Reddit reviews TOOGOO(R) Solar Panel Fold Bag USB Junction Box DIY Special For Charger 5V 2A Plastic Case Black
We found 1 Reddit comments about TOOGOO(R) Solar Panel Fold Bag USB Junction Box DIY Special For Charger 5V 2A Plastic Case Black. Here are the top ones, ranked by their Reddit score.
I've built quite a few of these kind of USB solar chargers. You're right - most of the solar phone chargers you can buy are next to useless.
Those plug-in usb car adapters generally have terrible efficiency. You'd be better off with one of these 12V DC USB converters: https://www.amazon.com/Agile-Shop-Converter-Module-convert-Adapter/dp/B01N4H5PNO/ref=sr_1_6
Or if you're handy with a soldering iron you could just attach one of these USB junction boxes: https://www.amazon.com/TOOGOO-Junction-Special-Charger-Plastic/dp/B074RCHKY3/ref=sr_1_1
Both of these would work with an input voltage as low as 8V, so you're not limited to a 12V solar panel.