Motor size?

Do It Yourself (DIY)
1

Hi, trying to figure out what size motor I’m going to need for a truck conversion. I’ve seen the info to size an electric motor to 1/3 the size of an ICE, have seen that you need an X size motor to cruise 35MPH, but I’m not finding the info I really need, like an X volt Y HP electric motor will act like an ICE with X HP and Y torque on the highway. Looking at different web pages for different conversions, it looks like there is a wide variance in performance for electric motors, but I’m not finding the correlating factor that would help me size the motor I’d need for my truck. And, from what I’ve seen I need to determine the motor size before I determine anything else. Can anyone assist?

The particulars I need for this conversion will make the target vehicle operate at least as well as it does with the gasoline engine in it. The vehicle will have a completed curb weight of about 3700lbs, and I will be looking for a 0-60 acceleration time of at least 6 seconds, a cruising speed of about 75MPH, and a top speed over 100MPH. Assuming I had unlimited power available, what size motor would I need to accomplish this? The truck’s current curb weight is 3000lbs with ICE installed, and this is before taking any weight reduction steps. If the electric motor can spin 5000RPM and have enough torque to get up to speed quickly, then I could probably forgo a transmission for it although putting a trans between the motor and rear end if necessary. Might not be the fastest into a headwind, but 5000RPM through a 3.42 rear end would put the truck’s top speed at just over 120MPH, making cruising RPM around 3300RPM for an 80MPH speed. If the motor can’t manage this, then a transmission would be needed. Essentially, I need the electric equivalent of a 250HP/275TQ gasoline engine that has a torque band from 2000 to 5000RPM and redlines at 5500RPM.

Main reason for the higher power capability is I use my truck as a truck and need to be able to tow/haul the occasional load.

Can anyone assist with the numbers here? Right now I’m only looking at whether there is a motor capable of doing this. If there is, I can come up with a way to power it.

2

Yes, there are electric motors that can do excellent acceleration.

Are you looking at using a AC or DC powered motor?

For the numbers you put up and the size of the vehicle you specify, you are going to be running some really high voltages. I think it is possible, but I also think your stuck using expensive lithium batteries to make those numbers achievable.

Read up on the Tesla roadster.

3

Net Gain makes some pretty powerful motors, I believe they recommend the Warp11 or Warp13 for trucks and SUV’s.

You can check them out here: http://www.go-ev.com/

4

I’d prefer an AC traction motor, but can’t find anything that isn’t locomotive sized. Not that I wouldn’t love that kind of power under the hood :cool:.

I’ve looked at the Warp motors, and see where they are used in dragsters, but has anyone got a real world review of how well one of these motors does? This is something I’ve not seen on the larger Warps. Thanks.

5

whats your budget?

are you ok with spending 20k on lithium batteries?

what range are you looking for?

Do some research on evalbum…
warp motors:
http://www.evalbum.com/mtrbr/WARF

netgain:
http://www.evalbum.com/mtrbr/NETG

6

No budget right now. Just exploring the possibility, once it looks feasible I’ll look at the money side.

7

well, best to look at budget first… seriously…it will COMPLETELY lead your design… AC is not cheap, neither is lithium.

anything is feasible within limits, the limit is budget and technology. Since you know there’s AC, DC, lead acid and lifepo, best to decide on budget before choosing a technology.

8

I disagree on budget being the first decision. If an electric conversion won’t do what I want, there’s no reason to spend time making up a budget. Once you come up with the way, you can start working on the means.

Thanks much for the links, checked them out and came across this site that is doing almost exactly what I want to do, except I plan on an S10 pickup instead of a BMW. Going over the site now to see what I can use from it, so far I’ve found the air conditioning and heating answers that I’ve been searching the last 6 months for. I greatly appreciate it for that, if nothing else!! :smiley: :cool:

9

I somewhat disagree with you, mostly because you have tons of options, but you need to limit it down by budget… to decide which direction to go. you’ve got AC and DC, lifepo and lead… all of those are possible… and AC and Lifepo being the most expensive, but giving you the most range and also being the most expensive.

Just finding the motor is going to be a challenge, and you would definately want to keep the transmission.

Start looking for a motor, and decide if its afforable… then decide what range you need and start looking at batteries.

