Strange Fluctuations - Leading to Premature Termination

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Mark
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Joined: Sun Jul 28, 2013 6:47 am
Location: Brisbane, Australia

Strange Fluctuations - Leading to Premature Termination

Post by Mark » Sat Aug 24, 2013 5:14 am

While doing some testing with both chargers, I've noticed some unexpected fluctuations in current and cell voltage:

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With a bit of investigative work, I've decided that this is actually caused by the fact that I have both chargers plugged into the same USB hub. When one charger pauses to read the voltage, the voltage supplied by the USB hub rises slightly. This then leads to an increase in current on the other charger. The code detects the increased current and reduces the PWM value to compensate but by then the other charger has started charging again causing the voltage to drop and the current to end up below the target.

Even though I've got the code checking the voltage during a brief pause, these fluctuations are enough to still cause variations in the voltage with the current off and can lead to early termination on some cells at least.

This probably won't affect most of you until you get a second charger and start using them together.

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