You can create price alert here, copy coupons and view price history. Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Voltage(V): 3.7V, Max. Discharge Current: 10A, 2900mAh
Price history and price alert
Price history (for all/most countries) for 4x Sony US18650NC1 2900mAh Battery is here.
Price records source(s): Gearbest
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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)).