# Formula ?



## Woodsmith (Jun 5, 2008)

EVEngineeer said:


> I need help in understanding the formula range[miles]=250 x capacity[kWh] / (mass[lbs]^0.6)
> 
> Where does the 250 come from?
> What number do I use for the kWh? Motor?
> ...


Where did you get that from?

I suspect that it might be an approximation that includes some constants to allow for some unknowns and some conversion from imperial to metric to simplify the calculations.

I tend to convert my input data to SI units then calculate and convert the output back to imperial.


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## nulluser (Mar 4, 2012)

That formula is just a best fit empirical model of battery capacities, range data, and vehicle weight. 

It is just to give a rough idea.


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## ruckus (Apr 15, 2009)

Don't use that formula! It is very flawed by only considering mass.

If you are stopping and starting or pulling hills mass is important, but if you are on flat highway aerodynamics is WAY more important than mass.

Go here:

http://ecomodder.com/forum/tool-aero-rolling-resistance.php

This tool is much better. At the magic speed of 60mph your KW needed is also your battery amp hours needed to drive for 60 minutes and go 60 miles.

Using the stock parameters (a small car) you can see it would take about 10kw/hrs to go 60 miles. That is 100% dead. So 12kw might do it. Add hills, your buddy, and some wind and you better make it 15kw.

Bottom line, get as many batts as you can fit/afford.

Good luck.


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## EVEngineeer (Apr 11, 2012)

Ok, great answers. I really appreciate it. I am going to get an aerodynamic shaped larger car, like a 2006 or newer Honda Civic. I can get one really cheap, plus I would make modifications to it, like switching out the side mirrors for something more aerodynamic. I would also put those full cover hubcaps on the wheels and maybe add those covers that are part of the car. I would also like to add recessed solar panels on the car, so it does not affect the shape of it.


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## EVEngineeer (Apr 11, 2012)

What do you people think I should get in order to achieve 65mph for ~100 miles range? I drive a little less than that every day at that speed. I drive a little city to at 45mph for about 25 miles range every day.


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## EVEngineeer (Apr 11, 2012)

What is the price range are we talking about here and why exactly? Is there ways of cutting costs? Could you explain why I would need the parts that you suggested please? Thank you. Also, I do not currently have the skills, but I know plenty of people who do, so I would have other people do it for me.


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## tomofreno (Mar 3, 2009)

EVEngineeer said:


> What do you people think I should get in order to achieve 65mph for ~100 miles range? I drive a little less than that every day at that speed. I drive a little city to at 45mph for about 25 miles range every day.


With a Civic you likely will get around 300 Wh/mile +/- 10% at 65 mph. So 100 miles would require about 30kWh. You want to discharge to no more than 20%, and if you do it everyday 30% will extend your pack life from 2000 to 3000 cycles according to the manufacturers (who knows really?). So 30 x 1.2 = 36kWh pack. If you want to drive that 25 city miles at < 45 mph, well add around 5kWh for a 41kWh pack, minimum, 45kWh would be better. If you use the motor Gotti suggested and a Zilla or Soliton Jr controller you could use say 71 cells for a nominal 227V pack (and set the controller to limit motor voltage to around 160 - 170V so you don't damage it). Then to get 45kW you would need 200Ah cells. At around $1.25/Ah delivered that would cost around $17.8k. Then just add motor, controller, charger, DC/DC converter, vacuum pump, stronger vehicle springs, bms,...costs, and figure out where you will put all those cells in a Civic. With the about 900 lb pack you may use more like 330-340 Wh/mile at 65 mph.


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## ruckus (Apr 15, 2009)

Here is a fairly good list of aero drag with a few mistakes.
http://en.wikipedia.org/wiki/Automobile_drag_coefficient

Don't forget you have to multiply the drag coefficient by the frontal area. 
scroll down the wiki page for a list of square areas.

Honda CRX, Eagle Talon (or other DSM), Mazda Rx7, Nissan 240sx, Dodge Daytona, in that order more or less. 

You can find a junk DSM with a blown motor and maybe already gutted with roll cage for pennies on the dollar... while a rusted out honda is like gold bricks.

All these light small cars need a full cage and racing seats/belts or when you wreck it's KYAB.


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## ruckus (Apr 15, 2009)

These guys are pulling your leg... 

I drove the 37 Jaguar 90 miles the other day and only used about 16kw of the 25kw pack. It is small and light, but definitely not aerodynamic. A civic/Talon would have used much less..

But I wasn't going 70...Speed Kills (your batteries)


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## tomofreno (Mar 3, 2009)

ruckus said:


> These guys are pulling your leg...
> 
> I drove the 37 Jaguar 90 miles the other day and only used about 16kw of the 25kw pack. It is small and light, but definitely not aerodynamic. A civic/Talon would have used much less..
> 
> But I wasn't going 70...Speed Kills (your batteries)


No, you're pulling his leg. 178kWh/mile in a Jag? Net downhill at 35 mph? I use about 250 Wh/mile in a 2260 lb Suzuki Swift at 60 mph, and about 180 Wh/mile at 35 mph.


