Lion Energy GO 20 Portable 20W Solar Panel Expired

Received mine today. I can confirm the dual male micro USB is unregulated 8V open circuit from the panel, and the two plugs are in parallel. The female USB ports on the box are separate. 1 panel won't have high enough voltage for solar controllers so I tried splicing 2 panels up in series and got 15.6V open circuit in afternoon sun.

In afternoon sun I got about 24W (13.3V at 1.8A) from the 2 in series which is less than I expected for the conditions, but maybe it was a bad connection (I was using alligator clips to temporarily connect the wires). A 100W rigid panel in the same conditions was getting 75-80W.

Yeah the 2 female USB-A ports are regulated at 5V so I'd trust it as much as any other cheap phone charger. They don't have any fast charge protocols so you will be limited to 5W or 10W depending on if you device is willing to accept 1A or 2A without any fast charge protocol.

If you leave your phone or power bank you'd want them out of the sun. If you put it under the panel's shade make sure the panel is propped up to allow airflow underneath or your phone will bake.

So I finally got these panels yesterday and today I did some basic testing to see what the output looks like.

First of all, taking the cover off the back of the panel is a destructive process. The plastic cover is screwed to the PCB from the side that's facing the panel on two opposing corners, and the PCB itself is glued to the panel making those screws inaccessible. You could probably drill out the screws by going through the back of the cover, but I wasn't in the mood for making a replacement cover. I did manage to get the end cap off which is just a snap-in fit over the USB A ports and I was able to see that each USB A output is fed by individual buck converters (2x inductor + 2x unidentified 8 pin chip). So they're not just linear regulators at least, which is nice, and the dedicated buck converter for each port means you can sustain higher current when both ports are in use.

I then tested it with a variable load in full southern california sun at solar noon with the panel pointed straight at the sun, and found that each USB A port voltage starts falling below 5V when it pulls anything north of ~1A. It holds 4.8V pretty well up through 1.8A, and once you get up to 2A it drops to about 4.5V. I was able to push it up to just north of 4A before the voltage fell off a cliff, but at 4A the voltage had dropped to very close to 4V. Long story short, any device plugged into the USB A port is unlikely to ever pull much more than 1.5A just due to the voltage drop, even at peak solar output.

That's not the whole story through, because I repeated the load test with a power bank charging from the other USB A port. The power bank was only pulling about 1.25A at 4.95V, but it kept pulling that amount even as the other port approached 4A. Even better, it maintained 4.95V until the load from the other port completely swamped the panel's output, at which point both ports dropped to < 2V of output. The peak output I saw is very close to if not slightly over the 20W peak output claimed for this panel. Unfortunately, due to the way USB charging works (e.g. devices tend to pull as much as they can until the voltage drops to around 4.8-4.9V), it's very unlikely that you'll hit 20W even with 2 devices charging in full midday sun. The buck inverters just aren't up to the task for 2A of output while maintaining 5V, but that's not the panel's fault...with a proper regulator connected to the unregulated micro USB ports I'd imagine 20W is pretty doable.