[meanderingthemaze]

Anyone know of any examples or resources on charging via solar panels?

I live in So Cal and it'd be a shame not to harnass that solar.

I know there is controversy over whether or not the weight of the panels make it worth putting them on the car. However, I'm doing a pickup and removing the bed. So if I'm already putting down a cover for the batteries, it might as well be doing something other than looking pretty right? I'll probably make a custom size panel to fit the car.

Thanks for any links or info you can pass on.

[Voltswagen]

Meander
Put the solar panels on the roof of your home.
You can't load enough panels on a car or truck to make any measurable difference.
A light vehicle will draw 50 - 60 amps crusing at 40mph. A truck...maybe 80 amps....maybe more.

Watts divided by volts = amps
http://www.atlantechsolar.com/calcul...onversion.html

Here are some cheap 200w panels.....note the size. http://www.dmsolar.com/solar-module-2.html

How many of these panels can you load on truck......3? Lets say they put out 26.9v per their spec sheet. 81v total (3) wired in series. How many amps does that convert to?
Here is another good site I found today for determining Solar Panel output:
http://www.ehow.com/how_4720927_volt...lar-panel.html

It's not about the weight of the panels...it's about the output.

[meanderingthemaze]

Thanks Voltswagen for the links and input.

I'm curious to hear what you mean by measurable difference, though. I've heard that you could increase your range by maybe 5 miles. Plus, I park my car in the sun all day at work. BTW, I'm about 6 degrees closer to the equator than where you are and get a lot more sun. Los Angeles is classified as desert. Another problem I have is that I rent, so I can't really do a solar panel installation at home, when I own I will definitely put them on my roof.

Anyway i specifically mentioned that I am aware of the controversy and didn't want to create another thread debated the advantage and disadvantages of solar panels on a car. That discussion has been done a million times already. I am making an guess that I will not only have a significant amount of solar paneling (about 20 sq ft), but that it'll be parked in the sun all day, trickle charging the batteries and prolonging their health. I have considered creating a hinge so that I could slant it in the direction of the sun while parked. And, no I am not under the illusion that this is a new idea.

So, I guess the specific questions I have are...
1) Should the paneling have the same voltage as the pack or slightly higher?
2) Or should I consider a transformer to get to the voltage i need?
3) Can i literally hook up to + & - ends of the pack without a charging system? Or should I at least have a shutoff to prevent over charging (for example if I charge it over night and then leave it parked in the sun all day without driving, could I over charge?) Or if the voltage is the same as pack voltage, then it shouldn't over charge, but then would I damage the solar cells if there is nowhere for current to flow?
4) Any other wiring considerations?

I realize that this is not a common practice so I will probably not get very much guidance. Just thought I'd throw it out there though. Thanks

[Sunking]

It is just a matter of physics. You cannot add enough panels to make any noticeable contribution. The very best and most expensive panels are only on the order of 17 to 19% efficient. At 100% efficiency (those panels do not exist or ever will) you can only generate 1000 watts/m2. So in So Cal about 6000 wh/m/2. So with 19% efficiency you are looking at 1/5th or about 1.5 Kwh/m/2. How many square meters do you have available on a vehicle? Not enough to make any meaningful difference. Not to mention the extra added weight and drag to carry around.

[Kelmark]

I am not a solar expert but have been looking at using solar on my conversion as well. I received the same reality check but have not been deterred. My original goal was to be able to get 4 mile at 35mph extra range. Running some numbers I realized even that would take covering my entire car with high grade cells. $$$

Instead I have now decided not to pursue running solar to my main pack. Instead I will be using them to keep my Aux battery charged. In turn I it will reduce the need from the main pack through the DC to DC Converter. This also saves power losses in the converter amplifying the benefit of solar.

Originally Posted by meanderingthemaze

So, I guess the specific questions I have are...
1) Should the paneling have the same voltage as the pack or slightly higher?

Normally the Voltage is slightly higher I beleive.

Originally Posted by meanderingthemaze

2) Or should I consider a transformer to get to the voltage i need?

If you feed to your aux batt the voltage will be low enough this won't be needed.

Originally Posted by meanderingthemaze

3) Can i literally hook up to + & - ends of the pack without a charging system? Or should I at least have a shutoff to prevent over charging (for example if I charge it over night and then leave it parked in the sun all day without driving, could I over charge?) Or if the voltage is the same as pack voltage, then it shouldn't over charge, but then would I damage the solar cells if there is nowhere for current to flow?

I will be using lithium for my aux batt so I will use some sort of cutoff so I do not damage the cell.

Originally Posted by meanderingthemaze

4) Any other wiring considerations?

They sell small solar car battery chargers, I am going to get one for my petrol car and look close at its componets and wiring.

Originally Posted by meanderingthemaze

I realize that this is not a common practice so I will probably not get very much guidance. Just thought I'd throw it out there though. Thanks

I am still in the early stage of my conversion so I don't have allot of answers yet. I will be using thin flexable solar cells, for your bed cover you can use solid solar panels with higher output. Just start researching weight to power output versus price.

The panels should help air drag on your truck if used as a bed cover just don't exceed the average weight of other bed covers and I don't see how there will be any disadvantage. The advantage will likely be around 1-2 mile extra range at 35mph so you'll have to determine how much to pay for that. Sorry I am not more help.

[Voltswagen]

Meander
Sunking pretty much summed it up for you.

