Right now the best price with coupon code for 5V 12V Solar is 11.99 USD (in Banggood). Just check coupons out (with price alert and history). You probably want to know what is the best price?
Latest price update (UTC time):
Banggood (11.99 USD)
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood. Is it a low price? Well, this price is higher than average price (8.17 USD)
Link: Banggood product page
Price: 11.99 USD
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Aliexpress
Click here… to search for 5V 12V Solar Panel 5W on Aliexpress
Here are coupons that you can use.
Price history and price alert
Check out price history chart (for all/most countries) for 5V 12V Solar Panel 5W.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).