Originally I started out with the plan to make a 4 battery charger that could handle both AA and AAA NiMh batteries. It would include an LCD that displayed everything real time and it would all be packaged in a sweet metal case. My first prototype board design included an LCD and handled 4 batteries. However there were some mistakes (as there almost always are the first time you design something). So I ended up with only a partially functioning prototype that cost me over $100 (with no sweet metal case). I realized I could not keep this up for very long without making some changes. This is where the design you see pictured in all the post comes in. This two battery version was created as a way for me to test ideas, prove design concepts and perfect the software, at a lower cost each iteration than the larger 4 battery version. I never meant to sell it, just use it for development. However I have had many requests to make it available as well.
Here is my plan:
In two weeks I am going to post this two battery version on Kickstarter. I say two weeks because after getting input from several people I have decided to make one last design change. I am going to add an external ADC with a built in voltage reference in place of the 1.8V ref (and a few other parts) that I added previously. What does this mean? It means after I finish this last modification to my design I should get resolutions down to much less than a millivolt and my temperature plots will be nice and smooth. In general this will be a great performance increase but only a $2 increase to the parts cost (the ADC cost more than that but I am saving cost by dropping the 1.8V ref and a few other parts).
If all goes well on Kickstarter then I will make this design all open source and use any money raised for the development of my more feature rich 4 cell version.