40$ per piece or for both?
2$ battery is with a high chance junk.
V10 is definitely junk and not made for eswitches
You need a driver for a momentary switch. There are lot of customs programmed drivers available, nanjg, nanjg with stacked chips or like above suggested aFET driver….
If you need cheap batteries and don’t need them quick check this thread:Suspiciously cheap Samsung 4.35v 3200mah from DX. (SOLD OUT) UPDATE : RECEIVED REFUND FROM DX!
If you want quality and are able to pay 15$ per pair than you will have a wide variety of quality cells available.