What voltage do I charge 3.7v Lithium-ion battery

Hello, I am wondering what voltage I should charge a 3.7v lithium-ion battery? Should it be 5v or does it not matter.

Is it a lithium ion (like an 18650) or lithium polymer (like an R/C car battery)?

This will dictate what kind of charger you need. You can't just connect both sides to USB and expect the battery not to explode.

Do some research about charging. Very often current control is needed as well as voltage control.
Just banging a voltage to the cells will kill them for good.

@IceChes, it's a 503035 lithium-ion battery / https://www.amazon.com/gp/product/B091FKGW8H/ref=ox_sc_saved_title_2?smid=A12BVTDSL0IKI0&psc=1

Get a 1S LiPo charger.

EDIT - The ones that plug into USB should work fine. There's circuitry onboard to charge the battery properly.

Something like this, check current capabilities.

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OK, thanks!

You cannot charge it with a voltage above 4.2 volts. You also have to limit the current to 800ma. You can go slightly higher in current if you have a dedicated protection circuit.

You might find 3.7v charger boards on eBay.