# Alternative power sources



## Therealriley (Jul 28, 2015)

I am trying to look at powering an EV car with other add ons to help gain more power as an extra source of electric charging as well as charging at home through the mains.

My idea would be to fit 3 large solar panels (on the bed of a pick up truck) on a hydraulic lift up cover for the bed and a universal solar panel sunroof if I can find one that could be fitted. 

Also I'm wondering why not fit small fans in the front grill for a wind turbine? Considering when your driving at 50-100mph or its km equivalent you must get some wind to the front of your car. 
I am an bit of a newbie to this so forgive me if this is just ridiculous.

I'm not really sure if you would have to hook it all up to trickle charge the main batteries or have additional batteries to power the cars extras like electric windows/ wipers and stereo etc but run on a separate power circuit. 

What would be a good set up for adding these additional sources?

I intend to do some reading up on it but thought I would ask your opinions to see if it's worth all the extra learning/reading. 

Or if you thought of any extra ideas yourself and you think it's worth a mention feel free to leave your comments. 
It would be cool to have a car that recharges while its sat at work all day.


----------



## Duncan (Dec 8, 2008)

Hi
I will start by assuming that you are ignorant and not simply a troll

Solar panels
Yes these will help - but not much
A 100% efficient solar panel would give 1Kw/m2
Actual panels you can buy are less than 20% efficient
You might get two square meters in your bed
But it's not at the right angle (square on to the sun)
so you might get 2 x 20% x 50% = 200watts
At 60mph your truck will be using 25,000watts - over 100 times as much

Fans and such will simply increase the drag - and you will need more power to overcome the increased drag than you will be able to harness from the fans


----------



## Therealriley (Jul 28, 2015)

Thanks. Im not a troll so guess I'm just ignorant.....


----------



## dougingraham (Jul 26, 2011)

In general it is not worth putting solar cells on a n EV. For all practical purposes you can't take advantage of them when you are moving because of the extra drag they will cause when facing the sun. I figured that if I covered the hood of my car I could almost get 400 watts of panels. This assumes the hood is propped up so as to face the sun. At my solar insolation value of 4 I would get about 1.6 kwh of charge from the panel per day while the car is parked at work. It takes about 300wh per mile so this is a little over 5 miles per day I could drive off of the sun. The cost of the electricity is less than 20 cents. If the panels were $400 it would take 2000 days of savings to pay for them. This is 5.4 years. There are additional costs however. The charger is going to have to boost the panel voltage up to pack voltage. Figure this to be $1000. Payback time is now 19 years. That is an optimistic analysis. My initial one a few years back actually put the payback point at over 40 years.

Something like a VW van with a large roof area and not many miles per day could possibly make this worth doing. But I suspect the best place to put the solar cells is on the roof of your house.

As for wind turbines on the front of the car, forget about it. It is always a loss. Range will go down. We have a special thread for that kind of discussion.


----------



## Roy Von Rogers (Mar 21, 2009)

Therealriley said:


> Thanks. Im not a troll so guess I'm just ignorant.....


No, your just not educated towards this subject.

Roy


----------



## Sunking (Aug 10, 2009)

You are wasting your time with solar panels or any add-ons. It takes more energy to over come the added weight and drag the panels can generate. 

Golf Cart folks found this out years ago when some company decided to make 250 watt panel to act as a roof of the cart. Even with a very high efficiency of 150 wh/mile or less. still does not do a single thing except make the manufacture rich. It would take weeks to recharge a golf cart battery on a 250 watt solar panel with tracking. Oriented flat to the Horizon cuts production some 50%. Instead of have a 5 Sun Hour Day, you get a 2.5 Sun Hours and at 70% efficiency only yields 250 to 400 watt hours in a day. That would get you an extra mile if it were not for the fact the added weight and drag would net you a loss.


----------



## Therealriley (Jul 28, 2015)

Hi thanks for your replies. This is why I wanted to ask before I spend more time reading into it. 

I was hoping to tackle the solar panels facing the sun issue by having the panels in the bed cover tilt using hydraulics. 
If I get very little gain then it's useless I guess. 

Thanks for the information.


