Battery current Continuous discharge current 10A, Battery Material Li-ion Lithium Ion Battery, Battery name 21700 cylindrical lithium ion battery, Battery features Large discharge current and high capacity., Nominal capacity 5000mAh, Battery internal resistance Within 25mΩ, Battery voltage 3.6V, Battery weight 70g, Battery specifications 21*70mm, Battery model INR21700-50E.
Basically copy coupon, view price history or create e-mail price alert. You probably want to know what is the 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. ($19.32): BGtorch9
2. ($19.32): BG8Alerabat
apply it in your 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): BGSSLG, MSAMSUNGLG, bGhOnEy10, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10, BGFLS15, 4BLF, BGAFF10OFF, BGCuponation10, BGHONEY2110, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BGFLBA, BANGGOODSD, BGTorch4, 00c906, BGtorch2, BGtorch3, BGAlerabatI
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Samsung INR21700-50E 3.7V 5000mAh 21700 Battery. The lowest price was: $11.18.
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)).