48V pack with a 119lbs forklift advanced motor. should we go with 350A 400A or 500A? i want enough torque in 5th to get decent speed though.
> 
> so what amps would you guys suggest for a slightly larger than a metro conversion?


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## Dink (Jun 3, 2010)

DavidDymaxion said:


> 48 V with 500 Amps will only be about 20 horsepower at the wheels. I have run my car (aerodynamic and ~2000 lbs) at 48 V. I would use it in the city on level ground, but it's not up to highway speeds or hill climbing at just 48V. Also, the high current draws needed at low voltages (Power = Amps * Volts, so you need more amps with lower voltages to get the same power) make the motor and controller run hotter.
> 
> If you were determined to make 48 V work (like going for a 48 V racing record), then you could do multiple 48 V packs, multiple motors, and multiple controllers -- but that would then be probably more money than just running higher voltage in the first place.


 Tell me if I'm wrong. But as I understand things it amps that give you torque/power, volts give rpm/speed. When will people learn hp don't mean @#$% for performance. In an ICE you build for max torque at a given rpm and hp will take care of it's self. What do you want power or speed? A desiel or 2stroke? Can't have cake and eat it too.


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## DavidDymaxion (Dec 1, 2008)

Agree amps => torque and volts => rpm/speed. I disagree amps => power, though. Power is amps * volts, it takes both. For instance, you can have a superconducting current with near zero voltage (it'll run for weeks), or you can have a voltage with no current. It takes both to make power and do real work.

For


> hp don't mean @#$% for performance


 it depends on how you define "performance." If you mean just get up a hill, but you don't care how fast, it's all about torque. If you mean top speed, or 1/4 mile time, power (hp) is important. Examples to illustrate this abound:

A heavy human on a bicycle can make more torque than a small car. Despite being far heavier, the car is much faster.

If performance is all about torque, and not about horsepower, I offer this gedanken experiment: Get a FWD van. Remove the motor, and weld a socket to the transmission input shaft. Put a socket wrench on the socket. Weld a long pipe onto the socket, going through the firewall all the way to the back of the van. Cut a hole in the roof so you can stand comfortably. Pad the edges of the hole do you don't decapitate in a wreck. Stand on the end of the pipe. You are now feeding the tranny input shaft about 2000 ft*lbs of torque! That's about 10 times the torque of the gas engine you removed. No matter how quickly you can jump up and down on the pipe, the van will barely move. You can only make about 1/2 hp. The 200 hp gas engine you removed could move the van at about 100 mph.

If I had to buy a sports car on just one motor number, I'd ask for horsepower. If I had to buy a truck on just one motor number, I'd ask for the torque.

If you specify both torque and rpm, now you have fully characterized the motor's output -- power is torque * rpm. It is a shorthand to just give the maximum power. Personally I think the number should be "integrated horsepower" as a measure of area under the torque curve.


Dink said:


> Tell me if I'm wrong. But as I understand things it amps that give you torque/power, volts give rpm/speed. When will people learn hp don't mean @#$% for performance. ...


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## JRP3 (Mar 7, 2008)

ewdysar said:


> A 12V 75Ah battery has a rated capacity of 1875Wh (V x Ah). If you're running 6 in series to get 72V, your pack rating is 11,250Wh to 100% depth of dicharge (DoD). If you're running 12 in 6S2P (series x 6, parallel x 2)configuration, you're up to 22,500Wh.


How did you come up with these numbers? They seem way off to me. Your math gives a 72 volt 75Ah pack almost the same Wh's as my 115V 100 Ah pack, 115 x 100 = 11,500 Wh.


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## ewdysar (Jun 15, 2010)

ewdysar said:


> A 12V 75Ah battery has a rated capacity of 1875Wh (V x Ah). If you're running 6 in series to get 72V, your pack rating is 11,250Wh to 100% depth of dicharge (DoD). If you're running 12 in 6S2P (series x 6, parallel x 2)configuration, you're up to 22,500Wh.
> 
> Eric





JRP3 said:


> How did you come up with these numbers? They seem way off to me. Your math gives a 72 volt 75Ah pack almost the same Wh's as my 115V 100 Ah pack, 115 x 100 = 11,500 Wh.


JRP3,

You are absolutely correct, you can see the error in the first calc. 12v x 75Ah = 900Wh, not 1875Wh. All the rest was based on that incorrect number. Don't know where that came from, I'd blame my calculator, but I know it was operator error.  That's why I try to list the calcs in my description so that others can call out my basic math mistakes.

