Input: 100 – 240V AC 50 / 60Hz, Output: 17.4V 4.5A DC, USB output: DC 5V 2A, for Xiaomi Mi Drone RC Quadcopter.
Just check coupons out (with price alert and history). What is the best price?
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Only one coupon available!
Link: Banggood product page
1. ($60.55): Parts8
coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): aff7off, TTxBG10, bgssaff9, AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019, 0e7f33, BGMPB2020, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGSS10%SW, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, 7d18f7, BGCuponation10, BGDAVIS, BGHONEY2110, BGquadpart
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Drone Battery Fast Charger. The lowest price was: $34.69.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).