Solar Slang

Solar Backpack chargers vary in price quite dramatically. I’ve seen $200 backpacks, and $99 ones. (all are low quality from China) Sometimes power goes out in my area all day. So I want a reliable one. So far I’ve got an expensive usb solar charger; which doesn’t come close to even charging. The techs say “I need more intense light” it’s winter blah blah blah” I’d really appreciate your opinion. Thanks