Aliexpress
Click here… to search for 2S-6S Parallel Charging Board for iMAX B6 B6AC B8 on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
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: apply it in your cart 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
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Here is price history (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).