I will usually catch this kind of typo, but was probably getting pulled away from the post after I had started it.

I deeply apologize, Sir. I'll try not to let it hapen again... 

Eric


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## OMT (May 10, 2010)

thanks for all the help guys!!! ill post up on my conversion, im sure it will turn heads, hoping to have to done in a few weeks!

i ended up buying an alltrax 72v 450amp controller for 340$ CND, and switching from 12X 12v-75A batteries, to 12X 12v-110A batteries!

ps: when i meant turn heads, this conversion has a part aluminum chassis, moded auro, and a laptop and garmin gps modified neatly( professionally) into the dashboard to give you battery % controller temp...ect and even internet access!!


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## Guest (Jul 23, 2010)

Just be sure you have a real good finned heat sink to that controller with a good fan. Don't skimp. You want the controller to last. Be sure you watch those amps with that controller. The controller will do you fine if you run it within the specs given. Not a bad price for a controller.

Pete


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## OMT (May 10, 2010)

should i limit the current so theres a less chance of over-amping for too long? or should i consider a simple water cooling?


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## Dink (Jun 3, 2010)

OMT said:


> should i limit the current so theres a less chance of over-amping for too long? or should i consider a simple water cooling?


 Doing both would seem to be the way to go. Limiting the amps though will lower the performance.


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## JRP3 (Mar 7, 2008)

I would not limit amps, you won't be drawing peak amps most of the time, and there are times when you might want the option. My 48 volt 400 amp Alltrax in the 6x6 runs cool with no heat sink or fans, even when my motor is getting hot. You'll have longer run times of course but I'd doubt you'll need water cooling.


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## Guest (Jul 23, 2010)

My experience is you DO need a good heat sink. Maybe not if your driving around at 25 mph or less but on the road, Put a finned heat sink and fan. They are easy to install and they work great. I'd also limit your current but limit it to just under the max your controller's max current. I would not limit it to 300 amps because I believe you should actually have more available amps than 400. I said with a low voltage system you will draw high amps for longer than a high voltage system. If you drive your car at it's max edge all the time you will smoke your controller. It is true that you most likely won't be driving full amps for most of the time but it's nice to know you have the ability to run more for longer if you have a controller that can handle more than you need. 

A heat sink is a MUST. 
Don't expect a hot rod of an EV with our voltage and amps. It will however be fun. 

Pete


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## 9852 (Jan 17, 2010)

I think G is right, a heat sink defenatly could not hurt, and since you have the ability to, I would go with just under max only to help the controller, but you will want more amps in the future, what you have is a great start, but for me it took two weeks, and I got a bigger controller, have fun.


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## Guest (Jul 24, 2010)

> .........but for me it took two weeks....


It took you THAT long? Dang after my first drive I wanted a larger controller. Just took awhile. 

Pete


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## Dink (Jun 3, 2010)

DavidDymaxion said:


> Agree amps => torque and volts => rpm/speed. I disagree amps => power, though. Power is amps * volts, it takes both. For instance, you can have a superconducting current with near zero voltage (it'll run for weeks), or you can have a voltage with no current. It takes both to make power and do real work.
> 
> For it depends on how you define "performance." If you mean just get up a hill, but you don't care how fast, it's all about torque. If you mean top speed, or 1/4 mile time, power (hp) is important. Examples to illustrate this abound:
> 
> ...


 If you read the whole thing not part, I used an ICE as an example, saying build for max torque at a given rpm and hp will take care of its self.......... Hp is not just torque*rpm. If that were true, a motor w/200 lbs of torque, turning at say 500 rpm would be what? Lets see, 200* 500= 100,000 hp.( I don't think so! ) There is more to the forumla for hp than tq * rpm. Also torque and hp cross on the dyno at 5252 rpm period. (physic's) So until 5252 rpm I guess Hp don't mean @#$%. How many motors do you have in an EV turning over 5000rpm? NetGain motors only rate there's to 5000-5500 rpm, except the warp 7's. Your FWD van thing, it is apples to oranges. Both need the same length torque arm for valid a valid test. Your last sentence is almost right. It depends on the rpm range that you are using, under the magic 5252 number it is the area under the torque curve that matters, and if over the torque has to be there or no hp.