----------



## arklan (Dec 10, 2012)

ok so to answer a couple of things

firs the wind turbine behind the grill idea; you will have more gains by blocking off the grill and not needing to press the pedal as much for a given speed. so wind turbines are a non starter there even if you put them in a spot that is going to have drag anyway.

not factoring in the dollar amounts, you can get peel and stick solar panels from ebay which are 136 watts. after 2 hours of using the entire piece at its rated wattage i would be able to drive my car 1 mile. peel and stick solar panels dont add any drag because they are as thin as paper and stick to the shape of your car (for the most part) the 136w one is 5metres long though so youll need to get a few and trim them down to the size of your car, these are amorphous thin film style panels and give about 80w per m2 under normal circumstances but being moulded to your car will mean probably about 40w per m2 as an average.
my car is quite tiny but if i covered the roof and bonnet of my car id get about 2square metres.
now, there is definatly a way to get around the boosting the voltage to pack voltage thing, and thats to use the panels to keep your 12v battery topped off, thus reducing the pull on your dc converter and the pack.
so on my car i would have 80 watts for about 4.5 hours on a good day.
thats 360 watt hours under good sunlight and parking orientation.
i would be able to travel about 1 and a half miles with that.

is it worth it? hell no, better to buy a couple extra batteries and have solid gains that u can see and feel than rely on the luck of the sky

the only benefit this would give is if you needed to park your car somewhere for a while and didnt want the 12v to go flat


----------



## Therealriley (Jul 28, 2015)

Thanks for the info. 
i see it's not really worthwhile. I have seen those flexi panels which is why I looked into solar panel sunroofs in the first place. I just assumed the bigger the better.
I originally thought I could use them as some sort of back up to the main batteries or use it to only power the stereo or powered windows etc. to squeeze out a couple more miles maybe.

I guess running batteries you can still have things that could be turned off if not needed to save power.


----------



## mortonsolar (Oct 10, 2015)

I have a solar powered golf cart and it works GREAT! For one thing, the golf cart sets most of the time. So, while it's just setting there for 3-4 days, it is ready to go by the weekend. 

We also have a 2012 Ford Transit Electric and plan to add a 345W SunPower panel which outputs 55Vdc. Does anybody know what the best method of connection would be for this?


----------



## bigmotherwhale (Apr 15, 2011)

https://www.youtube.com/watch?v=4cX-_eB8nkk
solar sounds like a good idea if you have enough space.
they must have around 2.2kw of panels, that's a reasonable amount of power even if it can only be fully used when stationary.


----------



## dougingraham (Jul 26, 2011)

mortonsolar said:


> We also have a 2012 Ford Transit Electric and plan to add a 345W SunPower panel which outputs 55Vdc. Does anybody know what the best method of connection would be for this?


Off the shelf, some kind of micro inverter that puts out 110vac and feed that into your charger.

Or add a second panel and wire in series and you could probably feed the DC output of the panels directly into the input of many chargers.

Best would be a custom MPT that could be configured to charge the batteries directly.

A 345 watt panel even if 100% efficient in the above electronics could at most give you about a mile per hour of recharge assuming you can point it facing the sun. Depending on where you live this would give an average of 2 to 5 miles of charge per day. More in the summer and less in the winter. So unless you don't actually use this much a single panel is not going to do much good. I am not saying you shouldn't do it, just that you probably will not be happy with the results. I think you would be better off putting the panels on your house and selling the power to the grid during the day and charging the vehicle from the grid at night when rates should be cheaper. This way you avoid the additional weight, air drag and complexity that adding a panel to the vehicle would impart.

Good luck!


----------



## dragonsgate (May 19, 2012)

Therealriley said:


> Thanks. Im not a troll so guess I'm just ignorant.....


Not all of us were born with 150 + IQ's Your questions show that you are uninformed but thinking and learning by asking questions. For a while I had a small solar panel on the back of my car hooked to the aux. battery. I was ok for keeping the vent fans running when parked on hot days. That was about all it was good for.


----------



## Paul9 (Oct 2, 2015)

I have a 90watt 12v flexible solar panel on the roof of my Suzuki Swift conversion. It is connected through a regulator (to prevent overcharging) to my auxillary battery. As the panel is glued to the roof, there is no increase in aerodynamic drag. I still have the DC-DC converter installed and wired through the same regulator. A switch on the dashboard allows me to switch between charging the aux battery from either the solar panel or the DC converter.

The solar panel has been on the car for about two years and basically the Dc converter does nothing but gather dust. I have used the converter twice in two years. Once every maybe 2 or 3 months, I notice the aux battery is getting too low and I recharge the aux battery overnight while I am recharging the car traction pack. I do drive the car every day.

My car does not have aircon and my setup would not handle a vehicle with aircon (I don't think).

Just my 20c worth.
Regards
Paul


----------



## MaxB (May 23, 2014)

Therealriley said:


> Thanks. Im not a troll so guess I'm just ignorant.....


Well, if it you makes you feel any better, the engineers at Ford are ignorant too.

https://media.ford.com/content/ford...ax-solar-energi-concept-goes-off-the-gri.html

I find it interesting that electric car people are playing the same game here that the ICE defenders normally do--insisting that the way they want to use their vehicles represents the one and only set of performance parameters which vehicles should be engineered to achieve. What if you never require your car or truck to drive more than a few miles at a time, at slow speeds? And what if it sits there in the sun for weeks between use sometimes anyway; and not parked near a house or other structure where external solar panels can be utilized, a train station perhaps? It's also worth pointing out that some places are a lot sunnier than others, so a setup that might be worthless in Maine is actually useful somewhere like Florida or further south.

