# New here, and I gots me an idear!



## Lensrc (May 9, 2012)

In the "Where do I start" sticky, It said to get the best info for a build idea is to post certain info. So here goes.

As to my skills: Here is were I work, www.hotrod-express.com , and attached is a pic of the last thing I built. I have a better than basic knowledge of BL motors, ie; I can build simple brushless motors (Google my nick..), but could not build a controller. I have access to a lathe or two, a mill various sheet metal tools and machines, well, all the stuff you see on my companies website. I am not here to pimp my employer, but I am proud of what we can and have accomplished. 

On to my idea. The goals are ~55mph top speed, 50 or better miles range, two passenger fair weather commuter. This design will be open wheel, preferably 4 of them. possibly sourced from a Geo Metro or similar car, along with the transaxle, maybe? Put it in the back....

I am interested in building my own motors, possibly. Converting through magnet trickery, or other frugal methods of getting the power achieved, are ideas I am especially interested in. My mind keeps working its way back to wheel motors. Maybe because they are the most familiar to me. I have built a few small outrunner motors for model aircraft. 

I need to work within my available equipment, so exotic metals like tungsten or titanium are out. As if I could afford that stuff. I hope to be able to afford enough chrome moly to build a safety structure around the driver and passenger to at least have some roll over protection. So the remainder of this thing will need to be done with aluminum tubing and sheet. Being I am not very good with the english wheel, this design will be a bit more "angular". 

I am also familiar with composite materials, having used them to build model aircraft, and to make parts for custom auto interiors. Even though I could throw down on some seats and things, the seating will be simple sprung slings.

What I need to figure out is the where do I find the stuff that the cheap S.O.B.'s are using. I caught something about forklifts.......I guess I need to go read the rest of that Wiki thing......It's probably there.

Guess I'm just trying to say "Hello!"

Leonard


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## MN Driver (Sep 29, 2009)

Forklifts seem to be the cheapest source of parts, often you need to actually buy the forklift, transport, and then strip what you want from the forklift. Of course it could be hit or miss with what type of motor is in it and if it is suitable for your conversion. Trying to get 55mph for 50 miles could burn out some forklift motors or leave you with not enough performance to do what you want with their voltage capabilities.

Sometimes cheap EV designed motors and controllers are found on ebay, craigslist, or other places and eliminate quite a bit of work. IMHO, to go 55mph you will likely be most satisfied with a controller and motor that can handle 144v, although there are guys here that say that less voltage can get you to 55mph, it depends on how much passing performance you want/need for your situation along with whether or not you are driving on the flat or need to deal with hills. Aerodynamics and total build weight also make a big difference. 50 miles of desired range puts you in the LiFePO4 battery category, gets a little spendy. What's your budget?


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## Lensrc (May 9, 2012)

I dont have one. A budget that is. As in I will have to save until I can get the first/next thing. I am good at sourcing things, If I have an idea of what to look for. Sounds like I got some cypherin' to do.....and more reading. I may not be able to actually afford to do this. I do know that if the payoff is not there at the end, I cannot build it. It would be against my nature. By payoff I mean total cost per mile travelled, for the life of the batteries, compared to more conventional travel. I could live with a comprimise on range, but not top speed. The road most travelled is 5 miles long, and has a few hills. 30 mile range gets me to town and back, but not to work.


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## Yabert (Feb 7, 2010)

Hi Lensrc

A small car don't need a lot of power to maintain 55 mph. For my 1900 lbs Smart fortwo, this represent 13-16 hp. And with my 12 Kwh battery pack (300 lbs) I can reach 50 miles at this speed..... Just like that, my top speed is around 100 mph.

The real question about your investment is how much time would you need to achieve proper payoff. With a potential of 2000-3000 cycle of charge, Lifepo4 cells price can be recover in few years (considering few $$$$ in gas per year).

Forklift motors are awesome for cheap conversion, but you talk about build BL motor (serious project!).
Give us your performance expectation and we can help you more.


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## Lensrc (May 9, 2012)

Yabert said:


> Hi Lensrc
> 
> A small car don't need a lot of power to maintain 55 mph. For my 1900 lbs Smart fortwo, this represent 13-16 hp. And with my 12 Kwh battery pack (300 lbs) I can reach 50 miles at this speed..... Just like that, my top speed is around 100 mph.


Did you just add your range to your speed to get that figure?


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## Lensrc (May 9, 2012)

Yabert said:


> Hi Lensrc
> The real question about your investment is how much time would you need to achieve proper payoff. With a potential of 2000-3000 cycle of charge, Lifepo4 cells price can be recover in few years (considering few $$$$ in gas per year).


Not the real question. Time is not the issue. total cost per mile, for the life of the battery, vs cost per mile with gas. If the battery has a time limit, regardless of cycles, then it would matter.