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## NintendoKD (Apr 29, 2012)

gottdi said:


> Wheel covers are OK. Don't bother with the Solar Panels. You will just ruin the vehicle for what it will require to do that. Your ideas may be valid to a point but if you do not have the skills just leave it be. If you want solar just build a solar parking stall with enough solar to actually charge your vehicle. I am quite sure the mirrors on an 06 or newer Civic are just fine. Again if you don't have the skills leave it be. Put in enough batteries and a good enough controller and go have fun. Oh did I mention gobs of money?


 You forgot the "GOBS OF MONEY" thing, oh! wait, there it is, AGAIN! LOL


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## NintendoKD (Apr 29, 2012)

ruckus said:


> These guys are pulling your leg...
> 
> I drove the 37 Jaguar 90 miles the other day and only used about 16kw of the 25kw pack. It is small and light, but definitely not aerodynamic. A civic/Talon would have used much less..
> 
> But I wasn't going 70...Speed Kills (your batteries)


 and your brushes, and bearings, and .... well you get the idea.


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## ruckus (Apr 15, 2009)

Well, maybe I used 18kw instead of 16. We are just getting the gauges hooked up, so it is a bit of a guess based on battery voltage. Like I said, I didn't go 70. More like 50-55. That feels FAST in this car. 70 feels like 100.

It is a tiny sports car, not the huge sedan you show...

www.northvalleyev.com

If you really want to go 65 for 100+ miles you either need to pick up a charge at work or get a hybrid.

Or pack a lot of lithium in a VERY aerodynamic car. Fighting the wind is where most of your energy will go at 65mph.


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## nulluser (Mar 4, 2012)

Here is what I did for my electric bike, and it ended up pretty close for low speeds:

Pack voltage * Pack Capacity * 50% DOD * 65% peukert = Available Energy

72V * 55a-h * 0.5 * 0.65 = 1287 watt-hours Available 

I estimated (from evalbum) that similar bikes average 150 watt-hours per mile at 50 mph. That would give me 9 miles at 50 mph. Likewise, the bikes are around 70 watt-hours per mile at 25 mph, giving a range of 18 miles.

These ended up being very accurate.

I did not take into account the different peukert losses at the different speeds. In reality the range is around lower at the higher speeds. However, there are fewer starts and stops and the higher speeds...

This will give a decent rough estimate. The online calculators can take you from 'pretty accurate' to 'pretty damn accurate'.



Here is the actual data:​ 
​Speed Efficiency Range
mph W-h/mile Miles
Measured Measured Estimated
5 42.0 30.6
10 51.0 25.2
15 66.7 19.3
20 60.0 21.5
25 68.0 18.9
30 73.3 17.6
35 74.3 17.3
40 90.0 14.3
45 124.4 10.3
48 139.6 9.2


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## EVEngineeer (Apr 11, 2012)

If I put lets say <10k and then the cost for batteries. How many lithium ion batteries would I need and which type would be best and the cheapest? I do not know to much at all about batteries. Also, if I was to add more than I need, would that extend battery life? If there is supposedly 2k full cycles of life in the batteries, then if I do not use them up to their max point ever, then would I be correct? Also, to the person who said good luck finding room in the Civic.... Isn't there room under the hood and where the spare wheel goes. I would probably get rid of the extra wheel and add run flats. I know that the lithiums are small in comparison to the lead acids so how much room would I need? There should be enough, if not I was thinking about rearranging the back seats so that way there is more room. I was thinking, if possible to remove the middle seat. Then I could make a tower of batteries in the middle (obviously covered somehow so no one dies), kinda like the center console in the front of the car where the driver is.


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## DIYguy (Sep 18, 2008)

EVEngineeer said:


> If I put lets say <10k and then the cost for batteries. How many lithium ion batteries would I need and which type would be best and the cheapest? I do not know to much at all about batteries. Also, if I was to add more than I need, would that extend battery life? If there is supposedly 2k full cycles of life in the batteries, then if I do not use them up to their max point ever, then would I be correct? Also, to the person who said good luck finding room in the Civic.... Isn't there room under the hood and where the spare wheel goes. I would probably get rid of the extra wheel and add run flats. I know that the lithiums are small in comparison to the lead acids so how much room would I need? There should be enough, if not I was thinking about rearranging the back seats so that way there is more room. I was thinking, if possible to remove the middle seat. Then I could make a tower of batteries in the middle (obviously covered somehow so no one dies), kinda like the center console in the front of the car where the driver is.


Hey I thought you are an EVEngineer????? lmao. Contrary to your statement, and FWIW, lithium prismatics are not much different than lead with respect to volume. Mass yes, volume. . . not so much.


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## Ziggythewiz (May 16, 2010)

They are lower volume in terms of usable AH. How much smaller depends on the leads you're comparing them to. Also keep in mind it takes 4 lithium cells to replace 1 12V lead battery.

1x12V 125AH floodie > 4x60 AH LifePo4:
60 lbs > 22 lbs
877"^3 > 376"^3

3x8V 135AH floodie > 8x60 AH LifePo4:
189 lbs > 44
2230"^3 > 752"^2

So around 1/3-1/4 the weight for lithium vs lead and 1/2-1/3 for the space.

