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Battery measurements at power on, V2 Recorder
dreamlayers:
Recently I noticed that the LCD dimmed a lot when spinning up the hard drive and the initial battery reading at power-on was always flashing low. If I tried charging, the reported voltage would quickly exceed 4.2V and the charging current was low, as if the battery was almost fully charged. I knew it was possible the battery needed to be replaced, but before I did that I wanted to try some things.
First I discharged the battery. For a long time I was using it in the car, where typically the maximum discharge is paused state for the idle shutdown duration. I know everyone says that lithium ion batteries don't have memory, and maybe not believing them was unreasonable, but I wanted to try anyways. I left the Recorder on and stopped with backlight on, and then when the battery icon started flashing, with backlight off. By the end of the day it was still on. I wanted to leave it on until it shut off, but then I went into the battery debug screen and saw the voltage was under 2V, which is too low for lithium ion. It was my understanding that lithium ion batteries or devices using them had to have protection circuits to avoid this, and this may mean the V2/FM recorder has no such circuit. This is why I posted those warnings regarding overdischarge.
Then I started to charge via USB. This led to a few hours of charging at full current (external voltage in the battery debug screen approaching 7.0V, which I think is mislabelled and means 700mA input current). Then charging became annoyingly noisy. I noticed the reported voltage was around 4.2V and the current was dropping. I also noticed that it was dependent on orientation, and that squeezing the top rubber bumpers boosted it. That meant it was time to clean the battery contacts again.
After cleaning the battery contacts, power-on battery state was about 70% when fully charged. Also, there was no visible dimming of the LCD due to hard drive activity.
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