Is it worth buying cheap power banks with solar panels? 🤔 

I'm not sure if you're reffering to same part of the video I'm thinking about, in 7:15 I'm measuring short circuit current to see what is the maximum power output (power generation) of the solar cell under load. In this instance the multimeter is being a load with almost no resistance. You'd usually measure current in-line (for example to see at what current it's being charged), because you want to measure current for a specific load (like charging a battery). However, to see effectiveness of solar panel I checked open curcuit voltage and short cuircuit current, so if it was 5mA@5V, that means for DC it's a simple multiplication - 25mW. I might've gotten something wrong somewhere, so let me know what do you think about this 🙂

@@pandaengineering 7:15 is the one that I was referring to, yes. I don't quite understand what you mean with short circuit current: The amp meter is still parallel to existing circuits on the board. The contact points you're measuring on might have a coating or so, and have a longer track, therefore more resistance. My thought is that the current will still mainly flow over the circuit board and hardly through the amp meter. That would explain the low amperage you measure. A solar cell of this size and type should produce a couple hundreds of milli amps under good lighting, 5 mA can't be right. But I don't know where you are measuring exactly and I may miss an important point here. Did you try to charge the battery only using sunlight? Might be interesting to see how long that would take and the calculate back to what the amperage of the solar panel approximately is. Any way, interesting video, thanks for sharing!

@@rvdboomgaard You're right, I messed up the measurements. I was almost certain that I did measure this without any load outside, but I may be wrong here since it was over a year ago. I tried again today with 4x 140W halogens and when I positioned it in the best spot it went almost to 170mAh imgur.com/CGZRDDq Problem is that at that point it's quite a lot of light (very close to the bulbs) and when I tried measuring lux with my phone (it's fairly accurate for something like this, +/- 10%) it topped at 32k lux (so sunny day, not scorching, but sunny) so I started to hold it at the distance where it just reached those 32k and it was showing almost 50mA. I can't get anything near 20k lux of daylight at this time of year, so there is no use testing it outside. The main thing is, before I posted this video I also tried to discharge the power bank and let it charge for 4 days on a windowsill outside - when I connected anything, it just blinked "low battery" and gave a bit of power for few minutes, so I thought the cell is really bad. I think that I have to keep it very close to the bulbs because there is a coating on the solar cell that decreases it's efficiency. Thank you so much for your comment, I'll add this info to description! :)

As a power bank it's fairly good. The solar cell is an "extra" that could charge it fully (in theory) in 2 days in full sun. If you plan to get solar as power on a camping trip and you don't live in place with lots of sun, I suggest getting a folding big solar panel with USB and place it on your backpack. This way it won't overheat the cells in a powerbank and it would actually charge it during the day. I personally just got several powerbanks as charging with any small solar cell in my location (~50°N) wasnt efficient enough.

I've got it on Aliexpress(I just looked for "usb tester" keywords), but after some use I think for higher loads like testing modern smartphone charges it's not good enough. Seems that USB connector wore off and it doesn't provide a positive connection. I'm thinking about getting one that's made by "Ruideng" or "Riden" (also known as RD) because it seems to be working much better looking at the videos posted on BigCliveDotCom channel.

@@pandaengineering thanks

Nah, customs in Poland are only interested if they can slap a tax or any other fee on anything for 20 USD or more. What Chinese sellers would also often do is that they ship the thing to their warehouse in the EU with other stuff and then send it inside EU where it won't be checked.

You can always disconnect the solar cell and test it out. It really depends on amount of sun you're getting, but I had one solar powerbank that had a photodiode instead of actual cell, so it didn't worked at all.

It's 208 grams when charged (probably 10 less when discharged).

@@pandaengineering Thanks friend

China bad

@@mangosrepent1817 agreed ... But china cheap

Depends what you expect from them. Also see the update in description (I incorrectly measured the current in the video). They should be a decent powerbanks (I still use it, cell it fairly good and keeps the charge), but you'd have to have Australian class sunlight to get them fully charged in few days :)

@@pandaengineering Luckily I have better sunlight than Australia, I'm in Sout Africa, thx for the feedback I appreciate it.

francous van vuuren haha me too, agreed I just ordered one on takealot for R155 it's the most affordable one but seems to be a Chinese clone of a really good brand so hopefully it'll come close to the same performance not expecting great things just simple emergency charging

See my other, more recent video with solar charged powerbank, there isn't even a solar cell there 😂 Sad truth is that those companies make fools from people that aren't technically minded.

@@pandaengineering is 8000 mah is limit of all pb or only solar pb?

It really depends on the cell they put in and what quality they are. I remember first offbrand li-poly batteries for cell phones, they were amazing... for first 3 moths. There isn't actual cap on the capacity of single cell as far as I know (some power banks come with 2 or more cells that are balanced by charging and discharging circuitry), but you have to consider that large capacity means it's significantly heavier and considerably larger. Actual 20Ah would be twice as thick at least. As usual, it's good to go with well known brands, they get the capacity *mostly* right. As for cells, I'd recommend Sony and LG, really robust and properly protected. As for solar pb, low capacity can mean that they designed it with realism in mind, that it can actually be fullly charged by solar cells.

It's not that bad, see pinned comment for correction - I messed up measuring it.

@@pandaengineering I'm just arguing with the seller now. They also claim the case to be water proof, which is not.

It can be really hit or miss with the sellers, they rarely know exacly what they have in stock. If I buy it domestically, they often just order stuff from China to my address so it's a better idea for me to order from Aliexpress directly - much cheaper and seller rarely argue and will give you a refund. At lest this power bank did what it said on the box (I've got a max current of 165mA from the solar cell) and is very good for USB soldering iron. I bought another one in a local store chain and after I gutted it, it had a fotodiode instead of solar cell, to it will show that it's in the sun, but that solar cell was just a piece of plastic with painted stripes ( ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5ExwxHYp_eI.html ). The thing is, that there could be exacly the same design with a good cell and it's really hard to tell either way before you actually get it and have a close look.

@@pandaengineering Some of those ebay stores were managed by people from China. Sometimes when you argue with them to a certain point they will start telling you some sob stories about how miserable they are and how their boss is abusing them to try to get you to leave them alone. Kind of funny. Those are usually from sellers that are already lying about their product in their listings. They like to sell these broken products with cheap price that they don't care about complains and refund request. The cost is so low that they'll just refund you and let you keep the stuff and ask you not to give them a negative feedback.

Those stories are relly something. My friend got in touch with a seller and he gave him his life story along with family pictures (!) and how he is in difficult situation right now. I'm sure they have earned a lot of those sympathy bucks using this method. What worries me is that some of those sellers start creeping into Amazon.