It's clear that this solar panel is just for a tiny top up, if it's really a proper solar recharge you're after you need the models with the fold out solar panels where you have several panels so you attach these panels to your backpack

Indeed, you should not count on recharging your Powerbank with the integrated solar panels, they only provide 400 mA. The total capacity being 24'000 mAh, it would represent 60h (and still in optimal sunlight conditions). On the other hand, 24'000 mAh is just enormous! And the Bank holds the charge well on the long term, so in that sense it's enough for me to easily charge 2 smartphones for a few days if I leave with it fully charged... in that sense the solar panels just allow to extend its autonomy a bit, but not to charge it! For that, you would need folding solar panels offering a much higher capacity, but that too has its price! As for its weight, it's true that it's heavy but I don't think it's because of the solar panels, but because of its protective and waterproof shell... and of course the internal batteries themselves!