# solar car



## Duncan (Dec 8, 2008)

Hi Tim

The first thing you need to do is to make yourself a basic spreadsheet

You need
Distance,
Watt hours / mile/Km
angle of your panels
time in sun
Power in from panels

Some of these numbers will be engineering estimates (wild assed guesses)

Put them on the forum and people will help you to be reasonable

This will tell you how practicable your plan is

I suspect it will tell you that the best way is to use stationary solar cells on your car port


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## Tm PV1 (Jun 5, 2010)

The motor pulls 300 amps at full acceleration, but I suspect it would only use about 25 amps for normal cruising through town (35 mph, fairly level). The car weighs about 850 lbs., a round trip to school and back is 15 miles. If my application gets through at where I plan to work, a round trip is 25 miles, both school and work have high speeds (~50 mph), a fair amount of turns, and two big hills (nice opportunity for regen on the trip in the morning). 

The panels on the car sit completely flat, providing over 1,000 watts in full sun. At school, the car would sit in the sun for approximately 7 hours before I drive it again, which will also sit in the sun until it sets at my house. I would prefer having the solar on the car in case that if something in the car would run the batteries near LVC, I could fix the problem and let the car sit for a little bit to gather some sun, then drive home extremely efficiently, where as if the panels are on my house, the car would be stranded as the school has no exterior outlets. This is the primary reason for not converting my brother's old Honda Civic. I made my own design which should be attached. Even though it says "not to scale, everything is except for the body's thickness, which would appear to be ~18", but it's actually going to be 26" from belly pan to solar array. Overall height is 59".

Nice guess on my name, my forum name is Tm (no 'i') PV1, which the name I have given to the car. I'm still trying to work out what the t and m should stand for.


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## Sunking (Aug 10, 2009)

Tm PV1 said:


> Hello, all. I am new here. Since October of 2009, I have had an interest in solar cars, the ones that are built for the solar races that take place. If anyone has been on solarpowerforum.net, I have a thread there, too, but I haven't been able to reach that website for months.


I am a Moderator on that forum. How can I help you? The site is up and working.


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## Tm PV1 (Jun 5, 2010)

It might be my internet, I keep getting that the server could not be found. I had a friend try it on his iPad, said he was able to access no problem. The last time I was able to access was before the big snow that hit the eastern US. Are there any new posts on my thread on solarpowerforum since the last time I replied?


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## Sunking (Aug 10, 2009)

Tm PV1 said:


> Are there any new posts on my thread on solarpowerforum since the last time I replied?


Cannot find the post using a few search terms I tried. I remember a few post in the past. What is your user name over there?

Anyway you are not going to get a lot of help over there as most of the membership is just clueless homeowners looking to stick it to the man trying to build DIY panels only to find out they cannot be used in a grid-tied application or fail shortly after they make them trying to use on battery systems and find out out they have to pay 30 times more for electricity trying to make it themselves. I am one of the very few engineers on that forum. So you will get more useful info here as the membership does have quite a few engineers and technicians. 

Now back to your project. I have not built an EV, so I want to make that clear. But I am an electrical engineer with 30 years or so of power generation, distribution, battery plants, and process control. I do however modify golf carts and learning the principles which is very similar to EV's.

One huge obstacle you will run into is just plain physics trying to power an EV by solar alone. In the golf cart world you can buy a roof with a 200 watt solar panel. 200 watts is about all you can get dues to th ephysical area limitations of the cart. Here is the point, the panel can only extend the range of just a few miles at best. It is incapable of fully powering the golf cart.

A golf cart is weighs around 550 to 700 pounds depending on the make and model. Battery to wheel efficiency is around 175 wh/mile depending on terrain and driving habits. Top speed using a 4.8 Kw motor is about 25 to 27 mph on flat level hard surface like a paved road. With a panel mounted horizontally flat at 0% tilt in Tuscon AZ in summer can only generate with a 5.2 Sun Hour day 200 watts x 5.9 hours x 66% efficiency = about 800 watt-hours. So when you factor in the battery to wheel efficiency of 175 wh/mile we are talking about 800 wh / 175 wh /mile = 4.5 miles range extended per day. 

So as stated in an earlier reply you need to sit down on work out the math to see what it will really take.


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## Tm PV1 (Jun 5, 2010)

Thanks for letting me know that I'm not missing much on solarpowerforum. I think my user name over there is T-solar, don't remember thread name. As for the car, i figured sticker rating of the array is 960 watts, plus the MPPT at 36 volts, so not much line loss. Even at reduced output of 700 watts, the math shows that I can charge the batteries in 11 hours, which is not a huge deal to me (battery bank size is 7,200 watts). At best, I figured a full charge in 7.5 hours, but I won't likely run the batteries to LVC every time I drive it. Since I use my own laptop for school, I will need to keep it charged up, so there is 200 Wh right there per school day, plus alarm system, EABS (lifts the solar array up with actuators for ingress/egress and maintenance), lights, ventilation, gauges, and radio. The only things that are constantly powered are the alarm, BMS, and the radio's clock. There is little phantom power in this. All the lights are LED's (depending on their brightness, I might substitute the LED headlights for halogens), and the radio I've found can be easily powered by a 12 volt, 15 watt amorphous solar panel during a rainstorm. My one friend is a big Apple computer fan, so I'm gonna see if he can make a custom alarm app for my iPod Touch, reason being is for the flexibility and the motion sensing. I have a parts list and description on my website at home.earthlink.net/~timster but they are a little out of date, so I'll hopefully update those soon. If my estimation of 25 amps cruising current is correct (which I hope it is), the solar array has the potential to completely power the motor (full output, of course). Sound realistic?


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## Roy Von Rogers (Mar 21, 2009)

Sunking said:


> I am a Moderator on that forum. How can I help you? The site is up and working.


Well, I cant get in to www.solarpowerforum.net either ???

Roy


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## Sunking (Aug 10, 2009)

Tm PV1 said:


> Thanks for letting me know that I'm not missing much on solarpowerforum.


 Your thread is still there. Last reply was from you on 2-21-2010



Tm PV1 said:


> I think my user name over there is T-solar, don't remember thread name. As for the car, i figured sticker rating of the array is 960 watts, plus the MPPT at 36 volts, so not much line loss. Even at reduced output of 700 watts, the math shows that I can charge the batteries in 11 hours,


 Ok first I am not sure how you calculated the charge time, but a huge mistake people make is assuming the panel develops rated power when ever th esun is shinning on it. That is really far from reality. Second most common mistake is people think if the shines for 14 hours per day they get a full 14 hours of rated power. Again not reality. 

For a vehicle you will will have to use a horizontal orientation with 0 Degree tilt angle. Next you have to determine your local area Solar Insolation data to see what kind of insolation you really have. Next is it varies by the season. For example let's say you live in Kansas City KS. Your December insolation is 1.9 hours and in July for a few brief days is 5.9 hours.

In December the most you could ever expect to generate with 70% efficiency is 960 watts x 1.9 hours x .7 = 1.8 Kwh, and in July 4 Kwh at the very best. If you could achieve say 400 wh/mile that is a range of 4.5 miles to 10 miles per day and only if the sun shines all day and all the power is strictly used for the motor.


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## Tm PV1 (Jun 5, 2010)

I calculated charge time by finding out how many watts the batteries will hold, which 36 volts * 200 Ah = 7,200 watts. If the solar would provide 960 watts for a full 7.5 hours (highly unlikely without a tracker), it comes out to 7.5 hours. My other charge time of 11 hours is more likely, but I only need enough charge to go 75 miles in a normal week. When I'm not driving it (on weekends is likely), I would probably leave the car sit in the sun, but be transferring power from the car to charge my solar battery at my house since the only solar panel on the house right now is a 15 watt amorphous that seems to work pretty well in any weather condition, but is still too small to keep the voltage up. If the monocrystalline panels don't perform as well in less than ideal conditions, I might make an amorphous solar array for those days or weeks where the weather isn't to sunny, since amorphous work much better in overcast (I've actually traced output on a full moon night ). Am I correct about this or have I been misinformed? Also, how much of an increase can I expect using an MPPT such as the Midnite Classic?


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## fishguts (Dec 19, 2008)

If you have deep enough pockets to build something like this, why not add fold-out panels to increase surface area? These would also allow you adjustment to improve the angle with the sun. Of course, you'd need to take up more parking space, but power-parking BMW's are already doing that! Oh, and that might make things interesting on windy days...


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## Tm PV1 (Jun 5, 2010)

I'm trying to keep the car as cheap as possible, but that idea sounds pretty cool.  Maybe after I get the car built, though .


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## dtbaker (Jan 5, 2008)

Tm PV1 said:


> I'm trying to keep the car as cheap as possible, but that idea sounds pretty cool.  Maybe after I get the car built, though .



if you are trying to keep car inexpensive.... you may be better served to grid-tie your PV array so you can benefit any sunny day, lower your house consumption, take fed/state tax credits, and get REC credits from utility co.

putting panels on your car you can't take advantage of any fed/state subsidies, you ruin your aerodynamics, and have to add weight and complexity to the car itself.


