01-08-2013, 11:23 PM | #46 |
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I think you have to perform the occasional deep discharge for the battery metering to properly determine the remaining power capacity of the battery. The normal method is to account for power usage levels and uptime and build up a total current or watts available profile and then subtract during discharge. You can get fancier, but it's probably not worth the work.
The occasional deep discharge to shutdown should only help to recalibrate the profile. The shutdown should occur prior to any internal low voltage shutdown circuitry in the battery kicking in as long as Kobo left the proper wiggle room. As to how the chapter size might effect current draw during sleep mode, what if the RAM being used is segmented and can be independently powered down if not being used? Buffer a small amount of text in memory and you have minimal current draw during sleep mode. STUPIDLY buffer multiple chapters and keep a lot of dynamic RAM refreshing and kiss your battery life goodbye. It's just a theory from a hardware dinosaur, but it might be relevant... OTOH, if you're trying to get maximum battery life out of a device like these, and the processor is fast enough, why even bother to buffer text in between page turns? Just preserve a few pointers and grab the text and render on the fly. It would seem like the lowest power consumption based method? Last edited by TechniSol; 01-08-2013 at 11:36 PM. |
01-09-2013, 12:56 AM | #47 | |
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One small nitpick, you mention watts available when speaking about battery life. Watts are the rate of energy usage, and what you actually want to know is watt-hours, the energy left in the battery, I think. |
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01-09-2013, 08:23 AM | #48 | ||
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01-09-2013, 05:52 PM | #49 | |
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It doesn't matter how the discharge happens. The bad epub will just have drained the battery quicker which is handy when doing the calibration. |
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01-09-2013, 10:40 PM | #50 |
GranPohbah-Fezzes r cool!
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Jusmee,
You're correct, it was a nitpick... Bwah, ha, ha... Basically, since regulated voltage would remain the same, you're really accounting for how many milliamps or Amps were consumed while the processor had uptime which could be expressed as Amp-hours, but more likely as millisecond or microsecond counts of varying power rates being consumed. If you multiplied that by voltage, you'd get watt/hrs or an equivalence for power, if you'd like. Since regulated voltage should remain constant, it's probably sufficient to just account for uptime for each power state in a variable and multiply each of those by the respective amperage draw for that operation mode on a per uptime basis and subtract that from the total estimated capacity when first starting the device. Later as the battery was cycled you'd re-evaluate that total estimated capacity and replace it with measured capacity based on the method espoused above. If all they're doing is putting an A/D converter on the raw battery voltage and estimating remaining charge from raw voltage under varying load, they'd better have a battery curve available to increase linearity if they want any kind of reasonable accuracy at all. The methods where you estimate load based on what's active or actually measure current draw are considerably more accurate. OTOH, it's an ereader, not a life safety device... |
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01-09-2013, 10:48 PM | #51 |
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No, not watts/hr, it's watt-hours, same as how you buy electricity - only then it's kilowatt-hours. Constant voltage allows you to quote amp-hours (or ma-hrs for most batteries).
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01-10-2013, 12:22 AM | #52 | |
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01-10-2013, 03:30 AM | #53 | |
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Yes it is!!
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01-10-2013, 04:03 AM | #54 |
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When you are just reading, does the battery % update ? It never seems to move when I am reading. I am hoping its because the battery is far superior to the Kindle, as that's what I want the most. But I am also concerned that I will be happily reading away with 38% battery and then it goes off on me at a bad time..
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01-10-2013, 08:45 AM | #55 | |
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Update. Just got home from work, 6 hours after device showed full charge and was put immediately to sleep. Pic shows where now. Just sent an email to support. Last edited by VelvetElvis; 01-10-2013 at 03:04 PM. Reason: Update |
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01-10-2013, 07:09 PM | #56 |
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I recently found out I can drain my battery in a few hours if I have WiFi on, so I only switch it on when I'm synchronising/downloading books when using the computer is not an option. Saying that, the battery usually jumps level usually jumps up a few tens of a percent when I switch the WiFi off, so the battery indicator probably isn't accurate under high usage.
Aside from that, the battery seems near infinite, and I'm really picky when it comes to advertised specs not being fulfilled. At the moment I'm reading The Idiot, a long piece of Russian literature that, if it were a hardcopy, could be used to bludgeon someone to death. I'm around half way through the book and approximately half of my reading time has been with the light on (lowest setting). The reader was charged before I started and now the battery is at 94%, so it's holding up well. With my font settings, that equates to 600 page turns, or about 10,000 turns if the battery indicator is accurate. That's stunning, considering the light has been on for a fair amount of those turns. It definitely took a couple of charge cycles for it to start performing like that - the first week I had to charge it way too often, but I was only putting the reader to sleep, so perhaps that was the issue. Now I turn it off completely, turning it on only once a day for a couple of hours of reading. |
01-11-2013, 04:03 AM | #57 |
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Thanks for the detailed report ib4l!
It's beginning to sound like the Glo uses a lot more power in sleep mode than the Touch does, also considering VelvetElvis' post above. Hmm. Or maybe it's the firmware version? |
01-11-2013, 04:28 AM | #58 |
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Okay, so, the cycle I was testing is now over. During reading, the battery didn't seem to drop at all. The battery was up around 95% for a while, then dropped to 54% and then to around 47% where it stayed for quite a while... and then dropped to 0% over night.
Averaged the battery dropped about 0.87% each hour which included mostly sleep mode and three reading sessions of about 45 minutes, and one batch of loading & reloading a book with processing and restarts. Overall that means the battery lasts 116 hours, or 5 days. And that's being generous because I don't actually know how far into the night the battery lost its charge. That's just crap. Details in the spoiler for who's interested. Spoiler:
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01-11-2013, 07:16 AM | #59 |
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So, testing the charing...
It went from 0% to 50% in an hour (or less, I didn't check until an hour after starting the charge). Then it stayed at 50% for two (!!) hours... I suspected the battery meter wasn't updating. So I unplugged the cable, reconnected it, and the battery percent changed to 96%... and instead of showing the "plug" icon in the battery, it's now showing the "check mark"... so it stopped charging at 96% (I now vaguely recall it won't charge unless it's under 95%). So what's up with that? Three hours in the charger, didn't update the meter and it didn't get further than 96%?? (Using the 2.5 hours charge as 'normal'.) I unplugged the Glo and synced it to try and get the battery below 95% so it might charge... once the sync had completed, the battery read 98%! I would have guessed a bad battery would charge extremely quickly... is my guess wrong? Could a bad battery also take forever and/or not get to its maximum charge? (Hmm that also sounds reasonable...) Last edited by Mrs_Often; 01-11-2013 at 07:24 AM. |
01-11-2013, 04:39 PM | #60 | |
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