Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is no active coupon in my database right now (for Banggood).
Link: Banggood product page
Price: -3 USD
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): 502C6B, AFfbG10, affbg10, BGEachine, BGEachine11, BGCITYADS2019, BGEachine10, BGVDay10%off, BGMPB2020, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGSS10%SW, Eachine11, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, BG11EACHINE, BGEachine2021, BGCuponation10, BGHONEY2110
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for Eachine EX2mini 7.4V 850mAh RC Battery.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).