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## fishguts (Dec 19, 2008)

dtbaker said:


> if you are trying to keep car inexpensive.... you may be better served to grid-tie your PV array so you can benefit any sunny day, lower your house consumption, take fed/state tax credits, and get REC credits from utility co.
> 
> putting panels on your car you can't take advantage of any fed/state subsidies, you ruin your aerodynamics, and have to add weight and complexity to the car itself.



And I've been looking for a way to put affordable photovoltaics on my house roof, even toyed with (and abandoned) the possibility of using broken chips and building my own, but seriously, "cheaply as possible" and "solar cells" are phrases that don't usually fit in the same sentence.


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## dtbaker (Jan 5, 2008)

fishguts said:


> "cheaply as possible" and "solar cells" are phrases that don't usually fit in the same sentence.


that is sort of true.... there are some sources for used panels that are still functional, but might have mechanical damage.... like check in with state highway dept. Sometimes they have solar powered signs or whatnot where the enclosure or racking is damaged, but the panel is still ok.


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## Sunking (Aug 10, 2009)

fishguts said:


> And I've been looking for a way to put affordable photovoltaics on my house roof, even toyed with (and abandoned) the possibility of using broken chips and building my own, but seriously, "cheaply as possible" and "solar cells" are phrases that don't usually fit in the same sentence.


You cannot make your own panels for a grid tied system. No local jurisdiction would issue a permit or inspect it, no rebates or incentives would be approved or issued, no utility company would connect you, and no home owners insurance policy writer would cover it. They have to be UL in the USA


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## Tm PV1 (Jun 5, 2010)

Actually, I've considered having the panels on the house, but like I said in an earlier post, I would like to be able to keep my power source with me, so I don't have to worry about finding a plug. Also, the car is gonna sit for long hours at a time in the sunlight, so I want to take advantage of the energy hitting the car. The design of the car itself revolves around the solar array. No edges of any solar panel catch the wind and increase air drag. This picture is of the Blue Turtle, the solar car built by the Walnut Solar Team out of California. They run in the Hunt-Winston Solar Car Challenge. The shape of my car is similar to theirs, but many things under the "hood" are different. There actually are other advantages to doing this compared to a standard EV conversion.
1. Less overall resistance
2. Lighter
3. Classified as a Motorcycle (three wheels)
4. Completely customizable
5. More room for solar

I've tried to get broken solar panels from the DOT in my state. After being directed to three different departments, I got told that they were the property of the state and were not for sale. Dead end there. Too bad, the panels they have look pretty powerful. I've played with different panels and the numbers in different ways and got my array cost down to around $6,000. When I first started, the array cost was around $35,000. 

My house has a small solar system installed on it already. There is a system that will be installed in the car to make it able to unload power to the solar system in the house. Overall cost of my car is about $18,000.


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## fishguts (Dec 19, 2008)

Tm PV1 said:


> This picture is of the Blue Turtle, the solar car built by the Walnut Solar Team out of California.



Almost an airfoil shape? That must be one slooooow car. Get much speed going and I bet there are lift issues.


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## Tm PV1 (Jun 5, 2010)

I'm pretty sure their car moves at an average of 30 mph during the race. If you look at my design in an earlier post in this thread, I've lowered the bumper so that there is only 7 inches lift from the belly pan to the bumper. The rise on the front is 17-19 point something inches. Here are pictures of my initial design and my final design with the lowered front bumper. The body's thickness from belly pan to solar array is greater than what is shown in the drawings, so the upper risers on the front and back extend farther than what's shown. The lower risers are true.


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## fishguts (Dec 19, 2008)

Tm PV1 said:


> I'm pretty sure their car moves at an average of 30 mph during the race. If you look at my design in an earlier post in this thread, I've lowered the bumper so that there is only 7 inches lift from the belly pan to the bumper. The rise on the front is 17-19 point something inches. Here are pictures of my initial design and my final design with the lowered front bumper. The body's thickness from belly pan to solar array is greater than what is shown in the drawings, so the upper risers on the front and back extend farther than what's shown. The lower risers are true.



I know you are confident that your design is sound and that you can pull this off, so more power to you, but that "race" car has a lot of solar cells and it only does 30 mph with what looks like flimsy ultralight underpinnings. I'm no expert on solar racers, but I assume they're as light as possible. You're looking to build a streetable solar car, right? I think that's a different thing entirely. I do like the idea of on board solar cells to augment the batteries. That way the car isn't dependent on the solar panels, just using them to boost the batteries with the primary charging happening from an outlet.


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## Sunking (Aug 10, 2009)

Tm PV1 said:


> I'm pretty sure their car moves at an average of 30 mph during the race.


Well that car was designed by a team of engineers with sponsors with very deep pockets, and everything was custom made right down to the solar panels. How deep are your are your pockets and engineering team to make a concept car?


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## Tm PV1 (Jun 5, 2010)

I probably should have also mentioned that as for lift issues, I also included through vents from the font lift to the rear to reduce the vacuum created at the back of the car. This will also remove some of the higher pressure air from under the front lift. The pipes running through the car will also provide a heat sink for the cooling of the electronics. As for the solar team, I believe that they themselves (high school students) designed and built their car. It's mostly built of wood, and they substituted some expensive materials for cheap ones. I saw a video of the team describing their car, saying that for electrical insulation, they used "ordinary noodles, stuff that you can find in your swimming pool." Their car weighs about 650 lbs without the driver, mine weighs about 680 lbs without the driver. Most of my car will be constructed with aluminum and tin sheeting. Here's the video link:

http://www.youtube.com/watch?v=7hr85BnrgsA


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## Tm PV1 (Jun 5, 2010)

I found an online insolation calculator. For my location and the array size and efficiency of the car, I can expect to get anywhere from 3.52 to 7.74 kWh/day. The array size I entered into the calculator was 165" by 72" with an array efficiency of 19%. I didn't take away the area of the dome because there will be solar panels on the top of the dome as well. Even with the relatively low energy in the winter months, I don't expect to use more than 45% of the battery (~3,240 watts) in any regular day.


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## Duncan (Dec 8, 2008)

Hi Tim

Did you allow for the fact that your car is not angled to the sun?

19% Have solar panels changed that much? The ones we used on the SolarStealth were 11%


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## Tm PV1 (Jun 5, 2010)

Were you and Zaxxon on the same team? In another post, he was talking about a solar car they built for the Winston solar challenge, and they raced from 1997 to 2003. The post is in this thread http://www.diyelectriccar.com/forums/showthread.php/home-grown-mini-ev-38988p2.html and it's post #19.

The car he's talking about is at http://www.winstonsolar.org/challenge/teams2003/stealth.shtml


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## Duncan (Dec 8, 2008)

Hi Tim

I am trying to remember the dates,
I was working for Cummins in Columbus Indiana from December 1997 to September 2001 and I got collared into helping the high school team

I think the team won in 1998 and I helped them to win in 1999
In 2000 they made a horrible thing with a table on top and in 2001 they were given a pile of titanium sheet and decided to make a car out of it

I understand why they did not want to use composites again (messy!!) but titanium! totally useless for that

The 1999 car was the most sophisticated with a composite aerobody

My guys were the aerobody/aerodynamics team we had lots of arguments with the chassis team

They didn't keep to their promised dimensions and we had to find an extra 100mm in height (luckily we had a cunning plan)

We were all mightily pissed when after leaving large single skinned areas to cut the holes for the wheels (incredibly important that the holes be as small as possible) the chassis guys cut the whole single skinned piece out!

I did have problems with some of the other adults - the suspension guy made all of the parts, at the end of the day his kids could not design and make their suspension

My kids could have designed and made another aerobody

I hate to say this but from an aerodynamic basis the current one you sent me a link to is not a patch on ours - I can see the whole wheel!!!

The top of the tire is travelling at *twice* road speed and you Know drag is Not Linear! - open wheels are crap for drag!!

Racing cars use them because of the rules

The problem with High School cars was that they had to make a new one each year, if they had kept one and developed it......


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## Tm PV1 (Jun 5, 2010)

That looks pretty good. Congrats on your wins. My design has only the bottom halves of the wheels showing under the car, and I'm working on how to get the wheel wells closed up as much as possible. I'm thinking about an hourglass shape. I have low rolling resistance motorcycle mag wheels on the front (ecopia solar car tires seem too weak and expensive for everyday driving), and the rear wheel is a 26" bicycle wheel because the transmission I want to use will only lace into bicycle wheels and I already have the trailing arm suspension. I'm also going to strengthen the back wheel with aluminum piping. The issue I'm having with parts and design right now is finding front suspension and steering knuckles. I'm thinking about taking the leading arm suspension off of our old ATV and making custom knuckles. Everything else seems like it will piece together nicely.


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## Duncan (Dec 8, 2008)

Hi Tm
Sounds like you have a good feel for the aerodynamics

Getting a good aerobody is not difficult the devil is in all of the details around the wheels and canopy

The best have a rotating turret around the wheels

However
I don't think this is a good idea on the road - I would not sell you life insurance
Somebody will KILL you

The problem is somebody will look straight at you and NOT SEE YOU

This kills thousands of motorcyclists - the car driver does not see the bike - his brain is looking for a truck or a car

Your low profile vehicle will simply not register

Flags up at SUV eye level would help - but an amazing amount of drag!


