# Solar Power



## mattW (Sep 14, 2007)

One of the proposed ways to extend the range of an electric car is through the addition of solar panels. A solar cell or photovoltaic (PV) cell is a device that converts light energy into electrical energy by the photovoltaic effect, a solar panel is a group of solar cells packaged together into one unit. Thus a vehicle (or any area) covered with solar panels exposed to sunlight will produce usable electric energy. In an EV this means that solar panels can be used either for on board charging or directly powering the controller/motor. PV cells are a non polluting renewable source of electricity with no moving parts and little required maintenance. 

*Common Questions About Solar Power and EVs.
*
_Can an EV run purely on the energy generated by solar power at highway speeds?
_Yes! Purpose built vehicles are able to achieve very impressive speeds using just the power of the sun. In the World Solar Challenge these solar cars compete against each other in a race across Australia running purely on sunlight and a small battery pack. The winner of the 2007 race, the Dutch Nuon Solar team, averaged 90km/h (56mph) in their solar car Nuna4 pictured below:​






​_Can a normal EV conversion __run purely on the energy generated by solar power at highway speeds?
_No. The reason that these solar cars can travel at such impressive speeds is because they are some of the most efficient vehicles in the world. These cars can travel at highway speeds using about the same amount of energy as your hair dryer, about 10% of the energy required by a normal sized car. They have extremely efficient solar cells covering 8m2 (86 sqft) to gain as much power as possible. Using Solar Cells on a standard conversion will give around a 5-10% increase in range and the ability to trickle charge the batteries when parked in the sun but not yield enough energy for anywhere near highway speeds. ​_Why aren't Solar panels a viable option as a range extender?
_The reason is due to the power to weight (and cost) ratio of solar panels:


> 'For some figures, typically you could fit about 200W of solar panels onto a car. Solar panels generally provide the equivalent of 5 hours at their rated power per day, i.e about 1kWh for a 200W panel per day, which is about 5km of extra range in a small vehicle. 5km may sound somewhat useful, but 1kWh worth of extra batteries weighs and costs less than a 200W solar panel! Also unless you're very careful with your installation, the increase in aerodynamic drag will quickly negate any extra range they can provide.*'


*Quote by Ian Hooper
​_Has anyone tried it before?_
Yes. There are some enthusiasts who have installed solar panels on their EVs with some success. For example the University of Maine Solar Vehicle Team added a substantial 1kW solar array to their Chevy S-10 EV which gave them a 10-15 mile range using solar power alone at moderate speeds compared to 100 miles with the battery pack.
​


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## jimy_f_84 (Jun 3, 2011)

Hi, new here.

My thoughts for my build is to have a solar panel that i could have it charge the batteries while i am at work, sine i spend there about 10 hours. any thoughts, is it doable?


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## Ziggythewiz (May 16, 2010)

Not unless your car looks like the one above.

However, a small panel can keep provide all your 12v charging needs if you don't drive at night, and more panels could provide an additional 2 miles or so of range.


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## NZero (Jan 30, 2010)

I disagree. Having competed in the Australia race the sun solar car challenge I love the idea of panels.

My Honda (E-Lude in the garage) could have a 140watt panel mounted on the roof for instance. With a good charge controller it could give my 120v pack 1 amp every hour so over 10 hours I've gained 10Ah and in my 100Ah pack thats another 10%.

If my battery runs flat somewhere I know that given some time I can limp back home. However given where I live a small turbine (800 watt) that folds up is far more viable.


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## Ziggythewiz (May 16, 2010)

NZero said:


> thats another 10%.


If you have a 20 mile range, that's 2 extra miles, as I said above. I think solar is a cool addition, but if your battery runs flat somewhere, you can walk home long before the solar will get you there.


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## NZero (Jan 30, 2010)

Ziggythewiz said:


> If you have a 20 mile range, that's 2 extra miles, as I said above. I think solar is a cool addition, but if your battery runs flat somewhere, you can walk home long before the solar will get you there.


But I have 100km range so thats another 10km and I would rather have that extra push then walk 10km lol. Not that I have panels installed but its only a matter of time.


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## Ziggythewiz (May 16, 2010)

How are you getting 62 miles off a 100ah pack? What's your kwh/m?

Assuming no other possible form of transportation, I'd walk the 10km home (2 hour stroll) watch 2 full football games, then walk back to the car and drive it home.


