Σάββατο, 10 Σεπτεμβρίου 2011

RECHARGEABLE BATTERY QUALITY MONITOR

       Using micro-controllers one can easily (!!!) make an intelligent rechargeable battery monitor in order to check if his NiMh or Nicads are in good condition. Let's take my favorite Arduino for example. It has 6 analog ports, so we can take a six battery holder, cut all inter-cell connections (they are connected in series), put a resistor in series with each cell (it we are keeping it simple - a current source would be much better) and measure and log the voltage as it drops through the resistor. We could also program some kind of Processing script to display the results graphically on the computer.
       Well, I used a different - and  faster approach. I used my intelligent 10-cell charger and my Sony TRV-22 DVR in photo mode and its simple intervalometer. TRV-22 can take photographs every 1, 5 or 10 minutes in memory stick (120 photos 640x480 resolution on 8MB memory stick)  I fully charged the batteries and then discharged them , photographing the charger's leds every 10 minutes. When a cell is being discharged a red led flashes slowly  and when discharging is over it lights steadily until full charge when it  finally becomes green. The fist discharged battery is the weakest and the last one has the maximum amount of energy. In the following time- lapse video you can see that batteries 8 and 9 are the first to begin charging (that means that are the first to discharge - the ones with the less energy) because their leds lite steadily first of all the others. Battery number 3 is the best because its charging begun 2h 45' after no's 8 and 9 (by examining the EXIF metadata in every pictures file).
      Night vision is enabled on TRV-22 because most of the process took place at night. Here is a video of the discharging sequence :  



The above procedure can also be accomplished with a web cam and a capture program with intervalometer function. There are a few free ones on the web. Timing error if 10 minute interval is used is +/- 10min. Following time lapse video shows charging sequence :






 
     

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