# Is this possible



## dtbaker (Jan 5, 2008)

what's your budget?
i.e. let's say you can afford 30kWhr of batteries.... $10k
driving around is going to consume around 400watt-hr per mile in a big vehicle, maybe more. That gives you an idea of range before recharge. then, if you figure charging from PV; how many hours of sun do you wanna park for? that gives you the size of array you have to cart around assuming you can keep the pack balanced while charging with multiple charge controllers since they are available only up to 48volts usually. Or, you need a big diesel generator.... so why go electric?


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## congellous (Mar 21, 2013)

Well mainly for total freedom from having to fill up. Self sufficiency living off the sun. Maybe even charge in daylight hours travel at night. Lets say it was sponsored by Lithium Ion batteries. Light weight vehicle with a reasonable range of 75 miles a day ? It's hypothetical or is it....


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## dtbaker (Jan 5, 2008)

congellous said:


> Well mainly for total freedom from having to fill up. Self sufficiency living off the sun. Maybe even charge in daylight hours travel at night. Lets say it was sponsored by Lithium Ion batteries. Light weight vehicle with a reasonable range of 75 miles a day ? It's hypothetical or is it....


I doubt you are going to find sponsors, but good luck.

Be a little careful with your specifics on batteries "Lithium Ion" is a lot different than the "Lithium Iron Phosphate" (LiFePO4) prismatics (we) suggest as better for the average DIY ev.

To get 75 miles a day, even in a small truck, you are going to need probably 35-40 kWhr of energy, especially after you load up the truck with the solar array equipment.... which would have to be probably an 8kW system to come close to generating 40kWhr on a sunny day. Thats at least 26 x 300 watt panels, portable racking, plus a bunch of charge controllers if you go direct DC-DC charging.

sure it can be done, but not cheaply.


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## congellous (Mar 21, 2013)

Ok well at those figures it's unfeasible. What has to happen to make it work ? Bring the mileage down. Lets say it's guaranteed sun all day and maximum of a fold out system on either side of the roof and the vehicle is as lightweight as possible carbon fibre, and batteries and a seat. $100k budget


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## dtbaker (Jan 5, 2008)

congellous said:


> Ok well at those figures it's unfeasible. What has to happen to make it work ? Bring the mileage down. Lets say it's guaranteed sun all day and maximum of a fold out system on either side of the roof and the vehicle is as lightweight as possible carbon fibre, and batteries and a seat. $100k budget


well.... PV systems run somewhere between $3/watt-$5/watt for fixed panel ground mount systems. total system cost in your case depends on how much racking you design and build yourself, how you do you charge controllers, etc, and how you juggle your battery capacity and desired daily range.

so if you want to start backward with $100k budget... assuming a small bus to allow enough weight capacity with room to live in, I'd guess you're looking at a minimum of $10k for the donor bus, $15k-$20k for the electrics (11" or 13" motor, 1000 amp controller, tranny adaptor, etc).
So, take $30k off the top for the bus conversion without batteries. Find a balance between how much juice you can generate per day at $4/watt x 5 hours of generation per day, and how big a pack you need to store it with whats left over using a price of maybe $.5/kWhr for the batteries considering elaborate charging design and BMS required. Range will fall out the bottom.... guessing a more conservative 600 watthr/mile (this is not going to be small or light), and using no more than 80% of pack capacity will determine max miles per day.


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## congellous (Mar 21, 2013)

OK thanks for that, lets say a BP sponsored trans continental competition to build a vehicle to cross Africa. I'm trying to break out of the pragmatic approach and design a vehicle that doesn't need fuel-ing is self sufficient, even if that is limited speed and range the project cost doesn't matter. I'm trying to work out where we are now technology wise and where we could be in the next 5 years as Electric propulsion is obviously the way forward if it can be recharged freely. It seems to me that the weight of the batteries/ mile is a factor.


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## Ziggythewiz (May 16, 2010)

dtbaker said:


> PV systems run somewhere between $3/watt-$5/watt for fixed panel ground mount systems.


They've been under $1/watt for years now.

They've gone up 30% recently, due to Obama's great concern for the environment, but are still ~$0.80.

I calculated that I could do my commute (~16 miles) on solar only with 40% efficient panels on my bug roof and hood.

With the 20% eff panels that are currently available, I could do half that, or with a fold out system, all of it.

So depending on the vehicle specifics, you could do a car or small truck that gets 10-20 miles / day off the sun without much difficulty or cost. 

As for travelling across africa, the batteries wouldn't be much of the weight. All the food and water you'd need for the year it would take you to cross would be the issue. Of course, for a PR stunt you don't carry all that with you, that's what the half dozen gas guzzling support vehicles are for.


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## dtbaker (Jan 5, 2008)

Ziggythewiz said:


> They've been under $1/watt for years now.
> 
> They've gone up 30% recently, due to Obama's great concern for the environment, but are still ~$0.80.


I'm talking full cost of the 'complete' system with racking and charge controllers or invertor.