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## Tm PV1 (Jun 5, 2010)

The top of the solar array is at 39", and the top of the dome is at the five foot level, so my car is taller than a Lotus, a Tesla, a Honda Del Sol, a Mazda Miata, et cetera et cetera. The dome is at eye level with my parents' Chevy Tahoe, although some reflective tape couldn't hurt. It would make people use the low beams.   And if that doesn't do the trick, I'm sure the all-around LED's would be noticeable.


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## Duncan (Dec 8, 2008)

Thanks Tm
I stand corrected!

At those heights with flashing LEDs you will be difficult to miss!!

Our car was about knee high!


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## Tm PV1 (Jun 5, 2010)

I know the LED taillights on Cadillacs are blinding even during the day. I noticed your car's height compared to the Dodge van in the background. I figured my car could be larger than others similar in shape because I'm not running in a race. I just need it to be practical enough for everyday commuting and maybe an occasional joy ride.  Side roads shouldn't be too much of an issue with at least 11" of ground clearance and a 117" wheelbase.


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## Tm PV1 (Jun 5, 2010)

I've been hard at work on the solar array and front suspension design. I nixed the solar panels I previously selected, and found cheaper ones that fit the car better and are probably lighter. Even though I lost about 100 watts of output, I saved $3,000. These panels' outputs (there are two different sizes) are a lot closer than the previous ones, allowing me to reduce to one MPPT charge controller, saving even more weight and money. Will hopefully post updates and pix soon. My car is in the site's garage with updates to the price and final weight. Unaccounted for items increased the weight from 850 to 900, but may have gone to 1,000 without other substitutions. Also, I am finally able to access solarpowerforum.net again. Thanks to whoever fixed it.


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## Tm PV1 (Jun 5, 2010)

I may have run into some issues with the PV1. I was looking at our ATV's front suspension, which is double arm suspension with drum brakes. I currently have motorcycle front suspension selected for the solar car. I also recently went to Tractor Supply Co. and found camper tires, and if I remember correctly, they should bolt together. Does anyone know where to find complete front suspension for a 2004 Honda Rancher 350 4X4, or of an ATV just like this for sale, whole or parts? Thanks.


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## gte718p (Jul 30, 2009)

Duncan,

that titanium monster the SolarStealth ran actually did fairly well. They ran into some electrical problems and then they ran into some repair problem. Malcom was an awesome welder, but welding TI in the field was a pain. They had the same weld in the suspension fail several times.

I was involved in the Winston race for several years, as a racer with Team Pegasus and then several years as staff. Its an awesome race. I've also been involved in college level racing for many years. I still consult with several teams even though I've been out for several years.

I hope it works out for you. Based on my experiances I would build an array on my garage and charge a dump pack during the day and charge during the day. Solar vehicles are cool, and obvisouly I like them however, they are about as practical as driving an F1 car to work.


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## Tm PV1 (Jun 5, 2010)

Got some more work done on the design and laid out the dimensions of the car with tape measures. I now have a very accurate layout.

•	Dome width – 30 in.
•	Dome height – 16 in.
•	Dome length – 36 in.
•	Vehicle width – 72 in.
•	Vehicle height – 55 in.
•	Vehicle length – 198 in.
•	Ground clearance – 13 in.
•	Vehicle vert. thickness – 26 in.
•	Array length – 165 1/2 in.
•	Array width – 72 in.
•	Wheelbase – 117 ¼ in.
•	Front overhang – 46 in.
•	Rear overhang – 39 in.
•	Front lift – 8 in.
•	Rear lift – 11 in.

And GTE, practicality is all how you design it. I've seen some solar cars where one person can get in it unassisted and drive away in a matter of seconds, and I've also seen them where it takes the whole team to get the driver in. If you're talking money-wise, a $16,631 solar car that costs nothing to run compared to a very expensive high-performance car that gets about 6 MPG, I'd put up with ingress/egress difficulty. 

How about the updated design? The 20 in. dome looked too big for the car, so I shortened it 4 inches. The big, grey boxes on the bumpers are those vents I was talking about in an earlier post.


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## gte718p (Jul 30, 2009)




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## gte718p (Jul 30, 2009)

arg I lost my post.

Anyway the previous post was my second car. The diminsion where the same as your car. It cost over 100k to build and had the best components available. It would not meet your stated design paramters.

I think your severly underestimating weight. Have you taken into account bolts, wire, welding wire, etc? My bet is it will be close to 1500 lbs. Thats based on seeing hundreds of solar cars. Your 1000w array will probably only produce 100 to 200 watts rolling down the street. Thats not a lot of power. Even parked you probably looking at only 500 to 600 watts. To get peak power you have to be facing the sun. Its why teams have very elaborate stands to point the array at the sun when parked. You will also have huge amounts of parasitic drag that I doubt you have even though about. You wheels and tires are horrible ineffecient, and the bearings and driveline you are planning on have large losses. 36 volts is going to be annemic at best. Even my 400 lb motor cycle needed to be upgraded to 50 volts to get out of its own way.

That being said with your budget your a long way to building an awesome EV that will meet your criteria. My suggestion is a standard metro or 914 conversion.

914 with blown motor $500
Impulse 9in kit $8200
http://www.evsource.com/datasheets/120V Impulse 9 Package.pdf
60 100ah batteries $7200
http://www.evsource.com/tls_lithium_hipower.php
battey management & etc $1000
------------------------------------
total $16,900

Its a setup that most people here would love. It should meet you EV goals. If you want to be off the grid build a fixed charging station like Otmars http://evcl.com/solar/. You will get more power out of an equal number of cells.


If you do build it definately take it down to the winston race.


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## Tm PV1 (Jun 5, 2010)

I only need 75 miles a week. As for weight, I figured in my weight plus an additional 50 lbs to make up for whatever and I'm below what's rated right now (900 lbs). So far, I have 640 lbs logged in components. As for power, my eZip Trailz is 24 volts with a 450 watt motor (.6 hp) that will very easily pull 170 lbs. up my road, which is not paved and has a slight slant to it without me pedaling. If I increase power by a factor of 22 (13 hp), increase weight by 830 lbs. (factor of 5), and double drag, I should still have plenty of power to overcome resistance and move. Just working on what seems to make sense to me. You have worked with solar cars before and obviously know more about them than I do. The only thing that is phasing me right now is how your car cost $100,000. By the way, I doubt my current setup is compliant with Winston's rules (LiFePO4 batteries, no redundant brakes, high efficiency solar cells, no discernible crumple zones, etc.)


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## gte718p (Jul 30, 2009)

100k solar cars are cheap. The averave is closer to 250k for the college level teams. 

Solar Jackets
25k for the NGM motor and controller package
30k for lithum polymer batteries
30k for 18% multijuncion solar cells
10k for array encapsulation
5k in power trackers.
10k for misc

There is was also almost 20k in carbon, kevlar, and nomex in the body, but we go all of that donated. We also had a sponcer donate time in their 30x60 foot autoclave to bake the car. We also had approximately 20k in custom machining that we were able to do in house. However not everyone has access to a couple of master machinist and a CNC lab.

13 hp is more then enough power. The problem I see in you power scaling. A 1000 lb car does not scale linearly from a bike. You have a huge surface area which will cause surface drag. Your shape is simple to make, but horrible for drag. You also doubled your number of wheels and tires which will double your drag. Higher rotational speeds will also increase your drag from bearings and tires.

That being said it is possible to do. The cheapest solar car I personally have seen was just over 10k. I don't think overall you will be satisfied with the performance. You said in your first post the speeds on the streets you travel is 50 mph. If your tooling along at 25 it is not comfertable nor safe even for short distances.


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## Tm PV1 (Jun 5, 2010)

For my parts;

motor and controller = $1,050 * D&D SepEx
Aluminum frame = $1,451
Lithium iron phosphate batteries = $2,400 * Thundersky
Power tracker = $750 * Midnite Classic
Monocrystalline solar array = $3,369 * 85 watt and 12 watt panels from HQRP
BMS = $300 * MiniBMS distributed

I know what you mean by drag, but wouldn't my car be a little more aerodynamic than me on a bike? 

I found this video on youtube. It's obviously more aerodynamic than mine but it shows that they can be used in traffic.

http://www.youtube.com/watch?v=9ApCQuLqyq0


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## gte718p (Jul 30, 2009)

Really no.

Your coefficient of drag will likely be a little smaller. However, if your leading and trailing edges are not well designed it will not be as much as you might think. To figure areo drag you multiply CD by wetted area (surface area), or frontal area depending on which CD you are using. The surface area of a human and a bike is nothing compared to that of a car. A quick example, I have two race trailers, both the same size and approximately the same weight. One is open one is closed. The CD for the open is huge, because there are all kinds of funk shapes and angles. However, towing the enclosed trailer I get 5 mpg lower gas milage because of the skins surface area.

You need at least two power trackers or preferably 4 or more. Your bubble will be shading part of you array at all times. Well accept for the 30 seconds that the sun is directly over head. If you don't have the array sectioned with a power tracker on each section that shading will basically kill the array. 

