Solar?

I've got a bike project coming up that needs low voltage solar. I don't plan to run the motor or charge the main battery on solar, but I will have a lot of non-optimal surface area and a bunch of low powered things I want to add to the bike. Everything can be run at 5 volts, as most is USB compatible.

I figure I need 4 watts continuous, 24/7. I want this to be separate from the main battery so I'll have a bank of 18650 cells.
What I can't figure out is hook a large number of tiny solar cells together, most of which will be in shade or darkness at any given time. So there will be a great difference in output, and almost always sub-optimal. My understanding is that getting this wrong will fry the solar cells, but I haven't been able to find a good explanation on how to manage this for around 1000 individual cells, all at different output levels.



OK, now the long winded bit. A month ago I was in a serious and stupid bike wreck. I was riding at maybe 10mph at sunset when my front tire (20 inch) dipped into a hidden hole and stopped dead. As the bike did a forward flip, I went headfirst over the handlebars, landing head first in the street. I was knocked out cold. Lucky for me, someone saw, blocked the lane with their car, and called 911. I had a concussion and needed a bunch of stitches, but I'm not dead, and will recover. Things could have gone much worse. The person who saw me wreck might not have, and the next car might not have seen me laying in the road in the dark. Also, I often ride where I might not be found. A few trails I like to ride can go months between people using them.
So laying in the ER i had a brilliant idea of a deadman switch. A series of sensors that can tell when my bike is on it's side and will set a count down timer. If I hit a button in that time, it will reset, but cycle this a few times just to be sure. If I miss hitting the button or don't pick the bike back up, it will send a Wifi alert to my phone. I'll have to wright an app, but the idea is to have my phone call 911 with my GPS location, maybe even with sending pics of the location. I think this idea would be amazing for people in mobility scooters who may have other health concerns as well. No monitoring service, no monthly fees, just help when no one is around. The idea needs a lot of development, but the first part is effortless and maintenance free power for the bike's onboard electronics.

Things I want to try to add to this are an alarm, lights, a camera, GPS tracking. But since it would also be usefull, I'll add wifi, usb charging, move the bike's light system to this power source with wifi control, weather monitoring hooked to the wifi, and provisions to monitor the battery and even kill the power to the bike by wifi Also a possible 4g connection.

The first tech problem to solve is how to get the most power from solar on an object that will move often, and rarely to never be in line with the sun. The answer is to use many tiny panels all over the bike frame and bag rack. But when that happens, there will often be a huge power discrepancy between panels. And that output will constantly be changing, maybe multiple times a second.

So the real question is how do I manage around 100 watts worth of tiny 0.1 watt panels all with different outputs that are constantly changing and get a steady and efficient usable output?

Drunkskunk said:

So the real question is how do I manage around 100 watts worth of tiny 0.1 watt panels all with different outputs that are constantly changing and get a steady and efficient usable output?

Click to expand...

You don't. Too expensive/lossy.
But what you can do is manage a whole lot of 2-5 watt single cells, each with its own boost converter. The TPS61200 is a good option there.

You can just buy a few small panels, but I'd see what area you need for your 4W then double it for cloudy daze.

Glad to hear you're ok. Best wishes on a 100% recovery.

The key is going to be selecting the right solar panels. You want small panels of the right voltage to run the charge controller for the extra pack. Then I think you just use diodes to separate the panels from each other, so when one panel has enough sun to generate voltage it charges the battery. There are lots of small panels in the voltage range you need, which are sewn onto backpacks and glued on other things to provide portable power.

You're really talking about 2 projects.
1. a bunch of small panels, which due to all the wiring and points of damage wear and failure probably isn't really worth it. Good idea in principle, but many practical pitfalls. A handful of small panels that each put out a USB type voltage, all in parallel on different parts of the bike makes more sense.
2. A cool sounding system to auto notify authorities of an accident, and you should throw theft prevention and tracing into the package too.

Drunkskunk said:

So laying in the ER i had a brilliant idea of a deadman switch. A series of sensors that can tell when my bike is on it's side and will set a count down timer. If I hit a button in that time, it will reset, but cycle this a few times just to be sure. If I miss hitting the button or don't pick the bike back up, it will send a Wifi alert to my phone. I'll have to wright an app, but the idea is to have my phone call 911 with my GPS location, maybe even with sending pics of the location. I think this idea would be amazing for people in mobility scooters who may have other health concerns as well. No monitoring service, no monthly fees, just help when no one is around. The idea needs a lot of development, but the first part is effortless and maintenance free power for the bike's onboard electronics.

Click to expand...

There are a few links in this search with something at least vaguely similar:
https://www.google.com/search?&q=911+%22deadman%22+app
and "anti mugging app" finds some others, though I haven't read any of them other than the first one
https://www.cheaprvliving.com/forums/Thread-Deadman-switch-911-auto-dialer?pid=106050
which according to the last post, the app's TOS says using it may or may not actually result in ever reaching 911. :/

Hopefully there is some useful info in there somewhere, though.




Now, regarding solar stuff...I'm not an expert, and have only read about them here on ES, for the most part. But, AFAICR if you use commonly-managed panels (all on the same converter or MPPT, etc), then when one cell or panel is shaded it reduces the output of everything else with it to it's level. So you would probably have to have separate converters for each panel or cell, if they're expected to be shaded differently at the same time.

Using a few panels that each have many cells, with one converter per panel, would be a more manageable option.

There are some smaller panels, like Cowardlyduck has on his Bike-E, that might suit your purposes. Even if they aren't optimally placed, if there are enough of them facing different directions, at least one of them will be getting enough sun to be making a useful amount of power.
https://endless-sphere.com/forums/search.php?keywords=solar&t=57751&sf=msgonly


Next, use MPPTs (or whatever converters) that *are* the charge controllers for the pack, to save on efficiency, as long as they can be paralleled at their outputs (I don't think all of them can). If they have to go thru secondary DC-DC conversions, you waste power in the second conversion, but if the efficiency point of the panel converter by itself for your usage scenario is less than that of the panel converter plus second DC-DC, then the extra stage is better..otherwise, not. (ok, I guess that's obvious, but I'll leave it in there ).

Doesn't sound to me like your panel would need to be so big it was part shaded, part not, much. I'm thinking something about 6x6 inches would be plenty.

100w of 12v panels would power a TV. You need a lot less.

Glad to hear no particularly hard to get over injury. My low speed crash still has my rotator cuffs aching like hell, 12 years later. Took about 8 years before the collarbones stopped hurting when a front went through in winter.

Amazing how it hurts to stop that suddenly. Mine was a water bottle stuck in the front wheel.