It's certainly worth pointing out to people that putting a solar panel on the roof of their EV isn't going to let them use it as a daily commuter without ever plugging it in, but I can't understand why this concept should be off limits for discussion. 

Also, it seems to me that covering the bed of a pickup truck with solar panels wouldn't add significantly to the weight of an already heavy vehicle and might actually improve its aerodynamics--a gain which would admittedly be meaningless in the low-speed, low-mileage vehicle I've described. Anyway, that's what I'm hoping to build someday because I have a need for it.


----------



## dougingraham (Jul 26, 2011)

MaxB said:


> It's certainly worth pointing out to people that putting a solar panel on the roof of their EV isn't going to let them use it as a daily commuter without ever plugging it in, but I can't understand why this concept should be off limits for discussion.


It is certainly not off limits for discussion. It has been discussed many times. What it comes down to is that it is not cost effective and it is difficult to come up with circumstances where is would be cost effective. You can almost make it work if you load up the roof of a VW van with solar panels and do a daily commute of 10 miles and you live in the right place. If you increase the distance you drive then you don't have enough collection and you still have to plug in. The problem is that electricity is too cheap and the solar panels and electronics needed to interface them to the batteries is too expensive. There is also the problem of summer and winter. You get plenty of sun in the summer and not nearly enough in the winter. So it works for only part of the year.

I did a careful analysis of this for my own car and if I park the car facing south with the hood propped up at the correct angle on the average I could recover about 4 miles of my 9 mile commute. About 2 miles in December and all of it in June/July. The electricity cost of that 9 mile commute is less than 30 cents. At that time the break even point on not buying the electricity was estimated at 40 years. Of course this neglected that you have to buy the panels and electronics up front and you pay for the electricity as you use it which makes the comparison quite a lot worse. It is better today because the solar cells are less expensive but the electronics to do the charge control are still going to cost too much since there is no off the shelf solution. And while you could do an inverter and then drive the regular charger this wastes about 30% of the energy so is not a viable solution.

And even with the negative analysis I still almost went ahead and did it just because of the cool factor.

Best Wishes!


----------



## MaxB (May 23, 2014)

Right, but I was just trying to point out that some people do have circumstances other than yours, where such solar panels would make economic sense. You're right though, I should have stipulated no easily accessible AC power source as a main element of those circumstances.


----------



## tenthousandclowns (Jun 21, 2012)

The 'solar panels on the roof' idea keeps coming back because it has some magic in it, not because it makes sense with today's panels and prices. But the point of a DIY discussion board is to discuss how things would or could work. The problem of heavy, unaerodynamic panels has been mostly solved with the thin, lightweight, flexible panels now available. The price still needs to come down. Efficiency still needs to go up. But if we gather experience and share results along the way, we will better know when and how this would be practical and competitive.

I have a lightweight van with a flat roof, live in the south, don't have a garage, and don't drive a lot... at some point soon this will make sense for me. I have read many times on this forum how it doesn't make financial sense, but I have never found a post about the best way to wire the panels to charge the pack.


----------



## dougingraham (Jul 26, 2011)

tenthousandclowns said:


> I have read many times on this forum how it doesn't make financial sense, but I have never found a post about the best way to wire the panels to charge the pack.


You wire the panels to get the highest voltage possible. It is most unlikely you will have a solar array with a higher output voltage than your battery bank. If the voltage is higher than the battery the charge controller only needs to be a buck topology switcher. If the voltage is lower then you need to boost the voltage before it can be used to charge the traction pack. The closer these voltages are the lower the current differential across the device will be and the more efficient it can be. This would need to feed into a MPPT charge controller. MPPT stands for Maximum Power Point Tracking and the way it works is to vary the load on the panels to find the point where the most watts are produced. The backside of the MPPT needs to know how to charge your batteries or at the very minimum know how to talk to the BMS so it can tell the charge controller when to stop. MPPT is important because you typically increase the output of the panels by 10% vs just loading them up. Unloaded solar cells are at the highest output voltage but are producing no power. Shorted output solar cells are producing the highest current but are producing no power because the output voltage is zero An MPPT increases the current draw while watching the voltage to obtain the maximum watts output. (volts times amps) Too much current and the voltage drops below the optimum point. Too little current and you have the same situation.

One big problem is that this MPPT charge controller does not exist for EV's and the ones for the Solar industry expect the common battery voltages of 12, 24, and 48 volts. I for example would need one for 48 LiFe cells or a 172.8 volt CC/CV point. Someone with a Leaf or Volt pack would need to be able to do in the mid 300 volt range.

One obvious idea would be to run the solar array output into an inverter and then feed that into a charger. This fails to work because a normal charger knows that it can always pull 12 amps at 110 volts and can't deal with an input that would vary in its power capability.

