Quote:
Originally Posted by Roy Hinkley
The specs on the EB-600, which, I have read that Kobo is based upon, shows battery information:
Battery: Li-Ion 3.7V, 1000 mAh, 8000 screen refresh.
Battery Charge Time: AC Adapter 4 hours, USB cable 6 hours.
I am guessing that they measured a page turn (blank the page, fetch the new page and redraw) would consue 0.125 mA.
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I think you mean 0.125 mAh, for 1/8000 of the battery's charge. But I think it's easier to think of the charged battery having 1hr x 1A x 3.7v = 3.7 WHrs of energy available from a full charge. So each page turn requires .4625 mWHrs of energy. In theory.
I find a specification for a Li-Ion battery of similar capacity, that says initial charging current should be simply be the current value of the capacity.
http://www.batteryspace.com/ProductI...-E%28A1%29.pdf
I find another recommendation that Li-Ion batteries should be charged initially at 0.7 x current value of the capacity.
http://www.electronics-lab.com/artic...n_reconstruct/
In the first case that would be 1000 mA; in the second, 700 mA. Both of these would be more than the 500 mA USB port spec. Hmm. The Kobo isn't the only peripheral to charge a Li-Ion battery from a USB port. Is the charging circuitry dumber, i.e. by asking for too much current is it pulling down the voltage? (Li-Ion batteries should be charged, generally speaking, at a constant voltage -- see the second link above for more info.) If so, this might support the notion that charging performance could be degraded depending on the current available at the USB port, which would depend on manufacturer/design. And, therefore, a wall charger or whatever with more available current would provide a fuller charge.
If not, i.e. if you provided less than those desired maximum currents and the voltage stayed where it should be, the battery would still charge fully -- it would just take longer. Which doesn't seem to be an issue here, because lots of us seem to be getting poor performance even when we leave the Kobo plugged in for hours.
I don't have access to any of the required bits and pieces at the moment, but this would be pretty easy to measure -- voltage at and current from the port when charging a fully-discharged Kobo (in a computer/Kobo configuration where the Kobo's battery isn't performing up to spec).
(Sorry to muddy the water, but now I'm confused.)