$6.99 – Working voltage: 5V, Working current: 0-400mA, Process: EVA lamination, Output power: 2W, Output port: USB, Product size: 157 * 94mm, Wafer: class A polysilicon, Conversion efficiency: 18.8%, USB cable length: 50cm.
When I was updating this page, then coupon price was $6.99 for 5V 400mA Solar Panel 2W (in Banggood). Go down and check coupons out. Remember to check price history if it is available. Best price?
Latest coupon and price update (UTC):
Banggood ($6.99)
Banggood warehouse is located in China. There is no active coupon in my database right now (for Banggood). Is it cheap? Good news! This is great price, coz it’s the lowest in CouponsFromChina database!
Link: Banggood product page
Price: $6.99
Additional Banggood coupons: first page and second page
This is the best price ever noted in my database!
Old coupons (from the oldest to the newest): BG589b2e
(these coupons are old, so probably won’t work)
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for 5V 400mA Solar Panel 2W is here. The lowest price was: $6.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).