These are just illustrative examples, for decent range and performance you'll want at least 100 AH or larger cells.


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## ruckus (Apr 15, 2009)

DIYguy said:


> lithium prismatics are not much different than lead with respect to volume. Mass yes, volume. . . not so much.


Hold on there... They are quite a bit different. First, they put out a much higher C-rating with much less sag. This means you can "undersize" the pack and kinda get away with it. By this I mean going high voltage with smaller batteries to get high performance with limited range. This can't be done with lead because the only size is big and heavy.

I definitely agree that more is better, just saying the small form factor of lithium is a little more flexible than lead.


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## DIYguy (Sep 18, 2008)

ruckus said:


> Hold on there... They are quite a bit different. First, they put out a much higher C-rating with much less sag. This means you can "undersize" the pack and kinda get away with it. By this I mean going high voltage with smaller batteries to get high performance with limited range. This can't be done with lead because the only size is big and heavy.
> 
> I definitely agree that more is better, just saying the small form factor of lithium is a little more flexible than lead.


I never said they were't different. Of course they are different in every way. My point was a generalization regarding the size, nothing else. Many newcomers think lithium is significantly smaller. Of course it is significantly lighter and u can use smaller packs.


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## PhantomPholly (Aug 20, 2008)

The easiest answer seems to be, treat 8Kwh worth of batteries as "1 gallon of gas" for calculating range, and don't use at least 20% of whatever your pack capacity is. Thus, if you want a 30 mile range in a 30mpg car, you should have (approximately) a 10KWh pack (8 * 1.2).

It gets tricky if you want really long range, because weight starts to have a bigger impact on "mph." Say, anything above 24KWh will start significantly reducing your efficiency.


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## EVEngineeer (Apr 11, 2012)

People keep saying that to reach highway speed and drive over 100 miles while doing so, that I would need for starters and aerodynamic car and as little weight as possible. They also say I need over 50k to pay for it all. I found this website. http://www.evassemble.com/index.php?main_page=index&cPath=1&zenid=u5hdlr0nvo4e1oune0ugbgt7e6 
So we have an example, can someone please explain to me which battery I would need and how many? I just do not see how I need to spend over 20k on batteries alone. I see a battery that says 48volts at 20ah(I do not know what ah is or how much or what it provides) for $619.00. I know that to just build the car without batteries included is under 10k, but not under 5k. I understand that part of it, but for the batteries I just do not understand. Maybe there is something that I am missing in information.


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## Ziggythewiz (May 16, 2010)

EVEngineeer said:


> I do not know what ah is or how much or what it provides
> 
> for the batteries I just do not understand. Maybe there is something that I am missing in information.


http://www.diyelectriccar.com/forums/showthread.php?t=668

Go read every link about batteries. It's a pretty fundamental part of an EV and you don't need to be planning anything without a firm grasp of it.


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## nulluser (Mar 4, 2012)

EVEngineeer said:


> People keep saying that to reach highway speed and drive over 100 miles while doing so, that I would need for starters and aerodynamic car and as little weight as possible. They also say I need over 50k to pay for it all. I found this website. http://www.evassemble.com/index.php?main_page=index&cPath=1&zenid=u5hdlr0nvo4e1oune0ugbgt7e6
> So we have an example, can someone please explain to me which battery I would need and how many? I just do not see how I need to spend over 20k on batteries alone. I see a battery that says 48volts at 20ah(I do not know what ah is or how much or what it provides) for $619.00. I know that to just build the car without batteries included is under 10k, but not under 5k. I understand that part of it, but for the batteries I just do not understand. Maybe there is something that I am missing in information.



Assume 300 watt-hours per mile. 

100 mile range would be 30kwh. 

The batteries you listed are 960 watt hours, so you would need around 40 of them for 75% depth of discharge.

At 619 dollars per pack, that would cost you 25k.


If the car actually averages 250 watt hours per mile, or even 350, the estimate of 25k in cells is definitely in the ball park for the data you listed.


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## EVEngineeer (Apr 11, 2012)

even at highway speed? like 65-70mph for 100 miles. You are saying I need 25k for that?


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## ruckus (Apr 15, 2009)

No, 25kw will not do 65-70 for 100 miles. The Jag has 25 kw and is good for 100 miles, but at a more moderate speed (like 50-55). They cost about $8,000.

The big question is 25kw of TOTAL ah, or 25kw of USABLE ah? It is far better to have more and rarely use it than to have too little, overuse it and toast it.

Draining the batts 90% will give you much shorter life than 60%.

I strongly suggest you get on evalbum.com and look up cars that are similar to what you want to convert. look at their battery pack and how fast/far they can go. This will give you a good idea of "real world" numbers. It is easy to twist the figures and think you can do more with less but that will be very disappointing in the end.


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## EVEngineeer (Apr 11, 2012)

I have tried looking at the album and I have found a handful, but they do not match up enough, because there is a lot that I am looking for. But besides that, they do not always list everything that I would like to know. like the battery situation


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## Ziggythewiz (May 16, 2010)

EV album or the garage here will usually provide a way to contact the EV owner. Don't be shy. We like to talk about our cars.