Leonard


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## Yabert (Feb 7, 2010)

Lensrc said:


> Did you just add your range to your speed to get that figure?


Let say 15 hp to maintain 55 mph: 15hp = 11.2 Kw.... so, with a 11.2 Kwh (kw per hour) battery pack, I can theoretically travel one hour. That is 55 miles.
At lower speed, you can expect longer range. Lower range with lot of start and stop.

Performance expectation??


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## Lensrc (May 9, 2012)

Yabert said:


> Let say 15 hp to maintain 55 mph: 15hp = 11.2 Kw.... so, with a 11.2 Kwh (kw per hour) battery pack, I can theoretically travel one hour. That is 55 miles.
> At lower speed, you can expect longer range. Lower range with lot of start and stop.
> 
> Performance expectation??


The goals are ~55mph top speed, 50 or better miles range, two passenger fair weather commuter.




> Just like that, my top speed is around 100 mph.


You did not answer the question. Where did the 100 mph figure come from. This is important to me, because if you added your speed to your range to arrive at that number, I can no longer listen to your advice. Either your car can go 100 mph or not. I don't live in some weird theoretical world.

Leonard


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## Yabert (Feb 7, 2010)

Ummm! A bit of learning. 

My car (or yours if comparable) need around 210 wh per miles to maintain 55 mph. 210 wh x 55 = 11550 w = 15.5 hp.

Battery capacity = 12300 wh or 12.3 Kwh... so 12300 wh / 210 wh per mile = 58.6 miles (a bit less because discharge battery to 100% isn't good). Well, let say a range of 47 miles.

Now, at different speed, my energy consumption is different. For example it is around 180 wh / mile at 35 mph and probably over 600 wh / mile at 100 mph.
In first case, theorical range without start and stop is: 12300 / 180 = 68 miles.
And at 100 mph: 12300 / 600 = 20 miles.

Hope this help.


Now, about performance expectation, I search to know if you expect accelerate from 0 to 55 mph in 4 seconds or in 40 seconds? What kind of acceleration do you expect?


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## Lensrc (May 9, 2012)

Well, I can see I ain't gonna get along here. 

See ya.

Admin, can you please remove my registration and info from this site.


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## Woodsmith (Jun 5, 2008)

Lensrc, I think you are misunderstanding what Yabert is saying.

His car is capable of a certain range at a certain speed, just as an ICE car can achieve a certain MPG figure at a certain speed. Higher speed uses more gas, lower speed uses less.
It is the same for an EV.

Yabert's car gets a certain range at 50mph, but it can also accelerate up to 100mph but at the cost of much reduced range.

There isn't anything funny or wrong about his calculations, or the methods he uses to calculate them. His figures are also backed up by real life driving of his car.


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## piotrsko (Dec 9, 2007)

Yabert also lives in quebec, and may be French.

Go search for Mizlplix and his hot-rod out near the great western cleft.


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## Lensrc (May 9, 2012)

piotrsko said:


> Yabert also lives in quebec, and may be French.


Well if I gotta suffer through language problems, I will see if I can find my info somewhere else. 

Goodbye.


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## njloof (Nov 21, 2011)

Wow. Someone left the barn door open and all kinds of critters wander in.


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## jk1981 (Nov 12, 2010)

Lensrc said:


> Well if I gotta suffer through language problems, I will see if I can find my info somewhere else.


But his English is as good as yours AND he's talking sense 

Some things you need to work out to help you price up your battery:

Power required to maintain a given speed (this changes with speed): The figure of 210Wh/mile @ 55mph (11.5kW or 15BHP) is reasonable for a small car conversion. Excellent aerodynamics will dramatically reduce this, using a pickup or open wheel hotrod will somewhat increase this figure. Either way it's in the ballpark.

Now we know you want to go 50miles and you use 210Wh/mile so you need 10.5kWH of battery. You could build a low voltage battery from high capacity cells* or a high voltage battery from low capacity cells**.

*A low voltage battery has to supply more current for the same power output, current heats things up causes inefficiency. Low voltage may also limit top speed depending on your gearing and motor.

**Real world components are voltage limited, your controller, charger and motor will all have voltage limits. For maximum efficiency (minimum battery/wiring current losses) you generally want to be near to those limits.

Say you want to use a 144V battery, what capacity cells are needed? You need 10.5kWh (actually a bit more so you only discharge about 80% of max capacity so 13kWh).

13000/144 = 90AH cells, 100AH cells are common or you could parallel up to 40AH cells and lose a little range. Li cells are ~3.6V each so that's:

40 x 100AH cells, ~14KWh, that weighs ~300lbs

Now cells have a continuous and a short term (~10second) discharge rating, this is somewhat sloppily for convenience given as a C figure, a multiple of the battery capacity. Say your 100Ah cells are rated 3C continuous, 20C max and you wanted to push them as hard as the spec suggests you can, what will they deliver?