What 100k buys you is effeciency. Your looking at 70-80% effecient for you motor and controller setup. The NGM setup claims mid 90%. 

At 100% depth of charge you only have 7.2 kwh stored in the batteries. My best guess is thats about 10 miles at 20-30 mph. Your probably looking a 15-20 hours of sun light for a full charge based on the array your talking about. With good sun you should be able to roll around at 5 or 6 mph almost indefinately. However thats not alot of fun.


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## Tm PV1 (Jun 5, 2010)

I have a scale model of my car which I tested the airflow over it yesterday. I still have to put the dome on, but when I tested it, the air hit the front bumper, and had a curve that would direct the air to hit just the upper part of the dome. It then came down and flowed across the array and had a real nice trailing edge. I didn't find much of any turbulence. 

I see what you mean about the trailers. I had somewhat the same thing in mind, since my car has all smooth surfaces, but me on the bike is like your open trailer, nothing uniform. I noticed one day going down a hill, upright, was doing 27 mph. I leaned down by the handlebars and centered the pedals, went up to 29.3 mph. So just that little bit of movement lowered my CD considerably.

I'll do some more work on the electrical stuff and see what I can figure out. I had my bike out yesterday figuring a couple things out. Since the car is five times heavier than the bike, if the resistance is also five times more, I would need five times more power to get the same performance of the bike in the car. That's with the same gear reduction. The car has a 3:1 reduction before the power even gets to the wheel, then the rear wheel's internal transmission will either reduce or increase the power further. The bike has almost no reduction.


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## gte718p (Jul 30, 2009)

Tm PV1 said:


> I have a scale model of my car which I tested the airflow over it yesterday. I still have to put the dome on, but when I tested it, the air hit the front bumper, and had a curve that would direct the air to hit just the upper part of the dome. It then came down and flowed across the array and had a real nice trailing edge. I didn't find much of any turbulence.


Thats kind of unavoidable but not what you want. You want to see the flow of air hug the bumper and pass directly over the body. Jumping up over the bubble is a bad thing. Your getting flow seperation. Its a function of the entire body of the car, leading, trailing edges and the body. Its why competition cars have the tear drop or airfoil shape across the entire length of the body.

Probably more important then the top is what is happening under the car? That ones actually harder to deal with as you need a rolling wind tunnel or a CFD program. Your going to have substanicial ground effects. Its unavoidable, but the higher the car is off the ground the better it is.


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## Tm PV1 (Jun 5, 2010)

Actually, I looked at my "wind tunnel" last night and the airflow was aimed too low on the car. I fixed it and retested it this morning. I found out that the curve is gone now that I have air going over the top of the car. I also noticed that the trailing edge was also improved. I'll upload pictures once I finish testing with the real wheels (rc chassis removed) and the dome put on.

p.s. If I would do the airfoil shape, the Walnut Solar Team would probably not like me too much, since my car is alot like theirs in the first place. I had to change the design so that I didn't just copy their car.


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## Duncan (Dec 8, 2008)

Hi Tim

A few comments
$100K ???
Solar Stealth's budget was about $20K 

Efficiency - standard motor / controller - should be in the 90's pay a ton of money ang gain a tiny improvement - not worth it
Solar panels - 11%

Weight / rolling resistance - the University cars were light - 300lbs
You can make a lightweight - just needs attention to detail and *balls*
Its easy to just keep adding weight - you need to trust your calculations / measurements

Materials
Composites are best - by a huge amount (and messiest) 
If using a wet layup S glass is stronger than an equivalent Carbon fiber layup (and cheaper)
(Epoxy Resin - the other stuff is not comparable and can't be used with foam)

This is because you will need more resin to wett out the fibers with carbon so you end up with a less efficient mix 

Try and get the vidoe of the making of the voyager

Aerodynamics

Keep the flow attached!!! - laminar flow is theoretically better but actually a pain
Use turbulators to ensure the flow is turbulent before trying to move the air back

The design around your wheels and dome is critical!!


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## Tm PV1 (Jun 5, 2010)

gte718p said:


> At 100% depth of charge you only have 7.2 kwh stored in the batteries. My best guess is thats about 10 miles at 20-30 mph. Your probably looking a 15-20 hours of sun light for a full charge based on the array your talking about. With good sun you should be able to roll around at 5 or 6 mph almost indefinately. However thats not alot of fun.



Judging by this, my car has an efficiency of 720 Wh/mile. 

The EV1 had an efficiency of 115 Wh/mile. My bike has an efficiency of 24 Wh/mile. If I keep my scale factor of 5, an 850 pound car with 5 times more drag and power than my bike gets 120 Wh/mile. but when you factor in solar input of about 100-400 watts, with the sun almost overhead on level streets, pointing south during my trip home, the batteries are not being drained. I believe there is some error in your calculations, unless I drive around with the parking brake on .

Duncan,
I've looked at carbon fiber, but it's too expensive to save a couple of pounds. I don't know about having a car THAT light. At 300 lbs., a very thin car could be blown off the road by a semi going the other way. The money figures shocked me, too. If I was going to dump $100k+ in a car, I might as well buy a Tesla Roadster. My motor and controller's efficiency is in the low 90's.


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## Duncan (Dec 8, 2008)

Hi Tim

The french team visited with us while we wer doing the stealth - their car was lighter than our batteries!

Carbon fiber is VERY expensive and only gives an advantage with a pre-pregs 

I am working on 200 - 300 Whrs/mile at highway speeds for *my car*

You should be at unstreamlined bike numbers - 24 whrs/ mile sounds like a target for your car (at 30 mph) 

30 mph - 25 whrs/mile = 750 watts continous

900 lbs - rolling resistance - 1% = 409 kg at 1% = 4kg = 40N (force) at 30 mph = 13 m/sec
power = 13 x 40 watts = 520 watts

Aero resistance ? 20N at 30mph = 260 watts - a normal bike is less than that 

add the two 520 + 260 = 780 watts = 26 watt hours / mile

Gotta keep it light! - gotta get those tires pumped up HARD!


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## Tm PV1 (Jun 5, 2010)

200-300 Wh/mile, at highway speeds, is about the same as the Tesla and EV1. Do you know of a device that can be put in the car and tell you instantaneous/average consumption/regen in Wh/mile? I've been looking, but haven't found anything yet.


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## gte718p (Jul 30, 2009)

Your absolutely right that if you are going to dump 100k in a solar car you should buy a tesla. I still think if your going to dump 16k in a car you should convert a 914, vw, etc. Solar vehicles are build for racing/technology development. They are the equivalent to F1 or Nascar. Nothing about them is practical or even ment to be. Solar vehicle racing has driven the EV field. The Team that developed the EV1 where from the GM SunRaycer Team. High Efficiency AC traction motor came out of the MIT solar car team and solar cars have been the driving factor for scaling lithium technology to the point it can be used in automobiles.

I expect your consumption to be in the 300-400 wh per mile. That based on the weights, the fact you are talking about an ATV front end, the tires you are talking about, and your aero package. Your going to be higher if you actually try to go to highway speeds. The EV1 was a billion dollar project. The interior sucked (my opinion) but otherwiase there was not a single piece of that car that was not designed for efficiency. 115 wh a mile is not easy to make. Solar cars do it, but again those are not cheap or easy. Scaling linearly from your bike is not appropriate. Some factors scale linearly some exponentially. 

Duncan is right to get your efficiency up you have to be ruthless in cutting weight. You also have to have your tires at very high pressure. This is not safe if the tires are not designed for it. The solar car standard tires are inflated to 170 lbs. You also need really really good bearings. 

Duncan
Solar stealths budget may have been 20k in cash, but at pile of TI and the machining services that Alcoa provide had to be worth at least that. 40 hours of machining per wheel x six wheels can not be cheep. The final car was an accumulation of 5 years of racing. The array on the final car was worth almost 20k encapsulated. However, they had motor/controller, power trackers, and tires from previous years.

I remember that French car. It was ridiculous. Two people picked it up and put it on the trailer the few times it was actually trailered at the race. I remember it passed our convoy in traffic on the freeway in LA. It really was amazing.

Good luck. I think everyone should build a solar car. I think its incrediable valuable experience. However I think your expectations are setting you up for disappointment. I hope you prove me wrong and I look forward to seeing it.


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## gte718p (Jul 30, 2009)

I'm not aware of any device that does wh display instantanously. Generally you get it buy multiplying current x voltage integating over time. Should be simple to do with a micro controller. The E-meter will show you the total kwh that you have uses.

On my race cars we used battery current as the instantanous indidcation of power usage.


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## Tm PV1 (Jun 5, 2010)

That's what I have in the plans right now. I'm using an ammeter to track both consumption and regen. I'll take a look at the E-meter. I finished the model and will do more aero tests. Hopefully the dome doesn't screw up the airflow.


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## Tm PV1 (Jun 5, 2010)

Got some pictures of testing. The picture from above the car shows airflow under the car. There is air deflected towards the sides because of the front axle assembly. Most of this won't exist in the actual car because only the bottom parts of the front wheels and a little of the suspension will be exposed.

