katsumbhong
Offline
Taichung, Taiwan

How's it going folks. I have a general question about electricity that deals with usb and battery chargers.

I went ahead and purchased hardware to make a rechargeable DMG via Zaxxon's project thread below:
http://chipmusic.org/forums/topic/11045 … ed-update/

I purchased the charger with a usb tip and am planning to fit either a Female USB port or mini-port to the DMG case for charging via USB.

The charger itself is rated with the following output:
DC 4.2V
0.5A

A USB 2.0 port connection on a computer provides the following:
DC 5.0V
0.5A (up to)
5A (charging)

It looks like I will be able charge the Li-Ion battery via a USB port but what I am having a little difficulty understanding is when the 5 amps of current run through a USB cable.

Is it 5 amps of current when the USB is plugged specifically into a charging port which is plugged into a wall socket for charing a device at the other end and 0.5 amps of current when the USB is plugged into a computer regardless of what is plugged in at the other end?

jefftheworld
Offline
Toronto, Ontario, Canada

The amperage is mathematically linked to your resistance and voltage. In this case your voltage (4.2v or 5v) and your resistance (the internal resistance of the battery and charging circuitry) are fixed, so the amperage will be fixed as well. When you so those listings for 0.5 or 5A it's talking about the maximum amperage you can draw.

Your charge circuit allows up to 2A, so on the wall charger, which can give up to 5A, it'll charge quickly. On the pc port which can only give 0.5A, it will charge more slowly.


TL: DR; There's nothing to worry about.