I see you guys have been discussing hub dynamos off and on for some time. But I'm thinking about a small, regulated solar panel to mount on my rear rack or on top of my rear rack bag. Who's found something light, small, durable and maybe flexible? How about rechargeable battery packs to go along with it?

While the PV equipment needed are commonly available I wonder if the combination of technical specifications make this very practical. Flexible PV panels are available from a variety of sources. But, their operational electricity production is pretty minimal. Batteries are also available. But they do add weight. Depending on how long you want the lights plus whatever else to operate you may need to use a supplemmental wall charger anyway. If you want to pursue checking it out give me a PM telling me what kind of lights you want to power and I'll help with the technical analysis.

I'm thinking that DC power for everything from MP3 player to GPS unit, to laptop computer would work for me in my work, plus short adventure-exploring trips. A small solar array to clip onto my rear rack bag to have backup power for a laptop computer. A solar panel twice that size for clipping atop the same rear rack bag and a couple panniers, hung on either side of the rear rack, to drive a GPS for exploring obscure roads and trails.

I'm an older guy who's adapting my riding style and my bike from straight mountain bike, to utility, touring, recreational and commuting. I know other Baby-Boomers who are reaching retirement age, but won't retire, are doing similar stuff with their lifestyles and bikes. We're old enough that we're spoiled with having energy-consuming gadgets on board with us. And we have a variety of them, depending on the day's uses-needs.

A "small solar array" is inherently a very low output solar array.

Don in Austin

I'm aware that a small array would be low amperage. But to keep a battery pack float-charged shouldn't be too big a challenge, should it?

As bicycles are used almost exclusively outdoors, and free solar energy is everywhere outdoors, why not capture some free energy? For touring and other non-road-racing bikes, why not?

A dynamo is far simpler & the best option for your requirement. The thing is all this Solar Panel thing-ma-gig will only complicate matters for you, and what if then it doesn't workout as you need it?? Hub Dynamos are really one of the most efficient bicycle-power generators out there. All you need to do is get one.

I've been using Shimano Hub dynamos & now I never have to worry about draining batteries on Garmin, Mobile phones and yes even lights

I'm not as concerned with another pound or two of weight, as I am with increased drag. Including cranking drag going uphill or into a headwind. We all enjoy having surplus kinetic energy to burn on those long downhills...

Yes, weight matters, too. But here's a news item that reflects my thinking. If the US Marines are now using solar in combat zones in Afghanistan, why not some old guy who is out on the docks with his bike and laptop computer? Or, using up his GPS batteries while exploring a couple of small coastal villages in a foreign land?

Solar Power Means Less Batteries and More Bullets for U.S. Marines
Published May 08, 2011
| The Wall Street Journal


Read more: https://www.foxnews.com/us/2011/05/08...#ixzz1LqpnYIKs

Well if you think that the drag from a dynamo will be more than 2 pounds of extra weight then you're really mis-informed. The so called drag is so insignificant you won't even know it if you were to sit on a bike with one & ride uphill.

As far as US military is concerned... they may have the best technology & budget at their disposal & oh yeah probably most of their equipment will already be 10times more optimized for low power consumption than yours or mine. But then to each his own.

A solar panel the size of a typical rear rack would probably be about 1/3 square foot. Solar cells put out about 10 watts per square foot, so you're looking at 3.5 watts at best, in full sunlight with the sun hitting the panel at a right angle. This will never occur. Also, the panel will be in the shadow of the seat/rider about half the time, even if you ride in an area with no shade all the time. I'd guess at best that you're going to see a net average output during the daytime of perhaps 1 watt.

Now, with a dynamo you're using the energy as it is produced, so you don't pay the penalty of storage. With a solar panel the energy has to be stored. Charging systems and battery together will be perhaps 50% efficient if you buy really good one. So now you're down to 1/2 watt. If you have a modest 3 watt LED system (front and back, not super bright), you will have to be in the sunlight 6 hours for every hour you want to run your lights.