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## ruckus (Apr 15, 2009)

EVEngineeer said:


> I have tried looking at the album and I have found a handful, but they do not match up enough, because there is a lot that I am looking for. But besides that, they do not always list everything that I would like to know. like the battery situation


Keep looking.  "I can't I can't" is certainly not going to get an experimental car built.

Sure, you may not see EXACTLY the car you want to build but there are plenty that are close. Use the sorted search tools to narrow in. After a while you will start to see the patterns.

this amount of kwh equals this amount of miles. Bigger car less miles on same batt. Smaller car more miles on same batt. If you want to go far and fast, I already gave you the short-list. There are a few more, use your imagination. You can find the aero drag, frontal area, and weight for almost any car.

Take the numbers for about the best car you can imagine getting your hands on and run it through the calculator I linked. Then you know exactly how many kwh you need to sustain a certain speed on flat ground. The calculator allows you to add resistance, wind, etc. so you can calc worst-case scenario late to airport in a rain storm at night with your fat uncle and mother-in-law with lots of luggage (good reason to get a 2-seater).

Go to Ecomodder.com and look how people get 120mpg. Many of the same techniques yield range improvements for electric cars.

Why don't you come back to us with several examples and how far they would go on a certain batt. We have given you everything you need to do it.

Cheers


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## EVfun (Mar 14, 2010)

Let's just pull some numbers out of thin air and take a look. Power consumption grows at about speed squared. In other words, it takes 4x the amps to go 70 mph compared to 35 mph. Since you are going twice as far in a given time the power consumed per mile (watt hours per mile) roughly doubles. This also suggests that it takes about 17% more watt hours per mile to go 70 mph instead of 60 mph. 

Perhaps your car can manage 400 watt hours per mile at 70 mph. You want to go 100 miles so that is 40,000 watt hours stored. You don't want to use the top 5% or bottom 15% to maximize life so you want 50,000 watt hours worth of Lithium cells on board. The cells are nominally 3.2 volts, but like any cell they will sag under load. Perhaps the actual average voltage is 3.1 volts. That means you need about 16,129 amp hours worth of cells (watts = volts * amps.) The cells are currently running around $1.25 per amp hour which means you are looking at a $20,200 battery pack. A pack of 90, 180 amp hour cells should work pretty good at meeting this requirement. 

People looking for a more modest range and mostly city driving may draw up a very different picture. Perhaps I'm looking at an average of 250 watt hours per mile in city traffic. If I only need a 40 mile range then I need 10,000 watt hours. I want to only use 80% of the available capacity too, so I want 12,500 watt hours on board. My cells average 3.1 volts average under load so I need 4032 amp hours on board. I might choose 40, 100 amp hour cells. At $1.25 per amp hour my pack cost would be $5000. 

My EV buggy is actually a bit more modest than that. The city consumption is right at 200 watt hours per mile (it weights less than 1200 lb.) The pack is made up of 38, 60 amp hour cells. It works out to a 28 mile range if I use only 80% of the available capacity. I know in a range test I can do quite a bit better, likely about 38 miles (based on a 32 mile range test when I only had 32 cells installed.) With a couple of spare cells purchased with the pack, it cost $3000. I'm working my cells pretty hard with a pack that small, but that is good way to learn about them.


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## EVEngineeer (Apr 11, 2012)

Thanks for the great info all of you. I appreciate the sharing of knowledge. I am new to this and I have been trying to read up about EVs and how they work. I just can't seem to remember it all, but I am taking notes.


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## EVEngineeer (Apr 11, 2012)

So I looked at the evalbum and I found this http://www.diyelectriccar.com/garage/cars/41 
http://etischer.com/awdev/

It's 100% complete and costs under 30k total. I also noticed that it's max speed is perfect for me and it's range is also perfect. Also, for everyone saying that something like this would cost over 50k, how did this guy do it in under 30k? I personally would add those moon wheel covers to the tires to give it better efficiency.


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## Ziggythewiz (May 16, 2010)

Who said over $50k? IIRC you wanted 100 miles hwy? This guy may get around 100 at 60. If you can match his workmanship, you'll have an awesome car.


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## TigerNut (Dec 18, 2009)

In the writeup the insurance appraiser nailed the value of the car at $52K. However, that does not tell the whole story - you only have to look at the whole car and see how meticulously everything was done to appreciate that no effort was spared to do everything to OEM or better levels of quality.

As I recall, Eric custom CNC-milled the motor to transmission adapter plate; while he may not have spent much actual cash on this, it requires you to have access to a fairly expensive machine, as well as the skills to use it. 

Likewise, the other bits of fabrication require significant amounts of mechanical and electrical skill, as well as the background to design everything in the first place, so that it looks like it belongs there.

In summary, it looks to me like he did it for 'only' 30k by investing >100k worth of his time and life/work background into it... you'd be unlikely to get that kind of finish on everything without either paying someone that was totally committed, or by doing it yourself, assuming you had the skills, background, and tools to do that level of work yourself.


