Touch Excessive Battery Use?

[Tinderbox (UK)]

Well the first link is the nook touch`s main page, so lots of people would have bought it under the impression you can get 2 months at a hour a day, like i did.

Also if you google you will find lots of reviews that state the hour a day as well.

http://www.engadget.com/2011/11/07/n...ands-on-video/

Originally Posted by afv011

That's a mistake on the first link. From the beginning, B&N has mentioned 2 months based on 1/2 hour of daily reading. Amazon changed their description on the kindle to read the same.

I have had 1.1 for a while and I don't experience any differences in battery life, for better or worse, compared to 1.0.1.

[afv011]

Originally Posted by Tinderbox (UK)

Well the first link is the nook touch`s main page, so lots of people would have bought it under the impression you can get 2 months at a hour a day, like i did.

Also if you google you will find lots of reviews that state the hour a day as well.

http://www.engadget.com/2011/11/07/n...ands-on-video/

I see your point. The info is clearly confusing.

In my personal experience, there are no significant improvements in battery life from 1.0.1 to 1.1, certainly not doubling it as indicated.

[RAH]

Originally Posted by geertm

The software needs to "learn" your battery. That is why you need to charge a few times before the software battery level is reliable.
...
When the Nook Touch was just released there were some Nooks with bad batteries that drained very fast. If you bought your Nook Touch when it was just released, it could be that you have a bad battery and need to replace your Nook Touch under the guarantee.

Yes, I had a very early Touch (bought it the first day it came out). But I returned it about 4 months ago and got a new replacement (I got lucky and it wasn't a refurb). The new one has the same problem.

I have charged it at least 4 times and it still hasn't learned. I always wait after recharging to see if is going to drain quickly (say about 12 hours). So far, I have to use my top-off routine to stop it from draining. That's the way it is.

[soondai]

Many thanks for the technique, RAH.

I too am now on my 2nd NST. My first one did the quick drain out of the gate. Thought I had a good one with my replacement, but found out different when I recharged it.

I'm surprised there isn't more out there on this issue. Doesn't seem like it can be that rare given that some of us have run into it multiple times.

As long as the "fix" continues to work, I'm going to follow your lead and not send out for another replacement. But I am not optimistic that it will get fixed with any future firmware updates.

[RAH]

Glad to be of help, soondai.

It's interesting to hear that I am not the only one who got 2 faulty Touches in a row. I agree that it must be more widespread than is indicated by online forums.

[betty77]

I have 2 more days before my 14 days are up. My first charge at 100% lasted last than a week. 2nd charge to 100% was done on 1/16 night and this morning it is at 89%. Is that normal discharge or should I exchange right away? I didn't even finish one novel on it.

[azazel1024]

Not normal unless you've used it a lot since the the night of 1/16.

Mine now seems to be "in line" with my expectations. I charged it the morning of 1/9 and I've probably been averaging 2hrs a day or reading roughly, since then. I just checked and I am at 69% battery life. Supposing it doesn't claim to need a recharge early, that seems to be on track for about a month of battery life at roughly 90-120 minutes of reading a day. I've pretty much plowed through all of a 720 page book (2nd smallest font size) in that time and I'll likely be able to manage another large book before I am getting down to around 20% charge when I plan to recharge it again (probably in about another 2 weeks).

That would be roughly 5 "average" size 300-400 or so page books on a charge which seems to be the "standard" for how long a charge should last.

So at least for me, not that I have throughly tested it, recharging it completly and then immediately rebooting it when I unplug it from the charge seems to work. Maybe there was simply some learning of the battery voltage by the nook that did it, but rebooting costs me little to do after each full charge, even if it is maybe the ebook version of blowing in to the NES cartridge and even if it isn't actually "fixing" anything, and that the nook "fixed" itself.

PS I must note as I am feeling embaressed about my slow reading, but these days with a not quite 4yr old and not quite 2yr old (4 in 2 weeks and 2 in 2 months) I get interupted a lot, so my roughly 2hrs a day of reading is including the entire time I am attempting to read, even if I am maybe only getting in 10 pages in a half hour because I have to keep putting it down to "address a situation". Other times I can plow through 20-30 pages in that time because I don't constantly get distracted.

PPS Despite my wife's suggestion that I return it, I haven't done it because I don't even have the gift recipte (though I doubt they'd stop me from doing a warranty exchange since I can't imagine they can't pull up the SN in their system to see when it was purchased), so I don't want to have to go through that rigamoral. On top of that, I have too much of a tinkerer mentality. I feel like, rightly or wrongly...usually wrongly ;D, that I should/can get something to work right if I give it awhile. I have a hard time admitting defeat.

[RAH]

Well, Betty, it sounds like your Nook is improving. As others have said, you should give them a few recharge cycles to learn the battery. But going down to 89% in a little more than 2 days is still somewhat too fast. It should lose about 2 to 3% per day. Even my problematic Nook, once I have topped it off, loses this 2 top 3% per day amount.

Hard to know what to advise, because it does seem to be improving. