A lot of people base their purchase on product Reviews, however not all sites will accept a bad review and publish it.
SPAMCORP, for example, will contact you if you try to leave a bad review and try to fix things (they will not publish the review). This, the solution, may make you happy, however it does not help others who will continue to buy a product based on just the positive reviews.
Bangood, DX and others will allow you to publish a bad review, making their reviews a lot more useful for the buyer.
I bought 2 solar chargers/power banks and was less than happy with them, from
SPAMCORP (more later, but it was mainly with capacity and charging rates, and one was a lot better than the other).
Based on my experience I wrote a 2/3 star review and also contacted
SPAMCORP. They contacted me immediately regarding the Reviews and we came to an agreement (got a refund for the one with the major issues) that I was fine with.
As a sidenote, the English of the staff of these sites has greatly improved in the past few years- definitely a huge plus for all.
However, the reviews were never published.
NOTE: they react, I believe, based on the star rating, so a few people sneak in a bad review, by giving 4/5 star ratings
To compare, read the reviews for this product, which I believe is the same in various sites and compare what you get (star rating and comments)on
SPAMCORP with the rest (I selected some indicative pages):
SPAMCORPhttp://www.[url=http://forum.multitool.org/index.php/topic,55947.0.html]SPAMCORP.com/mobile-power-bank/pp_1045.html#customer_review[/url]
Bangood
http://www.[url=http://forum.multitool.org/index.php/topic,55947.0.html]SPAMCORP.com/30000mAh-Solar-Charger-Battery-Power-Bank-For-iPhone6-Smartphone-reviews-p919239.html?page=3[/url]
DX
http://www.dx.com/p/universal-portable-5v-30000mah-li-ion-battery-dual-usb-solar-powered-power-bank-w-led-indicator-279255#reviewsamazon
http://www.amazon.com/30000mah-Portable-Solar-Panel-Power/dp/B00HPC170I