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Wednesday, September 26th, 2007

Power Consumption of a Yepp MT6Z

Categories: [ Science ]


Thanks to Niko's help, I managed to measure the current drawn by the Yepp while playing an MP3. The trick was to use a voltage source set to 1.2 V, and then read the current from the power supply's display. The first method I tried, using a simple amperemeter, doesn't work, unless the meter is set to measure 10 A currents. According to Niko, this reduces the amperemeter's internal resistance and minimizes the voltage drop it provokes, allowing the Yepp to get enough power to boot, but it also reduced the precision of the measurement to 10 mA steps. Here are the measurements:

  • 60 mA with no headphones or volume set to 0.
  • Between 60 and 70 mA with 13 Ω impedance headphones and volume to maximum.
  • 20 mA when paused.
  • slightly over 100 mA with the LCD backlight on.

From these values, one can easily calculate that while running, the Yepp consumes about 72-84 mW, and only 24 mW while paused. Moreover, with a 2500 mAh NiMH battery, it should run 35 hours.

However, NiMH batteries have a high self-discharge rate of 5-10% the first day and 0.5-1% the following days, so my 2300 mAh battery used over approximately 6 weeks (charge it, store it charged for 3 weeks, then use it to replace the old battery and use it for 3 weeks) has an actual capacity equivalent to 1400 – 1800 mAh, which in turn should give about 20 – 25 hours or usage.

[ Posted on September 26th, 2007 at 23:40 | no comment | ]