Quote:
Originally Posted by StamosD
My Sony PRS-T1 went into the Empty > Charge > Short Battery Life then the Empty > Charge > No Battery Life Mode....
...etc
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I did not know how to respond to this before, having been unsure of your now disclosed electronics background. But now I know I will pass on my general observations re the T1 USB/Charging side in case they add anything to your thoughts:
First, the T1 is the first USB charged device I have bought that did not come with an AC charger in the pack so their expectation is, as you have said (which for reasons I don't understand has raised the ire of one poster?), that users will generally use their PC USB port as the downstream charging port. Unfortunately the T1 Service Manual gives no detail as to the devices used in the T1 (and I have never dismantled one :-)) but I assume an integrated USB transceiver/charger is used or those in separate packages in which case the T1 likely complies with the USB Implementers' Forum's Battery Charging Specification.
As far as I know, Sony were not a contributer to that specification but Nokia were, and implemented much (or all?) of it for a number of years before it was finalised (I think their first USB charged phone came out in 2007?). I have used Nokia USB charged devices for some years and the T1's charging behaviour is very similar to theirs. Some users of earlier Nokia phones, anecdotally, had similar problems as to those being mentioned by some T1 users, and seemed mainly to be related to the Weak Battery Algorithm failing into a Not Ready to Connect loop, or similar glitch in the T1's charging intelligence and finding some way to force a way out of that. Your soft boot on charge solution seems to maybe point in a similar direction for the T1 as a means to force these sorts of issues.
Regarding chargers --- it seems from anecdotal evidence, that if a dedicated charging port is used for the T1 then D+ and D- need to be shorted at that port. All my dedicated chargers comply with the USB Implementers' Forum's specification so I have not been able to test this with a non complying one without them shorted, but while it is difficult to make assumptions about the T1's charging from unsophisticated forum users's anecdotal (and often plainly incorrect) comments, this does seems to be a pretty much demonstrated requirement and so also points to the T1's compliance with the specification.
Like most device manufacturers for a dedicated charging port Sony only recommend their own AC charger - unfortunately I have never found any detailed specifications for the Sony charger but expect it does not enumerate the downstream device (the T1) as it seems D+ and D- are definitely shorted in the charger (200 ohm max being allowed in Specification complying chargers) or in its captive cable's Micro-B plug as required by the Implementers' specification. In which case, assuming compliance with the Implementers' Spec., it will comply with that specification's load voltage and load current shutdown requirements and maximum D+D- leakage current. I would assume from that any charger used from the wild that does not comply within the Specification's max. D+D- leakage current requirement may fail as may any whose output falls into the "Charging Port Operation not Allowed" part of the voltage vs current graph in the Specification (charger operation not allowed if voltage falls below 4.75v for I=<0.5A I believe).