The picture of the side of the car shows airflow around it. Near the top of the array and the bottom of the car are collections of deflected air (marked by a slightly larger line). The darker lines on the dome is the path of the air on both sides of the dome.

The darker picture is the trailing edge of the car.


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## Duncan (Dec 8, 2008)

Hi Tim

THAT IS AWFUL!!
How did you come by that shape! Its terrible!

_*Rule ONE - The flow must remain attached*_ - as son as it detaches you get form drag

The air will remain attached where the body work is "pushing it" - as the body is getting bigger - the front!

As the body gets smaller it MUST do so slowly - slowwlly - this is because the forces are now trying to detach the airflow

The body must increase in size until the max - then reduce slowly, 10 or 12 degrees is good

This gives the blunt front and tapering look you see on the other cars - the tapering tail is all important!!!


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## Duncan (Dec 8, 2008)

Hi gte718p

Whrs / mile - 200 to 300 is a good guess for *60 mph* and a small car

At *30 mph* even a normal small car will be well less that - probably less than 100 whrs/mile 

Tim's solar car (before I saw the Aero design!!) should be a lot less than that 

Wheels / tires - its not going to be cornering hard, - bicycle wheels are able to cope with 100 Kg riders and 10 Bar pressures in very bumpy conditions (races)

I would build it light and try to get away with good bike wheels and tires - back to having the courage of your convictions (and some stress testing)


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## Tm PV1 (Jun 5, 2010)

Could be worse. If you watch Top Gear, you might have heard about the Hammerhead Eagle iThrust, what a terrible machine. I put together some charts. Let me know how realistic these figures are. They are based on an 80% DOD, which is 5,760 watts and there is no solar input (batteries only).


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## Tm PV1 (Jun 5, 2010)

Another reason why my car has its current shape is utility practicality. It has to be big enough to be seen as another car by other drivers, it has to be able to haul stuff (groceries, book-bag, etc.), and it has to have enough room inside for all the components that make it work. The picture below shows a car that, for me, would be unpractical. I would probably fall asleep if I drove like that, it doesn't look all too comfortable, and it doesn't have room for my book-bag or groceries.


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## Tm PV1 (Jun 5, 2010)

Hopefully, if all goes as planned, I'll have some real world data on the PV1 this time next year. I finalized design and parts and will start construction sometime in the next two months. I already have 2 of 19 solar panels, suspension, solar array frame, brakes, and a few other electrical parts. $14,000 left to go. Also, there is more data on the car at http://home.earthlink.net/~timster on the solar car page.


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## DIYguy (Sep 18, 2008)

Hi Tim,

Do you know of this guy? http://www.xof1.com/index.php

I met Marcelo a few weeks ago and saw his car in Toronto at a trade show. Perhaps reviewing his specs will help you? He is very approachable and he designed and built this car himself. (he is an airline flight attendant lol) Amazing fellow. We spoke for 35 or 40 minutes. I took the attached pic of him at the show.


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## DIYguy (Sep 18, 2008)

Tm PV1 said:


> Do you know of a device that can be put in the car and tell you instantaneous/average consumption/regen in Wh/mile? I've been looking, but haven't found anything yet.


Yes, the Cycle Analyst does it... and it's relatively inexpensive. They have a high voltage model for EV use (originally designed for bicycles) http://www.ebikes.ca/drainbrain.shtml


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## DIYguy (Sep 18, 2008)

Have you looked at these guys for motor/controller? Perhaps its out of your price range...but they apparently supply the motor for most of the solar racers/builders. http://www.ngmcorp.com/index.htm

SCM150 is an ultra-efficient, *7.5 kW* peak power motor especially designed for solar car applications where efficiency is key. An * in-wheel motor *having a variable gap mechanism that allows for the torque-speed characteristics to be changed on the fly. Used by more than 90% of *solar car* teams in the US.


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## Alexander_B (Oct 19, 2010)

the main 'problem' that if you want it really solar powered, you can't have a 'car'.

why? because solar power, 1 kw, takes up a flat space thats at least the size of a full car in dimensions, and with 1kw (and some battery backup) you can only drive a super light weight aerodynamic vehicle. (compare: canoo or bayliner)

looking at the solar racers:
they have about 2 kw of space tech solar panels, worth about $0.3 milion, and have a total weight (ex driver) of about 400 pounds, and feature a super refined aerodynamic shape that has extremely low drag, and is made of expensive carbon fibre. (another $100k, total vehicle price is about half a milion. yes, i know all this because the 'neighbours' built the solar racer that won the australia race like.. 4 times in a row, they are our neighbours because we built a speedboat with the same solar panels and construction tech, also worth/insured for $400k.

to look on the bright side, you don't need to go 75 mph continuously for a whole day, so your vehicle needs less contiunous solar power/weight and power/drag ratio, and can therefore use more battery to make up for bad weight, aero and lower solar power output. however, as stated, you're probably better off with stationary solar panels and a regular EV, because donor cars with a suitable flat surface that isn't a full size van or truck are nonexistant, and developing a vehicle from ground up probably won't happen either.

so nyah, have fun putting panels on the roof, you don't need a batt bank at home (thats where the grid comes in, you deliver electricity at day rate, and charge overnight at night rate, this way you even make extra money!) and building a nice ev.


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## gte718p (Jul 30, 2009)

DIYguy said:


> Have you looked at these guys for motor/controller? Perhaps its out of your price range...but they apparently supply the motor for most of the solar racers/builders. http://www.ngmcorp.com/index.htm
> 
> SCM150 is an ultra-efficient, *7.5 kW* peak power motor especially designed for solar car applications where efficiency is key. An * in-wheel motor *having a variable gap mechanism that allows for the torque-speed characteristics to be changed on the fly. Used by more than 90% of *solar car* teams in the US.



That setup is beyond just about everyones range. It's an incredible system I've had the pleasure of owning four of them with several teams. $35000 a pop you have to be really serious about racing.

I'm sending most of the teams I advise these days towards the etek. It's not as efficient, but MGM is a 99% solution. If the rest of your car is not up to par it's a waste. the money is generally better spent on better cells or batteries.


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## Tm PV1 (Jun 5, 2010)

Wow. I wasn't expecting that many posts in four days, but:

@Alexander, even though I call it a solar car, I actually designed (I'll go by its name) the PV1 after a solar racer, but made modifications to the design to avoid copying that team's car and to make it more practical for commuting. If you look back in the posts, there should be many drawings of the PV1. I'm not shooting for the records of most range per day, weight, and efficiency, but I am looking for the most economically feasible option with the highest efficiency. Currently, the D&D motor I have is about 88% efficient, which is okay with me for $1,000. The PV1 is bare-bones relative to a car, no ABS, TCS, ESP, or airbags, but building it hopefully won't be too difficult. It's built on an aluminum frame with A-Arm suspension on front and trailing arm on the back. It has three wheels so that it can be registered as a motorcycle, so no safety requirements by the state. The solar array is 885 watts, and the propulsion system is set up like an EV with the solar array as the range-extender/battery charger. I didn't design it to completely run off the array without a battery bank, I realize the limitations of doing that. It seems to be a misconception that I am doing that. The PV1 can run without its $3,300 solar array with only a dent in how I charge it and the range. There also will be solar panels on my house that will charge a reserve battery bank so that if I would need to, the PV1 can charge up off of the reserve, so I have panels in both places. Doing this instead of converting another car gives me several advantages, including cost, weight, solar incorporation, range, and efficiency. As for performance, my commute is 75 miles per week, 7.5 miles each way with 7 hours of sitting in between. Top speed is 50 mph. By the way, where I park has better solar position than my house does, so I want to take advantage of it. I wouldn't want to see the electric bill if I had to charge an EV every night, the power company is ripping us off enough. It would probably be different if we had a time-of-use meter, but we don't. I should have a parts list and an FAQ up on my website soon, hopefully. A lot of specs on the PV1 will be available then.

@DIYguy, is that the same guy that got pulled over in Alaska because someone reported a UFO on the road? Thanks for the links. I'll take a look at the Analyst and see how it fits in.


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## Alexander_B (Oct 19, 2010)

I seem to have skipped a few pages  my bad.

still even if you don't have the night/day dual rate meter, if your solar array delivers x kwh to the grid in one day, and you use x kwh to charge your car from the grid later on the same day, the meter would first roll back, then roll forward, and end up on the same number. 

(ofcourse, in theory, because in practice the fridge and such will also use power, so it will end up forward by the amount the fridge used.)

On the other hand, gas costs $7.57/us gal. here (€1.45 per liter), and 7.5 kwh of electricity costs $2.00 (worst case*) hence, the power bill, if you include fossil power from the pump, would go drastically down (at least, here) and down even some more in the long run with solar panels. (they do have payback time to take into account.)

