Dragging a geriatric solar panel into 2017
July 17, 2017 12:47 PM Subscribe
I have an old (approaching the age of majority) portable 12V solar panel. It seems too nice to throw out or donate, but I can think of exactly 0 uses for a tiny 12V solar system.
If possible, I'd like to find a way to use it to charge a USB battery pack (like this). I have several extras knocking around at this point, so I wouldn't need to buy one and it's not the end of the world if I mess it up.
My preferred difficulty level is "hobbyist/knows how to solder and use a multimeter, but not an electrical engineer" and I'd prefer to keep costs in the same ballpark as lower end modern all-in-one 5V USB solar things (like this one). So, let's say $40-60. Cheaper is ok, of course.
So, the questions:
1. The panel (actually, two panels in a nice zippered Cordura binder) were expensive/high quality when new, but are now 15 years old, at least, and I don't have a great sense of how solar panels age. They're each about 9"x11" and have a nice sturdy epoxy coating (?). I think they're Kyoceras. They've been stored in the dark at a controlled temperature for almost their entire lives--I'd wager that they have less than 200 hours total exposure to the sun. Is it likely that they'll produce enough juice, say 12-15W, to actually be useful?
2. What's the best option from going from 12V panel --> 5V USB battery pack? Do I want a specific type of DC-DC converter, or is there a product out there that's intended to do exactly this? Ideally, I'd like to be able to purchase a (more expensive) but amateur-friendly kit rather than individual parts--let's call this the Adafruit option--but it looks like most of these are built around specific 5V panels. The whole point here is to try to find a use for the panels I already have.
3. If my "charge a USB battery" plan isn't feasible, do you have any other suggestions?
If possible, I'd like to find a way to use it to charge a USB battery pack (like this). I have several extras knocking around at this point, so I wouldn't need to buy one and it's not the end of the world if I mess it up.
My preferred difficulty level is "hobbyist/knows how to solder and use a multimeter, but not an electrical engineer" and I'd prefer to keep costs in the same ballpark as lower end modern all-in-one 5V USB solar things (like this one). So, let's say $40-60. Cheaper is ok, of course.
So, the questions:
1. The panel (actually, two panels in a nice zippered Cordura binder) were expensive/high quality when new, but are now 15 years old, at least, and I don't have a great sense of how solar panels age. They're each about 9"x11" and have a nice sturdy epoxy coating (?). I think they're Kyoceras. They've been stored in the dark at a controlled temperature for almost their entire lives--I'd wager that they have less than 200 hours total exposure to the sun. Is it likely that they'll produce enough juice, say 12-15W, to actually be useful?
2. What's the best option from going from 12V panel --> 5V USB battery pack? Do I want a specific type of DC-DC converter, or is there a product out there that's intended to do exactly this? Ideally, I'd like to be able to purchase a (more expensive) but amateur-friendly kit rather than individual parts--let's call this the Adafruit option--but it looks like most of these are built around specific 5V panels. The whole point here is to try to find a use for the panels I already have.
3. If my "charge a USB battery" plan isn't feasible, do you have any other suggestions?
Your phone charging will totally work.
However, I've gotten a great deal of joy from hooking up a computer fan to it; it turns out they are 12V DC. Very simple, won't have a problem if the voltage is slightly off, and will cool you off on a hot day. Just go to the local computer retailer or wherever, pick up a case fan -- they're hanging in bubble packs -- for $5 to $50, and connect the red wire to positive and the black wire to negative. It will work just fine.
The other thing that's been great is charging AA and AAA batteries. Lots of battery chargers connect to the AC wall outlet using a 12V DC transformer/wall wart. I use an intermediate 12V battery (which is great for running that fan at night), and connect up everything with a charge controller as follows: Solar panel on "panel", 12V battery on "battery", and battery charger on "load".
Plus, that charge controller I have? Also has a USB connector for charging phones. Apparently a lot of them do.
I am not up on charge controllers; I got the one recommended by the Brown Dog Gadgets guy, which he sold me. However, if you look around for [12v solar charge controller USB] you'll probably get to what you need.
posted by amtho at 1:43 PM on July 17, 2017
However, I've gotten a great deal of joy from hooking up a computer fan to it; it turns out they are 12V DC. Very simple, won't have a problem if the voltage is slightly off, and will cool you off on a hot day. Just go to the local computer retailer or wherever, pick up a case fan -- they're hanging in bubble packs -- for $5 to $50, and connect the red wire to positive and the black wire to negative. It will work just fine.
The other thing that's been great is charging AA and AAA batteries. Lots of battery chargers connect to the AC wall outlet using a 12V DC transformer/wall wart. I use an intermediate 12V battery (which is great for running that fan at night), and connect up everything with a charge controller as follows: Solar panel on "panel", 12V battery on "battery", and battery charger on "load".
