How to make a battery charger?

So I was just wondering, what basic guid lines do you have to follow when making a battery charger for say a lithium-ion battery? How many volts do I need to supply to it? Do I need any protection diodes? How would I keep it from charging to fast, or trying to charge the charger?

Thanks!

Comments

[iceng]

Here is a simple circuit I found that you can build.
Since a mistake has explosive results be sure to place
a shield between you and this experiment.

I would recommend you read and understand this guide First.

A

[steveastrouk]

I wouldn't start out by charging Lion battery. Srcew it up, and it goes bang big-time.