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## Qer (May 7, 2008)

Dink said:


> Hp is not just torque*rpm. If that were true, a motor w/200 lbs of torque, turning at say 500 rpm would be what? Lets see, 200* 500= 100,000 hp.( I don't think so! ) There is more to the forumla for hp than tq * rpm.


*heavy breath* I find your lack of physics disturbing... *heavy breath*

Noone said what units were used, thus 200*500 is indeed 100,000 although not in horsepower. Two properly scaled formulas are:

Power (HP) = Torque (lb.in) x Speed (RPM) / 63,025
Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488


and depending on what units you use (SI-units, imperial units, mix, combination, bastardy mutations etc) you'll have to compensate for that. For example, if RPM is given in degrees per fortnight you will definitely need a seriously big divider to get the right result...


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## Dink (Jun 3, 2010)

I'm no physics major thats for sure. Just in an ICE, hp and torque always cross at that point. Thank you for posting the formulas. I new it was more than just tq*rpm. I believe you stated it properly in the performance forum, thread ; Torque is irrelevant or relevant. Posted by Major


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## Qer (May 7, 2008)

Dink said:


> I new it was more than just tq*rpm.


Well, not really. It's just that we tend to measure the rotational speed in turns per minute and some dork just HAD to invent a round wheel. Those two things fuck the formula up since minutes isn't really an SI-unit and the diameter of a wheel is 2*PI. That makes the number 30/PI "too high", but if we define rotational speed as radians/second we get that 5000 rpm is 523.6 rad/s.

I'm not sure what you mean with lbs, so I'll just use 200 Nm instead (which definitely isn't the same, but hey, it's just an example) and then we get:

W = Nm/s = 200 * 523.6 = 104.8 kW

Just to show you what I mean, here's the formula I showed before:

W = Nm * RPM / 9.5488 = 200 * 5000 / 9.5488 = 104.7 kW

I guess the value 9.5488 is a bit rounded off. 

So the problem with power = torque * rpm isn't that it's not a complete formula, it's that you MUST use SI-units for it to be correct. All those feet, pounds, inches, minutes, rpm etc aren't SI-units, thus you need constants to rescale the result since the in-data is broken by design!

Personally I think that those imperial and other non-SI units should've been thrown out with the trash centuries ago, they're just screwing things up when you try to solve physical problems. Do it right and physics is, actually, rather simple.


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## Dink (Jun 3, 2010)

I was meaning foot pounds of torque by, lbs. With the formula for HP. You can take any foot pound torque figure at 5252 rpm and the HP figure will be the same. Torque is the object until 5000 rpm or so is reached. So what I guess what I should have said was that the more amps the more torque, and the higer the voltage the more rpm. With best performance being to sustain max amps through the voltage range.


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## Tesseract (Sep 27, 2008)

Dink said:


> ...You can take any foot pound torque figure at 5252 rpm and the HP figure will be the same. ...


The equation hp = (ft-lbs x rpm)/5252 says that's not the case


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## DavidDymaxion (Dec 1, 2008)

No worries Dink, we're here to help and clarify. It's common to do equations in terms of concepts -- like speed = distance / time -- if units aren't specified you don't have extra constants floating around.

There is nothing magic about 5252 rpm -- that just happens to be a particular constant for a particular set of units for a particular equation.

There are plenty of electric motors that exceed 5252 rpm:


GM EV-1
Honda EV plus
Tesla
Fisker
Many (all?) AC setups



Dink said:


> If you read the whole thing not part, I used an ICE as an example, saying build for max torque at a given rpm and hp will take care of its self.......... Hp is not just torque*rpm. If that were true, a motor w/200 lbs of torque, turning at say 500 rpm would be what? Lets see, 200* 500= 100,000 hp.( I don't think so! ) There is more to the forumla for hp than tq * rpm. Also torque and hp cross on the dyno at 5252 rpm period. (physic's) So until 5252 rpm I guess Hp don't mean @#$%. How many motors do you have in an EV turning over 5000rpm? NetGain motors only rate there's to 5000-5500 rpm, except the warp 7's. Your FWD van thing, it is apples to oranges. Both need the same length torque arm for valid a valid test. Your last sentence is almost right. It depends on the rpm range that you are using, under the magic 5252 number it is the area under the torque curve that matters, and if over the torque has to be there or no hp.


