Max. continuous discharge current: 30A, Nominal capacity: 4000 mAh, Nominal voltage: 3.6 V, Discharge end voltage: 2.5 V, Charging voltage: 4.20 +/- 0.05 V, Standard charging current: 1.5 A.
Price history, coupons and price alert are available on this page. You probably want to know 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. We have found one coupon for this product!
Link: Banggood product page
1. ($11.87): BG10OFFAFF1
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): BGQBJ, linepayflt, BCNLXK, BGBFCR41, BgcLuBofErtA10, BGFLS15, BGAFF10OFF, BGTORCH, 4BLF, BGHONEY2110, BG10OFFAFF, BGwhielabel
(probably won’t work, but you can try them out)
Price history and price alert
Do you need price history chart (for all/most countries) for 1x Basen 21700 30A 4000mah Battery? There we go. The lowest price was: $6.44.
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)).