Output Current 0.5A/1A, Compatible with LiFePO4 / 3.7V/3.85V Li-ion / Ni-MH / Ni-Cd, USB port output 5V/1A, Input Power Micro USB DC 5V/2A, Output Voltage 4.35V/4.2V/3.65V/1.48V ±1%, Size 115mm×63.5mm×29mm (Length/Width/ Height).
Price history, coupons and price alert are available on this page. What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($18.65): FIN9777
2. ($19.85): BGAlerabatI
3. ($19.99): BG0b49b5
4. ($20.30): BGtorch2
coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGAlerabat15, BGtorch7
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for KLARUS K2 Battery Charger is here. The lowest price was: $18.65.
Price records source(s): 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)).