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## T1 Terry (Jan 29, 2011)

Solar charging is part of the plan with my conversion but it's just a little different to the norm. Mine is a 36 ft bus converted to a motorhome with 1kw of solar on the roof. Naturally at the moment it can't be a full electric propulsion system so it will start out as a hybrid but as the technology improves I hope to finally do away with the ICE altogether. A big motor, big controller and lots of batteries, outside reality at the moment so an electric assist using a smaller ICE will have to do for the moment.

T1 Terry


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## NZero (Jan 30, 2010)

Ziggythewiz said:


> How are you getting 62 miles off a 100ah pack? What's your kwh/m?
> 
> Assuming no other possible form of transportation, I'd walk the 10km home (2 hour stroll) watch 2 full football games, then walk back to the car and drive it home.


120v @ 100ah = 100 Kilometers of driving (at avg 85km/h)
I dont know miles etc but I'm sure from that you could tell me my useage.

Car is a stripped out Honda Prelude with light mag wheels and a low drag co efficient.


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## Ziggythewiz (May 16, 2010)

Have you driven 100 km on a single charge? Even if you could take 100ah from a 100ah battery, which you can't, you can only run it down to 80% DOD (50% recommended for longer battery life).


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## NZero (Jan 30, 2010)

Ziggythewiz said:


> Have you driven 100 km on a single charge? Even if you could take 100ah from a 100ah battery, which you can't, you can only run it down to 80% DOD (50% recommended for longer battery life).


Yup. They register as 121Ah (c5 rate) on a battery tester (when they are fully charged minus 3 minutes run time) and I would have been close to 80% upon arriving home. Car only draws about 250a accelerating (as I normally would in an ICE) and draws around 70-80 amps to keep it going. Could you tell me what my mile/kwh is???


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## Ziggythewiz (May 16, 2010)

The proper way to calculate wh/m is by dividing miles driven into amount charged measured using a killawatt, charger, or BMS. If we just use your numbers though, 120V*100AH/100 km = *120wh/km or 194wh/m*, which is incredibly low.

However, if your garage is correct, you have 2 strings of 100AH in parallel, which means your battery pack is 200AH, so 120V*200AH/100 km = *240wh/km or 388wh/m, *which is more reasonable for a 2500 lbs car. Your real numbers would be somewhat less if calculated measuring watt-hours in.

You can expect a 140watt panel to give about 700 wh/day in a good sun location, so you should be able to get an extra 3 miles/day using solar.


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## NZero (Jan 30, 2010)

Ziggythewiz said:


> The proper way to calculate wh/m is by dividing miles driven into amount charged measured using a killawatt, charger, or BMS. If we just use your numbers though, 120V*100AH/100 km = *120wh/km or 194wh/m*, which is incredibly low.
> 
> However, if your garage is correct, you have 2 strings of 100AH in parallel, which means your battery pack is 200AH, so 120V*200AH/100 km = *240wh/km or 388wh/m, *which is more reasonable for a 2500 lbs car. Your real numbers would be somewhat less if calculated measuring watt-hours in.
> 
> You can expect a 140watt panel to give about 700 wh/day in a good sun location, so you should be able to get an extra 3 miles/day using solar.


No the garage is quite off. I only use the one string but am planning on replacing my gels with Lipo very soon. Car is way under 2500lbs though, closer to 1900 plus 180 for the driver and that is soon to shrink aswell. There is no rear seating, door cards reduced, dash trimmed back etc so car is very light but on its down side roof is electric, mirrors are electric, lights pop up, windows are electric. So using many functions often would sap a bit too. 
However with the manual gearbox without clutch I can run the engine at its best for long periods so that certainly helps things in that department.


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## Ziggythewiz (May 16, 2010)

You should really get a kill-a-watt or something so you can measure the actual kWH/mile, and then go enter a contest or somethin, a wkh/mile of 150-200 is pretty awesome.


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## NZero (Jan 30, 2010)

Ziggythewiz said:


> You should really get a kill-a-watt or something so you can measure the actual kWH/mile, and then do enter a contest or somethin, a wkh/mile of 150-200 is pretty awesome.


Cool, I didn't realise I had anything special. The Vws on 72v and 96v could do about the same distance on Trojan 125 flooded batteries. The Subaru will be able to do an estimated 75-80Kms on 140Ah floodeds and that thing is a tank.