Yes, you do get more daily sun where you are vs my location.
So you might collect an extra 5 miles worth of amps in a day but then subtract for the increased drag co-efficient. I don't know what it would be on a truck but it would depend on the number of panels and the added weight.

There are a number of EV builders here on DIY who seem to have very deep pockets with vehicles surpassing $30K in cost but none to my knowledge who have added solar panels.

But at the end of the day........it's up to you........

[rmay635703]

Originally Posted by Sunking

It is just a matter of physics. You cannot add enough panels to make any noticeable contribution. Not enough to make any meaningful difference. Not to mention the extra added weight and drag to carry around.

Dead wrong if you are using lead acid batteries. Even a very very small charge rate 1/250 C reduces the rate of hard sulphation by about 50% in discharged FLA batteries. Meaning it is VERY worthwhile to have a small solar trickle charger mounted to the car, assuming of coarse you drive during the day and charge at night. Even when you are coasting or stopped during a trip solar starts to reduce hard sulphation.

But not worthwhile for range, only worthwhile to extend the life of your $600-$3000 investment. A small long trickle charge can occasionally have the side effect of equalizing batteries as well.

So yes Billy having a SMALL inexpensive solar panel on the car can be worthwhile. Just not for range.

Too bad I can't locate any inexpensive sources of new loose cells anymore 4 years ago they were 0.51 cents a watt, now $1.25 WTF? I would love to utilize the 4x8' roofrack area on my fathers 48v minivan to build a 400-800 watt array. To me that is fairly sizeable? And the 2-4hrs it sits between trips would likely gain back a sizable amount of range.

It would only have a payback to extend battery life but during mid day it would extend range about 5 miles at 25mph if that means anything. The cost of such a panel would not be recovered though in the form of electricity only potentially battery survivability.

So whether solar is for you is far more complex than those here claim, it has benefits beyond range and Depending on the shape and speed of your drive; your vehicle may gain a small additional range at midday.

Extending the lifespan of the most expensive part of the EV to me is the most important aspect of having solar, but whether it is worth thousands of dollars to add 5 miles range at low speed during midday is up to you to determine.

I would argue $50 for some little 5 watters to trickle your pack is a good investment though (assuming you have room or mounting to place them when parked). Afterall if your $1600 battery pack lasts even 10% more cycles (conservative estimate, much much higher if you exceed 50% dod occasionally) its probably worthwhile since the most money you will ever spend on an EV that is actually used will always be for batteries and solar panels generally hold value and last decades longer than your pack of batteries.

Food for thought
Ryan

[green caveman]

Originally Posted by Sunking

It is just a matter of physics. You cannot add enough panels to make any noticeable contribution. The very best and most expensive panels are only on the order of 17 to 19% efficient. At 100% efficiency (those panels do not exist or ever will) you can only generate 1000 watts/m2. So in So Cal about 6000 wh/m/2. So with 19% efficiency you are looking at 1/5th or about 1.5 Kwh/m/2. How many square meters do you have available on a vehicle? Not enough to make any meaningful difference. Not to mention the extra added weight and drag to carry around.

Yes, but since the vehicle is parked all day, you could come up with a creative fold-out system that would then benefit the users of surrounding parking spaces by providing desirable shade. So, if you fold it out to the size of the parking space, you'd have about 12m^2, three parking spaces would give you 36m^2 - 54 kWh (if your 1.5 Kwh/m/2 is correct).

Not judging whether this is good, cost effective, workable, whatever, just trying to not to stifle creativity.

[rmay635703]

Originally Posted by green caveman

Yes, but since the vehicle is parked all day, you could come up with a creative fold-out system that would then benefit the users of surrounding parking spaces by providing desirable shade. So, if you fold it out to the size of the parking space, you'd have about 12m^2, three parking spaces would give you 36m^2 - 54 kWh (if your 1.5 Kwh/m/2 is correct).

Not judging whether this is good, cost effective, workable, whatever, just trying to not to stifle creativity.

A very expensive fold out indeed, would have to make sure it couldn't be easily broken or stolen.

I still will say preventing battery sulphation is a far better use and would save the most money in the long run increasing the battery pack lifespan.

[meanderingthemaze]

I have removed the bed as you can see and I am planning to leave it off to reduce weight. But in California, by law you must have fenders or a bed that covers the back wheels as well as mud flaps, so I was planning on installing a flat bed to cover the batteries as well as the rear wheels.

How many square meters do you have available on a vehicle? Not enough to make any meaningful difference. Not to mention the extra added weight and drag to carry around.

I have about 20 sq ft. If you can explain why a flatbed made from solar panels would increase drag over let's say fiber glass or plywood, I would love to hear. It'll be the same shape and relative weight.

Extending the lifespan of the most expensive part of the EV to me is the most important aspect of having solar, but whether it is worth thousands of dollars to add 5 miles range at low speed during midday is up to you to determine.

Not to mention the 1500 or so miles a year that would not be powered by the dirty grid.

Yes, but since the vehicle is parked all day, you could come up with a creative fold-out system that would then benefit the users of surrounding parking spaces by providing desirable shade. So, if you fold it out to the size of the parking space, you'd have about 12m^2, three parking spaces would give you 36m^2 - 54 kWh (if your 1.5 Kwh/m/2 is correct).

Not judging whether this is good, cost effective, workable, whatever, just trying to not to stifle creativity.

I love it green caveman, rather than stifle, you have inspired me!