If you are like most people, you likely have a mixed pile of rechargeable batteries sitting around with no idea as to what kind of charge they can hold. You could watch a voltmeter for a few hours while you drain each and every battery, noting when it drops below its stated voltage – but then again, you have a life. Instead of wasting away in front of his multimeter, [BrianH] decided he would build an automated battery capacity tester to do the job for him.
He created a simple circuit that drains any AA battery, NiMh or NiCd, and records its useful capacity in milliamp hours. Since the ATMega168 microcontroller used has 6 analog/digital converters on board, he figured that he might as well design his tester to measure the capacity of three batteries simultaneously. [BrianH] wired the meter up to an old Nokia LCD, then moved his project to a perfboarded ATMega, freeing up his Arduino for other tasks. Once he had things reassembled, he packed it all into a handsome wooden box.
His writeup is chock full of details and source code, so be sure to check it out. We have video of the charger in action after the jump.
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