Lithium-Ion Battery Charging

Hello

A question about Batteries. I have 3; LI-ion 3.7V 700mAh batteries I need to know how to charge them with just the UNO, if at all possible. Or do I need to buy one of, such as Adafruits battery chargers?

Share your Knowledge please!
Thanks!

You need a charge control chip, or module. They monitor/control the current & voltage & all kinds of stuff that the Uno hardware is not set up to do.

Okay ill look into that! Can you recommend one? In the mean time ill do some research. I would like to charge all 3 batteries at once so idk if thats possible too with a module.

are these 3 batteries in series or parallel? or isolated?