Digital pins 0-7, Analog 2-5, and a RST, V+, and GND pin are broken out to two rows of pins, maintaining about half the pins in a familiar shape and organization. A JST connector for LiPo batteries like the ones available through SparkFun and Adafruit and an MCP73811/2 charger circuit makes the Demiduino well suited for portable applications. On the back, I’ve also included CR1225 clips for ~3v3 power from easy to find coin cell batteries, and a power switch to save battery life.
Demiduino, another tiny Arduino compatible board - [Link]
Paul Asselin has written a description of his design of a USB Lithium Polymer battery charger – [via]
I wanted to build a cheap USB LiPo charger and didn’t like the unavailability nor the price of the Maxim’s MAX1555. Searching for something better, I stumbled upon the Microchip MCP73831. It is still way too expensive in single quantities but there ain’t too many options.
The board is intentionally small and has a status LED. There really isn’t much more to it, it’s a single purpose device and just does the job. It is proudly Open Source Hardware.
This project is a tiny, lightweight LiPo battery voltage monitor/alarm system based on PIC microcontroller. [via]
This simple PIC project includes a simple A-to-D application that measures the voltage of a battery pack via a resistor divider network, compares it to a reference voltage (5v regulator) and then displays the battery voltage on 2 LEDs (indicating battery voltage strength).
Simple-Volt: LiPo Monitor System – [Link]
In this youtube video watch what happens when you overcharge a LiPo battery. As you understand a LiPo battery is extremely hazardous if mishandled. Please pay attention to the warnings for this type of battery!
LiPo Battery explosion - [Link]
This project describes how to build a portable solar charger tracker. It analyses the charging process. This unit connects with a small solar panel and a LiPo battery and keep track of solar panel voltage, battery voltage and current goes through the panel to battery charger. The design is intended for 6V panels and single cell LiPo batteries but can be adapted for any kind of panel and charger. Device is powered from batteries and uses Arduino Duemilanove. [via]
Portable solar charging tracker - [Link]
Alex at Tinkerlog writes:
For my latest projects I used a lot of single cell LiPo batteries. They are really nice. High power density, low self-discharge, no memory effect and they can deliver quite an amount of current. But LiPo battery handling is a bit more complicated than other rechargeable batteries. You have to take care of under voltage and over charging as that may destroy the battery.
I used the Sparkfun LiPoly charger, based on MAX1555, for some time and it works really well. The only thing I missed was a way to control the current. After some research I decided to try another chip, the Microchip MCP73833. [via]
LiPoly charging with MCP73833 - [Link]
Fast charger for NiCd, NiMh, LiPo and SLA batteries
The Universal Charger usage is very easy but some point must be strictly followed in order to avoid any problem in battery and charger management. First read the charger documentation, then follow these recommendations in order to have a good charger usage.
Universal Charger – [Link]
The LiPo calibrator built is a very simple circuit based on the LM317, one resistor and one trimmer that can give a voltage from 4 to 4.5V. The trimmering range (around the point of start) should be minimezed in order to have a very good and easy adjustement with a standard multiturn trimmer. If the user has a very precise and stable power supply or another adjustable power supply (capable to be trimmered at 4.200V) it can be used to calibrate the LiPo balancer element.
LiPo element calibrator – [Link]
The LiPo balancer cell acts like a big and very accurate zener diode; when the cell voltage is under a threshold fixed by the user the system is in “idle state” and watch only for the voltage with a equivalent resistance of some KOhm and a negligible current shunt. When the voltage reaches the threshold the balancer element will start to shunt current from the cell with an internal power resistor. [via]
LiPo Balancer – [Link]
In this project there are actually 3 chargers combined in a single PCB, each charger having an output voltage of 4.2V. You can cascade them to become charger fit for 2 or 3 cels Lipo pack. The transformer used is 3 x 8 VAC. As more and more devices are powered with LiPo batteries such a charger could come handy some day.
DIY LiPo Charger - [Link]