* the power bill for the average consumer here is composed of about 50% fixed fees and 50% of the kwh's used (at about €0.08-0.10 per kwh), if you consume power at an 'industrial' amount you can get is much cheaper, (thats what they did in the student-housing building here, one meter for 750 people, and the bills are actually very low)


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## Tm PV1 (Jun 5, 2010)

I noticed on our bill that the power usage can change by 500 kwh but the price stays the same. Also, we used air conditioning almost every day last year in August, but it stayed off in August of this year, and we added some more CFL bulbs. The bill showed we used more power this August than last, which makes no sense to me. I've even shut the entire house off via the main breaker and the meter was still creeping forward. The only time it actually stops is when the power's out. 

I have a system in the PV1 that will dump excess power to the house to slow the meter. Other uses the PV1 can have with an onboard array is that the car itself is a portable generator, supplying power anywhere the car is. If it doesn't have the onboard array, I can only use a fraction of the energy so I still have enough power to get to a plug. With my power source onboard, I can use power directly from the panels, leaving the batteries alone for the most part (depends on the external load). For example, my sister holds birthday parties in her front yard, which the only way to get power down there for the bouncy castle, coffee maker, and lights is by extension cords, which get pretty warm with the lights on, so I was hoping to run some stuff off of the PV1 to ease the load on the cord. So doing a solar car instead of an EV provides more uses of the car with less worry about battery charge. Also, Planet Green has an article about EV's in traffic jams, so there is another advantage, although I'm unlikely to be in that situation.


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## Alexander_B (Oct 19, 2010)

hm, thats odd, usually you pay a certain amount each month, and at the end of the year they check if you paid too much or too little (averaged), usually they take it a bit on the conservative side, so you get money back at the end of the year. thats why using a lot in one month doesn't affect the amount you have to pay that month. (or, thats my guess as to whats happening there.)

also, if you pull the main breaker, the meter should stop. unless the nieghbours are growing a certain kind of funky plant and are stealing your power... 

ah well, pv panels are fun  too bad I live in an appartment building, can't put any there, neither would it pay back, as the electricity here is included in the rent, lol.


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## Tm PV1 (Jun 5, 2010)

What our utility does is they have a whole bunch of charges and the actual KWH usage. They read the meter every other month, and estimate the month in between. The estimates are usually pretty close to actual, then they resynchronize on the actual read. 

Maybe a solar car can benefit you. Drive on pure solar power. When you don't drive for a couple days or more, plug the car into the apartment building with a grid-tie inverter like this one http://raymonium.com/envirotechs/frame.htm . You would probably need a cord for your outlets (unless you use US standard).This will lower the electric bill and, depending on the owner, could lower your rent by a small fraction. This is what is going into my solar car. I have a 36 volt to 24 volt converter to make this compatible.


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## Alexander_B (Oct 19, 2010)

I totally agree, but I know for sure that the company that owns the whole building isn't going to be helpfull, besides, the electricity bill is like <$15 a month. (remember what I said about industrial power bills?) and I don't want to wake any sleeping dogs about charging my EV on the shared power bill when I have it done  otherwise, if my situation was any different, I would have totally done everything you just described already


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## zeroemission (Sep 14, 2010)

apologies in advance for this huge wall of text, but i can't get this reply to post in paragraphs because of the URL i'm guessing. 1st off, yes, TOTALLY go with LEDs for any electric vehicle! they are many times more efficient than halogens. they get expensive when you want high outputs even if you DIY, but i bet you could scrounge up some cheap second hand parts at a salvage yard. a lot of newer cars have that telltale slightly blue tint to them. if you want maximum surface area for your panels at minumum weight, why not just build a lightweight aluminum trailer? if you rounded or wedged the leading edge, it would be very aerodynamic and if the only load you're pulling is a light weight film, then weight would be a virtual non-issue. if you're building a full sized car profile, you could even put the trailer in your wake where it doesn't alter drag at all. you could get a few watts out of something like a 6 foot wide by 20 foot long trailer. it wouldn't be pretty, but it would give you way more bang for your buck. you could even design the trailer so you can tilt your panels toward the sun when you're parked without adding much weight, cost or complexity. if it wouldn't require insane processing power to do it, you could even build a solar sterling engine like the 1st one (i think) that used tiny mirrors driven by printer motors to track the sun. such a system would be way more complex on a car though as those change their orientation constantly between turns & hills. at the time the unit i'm thinking of came out, it was a few % more efficient than the best solar cells at the time. i'm surprised you don't see mirrors used much with solar panels as they are much cheaper than panels and can make a panel work twice as hard or more. i don't know just how translucent they are, but i've seen some new holographic solar films that look like you could run a second layer of cells underneath them to capture even more energy much like the RGB (?) layered films in development. if the holographic solar cells are as translucent as they look, they would seem to be wasting potential energy. i couldn't find the almost clear looking film i saw a picture of recently, but this looks like a potentially good one for automotive uses as the dimples would lower your drag coefficient a little http://www.life.com/image/85206971 trying to post the URL as a link kept eating my paragraphs.


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## Duncan (Dec 8, 2008)

Hi Tm

Check your electricity meter - the old type advances in proportion to the power going through it -either way!
If you fit solar panels and an inverter and are producing more power than you are using the meter ADVANCES!! - you get charged for the power that you are sending back onto the grid!!

Dimples
if you have a streamlined shape (so the airflow stays attached) like a good solar car dimples will increase your drag by making the air turbulent and increasing surface drag

A golf ball has dimples all over it because its direction to the air is variable - on a car a better solution is to look at where the air can remain laminar and stuck to the surface 
(basically as the expands or stays parallel to the direction of travel) and fit turbulators 
(small bumps) at the ends of those zones to try and reduce separation as the car contracts towards its tail


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## Tm PV1 (Jun 5, 2010)

I did get it to spin backwards with that inverter once. I think the Coyote Water system was pulling the power, since it's on its own circuit outside the house. 

@zeroemission, as long as a link has "http://" in it, it'll automatically hyperlink.

google.com compared to http://google.com
No special formatting.

I've heard of the solar roll. I think they are pretty neat, but not the best choice for solar-powered vehicles, power:size ratio.


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## Tm PV1 (Jun 5, 2010)

I have made another upgrade to my solar car. I added a second seat behind the driver seat for more versatility. This also provides better weight distribution and the solar array fits together better. Drawings to follow.


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## Duncan (Dec 8, 2008)

Hi Qxp2003818

_*I would also like to be a solar car*_ 

We havn't had any of those conversions - sounds messy!
But I suppose if Dr Frankenstein could manage it...


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## Tm PV1 (Jun 5, 2010)

New Year's updates. The aluminum frame has been changed from 2" round to 2" square. This brought the price down by $400. I have purchased 85 watt panel #3, making total investment so far $1,080.57. Remaining total is $13,276.15. Also, updated drawings of the two-seater design are below. I'll have another drawing uploaded once I compress it. Construction can hopefully begin before the end of this month. The grey line off the rear bumper is the radio antenna.

I have also run into some issues. I live in PA, but I am not sure how to get a VIN and register the PV1 in my state. Their websites are no help, as it is very unclear whether or not a 3-wheeled, enclosed cab vehicle is a car or a motorcycle. I need to know if anyone has any ideas. I will probably go to the DMV this week and ask, but I doubt they'll know anything about this.


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## Tm PV1 (Jun 5, 2010)

I'm pretty sure that my solar car is a 'motorcycle', therefore I can get by with easier to comply with inspections and cheaper insurance. In my searching for this information, I found out that I cannot have any parts sourced from off-road vehicles. I now have to find new suspension since I had planned to use the suspension off of my old ATV, I rolled back to an earlier design which used motorcycle forks and tires for the front. This increased the price, but I now have better brakes. I also found another problem with my drawings, had to completely redo the array layout. Pix and further info coming soon.


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## Woodsmith (Jun 5, 2008)

Duncan said:


> Hi Qxp2003818
> 
> _*I would also like to be a solar car*_
> 
> ...


I'm sorry to report that the spammer went to see Dr Woodenstein, and the good Dr zapped him off the face of the forum!


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## Tm PV1 (Jun 5, 2010)

Talked to an enhanced inspection station, my PV1 is a kit-car. Not sure about insurance yet, but the price took a big hit with drivetrain redesign and body paneling, climbing towards $17,000. Also, weight is closing in on 1,000 lbs. 


Happy to report the three 85 watt panels are working beautifully, took ~$100 off the utility bill, even with a price hike. I am currently generating at about 52% capacity with less than ideal positioning at a 40 degree north latitude location. With the panels on the PV1, I expect an average generation near 430 watts, with a peak near 600-700 watts at noon. 

The picture below is my RE system. Pictured is the Air-X 400 watt turbine, a 15 watt solar panel from Northern Tools, and the three 85 watt panels that will go on the PV1. The system is going to have a major overhaul when construction on the PV1 is complete and I'm waiting for a VIN plate (takes about a month). 80% of the wiring will be removed, replaced with a remote-start inverter and 110 VAC lines, the batteries will be replaced with 200 Ah AGM storage batteries which will be located much closer to the solar/wind, and a more advanced charge controlling system will be put in, including a SOC meter on the 12 volt side, a low-voltage cutoff, and power transfer interface for connectivity to the PV1. 

Current PV1 status: 3 months behind schedule.


