Tuesday, June 4, 2013

Build Your Own Lithium-Ion Power Pack To Charge USB Devices

USB Power packs are a handy way to charge your mobile phones, tablets and other gadgets. They work especially well for camping, emergencies and even around the house where it isn't convenient to plug in a wall charger.

The problem I have with most of the power packs on the market is that their expensive, low capacity and the batteries inside them cannot be replaced, making these devices basically disposable. Some of the better packs have 18650 Lithium-ion batteries inside, but they tend to use cheaper cells and fewer of them.

I set out to build a decent USB power pack which took 18650 batteries, and I quickly found this model. It definitely gets mixed reviews, but it was cheap and had the features I wanted, so I gave one a try. I'm glad I did, because this is a great little device.

18650 Lithium-ion Based Battery Pack, Front View

18650 Lithium-ion Based Battery Pack, Charge Indicator

18650 Lithium-ion Based Battery Pack, Charge Indicator Button And Lights
18650 Lithium-ion Based Battery Pack, Top View

Getting Started

This unit takes 4 18650 batteries. I'm not sure if it takes protected cells, but it doesn't need them,
18650 Lithium-ion Based Battery Pack, Empty
18650 Lithium-ion Based Battery Pack, With Harvested Sony Cells
Shown with harvested Sony cells
as it has its own protection circuit. I put 4 green Sony batteries in mine, which I harvested from a new-ish laptop battery. They went in hot off the charger.

When the batteries are replaced in the unit, there's a little button on the circuit board you have to press in order to activate the protection circuit. Once the reset button is pressed, you can install the cover back on the unit.

Warning: Lithium-ion batteries can be dangerous if not handled properly. Before you start, why not drop by the Battery University, which is the best resource on the web.

Testing The Unit

To test my unit, I used a spliced USB cable that I made from ... splicing a USB cable. I like to test these sorts of power packs first because it's usually going to have something expensive plugged into it. There's no way I'm going to fry my wife's new Android phone.
18650 Lithium-ion Based Battery Pack, Tested With Multimeter
I used a spliced cable to test

Charging The Power Pack

To charge the power pack requires a mini USB cable. Then it can be charged from any USB 5V
power source. When it's plugged in, the little green light next to the mini USB port will turn on, indicating that the unit is charging.

On the side of the unit is a little button with three multi-colored lights next to it, which I assume is some sort of charge indicator. It looks like it was meant to light up a 60's style disco ball, but I guess as long as it is accurate, then it doesn't matter what color the LEDs are.

18650 Lithium-ion Based Battery Pack, Charging From Laptop

Note About Devices

This unit can charge most devices that can plug into a standard USB port. But because this particular unit does not do anything with the data pins, some devices like my ZTE Engage phone will not charge from it. The power pack only uses the + and - power pins on the USB cable.

Confirmed Devices:

-- HTC One
-- Samsung Galaxy S3
-- Kindle Fire (1st gen)

Charging Your Devices

To charge your device, just plug it into the main USB port and turn the red rocker switch to the ON position. The large LED light in the center will then light up, letting you know the unit has power. At this point, anything that can be charged with this unit should start charging.

NOTE: My wife hates the center large LED because it lights up the bedroom when she's charging something. There are a number of things you can do. Just snip the pin if you don't care about it, and it will have the upside of giving you a little extra juice for whatever you are charging, but the down side is you won't have that cool flashlight in an emergency. So, for my wife's power pack, I just used a square of electrical tape and covered the LED. If it ever needs to be an emergency candle, we can just take the tape off.

18650 Lithium-ion Based Battery Pack, Charging Bluetooth Headphones
Charging my Bluetooth headphones

18650 Lithium-ion Based Battery Pack, Charging HTC One
Charging the wife's HTC One

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