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## EVEngineeer (Apr 11, 2012)

I agree and understand about the skills part, because I do not have the skills. I know plenty of people though who could build it. I believe I would have to give about 10k to the people who would be working on it for me. But still that leads us up to under 50k and if you look back in this thread you will see that some people said I would have to spend over that amount. That is not the part that I am so concerned about right now though. I posted that link to that guy, because it shows what he did in detail to basically reach my goal. I would like to know detailed information that I can't get from him, because from what I saw there is not any contact info. I would like to know, would a Honda Civic 2006-2013 be a better choice, to increase range. Would adding those moon wheel cover add range? Would adding a solar panel recessed into the trunk or hood add range? Things like that. I want to know why he gets the range and speed that he gets and I want to know how to improve on it. I know that some of you will not have the answer, because you do not own the car that I posted a link to, but without testing it, what do you believe would happen.


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## EVEngineeer (Apr 11, 2012)

I just read on his webpage that he painted part of the car and bought the car which in total ended up costing him under 4k. I personally will be getting the car either for free from a friend that gets cars with blown engines (might pay him a little to take the engine out, if it isn't already) or buy one for under $500. I would not paint the car, unless it really needs it. But I know that could get it fully painted for somewhere between $200 and $500. In other words, he spent under 4k and I would be spending less then 1k in total for these two things.


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## Ziggythewiz (May 16, 2010)

EVEngineeer said:


> People keep saying that to reach highway speed and drive over 100 miles while doing so, that I would need for starters and aerodynamic car and as little weight as possible. They also say I need over 50k to pay for it all.


Where did someone say over $50K? I looked back through the thread, and did not see it. The closest I saw was you claiming people were saying that. 

As for etischer's contact info, it's in the first word of the first link you posted.


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## TigerNut (Dec 18, 2009)

Ziggythewiz said:


> Where did someone say over $50K? I looked back through the thread, and did not see it. The closest I saw was you claiming people were saying that.
> 
> As for etischer's contact info, it's in the first word of the first link you posted.


Hey Zig,
It's (indirectly) from here:
http://etischer.com/awdev/, 2010/05/29 update.

EVEngineeer: Several times you've mentioned that you can get things done for very little cash outlay, but that you don't have the skills to do it yourself. I don't know what the cost of labor is in Florida, but it's generally a rule that "you get what you pay for", and the thing is that the work required to do a top-notch EV conversion is not something that can be successfully farmed out at $10 an hour.

Let's review etischer's conversion. For each step you have to figure out if you could do this or what it would cost to get the equivalent thing:
1. He bought the car and brought it home himself.
2. He bought a surplus AC motor at maybe 50 cents on the dollar.
3. He bought a low-power AC inverter and engineered his own high-power IGBT drive, then did all his own debugging and rebuilding until it worked.
4. He converted his Passat from automatic to manual, but reworked the shift linkage so he could select a couple of gears from the manual transmission using the auto shift lever. Reverse is also worked into that somehow.
5. He built his own battery racks.
6. He did all the other wiring of the car's high voltage system
7. He custom made a motor coupler and transmission adapter; then later rebuilt the trans adapter to rotate the motor 90 degrees.

There are many other steps that I'm not going to detail... but anytime that you think 'I can get that done for less' you have to consider that you're planning to farm everything out, while etischer spent the money on the parts AND did most of the fabrication work and installation himself.

Labor in Florida might be cheap... but etischer's conversion required a great deal of engineering on top of the fabrication and installation time. Engineering time is expensive especially when you have to pay for it.


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## TigerNut (Dec 18, 2009)

EVEngineeer said:


> I agree and understand about the skills part, because I do not have the skills. I know plenty of people though who could build it. I believe I would have to give about 10k to the people who would be working on it for me. But still that leads us up to under 50k and if you look back in this thread you will see that some people said I would have to spend over that amount. That is not the part that I am so concerned about right now though. I posted that link to that guy, because it shows what he did in detail to basically reach my goal. I would like to know detailed information that I can't get from him, because from what I saw there is not any contact info. I would like to know, would a Honda Civic 2006-2013 be a better choice, to increase range. Would adding those moon wheel cover add range? Would adding a solar panel recessed into the trunk or hood add range? Things like that. I want to know why he gets the range and speed that he gets and I want to know how to improve on it. I know that some of you will not have the answer, because you do not own the car that I posted a link to, but without testing it, what do you believe would happen.


As ziggy noted - a lot of this information IS available on his build page and if you want to know, ask him directly via PM, or on his build thread: http://www.diyelectriccar.com/forums/showthread.php/converting-2001-passat-15363p27.html. You have to start doing some of your own digging and analysis instead of asking everyone to provide and summarize the information you're looking for.

Moon wheel covers: Generally they can help. Want to find out? Go buy some (they're like $30 each on JCWhitney or something) and do a mileage test on your existing car.
Solar panel: We've beaten this to death. Best case you can get about 200 or 300 w-h from panels that fits on the hood and trunk, and that's a drop in the bucket compared to the overall power requirements. Such a panel would fractionally increase your range, but at substantial cost and complexity.
Civic vs. Passat: The Passat is more aerodynamic in terms of Cd, but bigger and heavier. Probably the CdA and rolling resistance of the two vehicles would favor the Civic slightly, IF you can keep the weight down.