Just to get you some real world prices and options for AC,
http://www.metricmind.com/prices.htm

and for DC:
controllers:
http://www.cafeelectric.com/shop/index.php?main_page=index&cPath=1
motors:
http://www.go-ev.com/End_User_Pricing.html

that will give you an idea of cost of just the motor and controllers. Batteries are another issue altogether. But for what you want, I’d estimate $20,000 at the least for LifePo batteries, but only 3-4 grand for lead.

10

Bummer. Thanks for the links. Looks like it’ll take about 2 years to put back enough cash after the kids move out. This puts being able to do what I want back to 2014. The first kid moves out this year, the second wants to go to college so will be around for the next 5 years. Oh well, guess that gives me plenty of time to work out the details then ;).

11

yeah, cost leads design…many times thats the case in my job as an engineer with Leviton, customers have a budget, and they want functionality, but they can’t afford the high quality products, so they settle for the cheapest solution to get what they NEED and pass up what they want.

I’m going series wound motor, SLA’s and a decent controller for my motorcycle. It WILL be LiFePo and AC within 2 years.

12

Thanks. What I’m doing isn’t a “git 'er 'dun” project though, this will be a “git 'er 'dun right” project. Step one, empty the nest, step two, build a smaller, FAR more efficient house, step 3, build a shop with some room to stretch, step 4, start building an electric car from the ground up. I plan to base it off an S10 ext cab like the one I have now, but with some real time, care and effort put into it. The only other vehicle I’d consider for this would be an early 70s GM muscle car like the ones I grew up in. Right now I’m just trying to track down what is needed so I’ll have a list of parts and prices. The time it takes to come up with the money or complete the project won’t be important, the important part will be the project itself.

In other words, I’m starting the transition from doting father and family man to obsessive car nut hobbyist. :p:p;):slight_smile:

13

see, thats realistic…

Just watch the weight, see if you can lighten up the chassis/cab/bed.

now I see how you are aproaching it, plan now, buy MUCH later.

14

Yep. Heh heh… I’ve already got plans to lighten the vehicle with fiberglass parts, lightened high performance suspension parts, and frame work. Been trying to decide between sliding an El Camino frame under the truck, or just build a tubular frame for it. Either one will be lighter and just as strong. I can do the El Camino frame myself, and pulling all the engine related systems will drop quite a bit of weight. I do want a roll cage in the truck for safety.

I also want to do something a little different from the normal EV crowd. Rather than powering the truck with a large battery pack and plugging it in every night, then trying to build the suspension up enough to manage the ton or two of batteries I’d need for range, I thought I’d do a small battery pack and an on-board turbodiesel generator. The advantages to this would be less weight and unlimited range, as all I’d need to do is stop by a gas station and refill the diesel tank when it ran out. I consider anything with a 10 minute reload of a commonly available fuel to have unlimited range.

A diesel engine used for a truck has to be large and strong enough to operate the truck in a large variety of conditions with various loads, but a diesel engine used to operate a generator only has to operate at a specific RPM to match the generator head. Therefore, the engine can be optimized for that RPM level, and can be smaller since it’ll never have to turn more than the generator at max output. A diesel is also most efficient running wide open, and less efficient at cruise speeds. A turbocharger will also increase the efficiency and power of a diesel, allowing the motor to be sized even smaller and using less fuel. This is proven out with diesel electric locomotives, which are able to move thousands of tons at a respectable clip while burning only 3 gallons of fuel to the mile. In order to match this with a tractor trailer, you’d need some 450 trucks that get 60MPG to move the same load as that train, if my figures are correct. At worst, the 3gpm is just for the locomotive, which itself weighs many tons. Tracks aren’t the greatest things in the world for traction either.

With a small turbodiesel driving a generator head (and with all appropriate emissions controls) the truck would not need a huge battery pack. So, this will save a ton or so of weight on the truck, requiring less power to drive it, allowing a smaller generator and electric motor. With less weight, the truck will be faster, more agile, and will get better fuel economy. I would have a battery pack on board that could operate the truck for a few miles, but its main purpose would be to serve as a power buffer/regulator between the genset and the motor, not as a main power source.

