Just a little update on this ongoing project.
I am working on various spinoff charger solutions, from dead simple like this one to more elaborate.
This is a near finished prototype, some bodge wiring required to communicate with the arduino it will be supporting but can work as standalone as you see here. It looks great with the burgduino battery shield but i am having problem finding long enough stackable headers, any ideas for (prefferably cheap) sources?
It also works very well with the burgduino logic shield but that is a whole other story as i am reworking that aspect of the project all together with an atmega328 instead of atmega8, rotary encoder instead of keypad and oled instead of 1602 lcd.
The actual charger displayed here has 5V micro USB or 5-45V DC jack input, charges cells with 50-100-250-500-750 or 1000mA selected from the dip switch, of course has protection for the cells including NTC (optional, can be disabled) and the batteries are actually connected to the screw terminal so the interconnection is part of what i am working on improving really.. i think brass standoffs!
Then there are two boost converters, one fixed 5V1A to supply power to the arduino and a second adjustable from battery level 3-4.2V up to 12V/1Amax. The adjustable boost converted can be disabled or enabled by onboard switch but can also be controlled by the arduino (D7). It also drives battery voltage, charge current and adjustable boost converter output measurements to the arduino (A1-A2-A3),
Last but not least, this is the type of charger/ups which will happily charge the battery while supplying current to the arduino/external load (1A max combined) via power path implementation. It is also possible to connect any load to directly to the battery for example an external boost converter, in which case depending on battery quality/condition it can draw up to 2.5A but if charging at the moment, the batteries will support the output while discharging ....
If by chance anybody wants one of these prototypes to play with, i can sell 4-5pcs for 10$ each, also if someone wants to review the prototypes or use them in a project that will be made public, let me know... last, but not least this version uses TP/TC4056 as main charger IC, in future versions i plan to use a different charger and protection IC set allowing the same design and pcb to support either Li Ion / LiPo or LiFePO4 batteries...