Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (14.87 USD): BGGAL8
Coupon (14.87 USD): BGRCParts8
Coupon (14.87 USD): MVC8SPRING
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): Charger12, Parts8, AFfbG10, BG10BC, BGMPB2020, BGAFF10OFF, bGhOnEy10, BGBC1, BGdragonBoat, BGRCBC7, BGSS10%SW, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, BGCuponation10, BGBCSpring1, 13f142, BGHONEY2110, BGRCBC11, BGSFBC1, BG1efeb0
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Check out price history chart (for all/most countries) for 2S-6S Parallel Charging Board for iMAX B6 B6AC B8.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).