And it's not bright and sunny every day either. You'll still need the ability to charge your system from mains power.

It's a laudable idea but I think the idea of portable solar charging is not a great one. I think you'd be better buying a modest 50 watt panel for your home, charging a 12v battery there all day, and using it to charge your bike batteries at home every day. It would still be pretty cheap and you wouldn't have to carry that stuff with you.

You didn't take me up on my offer to help you design a system so I suspect this is more of a casual post count booster thread. PV on a bike can be done but, like almost things there are trade offs.

At my age, I'm way beyond keeping track of how many posts I make in different forums and blogs. The LinkedIn and other business networking sites where I spend much of my time don't even have a post counter. Anyway, lights might be the purpose for on-board electrical for some folks, but not for me. As mentioned a few times above, my need is for electronic gadgets - such as GPS in exploring and shopping nearby communities, plus keeping backup battery power charged up for a laptop computer for business uses (out on the docks and other locations within a large marina).

You can do it pretty cheap and easy. Harbor Freight sells a solar power battery keeper for cars. It is not too large and it is already 12v. Just cut the cigarette lighter plug off and splice in a socket. Then you can plug in any car adapter for cell phones or other low power device.

The main problem is going to be that it is only 1.5 watts. That is not much at all. It probably won't even keep a phone charged that is in use.

https://www.harborfreight.com/15-watt...ger-44768.html

Here is a 5 watt model but it is significantly larger:

https://www.harborfreight.com/5-watt-...ger-41144.html

Neither one of them is going to be able to power up a laptop.

I had a similar 5-watt solar panel on a sailboat I owned. Kept the 12-volt house battery charged. The battery ran navigation lights, lights down below, a TV and a radio or two. But sure, the solar panel couldn't keep up with power consumption. Just slowly float-charged the battery. That's what I'm thinking for the bike. Just need a more efficient, flexible solar panel, and lighter battery.

Okay, you guys are right. It can't be done. And these guys can't be doing it...

https://www.powerfilmsolar.com/total-...power-pack.php

Dimensions-23 x 14.5

This is the deal killer here as others have noted. Its a small sail.

Do a web search for bruton solar. They make a pretty small system that is good for mp3/cell. Not for laptop which requires a LOT more power.

Gee if you can't even keep track of what you do and where you do it of what possible value can your thread be? You already think you know the basics. You spend a lot of time on the internet so surely you know how to find and read a parts catalog. All in all this thread seems to be a waste of time for all.

You're right. I'm wasting my time here. I thought you were smart. Or at least experienced in the topic. My error.

Very experienced. Designed several systems. Also, several people I know have powered all kinds of stuff on bikes. But you blew me off saying you couldn't be bothered keeping track of who you were talking to or what about. Then you made posts that were sarcastic at their most charitable. So, figure it out yourself. I regret even offering to help.

I sort of looked into this idea. I would use only one or two panels and have these charge a small efficient battery pack. Then use this to charge the devices. This is because most devices will work best when the draw is continuous. I think the 12volt car/cigarette lighter is the only way you'd find a sane level of compatibly.

That being said, automobiles have an obscene amount of surface area and exposure time available for solar energy collection. But even pure EV's have opt'd not to employ the technology (there are a few rare instances).

On a bicycle it is impractical aerodynamically, and you don't give a **** but you'd need an expensive and/or heavy panel aimed more or less at the sun light to produce anything strong enough to generate "charge" on a battery.

Wallmart has a panel 11X18 and ~4 pounds that will put out 18watts. It could be somewhat usable. Flexible paneling seems sloopy to me. Wiggling and waggling is an energy loss. Firmness gives you control and returns your energy.

Some already have batteries build in. That's a plus because you won't need to spend $ on the fancy charge controller. Depends on how far you want to go with it.

Obviously if reason and logic were strong points, this thread would not have been started, considering so many strong dynohub options are already available, with data to show their effects.