How did he go fast: He's got a 90 HP motor, and a battery pack and controller that can drive it at near that power level for enough time to get over 100 MPH. 
How would you improve on that: Less drag, less weight, more battery power rating. Practically, that would be tough for you to achieve within your budget.


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## SandRailEV (May 11, 2012)

Things that make you go "hmmm"...

Sounds like it's time for EVEngineeer to do some engineering for himself.. There's everything on this site one would need to design a reasonable EV without even being an engineer... There's also enough supplier links to the parts and supplies to build one. What am I missing here???


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## EVEngineeer (Apr 11, 2012)

I made a mistake the 50k comment was not in this thread, but people did say it to me in other threads, I just can't remember where it is now. But someone earlier in this thread did say I need "Gobs of money". 

I know that I can't get someone to work $10 an hour, but I can get someone for about $50 an hour. I know a lot of people though who would do me a favor and give me service for real cheap or free. I know people who do not charge much for their time, but they make a small profit off of the parts.


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## Ziggythewiz (May 16, 2010)

The $25-30K it takes to build a 100 mile EV certainly qualifies as "Gobs of money" to me. It's really not that complicated. High mileage merely requires more batteries, it doesn't necessarily mean better build quality, though that is typically found in such vehicles (like corbin's bug or etischer's passat) because when the total package gets that expensive, making the little things look really nice doesn't cost that much.

A 100 mile EV definitely puts you in OEM territory cost wise, so unless you're really an engineer type you may be better off just going that route as OEM has a $7500 advantage over DIY.


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## ruckus (Apr 15, 2009)

SandRailEV said:


> Sounds like it's time for EVEngineeer to do some engineering for himself.. There's everything on this site one would need to design a reasonable EV without even being an engineer... There's also enough supplier links to the parts and supplies to build one. What am I missing here???


Yes, it is not even "engineering". More like some basic math and assembly. The engineers already designed everything needed.

If you really want to go 70mph for 100miles you should not be even thinking about cars like the passat (a brick). I already gave you the short list. I guarantee a Honda CRX hf will go MUCH further and faster on the same battery. Wind resistance is EVERYTHING at 70mph. Are you aware that wind resistance is drag coefficient MULTIPLIED by square area? 2 cars might both be listed as .29, but if one has 2 extra square feet of frontal area it will be an absolute dog compared to the other.

Did you go to the eccomodder calculator I linked and run a few cars? I can't believe you would consider a passat if you had done that.
http://ecomodder.com/forum/tool-aero-rolling-resistance.php
This is the single most valuable tool you will find online. Don't round the numbers down. Always round up or you will be sorry.

Everybody is here to help you, but you have to show some initiative. If you can't bother to follow the link and run a few easy calcs then how can you expect us to spoon feed you?


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## TigerNut (Dec 18, 2009)

EVE, it strikes me that you're being somewhat naive about the money aspect, about people's willingness to devote time to your cause, and also about how long it will take to do even a 'catalog' EV conversion. By that I mean one where you can buy most of the components essentially 'off the rack' and there is only a minimum of custom fabrication required on your car.
etischer's Garage entry (http://www.diyelectriccar.com/garage/cars/41) shows 500 hours build time, and it's pretty apparent (at least to me) that he did not start from knowing very little about power electronics, car mechanics, or metal fabrication. At $50 per hour, 500 hours works out to $25000. Now, you may say that you can get some or all of the work done as a favor. But, 500 hours, at 8 hours per day, 5 days per week, comes to nearly three months. How many people do you know that can devote that much of their spare time or donate that much of their work time? 

It's better to start trying some of your own experiments and fabrication work, even if it's not currently going towards an electric car. Doing things is a much better learning experience, than just reading and directing others to make your dream come true.

In the past 25 years I've been playing with cars, I've learned to do oxyacetylene cutting and welding; TIG and MIG welding; sheetmetal bending and forming; fiberglass, bodyfilling, and painting. I own a milling machine and lathe so that I can make most of my own steel, aluminum, and plastic parts, and I've rebuilt engines, transmissions, and differentials both in stock and highly modified form. I've built my own tube-frame race car (AE86 Corolla) from the ground up. Through all that I've had many highly skilled and knowledgeable people help me - not by doing the work for me, but by letting me watch what they were doing or by answering my questions and then by trying stuff myself, until I learned how. The hands-on process teaches you much more than just how to turn a wrench, and there is no substitute for putting in the time in the shop.


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## EVEngineeer (Apr 11, 2012)

I was not considering the passat.