Plus, that charge controller I have? Also has a USB connector for charging phones. Apparently a lot of them do.
I am not up on charge controllers; I got the one recommended by the Brown Dog Gadgets guy, which he sold me. However, if you look around for [12v solar charge controller USB] you'll probably get to what you need.
posted by amtho at 1:43 PM on July 17, 2017
Just pick up one of those USB chargers that plug into a car cigarette lighter socket. Cars electrics are 12V, so it should work fine. If you want to be super-fancy about it, you can use a charge controller and a 12V battery to store the power until you need it, but that's going to cost way more.
posted by pipeski at 2:34 PM on July 17, 2017 [2 favorites]
posted by pipeski at 2:34 PM on July 17, 2017 [2 favorites]
question 1.
you have 2 panels (that I'm assuming function as 1?) of 9"x11" this gives you 198 in^2 or 1.375 ft^2 of total area. The consensus I arrived at after googling is to budget ~10-13W/ft^2 in full sun, using the lower bound since your panels are older gives 13.75 peak watts available. Knowing nothing else about your panels (is the 12v open circuit or regulated? if it's open circuit, the voltage will dip with load and possibly piss off your DC-DC converter) this gives you enough power budget to consider doing USB charging.
question 2.
Just getting an aux power jack (aka cigarette lighter port) to connect to your panels and use a car phone charger that is below your watt budget (I wouldn't go any higher than a 10W single port charger) you should be fine to charge a battery pack. give the ridiculously low cost of car chargers it's essentially zero risk. I really like this pack since it can charge an external device while it's plugged in.
posted by Dr. Twist at 3:18 PM on July 17, 2017
you have 2 panels (that I'm assuming function as 1?) of 9"x11" this gives you 198 in^2 or 1.375 ft^2 of total area. The consensus I arrived at after googling is to budget ~10-13W/ft^2 in full sun, using the lower bound since your panels are older gives 13.75 peak watts available. Knowing nothing else about your panels (is the 12v open circuit or regulated? if it's open circuit, the voltage will dip with load and possibly piss off your DC-DC converter) this gives you enough power budget to consider doing USB charging.
question 2.
Just getting an aux power jack (aka cigarette lighter port) to connect to your panels and use a car phone charger that is below your watt budget (I wouldn't go any higher than a 10W single port charger) you should be fine to charge a battery pack. give the ridiculously low cost of car chargers it's essentially zero risk. I really like this pack since it can charge an external device while it's plugged in.
posted by Dr. Twist at 3:18 PM on July 17, 2017
Response by poster: that I'm assuming function as 1?
Yes--currently wired in parallel. They're kind of set up like the inside surface of a Trapper Keeper.
12v open circuit or regulated?
VOC measures about 17V.
posted by pullayup at 3:27 PM on July 17, 2017
Yes--currently wired in parallel. They're kind of set up like the inside surface of a Trapper Keeper.
12v open circuit or regulated?
VOC measures about 17V.
posted by pullayup at 3:27 PM on July 17, 2017
Response by poster: One more follow-up--is there a meaningful difference between using a car phone charger and something like this? More generally, if I'm picking an accessory/cigarette lighter USB charger, what should I be looking for?
posted by pullayup at 3:35 PM on July 17, 2017
posted by pullayup at 3:35 PM on July 17, 2017
If you know how to use a multimeter, you should be able to find out how many watts this thing makes and therefore what you can usefully do with it. Just put it in the sun and get the voltage and amperage.
posted by Anticipation Of A New Lover's Arrival, The at 6:12 PM on July 17, 2017
posted by Anticipation Of A New Lover's Arrival, The at 6:12 PM on July 17, 2017
Here is a $14 charge controller with a USB jack built in. Another one for $20. (these came from searching for 12v charge controller with usb).
If you connect one of these to your solar panel they should do what you want. I will say that I discovered that some charge controllers don't work without also having a 12V battery connected, so you might want to check that.
posted by amtho at 9:17 AM on July 19, 2017
If you connect one of these to your solar panel they should do what you want. I will say that I discovered that some charge controllers don't work without also having a 12V battery connected, so you might want to check that.
posted by amtho at 9:17 AM on July 19, 2017
This thread is closed to new comments.
I suspect there are a bunch of odd little mechanical tasks that you can automate for daylight hours. Things we thought about after setting up this fan: putting a small fountain in our birdbath that could run off the panel, connecting the panel to a small battery and a string of LED lights to mount in the branches of our sidewalk tree.
posted by late afternoon dreaming hotel at 1:06 PM on July 17, 2017 [3 favorites]