Portable Solar Power charging


#1

What do you guys think about using solar power to charge the batteries while out flying? I’m thinking of having two groups of batteries, one charging on the ground, while the other is being used in flight. Land, switch batteries, repeat!

Here’s an interesting portable solar charging system:

https://www.powerfilmsolar.com/products/foldable-solar-panels/

The highest power system is 220 watts and weighs 14 lbs. How long would it take to charge a 40 min flight time battery pack with this?

Wouldn’t it be awesome to have a wing made out of solar panel material to power in flight? The tech probably doesn’t exist yet, but we can dream…


#2

Let’s say you’re battery is 12S (50V) and 20Ah. Charging it at 220 Watts will mean 4A or so. Charging time works be around 4.5 hours.

Now I don’t know how long you can fly on such a battery but probably not long.


#3

40 minutes is going to require something like over 3kWh of usable battery capacity, most likely.

The math doesn’t work, unfortunately. 3000 / 220 = 13.63 hours. This assumes perfect efficiency of the charger and electronics, and assumes max solar radiation.


#4

Thanks for doing the math for me :wink:

I guess I’d need 10 of these solar panel systems to charge in an hour… way too cumbersome.

Now, if I could power a high capacity charger with my Tesla, I guess I could transfer some of the Tesla’s stored capacity to the OpenPPG batteries and fly almost anywhere! Is there a way to get that much wattage out of a Tesla?


#5

On the other hand…

@Pdwhite mentioned that he is using this 350 watt charger and I believe he said it would charge his batteries in 1-2 hours. Then you would only need 2 of the 220 watt solar panel systems to power this charger… am I missing something here?


#6

That is 350W for each channel, so 700W total. Plus, Paul was likely talking about his setup with 2 batteries, which will be less than 20 minutes flight time.

Doesn’t change the math. You will need a solar array the size of a small roof to charge in the field for a sizeable battery. The math gets a lot worse when you consider losses in charging.


#7

Cool! What Tesla do you drive? I have a BEV too, but not Tesla fancy. Electric is the future of transportation!

It is possible to charge from your Tesla (or any car). Just charge off the 12V battery with any RC charger. Should be accessible by the frunk, if i recall.

You just need to make sure the car is on and the DC-DC converter is energized so it powers the 12V, else you will run that down quick!

For most BEV’s that just means key’ing to the ON position, so that HV contacts close. I know some Tesla’s are different in that they stay ON… just make sure the car is keeping the 12V up.

Of course, there are some losses in the DC-Dc converter, but you have a lot of capacity, it should be fine. The power you charge at will ultimately be limited by the DC-DC converter.


#8

I’ve seen several van builds (home made RVs) with 1000 watts of solar installed on the roof, so the possibility isn’t at all off the wall with a decent sized vehicle: https://www.youtube.com/watch?v=bbA3Rrmxayk

It may sound silly, but I will test using my vehicle alternator to keep a house battery system constantly powered, which will be used to charge the lipos. Although this system is ultimately powered by gas, it can be supplemented, even to the point of being fully powered, by any amount of available solar. Take a look at the class B Roadtrek power systems to get an idea of how practical this is. While driving, there’s an enormous amount of power available from the alternator, and even if not ‘green’, it enables us to take advantage of the other OpenPPG features: light weight, small (even potentially hikeable) size, zero torque, etc.


#9

A couple of big deep cycle batteries in the back of your car. Hooked up to an isolator so recharges while driving. Use these as a power source to run your charger.


#10

It looks like we wrote at the same time. This is exactly what I’m doing.


#11

I’ve got the Model S :sunglasses: best car I’ve ever owned by far. But I think that there’s a separate 12v battery to power the internal lights and USB ports, etc, separate from the main large battery pack that powers the propulsion. I wonder if using the 12v to charge OpenPPG batteries would run the battery down.


#12

Yeah, that is my point: so long as the car is on, the Dc-Dc converter keeps the 12V system charged. The HV battery charges the 12V battery. This replaces the alternator in a conventional car.

It is typical in most EV’s and hybrids to have a Dc-Dc converter capable of 1kW or greater. Thus, you can charge from it at a fairly high rate! It will work well.


#13

#14

Not to push you away from portable solar, I love looking at new ways to be green and save money… Now if you’re looking into solar at all, even on a diy scale, make it a permanent thing. Even if this is sitting in your yard. Any investment in panels only pays off when they are in use. Lets be generous and say you’re only getting sun on those panels 2/3rds of the week because of the weather. They already only run roughly at 25%, but let’s ignore that for now but again we’re cutting our useful percentage. Now let’s say that you’re only flying 25% of those good days, again you’re cutting into the use of those panels. On that note if you really monitor the panels closely as me and my friends do that have them as soon as you shade out one portion of that panel you have pretty much knocked it off the grid. So don’t shade your panels!! Back to the point, as others have said make use of an inverter off the car or have a second pack of batteries but the investment and the practicality of the on-site charging, which is a large quantity with additional investments in quick Chargers Etc is not worth it unfortunately. But if you’re looking for panels at all, my friend and I support you 100%, And it’s addicting once you get into it :slight_smile: p.s. I drive a chevy volt, I know its no tesla but we both love ours!


#15

Also you have to keep in mind that solar panels aren’t always going to be producing at the maximum rated power. The best solar panels are only around 25% efficient with today’s technology so a lot of the suns energy isn’t being converted into electricity. The 220 watts is the maximum that panel will produce with the perfect conditions. Also keep in mind that the ratings are tested in a lab setting so you will be getting less output in real world conditions. The actual output is based on a lot of different factors, time of day, location, cloud cover, the quality of the cells. As I am sure you have already gathered it wouldn’t be that economical or practical to quickly charge your batteries with this. You would be better spending your money on multiple batter packs.