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 (76.17 USD): BGRCParts8
Coupon (76.17 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): 502C6B, TTxBG10, BGss9%rc, bgssaff9, AFfbG10, affbg10, BGDJIB15, BGBFAFF2019, BGCITYADS2019, BGVDay10%off, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGSS10%SW, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, BGCuponation10, BGDAVIS, BGHONEY2110, Parts8, BGquadpart, BG1efeb0
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for 4500mAh 15.2V 4S RC Battery For DJI Phantom 3 is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).