As most generators sized to run a house can run on as little as a gallon of gasoline per hour, a similar sized diesel should be able to run off at least a gallon an hour, if not less. If that gallon per hour can allow the generator to provide enough juice to run the motor at 60MPH, that’s 60MPG. If it can run it on half a gallon, that’s 120MPG. I could easily live with a 120MPG vehicle that could clip the quarter mile in 10 seconds. :smiley:

Can anyone see a fault with this plan? The way I see it, if it works for a train it should work for a car, and if for some reason it doesn’t I can always use the generator as a house backup and slap a ton of batteries in the engine bay. If it DOES work, then I’ll have a backup generator anywhere I go.:slight_smile:

15

Question, for anyone who knows their electrons: Look at the information in this page. Looking at 1PV5135-4WS28, what sort of generator would be needed to drive this motor? It works out to needing 150KW of energy at max. Now generators usually like only running at half load, which would mean I’d need a 300KW generator. The problem with this is, a 300KW generator is about 15ft by 10ft by 10ft in size, which will hardly fit under the hood.

What I don’t understand is how this motor can be fed by a small battery pack that is recharged in 3-4 hours, and can hold some 50-200 miles of range depending on the batteries used.

Obviously, I’m missing something here. Might have to look at some other sort of electric motor, if this is accurate.

16

I’m not an expert on this but from what I’ve read generators cannot independently power the car/truck. The output from a generator can only compensate for some of the battery use. Batteries are still being used far more than a “buffer” between the generator and motor. There are a few EV drivers on the evalbum site that use generators. While the generator extends range, it certainly isn’t unlimited. The batteries will still be draining all the time, so a generator only moves the goalposts of DOD.

17

We all could. If such a thing were possible, you’d be able to buy one. The project you are describing is essentially a diesel powered hybrid, a Toyota Pruis-type vehicle with a diesel engine. You mentioned earlier that you want a top speed of 120 mph. It takes a lot of horsepower to move an S10 at 120, probably around 200 or so. You either need a really big battery pack or a really powerful ICE to produce this power. A small diesel generator and a small battery pack combined just cannot produce the horsepower required to move down the road that fast or accelerate through a quarter mile in 10 seconds. If you’ve been around race cars you know that a 10-second car has 500+ horsepower.

A Toyota Pruis has IIRC a 70 hp ICE, and I’m not sure what size battery pack it has. A Pruis has a top speed of less than 100 mph and runs around an 18 second quarter mile. If you want to go faster and quicker than that, you need a bigger ICE and more batteries.

18

I recall reading that VW or some other European manufacturer is planning on making a diesel hybrid soon. It makes sense, given that diesels are more efficient with energy use.

19

Not quite. The S10 will go about 100MPH now with a 125HP 2.8L V6/auto engine in it. The 96 Tahoe I used to to have was much larger with a larger wind profile and was 1600lbs heavier, and would go somewhere north of 130MPH with a 210HP engine. And, there’s little incentive for the auto makers to do anything more than is required to meet the EPA standards existing at the time. Whether such a thing is possible is not relevant, whether such a thing is PROFITABLE is. You’d think that selling cars that get extreme mileage would be very profitable for the automobile companies right now, but they fight tooth and nail against anything that requires an increase in MPGs. Sometimes I wonder if the oil and gas industry and the automobile industry aren’t heavily invested in each other, which would make selling large gas guzzlers the most profitable vehicle all around. Sell the vehicle at a premium, then keep making money off it at the pump.

The Prius isn’t what I’m after, it is an ICE driven vehicle with electrical boost on it, which is what makes it a hybrid. The ICE still provides power over 35-40MPH or whatever, and both of them together provide any high power boost needed for passing. Having two different motors driving the car’s drivetrain via a mechanical connection is what makes it a hybrid. What I’m after is no mechanical connection between the ICE and wheels, making it a diesel electric vehicle instead of a diesel electric hybrid. This also means that my diesel engine would only run at whatever RPM was required for it to turn the generator at its required RPM, usually about 3600RPM.

Higher speeds can come later if necessary, I rarely drive over 80MPH anymore but I do tend to cruise 75-80MPH. I just want the capability of going up to 125MPH on occasion. Initially, being able to go 75MPH max would be great.

From the Tesla website:

“The
pack operates at a nominal 375 volts, stores about 53 kilowatt hours of electric energy, and
delivers up to 200 kilowatts of electric power.”