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## Dink (Jun 3, 2010)

I did not have any intent for this to become what it has, as a drag racer,yes I want performance. But you have to learn when you delve in new waters. I have run many ICE motors past 11.00 seconds flat. That is not why I'm here. I do tree hug for reasons, being I love them. But to the point of life first. So, I am trying to go fast and not have 15 gal of cost and poluntants. I will continue to drive my 65 GTO at the mpg it gets. Just it would be more fun to have the same ET, under a green scope. Take Qer's HP formula and punch the numbers. 5252 is the cross rpm, for HP and TQ with an ICE.


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## Dink (Jun 3, 2010)

DavidDymaxion said:


> No worries Dink, we're here to help and clarify. It's common to do equations in terms of concepts -- like speed = distance / time -- if units aren't specified you don't have extra constants floating around.
> 
> There is nothing magic about 5252 rpm -- that just happens to be a particular constant for a particular set of units for a particular equation.
> 
> ...


 Yes you can feed any value to the thing if you input the factors correctly. HP is Torque, yes, but power is that torque applied buy rpm. The 5252 is a magic number.That is the number that TQ becomes HP! Want to bet money? ICE's are different than EV's true. What doe's the weight make.


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## Dink (Jun 3, 2010)

David, Why are you yanking me? I'm learning and you are a wha.....t. If you know better,thanks for the help. I started with ICE's. You seem to have a problem with HP! Car not do what you wanted? Ilove the people thinking thattheu are controlled.


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## Tesseract (Sep 27, 2008)

Dink said:


> ... Take Qer's HP formula and punch the numbers. 5252 is the cross rpm, for HP and TQ with an ICE.


What do you mean "5252 is the cross rpm"? 5252 is just a constant to make it possible to convert torque in ft-lbs and speed in rpm into power in hp. If I change that number to 7040 I can get power in kW instead. 

Take a good look at "Qer's HP formula":

*Power (HP) = Torque (lb.in) x Speed (RPM) / 63,025*

Qer is from Sweden so he sometimes makes weird choices when it comes to American units. In this case he used pound-inches for torque, which is a bit small for cars. If you substitute pound-feet for pound-inches the constant 63025 has to be divided by 12, right, because there are 12 inches in a foot and then the equation becomes:

*Power (HP) = Torque (lb-ft) x Speed (RPM) / 5252*

Now, let's plug some numbers in to this equation and see if you still want to make any bets that torque only becomes hp at 5252 rpm (which, to put it bluntly, is flat out wrong).

(lb-ft) | RPM | HP
-----------------------
50 | 500 | 4.76
100 | 500 | 9.52
150 | 500 | 14.28
200 | 500 | 19.04

As you can see, HP goes up with torque just fine. This is an algebraic equation, Dink, so not something you can really argue with. It is what it is. If you still want to bet money on this I am more than happy to wager against you.




Dink said:


> David, Why are you yanking me? I'm learning and you are a wha.....t. If you know better,thanks for the help. I started with ICE's. You seem to have a problem with HP! Car not do what you wanted? Ilove the people thinking thattheu are controlled.


Tsk-tsk... You've really gone and stepped in it now.


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## Guest (Jul 25, 2010)

65 GTO. Nice. 

Pete


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## Dink (Jun 3, 2010)

Tesseract I seem to be good at stepping on it. It gets responses though.The orignal topic was power at 500amps. The more amps the better avaible torque, yes? The higher the avaible volts the higher rpm,yes? So the highest amps you have continious will give you the best power (bad term) through the rpm range that the volts will allow,yes? As for the bet lets understand the bet first. I'm saying that you take an ICE, the torque and hp will be the same at 5252 rpm (if the motor can do it)under load. Torque is it till 5252 rpm,yes? Back to the bet. You take the formula from Qer, Power(HP) = Torque (lb.in) x Speed (RPM) / 63,025. Use 5252 as the rpm point and I'll bet that no matter what torque figure you put in it, the hp will be the same at that rpm, if you round the decimal points. For a buck? (it will cost more to mail it)


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## Tesseract (Sep 27, 2008)

Dink said:


> Tesseract I seem to be good at stepping on it. It gets responses though.


Maybe it does, but keep in mind that you aren't _entitled_ to anyone else's knowledge. If you're a jerk to people here then you'll only hear crickets when you ask a question... 



Dink said:


> The more amps the better avaible torque, yes? The higher the avaible volts the higher rpm,yes?


Spelling aside, yep.



Dink said:


> So the highest amps you have continious will give you the best power (bad term) through the rpm range that the volts will allow,yes?