I hope that answered your question.


----------



## tenthousandclowns (Jun 21, 2012)

Thank you Doug! That is the train of thought I was imagining. Yes, my first thought was to wire them in series for the highest voltage. That may make them most susceptible to partial shading losses, but may give the best results.
My second thought was to have a larger 12v battery, and charge that with a mppt charge controller... and then somehow have a proper switching to run a 1kw inverter to one of my 1kw chargers when the 12v battery is full... To me this seems like by the time I get the power to the tires, most of it would be frittered away in the various heatsinks along the way. But it would leave me with a nice 1kw emergency power supply.
A while ago I asked one of the chinese sellers on ebay of small dc/dc boost converters about a higher voltage booster and they said they hadn't heard of one.... perhaps there is one out there somewhere.
Paul9, I think your system of using the solar to power the 12v system, while keeping the usual DC/DC as a backup, may be the best for now.. although it doesn't allow for the enticing sunshine-to-wheels-turning.


----------



## Paul9 (Oct 2, 2015)

tenthousandclowns:
I originally toyed with your idea. I have a 96v dc Suzuki Swift (Geo Metro) hatchback. I wanted 8 solar panels to be wired in series to give me 96v put through a 96v regulator straight to the traction battery bank.

As Doug says, I couldn't find a regulator that would handle more than 48v. Second problem was finding 8 solar panels to fit! The largest panels I could find that would fit on the roof and front bonnet were 20watts. The max amps I could expect would be about 1.5amps. Almost useless.

I went with the auxillary battery "system" I described and kept detailed records. I also swapped all but my headlights out and replaced the blinkers, brake lights etc with LED versions.

The "fuel" savings I calculated as being between 3% and 7% depending on driving conditions. An average saving of 5% may not be much but 3 or 4 5%'s can help range and performance noticeably!

Cheers
Paul


----------



## tenthousandclowns (Jun 21, 2012)

Yarr I am in it now. I have ordered four 100 watt flexible 18v panels. I am referring to this system as an 'income disposal system' for the time being- it is probably pretty efficient at that. They will fill the roof of the van. Seems like it will be too much power just for the 12v system.. so probably we'll need a way to boost some of it to 120+vdc.


----------



## Sunking (Aug 10, 2009)

You do know Thin Film Panels efficiency is half that mono panels, and life expectancy is only a few years right? 

Thin Film Panel efficiency is in the range of 10% compared to 20% of mono panels. What that means is for a square meter of panel surface, you only get half the power of what a mono panel can generate. At 20% efficiency a 1 meter square panel is 200 watt panel.

The next challenge you cannot solve is panel tilt and orientation. In a stationary application the panels can be oriented Solar South with optimum tilt angle above the horizon with no shade from sun up to sun set. Unless you live near the equator, panels pointing straight up do not generate very much power. 

Example where I live in December with a Solar South orientation and Latitude +15 degree tilt we receive 3.4 Sun Hours which means a 100 watt panel into a battery generates roughly 230 watt hours of usable power into a FLA battery. 

Take that same panel and point it straight up or Zero degree tilt reduces Sun Hours to 1.8 which means 120 watt hours of usable energy into a FLA battery.


----------



## evmetro (Apr 9, 2012)

I have spent a lot of time contemplating the use of solar panels for use on an EV. I conclude that solar panels are an excellent source of fuel for an EV, but there is one catch. When you leave your driveway, the solar panels need to stay home, and you should drive away in an unencumbered EV so that you can use the least amount of that solar energy that has been harvested. 

If you are willing to sacrifice some energy efficiency for the joy of experimenting with the use of alternative energy while underway, it would make the most sense to wire the panels in series for a higher voltage than the pack, and let them feed the pack directly. That higher voltage needs to have a high voltage cutoff circuit to ensure that neither the pack or any one cell gets overcharged. Since the use of solar panels on an EV that is underway is recreational, I would probably wire up an either/or circuit so that when either the main pack or the aux pack becomes isolated from the panels by the high voltage cutoff circuit, it would divert the solar DC to the other pack. It does not add up to use solar panels in an EV, other than the rare case of an EV that sits in the sun for long periods and then is used for a very short duration, but I completely understand the joy of playing with stuff like this, and encourage it.


----------



## MaxB (May 23, 2014)

MaxB said:


> Also, it seems to me that covering the bed of a pickup truck with solar panels wouldn't add significantly to the weight of an already heavy vehicle and might actually improve its aerodynamics--a gain which would admittedly be meaningless in the low-speed, low-mileage vehicle I've described. Anyway, that's what I'm hoping to build someday because I have a need for it.


Wow, may not end up building one after all:

http://www.e-ride.com/e-rideEXV4-Equipped-w-Solar-Panels-inventory.htm?id=1058671&used=1&vin=


----------

