Rafael Larios combined his car battery troubles with the willing to try Arduino family of microcontrollers to one neat and small battery tester:
" Last winter I experienced some problems with my car battery. I knew that it was about time to replace it so off I went to buy a new one. This fact reminded me of an old article about a car battery/charging system diagnostics kit I had seen in one of those 1980s electronics magazines.
That magazine 19s battery monitor relied on an IC that had several analog comparators arranged in a way similar to the ones in the old LM3914. This made me think about designing a more up to date battery monitor with today's microcontrollers in mind which could use a low LED/resistor count and a reduced PCB size and possibly fit inside an empty 1oz Tic-Tac box.
I had originally envisioned building this battery monitor around Microchip's PIC12F675. However, after reading several instructables on microcontrollers I realized that everybody seemed to prefer Arduino. I concluded that it was about time to get my feet wet in this family of microcontrollers."