The Tesla has on board, after a fresh charge, 53KWH of power and has a range of almost 250 miles at highway speeds. Since they use the standard EPA 55 HWY 45 CTY driving cycle, this will include some regenerative braking input, which is really just putting back lost momentum, not actually adding to the power. So under strict highway driving, 250 miles of range should be correct. This means it’s just using 212WH per mile to move the car. Am I reading this correctly, and if so does this not mean that a tiny generator would be able to power a Tesla? I mean, show me how I’m wrong here. :confused: Does it really take this small amount of power to move the car? Is my math off? I’m not trying to be argumentative here, just trying to see why I’d be wrong about this if I am. I arrived at 212WH per mile by dividing 53,000 watts as listed by the Tesla folks divided by 250 miles to get the watts used per mile. And this is assuming that there’s no low voltage cutoff on the car and it uses the full 53KWH of power, or that it does have a low voltage cutoff and the 53KWH is what’s available for use. I can almost generate 212WH of power by strapping buttered toast on a cat’s back and dropping it. This is the power needed to run a 100 watt light bulb just over 2 hours. And if I’m correct, then there’s no reason for this to not work, but I don’t know what size generator would be needed.

In answering this, remember that the folks that build the generators to extend the range are moving the car, plus the generator, plus anywhere from 1000 to 2000lbs worth of batteries. And, their goal is no ICE at all, different from my goal. They could easily mount a larger generator, cut battery weight, and extend the range indefinitely.

EDIT - I just saw what I missed, that 275WH isn’t per hour, it’s per minute. Need a generator that will generate 30KWH to drive this thing. :frowning: Thanks folks, I find this very, very disappointing, but now I understand why it won’t work.

MODEL NUMBER 5402
ENGINE 1.6L Generac 4-Cylinder
ENGINE RPM 3600
VOLTAGE/FREQUENCY 120/240 Volts / 60 Hertz
LP POWER CAPACITY 30,000 Watts
NG POWER CAPACITY 30,000 Watts
FUEL TYPE LP (Propane) or Natural Gas
NG FUEL CONSUMPTION (50% Load) 300 cu.ft/hr
LP FUEL CONSUMPTION (50% Load) 3.3 gallons/hr
COOLING SYSTEM Liquid-Cooled
LIMITED WARRANTY 2 Years
WEIGHT 935 Lbs.
DIMENSIONS 62.2"L x 29"W x 33.5"H
MOUNTING PAD Concrete (Not Included)
DECIBEL RATING 73.0 dB @ 7 meters
ENCLOSURE Steel

20

Having two different motors driving the car’s drivetrain via a mechanical connection is what makes it a hybrid.

actually its got 3, one ICE and 2 motors that operate differentially.

I just want the capability of going up to 125MPH on occasion.

why, are you drag racing?

Am I reading this correctly, and if so does this not mean that a tiny generator would be able to power a Tesla? I mean, show me how I’m wrong here. :confused: Does it really take this small amount of power to move the car? Is my math off?

nope, its a light as heck car, lots of carbon fiber, aluminum and plastic. Plus LiFePo, its just 1-200 lbs over stock weight of an Elise (forget where I read that). Its also aerodynamic, which helps alot. Many small EV conversions can get lower than 250 Wh/mi.

I’m not trying to be argumentative here, just trying to see why I’d be wrong about this if I am. I arrived at 212WH per mile by dividing 53,000 watts as listed by the Tesla folks divided by 250 miles to get the watts used per mile.

your calculation is right, numbers are wrong. It is 53,000Wh, and miles is 221. Thats 239-240Wh.mile… still, an outstanding number.

I can almost generate 212WH of power by strapping buttered toast on a cat’s back and dropping it. This is the power needed to run a 100 watt light bulb just over 2 hours. And if I’m correct, then there’s no reason for this to not work, but I don’t know what size generator would be needed.

you need to generate in 2 minute the 240Wh required to stay in equilibrium, otherwise, you’re just draining the batteries slower, but there would be a range limitation eventually. If you wanted to go 40 miles, you’d need 24040=9600W generator running for an hour. Thats a large generator. If you only wanted to go 10 miles, then 24010=2400W gen running for an hour. But if you go over that 240Wh/mi cruising rate all bets are off.

They could easily mount a larger generator, cut battery weight, and extend the range indefinitely.

When you say easily, where would you intend to put it? in a different car? Because its not fitting in the tesla, not a 10,000W generator, with gas and breakers, cables. If you add that generator, add another 500lbs of weight.

275WH isn’t per hour, it’s per minute.

no, its per mile, you were right.