That's correct.



Dink said:


> As for the bet lets understand the bet first. I'm saying that you take an ICE, the torque and hp will be the same at 5252 rpm (if the motor can do it)under load.


Gotcha, but you still lost the bet anyway. See below



Dink said:


> Torque is it till 5252 rpm,yes? Back to the bet. You take the formula from Qer, Power(HP) = Torque (lb.in) x Speed (RPM) / 63,025. Use 5252 as the rpm point and I'll bet that no matter what torque figure you put in it, the hp will be the same at that rpm, if you round the decimal points. For a buck? (it will cost more to mail it)


Good thing you only offered up a buck... I was going to bet you a Soliton1 

Read 'em and weep, cowboy:

(Torque x RPM)/63025 = HP

(100 x 5252)/63025 = 8.33hp
(110 x 5252)/63025 = 9.17hp 
(120 x 5252)/63025 = 10.0hp
(130 x 5252)/63025 = 10.8hp

Every 10 lb-in increase in torque adds another ~0.83hp at 5252 rpm.


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## DavidDymaxion (Dec 1, 2008)

My apologies if it came across that way, there's no intent to offend you or yank you.

I am a kindred spirit, I have a 300 hp gas car I love to race. I have run it (as we as several other cars) on the Salt Flats, on the drag strip, on the big track, or on a bunch of autocrosses. The goal is my 9Electric will replace most of my gas racing and daily driving.

Check out my web page to see where I'm coming from: http://ExplodingDinosaurs.com


Dink said:


> David, Why are you yanking me? I'm learning and you are a wha.....t. If you know better,thanks for the help. I started with ICE's. You seem to have a problem with HP! Car not do what you wanted? Ilove the people thinking thattheu are controlled.


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## Dink (Jun 3, 2010)

I'm sorry, I acted poorly. I ment no offience I'm used to ICE's.
What I have learned running them is torque is king till 5200+. Not to strart things but I understnd things as torque is power and rpm is the speed it is applied. I'm sorrry, I want to learn.


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## Dink (Jun 3, 2010)

Dink said:


> I'm sorry, I acted poorly. I ment no offience I'm used to ICE's.
> What I have learned running them is torque is king till 5200+. Not to strart things but I understnd things as torque is power and rpm is the speed it is applied. I'm sorrry, I want to learn.


PS. Blowing things up is a hard way to learn. Sorry


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## TX_Dj (Jul 25, 2008)

Dink said:


> I'm sorry, I acted poorly. I ment no offience I'm used to ICE's.
> What I have learned running them is torque is king till 5200+. Not to strart things but I understnd things as torque is power and rpm is the speed it is applied. I'm sorrry, I want to learn.



You almost have that right.

Torque is the force that does the work.
Torque + RPM makes horsepower, the measure of work done over period of time.

If you have a little torque and a lot of RPM, you can still make big horsepower, because you're doing that little bit of work very quickly.

If you have lots of torque and low RPM, you can still make big horsepower because you're doing a lot of work in a shorter period of time.

Example:

500 HP turboshaft engine turning at 25,000 RPM produces 105 lb-feet torque.
500 HP turbodiesel turning at 1,600 RPM produces 1641 lb-feet torque.

Both examples are doing the same amount of work per period of time, but depending on the application, one is better suited than the other. To make the turboshaft run a semi-diesel, you would need a more significant gear train to take 25,000 RPM down to road speeds and still have enough torque at the wheels to move 80,000 lbs from a stop. Similarly, you'd need a much more light weight helicopter to handle the far heavier turbodiesel engine, which just won't work.

The hairs we're splitting when we compare ICE to EV torque/HP is the POWERBAND location, and the quantity of torque vs. RPM.

A typical (gas) ICE will produce it's peak torque around 3500 RPM. An EV will produce it's peak torque around 0 RPM.

Torque is what moves you. When drag racing, as you know, you try to target your launch around the peak torque RPM of the ICE you're using. Even still, RPM will drop for an instant as things hook up, and you have to climb back up to torque. EV gets full torque right off the line.

Lets say you make an EV that generates 1000 lb-feet torque at 1000 RPM, vs. an ICE that generates 300 lb-feet torque at 3000 RPM. The EV is making 190 HP at that point, and the ICE is making 171 HP at its point. Thus, the EV is doing more work per unit time.

Hope this helps.


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