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Old February 9th, 2012, 12:15 AM   #147 (permalink)
Mr. Ed
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QFT...voltage would definitely be something controlled by the kernel

Originally Posted by erict206 View Post
I have had my SR for 2 weeks and the stuck battery meter has been an irritation, minor compared to many others I'm finding as I transition from Blackberry.

However, this has been a fascinating thread and the level of detail and gathering of empirical evidence is impressive. While not an electrical engineer, I have done quite a bit of electrical work on my boat and learned a few things that may be pertinent.

First, the cable could be significant. There is a noticeable and material voltage drop that occurs through wire. The amount of loss is a function of wire length and gauge. A difference in wire length of a couple feet does make a difference. Longer cable/smaller wire means more voltage drop. Perhaps the component that regulates battery charging (whether in the battery or in the SR itself) is very sensitive to voltage and this somehow throws off charging.

I'll shoot down my own observation though. The problem doesn't seem to be charging the battery but rather measuring battery capacity.

Second, battery capacity is calculated based on voltage and temperature. Battery voltage drops as the battery is used. Also, battery capacity drops as temperature drops.

It would be interesting if someone plotted the battery temperature and voltage of the battery both when capacity is reported correctly and when it's stuck.

Perhaps there's a defective battery temperature sensor or voltage meter that causes the capacity to be falsely calculated.

While possible, it seems unlikely that there's a defect in the hardware (temperature and/or voltage sensor). So most likely this is a software issue. Mr. Ed's kernel experiments support this. Whatever is supposed to trigger a new reading of the temperature and voltage is failing.
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