Ziggythewiz said:


> I calculated that I could do my commute (~16 miles) on solar only with 40% efficient panels on my bug roof and hood.
> 
> With the 20% eff panels that are currently available, I could do half that, or with a fold out system, all of it.


wow, I dunno how you figure that... where/how would you store a 'fold out system' on a bug? including charger controller(s) or invertor? would you get the same efficiency given the added weight and transport rack on top? for 16 miles, how many kWhr do you consume 8kWhr or so? That means you need at least 1.6 kW of fixed panels in the sun all day with unshaded southern exposure at 30 degrees or so.... thats 5 or 6 full size panels depending on brand etc.




Ziggythewiz said:


> So depending on the vehicle specifics, you could do a car or small truck that gets 10-20 miles / day off the sun without much difficulty or cost.


not saying it can't be done... only that its not particularly easy, or cheap.


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## congellous (Mar 21, 2013)

Ziggythewiz said:


> They've been under $1/watt for years now.
> 
> They've gone up 30% recently, due to Obama's great concern for the environment, but are still ~$0.80.
> 
> ...


I thought so.... so it's 5000 miles from Dakar to Cairo. Every stop is a town for food and water. Lets say averaging 30 miles a day, be about 5 months. So back down to just batteries. Apart from the vehicle, the costs would be peanuts for food and water and the transport is free. Say 5 P.V panels at 250w each could be fitted how big a battery bank would be needed ? Like I said with a suitcase diesel generator like a kipor as back up to charge up as back up and the best batteries. I mean what could go wrong !


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## dtbaker (Jan 5, 2008)

congellous said:


> Say 5 P.V panels at 250w each could be fitted how big a battery bank would be needed ?


2.5 kW of fixed panels, facing south, no shade, correct elevation for the middle 5 hours of the day would get you around 12.5kWhr.... you MIGHT be able to get a little more if you babysat the panels and could manually 'track' to rotate them a couple times during the day to face directly toward the sun.

So, you'd need something along the lines of a 15kWhr pack at least for this model with 5 x 250W panels.




congellous said:


> I mean what could go wrong !


you crack me up.
setting up and breaking down PV panels on portable racking daily thru a desert.... ?!


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## congellous (Mar 21, 2013)

dtbaker said:


> 2.5 kW of fixed panels, facing south, no shade, correct elevation for the middle 5 hours of the day would get you around 12.5kWhr.... you MIGHT be able to get a little more if you babysat the panels and could manually 'track' to rotate them a couple times during the day to face directly toward the sun.
> 
> So, you'd need something along the lines of a 15kWhr pack at least for this model with 5 x 250W panels.
> 
> ...


I wanted them to go on the roof on an angle bracket but there is plenty of all day intense sun to rely on, how far can you get on 15kWhr/ day


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## dtbaker (Jan 5, 2008)

congellous said:


> I wanted them to go on the roof on an angle bracket but there is plenty of all day intense sun to rely on, how far can you get on 15kWhr/ day


you want to DRIVE with a 5 square meter fixed 'sail' on top of a vw BUG?
How fast do you think you can go without breaking everything?
You'll have to be parked to charge regardless... The energy is coming in at 2.5kW max, and you need to expend more than that to get any kind of speed.

Your tactic would be to park and maximize your charge all day, pack up and drive about an hour or maybe two at some efficient speed if you want to maximize range, and set up camp for the next day.... The actual range totally depends on the size, weight, speed of the vehicle you end up with.

...I gotta sign off this thread, good luck


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## congellous (Mar 21, 2013)

Well thanks for your err... comments. A did say a van BTW good luck with being miserable


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## Ziggythewiz (May 16, 2010)

dtbaker said:


> where/how would you store a 'fold out system' on a bug? including charger controller(s) or invertor? would you get the same efficiency given the added weight and transport rack on top? for 16 miles, how many kWhr do you consume 8kWhr or so? That means you need at least 1.6 kW of fixed panels in the sun all day with unshaded southern exposure at 30 degrees or so.... thats 5 or 6 full size panels depending on brand etc.


If I were to do a fold-out system, which I wouldn't but if it had to be done shouldn't be too tough, it would just be some hinged brackets to fold out briefcase style, to get 3x the area. Driving a brick at low speed the aerodynamics are irrelevant and the weight would be more than offset for me by switching to lithium. I get ~250 wH/m, so would need ~4 kWh / day. Even in Houston, you can count on a panel's rating x 6 hours full sun most of the year, I'm sure Africa is better. That's with no tracking..stick anything on a roof and the sun is generally overhead.

Buuuut....the key here is the low daily range. In my case it would be feasible, but to do 30 miles a day you're going to need to cut your weight in half or more (think solar challenge style roach mobiles) or make a big production of setup and takedown of your solar system every day.


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## congellous (Mar 21, 2013)

Thanks, yeah interesting. The best batteries the lightest vehicle probably custom built. Fold out solar panels.... yeah why not sounds pretty easy really. Like I say day time charge then travel at night....


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