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## Tm PV1 (Jun 5, 2010)

Further work done on the specifics. Here's what I have:

3:1 gear reduction
direct chain drive
@ 60 mph, motor rpm = 2354.25
max speed = 76.45 mph
torque at wheel ~ 135 ft/lbs.
weight ~ 950 lbs.
cost ~ $17,000 

Designed the solar array frame over the weekend and plan on getting pipe within the next week. This will be the first component constructed for the PV1. I figured it's easier to change the size of the car than it is to change the size of the solar panels that I already have a few of. Building the array first will also allow for proper fitment to the car. Plan to start within the next 7 days.


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## Tm PV1 (Jun 5, 2010)

July update. The PV1 is now six months behind schedule. I am currently working out bugs and still trying to find front suspension and brakes. I made improvements in the array, newer panels have been released which pack 3 to 5 watts more power per, raising total power to 910 watts. Solar array frame tubing will be purchased in the next week. Also, work is being done to trim weight and cost. Right now, price is at $16,700 and weight is at 935 lbs. I am thinking of using the front suspension and brakes off of a Can-am Spyder trike. If anyone knows of one for sale cheap, even salvage, let me know. Or even where I can find complete suspension for one, all I can find are lists of every part down to the washers.


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## Tm PV1 (Jun 5, 2010)

August update. Ordered the solar array frame and a 15 watt solar panel. Real construction starting this month. Also, a change to the dimensions of the car and the solar array. The car has been shortened in length and width, 55 watt panels instead of the 90 and 15 watt panels will be used, cleaning up the appearance and simplifying construction, but the car has gained approximately 60 lbs. due to an error made several months ago during component pricing, breaking the 1,000 lb. mark. The price, however, has gone down, but by an unknown amount at this time.


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## jk1981 (Nov 12, 2010)

Are you planning a welded aluminium spaceframe for the main load bearing structure?

If so I'd urge you to reconsider - aluminium is a poor choice for this, it's harder to weld for starters, the heat affected zone around the weld is horribly weak unless you have the finished frame heat treated, assuming you don't then weight for weight mild steel will be much stronger, cheaper and less bulky. Also aluminium fatigues and cracks very readily even at very low stresses, steels generally don't, obviously you can massively overbuild to get round this (huge weight and cost penalty) and you might get away with a light alloy frame in a racer because it will see relatively few load cycles but this isn't true of a daily commuter vehicle. A glued and riveted aluminium monocoque if properly designed will likely outperform a good steel spaceframe but a good steel frame is a damnsight easier to both design and fabricate.

As to the aerodynamic design, I don't understand why you're resisting using a more conventional aerofoil profile, the potential drag savings will be *huge* and there are some great software packages available to help with the design (try profili for example, it's aimed at model makers but capable of scaling up to full size and easy to learn/use). A significantly more efficient design needn't eat up much of your internal volume, visibility nor make fabrication prohibitively difficult.

As to the bubble, I don't know what the deal is in your state but here in the uk for a roadgoing car you have to have certified and etch marked laminated safety glass for the forward facing screen and you need to have some sort of effective rain clearance mechanism (basically wipers though I'm not sure they actually stipulate how it has to be achieved). Open cockpits have more lenient regulations as do bikes (including trikes which might be worth looking into if you have a similar situation). Blending a flat safety glass windscreen into an aerodynamic rear bubble isn't going to be easy or especially effective (though still better than the flat plate, sharp transitions body design you have at present).

Good luck with the project, I hope you find solutions to the problems.
jk


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## Tm PV1 (Jun 5, 2010)

October updates.

The PV1 has moved to the beta stage with a more appealing look. Construction still has not started, though I do have the frame for the solar panels. I found components for the front wheels, suspension, brakes, and steering at a good price. I've also done some number crunching and found that the PV1 will not be quite as autonomous as I previosly thought. I figured that I can commute for 4 days before I need to plug in. Here's my figures:


Assuming an economy of 20 kwh/100 miles (200 wh/mi), and a daily solar generation of 1.35 kwh (1,350 wh), the PV1 can be driven 15 miles daily for 4 days using a net energy of 1.65 kwh/day.

Energy in the batteries after that day's usage:
Sunday 7.20 kwh
Monday 5.55 kwh
Tuesday 3.90 kwh
Wednesday 2.25 kwh
Thursday 0.60 kwh
Friday -1.05 kwh

450 watts of solar for 3 hours, equals 1,350 wh (1.35 kwh). Driving usage is 200 wh/mile for 15 miles, equals 3,000 wh (3 kwh). 3,000 wh usage minus 1,350 wh generation equals 1,650 wh net usage. 1,650 wh times 4 days equals 6,600 wh usage, 92% DOD on the LiFePO4 batteries.

An additional 1.05 kwh is needed for the commute on Friday, which can be pulled from the RE at the house. It will also need an additional offboard charge for the next week.


These are ballpark figures. Usage may be more or less, generation will probably be a little more.

As for the frame, it is aluminum, but I might seek the help of a local metal fabrication business to weld it together. The suspension subframe is steel, so would stainless steel plates between it and the aluminum prevent galvanic corrosion?


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## Ziggythewiz (May 16, 2010)

Is the car to be driven on Sat? If not you could charge just once mid-week.

Are these lithiums good to 100% DOD with no adverse effects? I know some are rated for > 2000 cycles at 80 and > 3000 at 70, so charging a couple times a week would be a small price to pay to help your cells last an extra decade.


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## Tm PV1 (Jun 5, 2010)

Only one Saturday per month expected to be driven, about the same distance. I was thinking to give it about 2 or 3 kwh either Wednesday or Thursday, and a full charge overnight into Monday. Should almost always be parked on Sunday. I believe they have 3,000 lifecycles at 80% DOD, but with that midweek charge, leaving 2.25 kwh in the batteries, that's about a 70% DOD. Of course, with more storage capacity, I could manage a week away from a plug, but that adds weight and cost, so I'm happy the way it's set up. The solar generation is about 50% capacity, which is what I'm seeing with my panels in my off-grid system. I just hope that 200 wh/mile is an overestimate on usage for a 3-wheel, 1,000 pound car. If not, I'm looking at three charges a week at least.


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## Tm PV1 (Jun 5, 2010)

I worked out the math and got it down to one charge per week, which would use 5.3 kwh from the wall, compared to 7 kwh before. 

One mid-week charge
S 5.25 kwh
M 3.60 kwh
T 1.95 kwh + full overnight charge, starts at 73% DOD
W 5.55 kwh
T 3.90 kwh
F 2.25 kwh
S 3.60 kwh

It still has its daily net usage of 1.65 kwh, factored in above. KWH above show the remaining charge after that day's activity (except wall charge).


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## Tm PV1 (Jun 5, 2010)

Here's a summary of the specs of the current setup. The PV1 is powered by a 900 watt, 60 volt monocrystalline solar array, split into three strands of 5 panels each. This is fed through a Midnite Classic MPPT controller to charge a 36 volt, 200 ah LiFePO4 battery pack. The PV1 is propelled by a D&D Sepex motor with a 300 amp Alltrax controller with regen brakes. A DC-DC converter powers all the 12 volt stuff and charges the auxiliary battery. The aux. battery powers the radio's memory, the EABS (Electrically Actuated Body Separator) system, the hazard lights, the contactor, and the alarm system. This battery is maintained by 5 and 15 watt solar panels when the car is off. All exterior lights are LED's except for the headlights, which are halogen. The interior light is a small fluorescent light. The Pedestrian Warning Chirp and backup alarm are from the EV1. The drivetrain is setup as a reverse trike (2 wheels in front, 1 in back) with front suspension, brakes, and steering all pulled from a 2002 GEM. The rear wheel is powered by the motor and is off of a motorcycle along with the hydraulic disk brake and suspension. The front brakes will be converted to electric drum brakes. I'm still not sure about the parking mechanism, but it will most likely be a pin that drops into a hole on the chain to lock it. The PV1 has two, in-line seats.


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## mizlplix (May 1, 2011)

TM: Aluminum in it's normallized state suffers no losses of strength when properly TIG welded. But, if the aluminum is in any other state, it will have a heat releated loss of strength immediately along any weld due to the heat/cooling cycle of welding. Still not a big deal. There is not really any good way to reheat treat an aluminum weldment after fabrication to produce a consistently formed structure. (for us little guys anyways, motorcycle and bicycle builders do it every day.) 

SO, my recommendation is to use Chrome Moly for the main frame members so you can go ultra thin (4142 Chrome Moly can go up to 120,000PSI tensile) and then 1030 Carbon Steel (around 60,000PSI) tubing for anything that must be bent or formed into shape. MIG welding can be very effective with this style of construction as the gas shield occludes the hydrogen which aggravates embrittlement.

Miz


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## Tm PV1 (Jun 5, 2010)

How does 4142 chrome moly or 1030 carbon steel compare to aluminum in weight and cost? My current setup uses 2" square aluminum tubing that weighs 1.5945 lbs/foot. The frame weighs 252 lbs and costs $903. No bending is required for my current setup due to the flat plates. It would be difficult to curve the solar array as I am using off-the-shelf solar panels instead of a custom array built cell-by-cell to save cost and time. This also makes repair much easier as I just unplug and replace broken panels instead of having to redo the entire array for things like hail damage or rock chips. Here's the link for the aluminum tube:

http://www.onlinemetals.com/merchant.cfm?pid=9724&step=4&showunits=inches&id=1270&top_cat=60


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## Tm PV1 (Jun 5, 2010)

gte718p said:


> Solar vehicles are cool, and obvisouly I like them however, they are about as practical as driving an F1 car to work.