I just found this too. http://www.diyelectriccar.com/garage/cars/286 
This truck weighs about 1,500lbs more than what I would get if I had lets say a honda civic 2006+. The donor cost is 4k, I would get it for under 1k (closer to free if not free). If it cost him 30k to build this. I'm sure if I got the same stuff put in to the civic, the car would be able to travel faster and farther. The only differences between the two vehicles would be boxy truck vs. aerodynamic civic and air conditioning (a must in Florida). Now the question is how much farther and faster? My guess would be over 90 mph, which btw the 87 is fine. I do not need to drive faster than 75 mph. If he gets 65 miles range at 55mph, I would guess 75 miles range at 65 mph. That's actually what I need. 75 miles range at 65mph, but I want the car to be a little better than that. One for a cushion and two because you should not drain the battery fully.


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## ruckus (Apr 15, 2009)

DUDE! Why are you "guessing" I GAVE YOU THE CALCULATOR. RUN SOME NUMBERS. It took me all of 30 seconds to calculate the proper battery size for your car. I am waiting for you to come back and say, "I think I need this many kwh for such and such car, is this correct?"

Or even come back with, "I don't understand how to convert watts to kw", or "what do I put in this part of the calculator".

ANYTHING other than "I guess..."


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## dladd (Jun 1, 2011)

EVEngineeer said:


> I was not considering the passat.
> 
> I just found this too. http://www.diyelectriccar.com/garage/cars/286
> This truck weighs about 1,500lbs more than what I would get if I had lets say a honda civic 2006+. The donor cost is 4k, I would get it for under 1k (closer to free if not free). If it cost him 30k to build this.


Once again, you are ignoring labor and personal skill level. His batteries alone would be $16k (65 200ah cells), dual Kostov 11's and a Soliton is what, ~$8k? That only leaves $6k for everything else! BMS, charger, wiring, labor, rack fabrication, and all the little stuff.

Stop looking at what other people say it costs and price it out yourself. And don't compare a Land Rover to a Civic, that just doesn't make sense! 

Here's an interesting one to me, http://www.evalbum.com/2224

It's interesting because it's an identical battery pack to what I have in my car. It's a bit lighter, runs regen, and I suspect he's much more into hypermiling than I am. However, he states a 100 mile max range, with 80 miles being typical. And there's plenty of data on his page to back that claim up. Total cost is listed at ~$25k which seems a bit high, but I think includes his original battery pack too. 

With a basic DC system, normal driving, and the same cells I get ~50 miles real world range to 80% DOD. Quite a difference... Just sayin, there are lots of data points on evalbum. some will be more applicable to your situation than others.

Most importantly, start a spreadsheet. List all the components you need. Be detailed, list them ALL. Down to the lugs and crimp tool. Include tax and shipping. Make it as complete as you can. Add in the expected labor costs for each individual part that you will need help with (in my case, I can't weld, so I paid a welder every time I built a new rack component). See what you end up with. When you've done the research and made the spreadsheet, post it here for people to offer their input.


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## Ziggythewiz (May 16, 2010)

I think this has become another troll thread like the wind powered EV one. 

So and so did it for $X, but for me it'll be cheaper.
He used a truck, but I'll fit all that and more in a little car.
I'll just ignore all advice and just keep making up numbers and asking for solutions.


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## EVEngineeer (Apr 11, 2012)

to ruckus: I'm sorry but that calculator is to much for me. It's difficult to find the correct numbers and I know that I should not round it. The only thing that I know is correct was the Cd at 0.31 and that's about all I got exactly. I believe the weight of the car would vary all the time, so I was going to use 3,500lbs, but I think it would be best to have a worst case scenario for everything, so that way I am not surprised in a bad way in the end. So, I think 4,000lbs is a better number. I only weigh about 125lbs, I'm pretty skinny. I do not have the car yet, because I want to get everything straightened out in my mind and in the mean time save more money, so I will be much better prepared. It may be a month it may be five years before I get around to doing this project. So, who knows what car I will get, all I know is that it will be real cheap or free and it will be big enough to hold 2+ people and have a place to store things like groceries (aka trunk lol). 

dladd: great suggestion. I have been taking notes, so I will have to eventually put it together on a spreadsheet, which is what I was going to do anyways, but I guess I could get started on that sooner. It won't be very complete though, do to my lack of knowledge. 

ziggythewiz: I was taught in school to figure things out on my own, but at this level it's pretty damn hard to figure things out, without the proper knowledge behind it. So the best way for me to learn is to ask questions as bizarre as they may be. I have not asked all of my questions, because I did learn some things and I did find some things on my own. I had to learn on my own, before I found this forum. I did not know this forum existed until I think the day I signed up for it, if not then it was only a couple of days before at the most.