3*100 = 300A, 300A*144V = 43kW so you can easily cruise at 55mph (11.5kW). It's this figure after transmission losses that limits your top cruise speed (unless motor, controller or cops do before that, probably to something in the region of 80mph depending how bad your aerodynamics are).

20*100 = 2000A, 2000A*144V = 288kW! this is where you run into some problems, cells have internal resistance, this heats them when they're passing 2000A and it causes the voltage to sag so in reality you won't get anything like 288kW even briefly, maybe ~200kW. That, assuming you want to push your battery really really hard is the power available for acceleration (after various transmission losses, maybe 20% are accounted for so 160kW).

Now you have a max power available for acceleration and you can estimate weight (say 1200kg) you can make a rough performance estimate.

160kW means you can add 160 kJ/second of kinetic energy. At 55mph (24.4m/s) you have 0.5 x 1200 x 24.4^2 = 358kJ of kinetic energy. From that you can see 0-55 ~ 2.3seconds (360/160 = 2.25), amazing! Well, not quite. That all assumes you can convert all of your (high stressed battery) power to kinetic energy at the maximum rate it can theoretically deliver it. Take a more realistic, less damaging discharge rate of 5C and you get ~8seconds, add time for a shift and account for the fact you'll not be supplying 40kW continuously to the wheels and you're looking at somewhere maybe around the 9-10second mark. Sprightly but unimpressive.

You can get higher C rated batteries if you want more performance (at the cost of range at a given price) but a 13kWh pack will already be pretty expensive and I think realistically for an open wheel hotrod you'll be needing a lot more than that given the poor aerodynamics.

jk


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## Tesseract (Sep 27, 2008)

Lensrc said:


> Well if I gotta suffer through language problems, I will see if I can find my info somewhere else.
> 
> Goodbye.


Alright, troll. Try out the EVDL - they have plenty of scoffing curmudgeons you ought to get along with just fine.


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## Yabert (Feb 7, 2010)

Strange situation! I hope my bad english isn't the main problem...
My goal was just to indicate how calculated energy required to have a range of 50 miles with a small car.

Thanks Woodsmith to have try to clarify.


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## Woodsmith (Jun 5, 2008)

I really don't think it was your English, Yabert. I, and I guess others, understood it fine.


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## Ziggythewiz (May 16, 2010)

I think the language barrier was of the math variety.


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## Lensrc (May 9, 2012)

Yabert said:


> Strange situation! I hope my bad english isn't the main problem...
> My goal was just to indicate how calculated energy required to have a range of 50 miles with a small car.
> 
> Thanks Woodsmith to have try to clarify.



It is. And being you people started the name calling, and inferring I may be unable to understand, you can all go **** yourselves.

Goodbye.


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## njloof (Nov 21, 2011)

Lensrc said:


> It is. And being you people started the name calling, and inferring I may be unable to understand, you can all go **** yourselves.
> 
> Goodbye.


Lensrc, I'm having trouble with your English. What do you think the word "Goodbye" means?


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## TigerNut (Dec 18, 2009)

Lensrc said:


> It is. And being you people started the name calling, and inferring I may be unable to understand, you can all go fuck yourselves.
> 
> Goodbye.


Well you did come out and start that ball rolling by implying that Yabert's English was something to cause you suffering. 

Hopefully you read enough of his build thread to figure out that over the last year and a half he built the car you were talking about in your first post:


FWD transmission on the back axle of a small car.
Forklift motor (at least to start with)
The range you want
It does wheelies.
You might also soon realize that the world extends beyond Kansas, not everybody speaks English, and if you want something from some of those folks, you should appreciate the fact that they'll mostly use English, even if it's not perfect, to try to talk to you, and it's pretty rude to infer that your inability to understand it, is somehow their problem.

- Kostov motors are made in Bulgaria
- Soliton's controller software is written by a Swede
- Your lithium batteries are going to come from China
- Currently, the most hotly anticipated electric supercar is being engineered and built in Croatia.

Good luck with your insular viewpoint.


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## Chad (Aug 1, 2008)

hahaha I think I just positively zapped the gigabits into the intranet of my zip drive.



> goodbye |ˌgoŏdˈbī| (also good-bye or goodby or good-by)
> exclamation
> used to express good wishes when parting or at the end of a conversation.
> noun ( pl. -byes |gʊdˈbaɪz| or -bys)
> ...


He forgot the good wishes, and the end of the conversation part 

P.S.
In Canada, all our igloo's are electric fwd.


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