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## crack monkey (May 30, 2011)

I am working on a design for a buggy and i want to use solar as the primary means for recharging (even if it takes a few days to do it) can anyone recomned a charge controler that would work well?

the charge controlers that i have been looking at need more voltage and are putting out less charge... midnight solar and outback power have been the ones i was looking at.

battery size is 72 volts
I am looking at bp solar 350j 50w 12v panels.. they are compact (40"x21")and about $250 each

thanks


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## T1 Terry (Jan 29, 2011)

crack monkey said:


> I am working on a design for a buggy and i want to use solar as the primary means for recharging (even if it takes a few days to do it) can anyone recomned a charge controler that would work well?
> 
> the charge controlers that i have been looking at need more voltage and are putting out less charge... midnight solar and outback power have been the ones i was looking at.
> 
> ...


The easiest way I can see is to split the pack into 3 x 24v packs and charge them in parallel. you need a fully adjustable solar regulator like the Plasmatronic PL20/40/60 unit so you can control the voltage and the current if you have a big solar system. If you have the $$ a home pack with one or two extra cells could be charged during the day and the linked to the vehicle to recharge the pack fairly quickly.

T1 Terry


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## FirstRodeo (Jun 21, 2011)

I agree with the use of solar panels on cars also. If there is not one technology that can get us off fossil fuels why not combine solar and electric. Why not put a wind turbine on there to and use solar, electric, and wind to power a car.


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## louismoulton (Apr 23, 2014)

I am slowly converting a Fiat 126 to electric and it will have 200W of solar. It is a 48Volt system using a 48V controller. I have estimated I might get as much as 10 km of solar per day. This would be awesome. I really only need the car to travel about 6 km a day. Better still most days I don't use a car but cycle, so for the two or three trips a week I need a car, the fuel would have been paid for when converting the car. These are flexible panels direct from China, which will be glued to the roof and bonnet (hood) with silicon. I am still a long way off getting it working and the panels are not here yet. As for speed, I doubt it with a 48v system. Range should be over 40km as the batteries are 4x12v at 150A hr.


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## Duncan (Dec 8, 2008)

Hi Louis

200w will give you 800watthrs/day (ish) - maybe 4km - 10 would be 80whrs/km - 128Whrs/mile - which is in world record territory

4 x 12v x 150Ah = 7.2Kwhr
As they are 12v I assume lead 
So actual (due to the demon Puekert) 3.6Kwhrs
Usable ~ 2Kwhrs (you kill Lead acid very fast at high levels of discharge)

Assume 200whrs/mile - 10 miles - 16Km

What range do you actually need?


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## Sunking (Aug 10, 2009)

louismoulton said:


> I am slowly converting a Fiat 126 to electric and it will have 200W of solar. It is a 48Volt system using a 48V controller. I have estimated I might get as much as 10 km of solar per day. This would be awesome. I really only need the car to travel about 6 km a day. Better still most days I don't use a car but cycle, so for the two or three trips a week I need a car, the fuel would have been paid for when converting the car. These are flexible panels direct from China, which will be glued to the roof and bonnet (hood) with silicon. I am still a long way off getting it working and the panels are not here yet. As for speed, I doubt it with a 48v system. Range should be over 40km as the batteries are 4x12v at 150A hr.


Good luck because even the guys with 900 pound golf carts get that much. Just too many things working against you.

Even with a MPPT controller in summer only get 300 to 400 watt hours from a panel with a 0 degree tilt angle. Basically just adding dead weight to carry around.


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## louismoulton (Apr 23, 2014)

I only need a 20km range. The car will probably do three 7 km trips a week. If it is used more I will charge it up with the mains. The dead weight is not too bad as these are the light weight plastic backed panels. 
The real proof will be once I have put it together as to what it really does. This won't be done for months, and then I have the joy of registration.


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## Duncan (Dec 8, 2008)

Hi 
Is that Geraldine as in on the way to Christchurch?


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## louismoulton (Apr 23, 2014)

Yes. Why do you live near? I have various questions about the low volume process etc if you do.
Thanks


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## Sunking (Aug 10, 2009)

louismoulton said:


> I only need a 20km range. The car will probably do three 7 km trips a week. If it is used more I will charge it up with the mains. The dead weight is not too bad as these are the light weight plastic backed panels.
> The real proof will be once I have put it together as to what it really does. This won't be done for months, and then I have the joy of registration.


All I am saying is don't expect too much. I know a lot of people who have tried it. Heck I even helped them. Most have converted it to 12 volt to run their stereos and lighting by adding a 12 volt auxiliary battery because they just did not notice any improvement. Here in TX we do have pretty good solar insolation. 

Golf carts, especially factory golf carts are not very efficient. Depending on conditions 150 to 200 wh/mile and I think that works out to 93 to 120 wh/Km. Some of the newer AC models do quite a bit better, but DC is not.


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