POWER PAK
Table of Contents
This manual describes version 2 of the POWER PAK.
Features
Operation
The POWER PAK is designed for use with protected 18650 batteries that have the button top. While you can fit unprotected 18650 cells with some work, I didn't put any discharge protection on the PAK itself. It can safely charge any 4.2V lithium cell but it won't stop discharging an unprotected cell until it reaches somewhere less than 2V, well past the recommended cutoff of 3V.
The device can supply 1.5A (7.5W) and charge (briefly) at a max of 1A (5W). It gets hot. The chips have thermal cutoffs and won't cook themselves but don't put the circuit side next to anything that might melt at ~180°F.
You can charge it on the IN port at any time by connecting a power source. While the battery is charging, the yellow CHG light will turn on. When it's done charging the light will go out. Charging takes about 6 hours in my experience. You can calculate from this that the actual charge rate is somewhere less than 500mA and this is due to thermal limiting.
The OUT port and VOUT is turned on by flipping the power switch towards the outside of the device. The red PWR light turns on when the output is on. You can charge and discharge simultaneously but if the output is supplying full current the heat generated will limit charging significantly.
Headers
Three 0.1" pin headers are provided on the OUT side for hardware hacking.
VBATT is connected directly to the positive battery terminal. It can be used to monitor the battery voltage or connect an external battery in place of the 18650.
VOUT is connected to the 5V output. It's useful for powering hobby 5V devices like an Arduino.
GND is connected to circuit ground and the ground lines of any connected USB devices.