Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. There is one coupon right now! Check this out.
Link: Banggood product page
Coupon (57.99 USD): BANGGOODSD
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): e2bcea, linepayflt, EYBG, eybg, BGTORCH, BGBFCR41, bGhOnEy10, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10, BGCLUBOFERTA10, BGFLS15, BGAFF10OFF, BGCuponation10, 4BLF, BGHONEY2110, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BGFLBA
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for 8x Panasonic NCR18650B 3400mAh Battery is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).