Build #2 Progress, Dec 23, 2011 - 2900maH Rundown Test

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Ok, after fighting with Christmas lights that never seem to want to work, it's nice to play around with a light that actually does what it's supposed to. Here's the run-down curve for the new 2900mAH pack paired with the DS-500 running on high (level 5) in steady mode. This is the classic lithium-ion discharge curve, although you can see a few things that are specific to this particular application.
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Intially, the pack was fully charged at 12.57 volts. Upon turning on the light and drawing right at 1 amp out of the pack, you'll see about a 0.3V drop. This is totally normal and partially due to the internal resistance of the batteries themselves and to some degree the forward resistance of the battery's protection circuitry. Most interesting to me on this curve are the relative locations of the medium and low voltage warning indicators. This wasn't the first run-down test that I performed. In fact, this test was using new limits for the trip points. It appears that I was being a bit too conservative on my initial settings of 11.1 and 10.7 for the medium and low warning, respectively. So in this curve, the limits had been changed to 10.9 and 10.5. You can see from the small "pulse" in the middle of the plot that 10.9 is a pretty good indication of 50% life remaining. However, I may actually drop to 10.4 for the final 20% indication. The reason that these events even show up on the curve is that the taillight is using the main LEDs to flash out the battery status. When in steady mode, the "flash" is actually a momentary off, so you're seeing that 0.3V drop go away just for a moment. For the low warning region, since the time scale is so compressed, the 0.3V blip that occurs every 5 seconds looks like it's occurring continually.

Run times were right at what I expected. One thing to note is that even after the light cuts off at the highest power level, you can still turn the light back on at lower power levels (preferably level 1 or 2) and get a good 10 to 20 more minutes before it shuts off again at the lower power levels.
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