Quote:
Originally Posted by NullNix
No device with a lithium-ion battery has a state in which the battery does not slowly drain when it is not used, both from self-discharge and because the battery circuit is required by contract to always be powered or they won't license you the patents to let you build one.
But more generally... modern machines' power architecture is far more complex than you seem to think. They have a wide variety of power states in which different components on the motherboard are at different power levels: the machine typically knows the levels available, the clock frequency (if applicable) each level implies and any appropriate dividers, the amount of power they save, the dependency graph between the various power-variable components (so you don't turn something off that something else that hasn't been turned off needs to have powered on) and the state transition cost (both in power and time). There is no single 'sleep mode'. There is a ferociously complicated and endlessly oscillating mesh of changing power states. With appropriate debugging tools, it can be hypnotic to watch the state transitions, particularly if some components are being reawoken on overlapping but distinct regular schedules: you get moire patterns and everything.
It is likely that significant parts of the system are unpowered even when you think the thing is in use (the most obvious part being much of the e-ink display). It is also likely that significant parts are powered even when you think it is "turned off". You can't tell just by looking at it, and you certainly can't tell by looking at the incredibly unreliable meter which is battery percentage (a proxy for battery voltage). The operating system on an embedded platform like this one will have a good idea, but it might not be too willing to tell you. (On larger systems, even the operating system is probably too far up the stack to tell just what power state various parts of the system are in.)
The question is not "is it turned completely off?". The question is "*which components* are powered down?". Unfortunately the RAM is one of the most power-hungry non-solid-state classes of components out there, and also one of the hardest to turn off or even turn down. I vaguely wonder if sleep mode saves some power here by shuffling everything into one RAM bank and turning off the other one to save power, but given the degree of change this would require to the Linux kernel, I really, really doubt it ("ferociously hard" doesn't even *begin* to describe it). It just seems like it would be a nice thing to do (but they're almost certainly not doing it).
(If the Sony isn't running Linux, it's possible it was running an embedded OS that allowed faster boot and/or possibly a RAM compacting scheme that allowed it to shuffle literally *everything* out of much of the RAM and shut it down. But I have even less idea if that might be true.)
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Even if the battery is not 100% turned off, it lasts a lot longer then a Reader in sleep.
Sony used Linux before moving to Android for the T series. Sony had a feature where if you didn't use it for 3-days, it would shut off and preserve the battery. It worked very well.
Amazon's way of doing it is to not allow shitdown so the battery doesn't last as long and they can sell more Kindles when people need to buy a new one since the one they are using no longer keeps a charge well enough much sooner then it should. So if you buya Kindle for a backup, you have to remember to keep charging it and eventually, you can kill off the battery before you get to use it. It's a very poor way to sell more Kindles. It's a scam (IMHO).