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## TigerNut (Dec 18, 2009)

EVEngineeer said:


> to ruckus: I'm sorry but that calculator is to much for me. It's difficult to find the correct numbers and I know that I should not round it. The only thing that I know is correct was the Cd at 0.31 and that's about all I got exactly. I believe the weight of the car would vary all the time, so I was going to use 3,500lbs, but I think it would be best to have a worst case scenario for everything, so that way I am not surprised in a bad way in the end. So, I think 4,000lbs is a better number. I only weigh about 125lbs, I'm pretty skinny. I do not have the car yet, because I want to get everything straightened out in my mind and in the mean time save more money, so I will be much better prepared. It may be a month it may be five years before I get around to doing this project. So, who knows what car I will get, all I know is that it will be real cheap or free and it will be big enough to hold 2+ people and have a place to store things like groceries (aka trunk lol).
> 
> dladd: great suggestion. I have been taking notes, so I will have to eventually put it together on a spreadsheet, which is what I was going to do anyways, but I guess I could get started on that sooner. It won't be very complete though, do to my lack of knowledge.
> 
> ziggythewiz: I was taught in school to figure things out on my own, but at this level it's pretty damn hard to figure things out, without the proper knowledge behind it. So the best way for me to learn is to ask questions as bizarre as they may be. I have not asked all of my questions, because I did learn some things and I did find some things on my own. I had to learn on my own, before I found this forum. I did not know this forum existed until I think the day I signed up for it, if not then it was only a couple of days before at the most.


You have to figure the real world into your calculations. That's both a limitation and a help... for instance, the gross weight limit on any Civic is not going to be more than about 3400 pounds - the total load capacity is about 800 pounds, including driver, passengers, fuel, and cargo. The curb weight of a 2006 Civic is 2600 pounds; therefore, if you count yourself, a passenger, and cargo as (let's say) 400 pounds, your battery weight can be no more than 400 pounds (for reference, a gallon of fuel weighs about 7 pounds, so a stock Civic can probably carry about 110 pounds of fuel, max). That battery pack in glaurung's range rover weighs about 900 pounds... there are advantages to trucks and larger sedans that have big cargo capacity.

If you exceed the gross vehicle weight rating, you can't get your car licensed.

For the other parameters in that range estimator, you can search around and find worst and best case figures that would apply to your target vehicle, and then see how that affects your range. You may be surprised that some components affect the range much more than others.


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## Ziggythewiz (May 16, 2010)

EVEngineeer said:


> who knows what car I will get, all I know is that it will be real cheap or free


If you're serious about building a 100 mile car a free donor would be a terrible choice. That's the place I most wish I had spent more. Why would you spenk $30K and hundreds of hours on something worth nothing?


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## ruckus (Apr 15, 2009)

EVEngineeer said:


> I'm sorry but that calculator is to much for me..


How is that possible? They already fill it out for you with an "average" car like the Passat. Look at the watts needed to go 70mph. 15000w. My 3rd grader knows that 15000w = 15kw. If you drive at 70 for an hour you will need 15kwh and go exactly 70 miles. But you want to go 100 miles so you take 15 x 1.3 and get 19.5kwh. Since the battery will weaken with age you need to start out using 70%. 19.5 x 1.3 = 25kwh. 

Simple.

If you get a small aerodynamic car and do a few aero modds (ecomodder.com) you can get that down to about 12 x1.3 x1.3 = 20kwh 

If you run a 120v system it would be 20000w / 120v = 160ah batteries
If you run a 240v system it would be 20000w / 240v = 83ah batteries

Now since this is just an estimate you should get another 20% just to be safe. So you are in the 24-26kwh range for your pack.

I get a price of about $10,000 minimum for the pack. But I am terrible at doing math in public and probably made a glaring mistake.. 


If you read a couple of blogs or build threads they will explain all this for you. If you are 5 years out from building, then read for a bit, there is no need to hurry.


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## EVEngineeer (Apr 11, 2012)

i've been reading all over the place. I will continue to read books about this and more stuff on this forum. I just like to post these questions, because I figure that it would help me understand things quicker and more efficiently if they are direct questions instead of the general ones that I see constantly. I want specific answers.


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## TigerNut (Dec 18, 2009)

EVEngineeer said:


> I want specific answers.


That's nice, but what we're mostly trying to get across here, is that it's up to YOU to take the general information that exists (and that we're giving you), and apply it your specific wants, needs, and budget. 

What you're asking for, by way of a kindergarten analogy, is cardboard stars, when you've already got a sheet of cardboard, scissors, and pictures of other stars in front of you. A kindergartener will learn a lot from picking up the scissors and doing some cutting. You will learn a lot from trying to fit the various pieces of Internet EV-car lore into your dream. Just don't run with the scissors


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## SandRailEV (May 11, 2012)

EVEngineeer said:


> i've been reading all over the place. I will continue to read books about this and more stuff on this forum. I just like to post these questions, because I figure that it would help me understand things quicker and more efficiently if they are direct questions instead of the general ones that I see constantly. I want specific answers.


Having others give you specific answers won't help you learn a thing. Doing your own math will likely help you to understand the physics needed to design an EV of your own... All I see in most of your posts is "I want" "I want" "I want" "I want" "I want" "I want" "I want" "I want".....

It's time to start doing for yourself...


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## ruckus (Apr 15, 2009)

SO THIS THREAD IS CLOSED THEN? All in favor no longer reply... anyone?.... anyone?... GOOD.

You will continue reading and take what we have given you and run a BUNCH of calculations and then open another thread at a later date in which you ask intelligent questions and have a little bit of an idea what you are talking about at least enough to PROPOSE a system for us to critique rather than ask us to do 3rd grade math for you?

Cheers everybody!


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## EVEngineeer (Apr 11, 2012)

Thanks everyone for helping me


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