Speaking of that, I just stumbled across this article:

http://www.dailymail.co.uk/news/art...lds-170mph-F1-car-motorbike-banger-parts.html


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## Jason Lattimer (Dec 27, 2008)

Tm PV1 said:


> Only one Saturday per month expected to be driven, about the same distance. I was thinking to give it about 2 or 3 kwh either Wednesday or Thursday, and a full charge overnight into Monday. Should almost always be parked on Sunday. I believe they have 3,000 lifecycles at 80% DOD, but with that midweek charge, leaving 2.25 kwh in the batteries, that's about a 70% DOD. Of course, with more storage capacity, I could manage a week away from a plug, but that adds weight and cost, so I'm happy the way it's set up. The solar generation is about 50% capacity, which is what I'm seeing with my panels in my off-grid system. I just hope that 200 wh/mile is an overestimate on usage for a 3-wheel, 1,000 pound car. If not, I'm looking at three charges a week at least.


 I think 200 watt hours is way much. I've seen compacts weighing twice as much do 150.


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## Tm PV1 (Jun 5, 2010)

150 Wh/mile would be great. That would reduce wall charges to 1 every 2 weeks. With usage and solar generation, I would net use 900 Wh a day, down from 1,350 Wh. Since only 4 kwh would be pulled from the wall every two weeks, the solar panels I have on the house (270 watt capacity) would have no problem making up the difference.


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## Tm PV1 (Jun 5, 2010)

This is just me brainstorming, but I was looking into training and a career after high school and found a place. They do apprenticeships and on-the-job training. On the form, it says that some sites may be up to 75 miles away, making for a 150 mile round trip from the main building. The building is 30 miles away. This would make a 210 mile round trip. If I would add 5 more packs of batteries, this would give me a total storage of 43.2 kwh. At 200 wh/mile, this would be a 216 mile range. This may seem like a stretch, but I have a couple of extra kilowatts coming in from the solar, which would amount to about 45 kwh, making range 225 miles. Weight would come in at just about 2,000 lbs and increase price to $30,000. Should I beef up battery capacity or just buy a Volt?

As a side note, finding a 110 outlet on a job site wouldn't be impossible, for a 10 amp charger.

At home, I found a charger that would plug into a level 2 EVSE and charge the car in 10 hours.


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## Jason Lattimer (Dec 27, 2008)

You may want to do some research on Dave Cloud's Dolphine. I think it is on ecomodder.com. He has a 30kwh pack or so and has gone 200 miles or so.


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## DIYguy (Sep 18, 2008)

Tm PV1 said:


> This is just me brainstorming, but I was looking into training and a career after high school and found a place. They do apprenticeships and on-the-job training. On the form, it says that some sites may be up to 75 miles away, making for a 150 mile round trip from the main building. The building is 30 miles away. This would make a 210 mile round trip. If I would add 5 more packs of batteries, this would give me a total storage of 43.2 kwh. At 200 wh/mile, this would be a 216 mile range. This may seem like a stretch, but I have a couple of extra kilowatts coming in from the solar, which would amount to about 45 kwh, making range 225 miles. Weight would come in at just about 2,000 lbs and increase price to $30,000. Should I beef up battery capacity or just buy a Volt?
> 
> As a side note, finding a 110 outlet on a job site wouldn't be impossible, for a 10 amp charger.
> 
> At home, I found a charger that would plug into a level 2 EVSE and charge the car in 10 hours.


Just my humble opinion,. . . but, never make changes like you are suggesting based on getting a job and what that job may entail. You really have no idea where u will end up or the requirements after u get there. If u want to make the changes, just because u want to. . . fine, but don't disguise the reason. I like to say to my kids, make the right choices for the right reasons.


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## Tm PV1 (Jun 5, 2010)

I might as well build an electric car with amazing range since I'm building my area's first solar car. 

Anyway, I'm going to start the car out with its original 7.2 kwh pack, and then go from there. If the car has enough range like that, great. If not, I'll just add the battery strings as needed until I have enough range. I have the room in the car already, the only extra that is needed is a beefed up charger, cable, and the BMS cell boards. The strings will wire in parallel with each other, so they are modular. That much battery is quite an investment, but the batteries will last much longer that way due to reduced current and less cycling, granted I'm not traveling more than 180 miles. But I know sooner or later I'll need that 200 mile range.


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## Tm PV1 (Jun 5, 2010)

Okay, now that I've discussed adding 700-800 lbs of batteries to get a 225 mile range, the thought of weight and the power of the motor to be able to propel the car came up. Right now, with the standard 7.7 kwh (made an error, my 7.2 was actually a 7.7 kwh), the car weighs 1,200 lbs. After adding the big battery bank, the car will weigh almost a ton if not more. The motor I have is a SepEx 300 amp. It has 135 ft/lbs. of torque at the wheel with a power output of 10.8 kwh. There is a 3:1 reduction and the motor maxes at 75 mph. Would I need to bump this up to a more powerful setup?


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## Tm PV1 (Jun 5, 2010)

Here's the details on the big battery:

Thundersky 400 Ah

36 cells are wired 3 parallel, 12 series. 3 cells are wired in parallel to make 12 bricks, and the 12 bricks are wired in series for a pack of 1,200 Ah at 38.4 volts. 

I have the miniBMS on one cell of the 3 in parallel, one for each brick. 

200 Wh/mile gives a 230 mile range. 

Haven't calculated how long the solar takes to charge the battery, but I do have a 6 KW charger that works with a Level 2 EVSE for a 10 hour full recharge.

The pack costs $8,949.60 and weighs 1,087 lbs. This brings the car to $23,221.25 and 2,070 lbs.


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## Ziggythewiz (May 16, 2010)

I'd say go solar and short range (if I had 40% panels on my bug I'd never have to plug in!) or go long range and forget the solar. All that extra weight will make the solar negligible.


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## Tm PV1 (Jun 5, 2010)

Maybe. I used the range calculator on EV Source's website, and it says the weight savings will give me an extra 22 miles (230 pound difference). The solar should generate about 10 miles of range (3 hours of 50% output, 1,650 wh). So, I'm basically saving 12 miles by leaving off the panels. The figure is a little different if I stretch one charge over two days.

The panels would take 28 days to fully recharge the batteries.


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## Tm PV1 (Jun 5, 2010)

I did some work and got a more powerful motor. It is a 72 volt PMAC motor with 40 hp. peak. It has 66 ft/lbs. of torque, 264 ft./lbs. at the wheel with 4:1 reduction. The battery pack has been reorganized into a 24 series, 76.8 volt 400 Ah pack which stores 30.7 kWh, equating to a 153 mile range (162 mile range with a day's worth of solar input). The car weighs 1,700 lbs.

For comparison, the Tesla Roadster has 295 ft/lbs. of torque and weighs 2,700 lbs. and accelerates to 60 in 4 seconds. Of course, this acceleration is due to 200 kW going into the motor, where my motor has 30 kW going into it, I DON'T expect this kind of acceleration. I'm just wondering what kind of acceleration I would get. The motor should be able to get me to 80 mph.

Also, an energy economy of 200 wh/mile sounds reasonable, especially compared to a RAV4-EV. This data pulled from a RAV4-EV owner (http://evnut.com):

Average Consumption from pack: 250 Wh/mile
Most drivers report that on a flat, windless stretch of road, an indicated 60mph (about 56mph actual) equates to 100 miles of range. (26 kWh battery, equals 260 wh/mile)
At 45mph (indicated), I have calculated almost 150 miles range. (173 wh/mile)


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## IamIan (Mar 29, 2009)

Tm PV1 said:


> I'm just wondering what kind of acceleration I would get.


You can solve backwards.

F=ma ... or A = F/M

Where you know the Mass of the object.

The Force changes due to the 30kw limit... and your low end torque limit at zero RPM.

Power ( in kw ) = [(Torque Nm ) *2Pi * RPM] / 60,000

If you plot the changing motor force as the rpm changes ... the rpm changes due to vehicle speed and the gear ratio between them.

If you want to get fancy adjust for rolling resistance and aerodynamic drag.

Or the crude ... short version ... ignoring aerodynamic and rolling resistance differences ... Tesla has ~7x more power ... if you both weighed the same you would accelerate ~1/7 as fast ... sense you weigh less you accelerate faster than ~1/7 ... or about ~4.4x longer to accelerate to a given speed ... or you can do the longer version to include the aerodynamic and rolling resistance loss corrections.


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## Tm PV1 (Jun 5, 2010)

Thanks for the info. That rate of acceleration isn't bad, about the same as the RAV4-EV, which has a 50 kW motor. Maybe the next time there's no traffic behind me at a light, I'll try this rate of acceleration (at least up to the speed limit) to see what it's like.


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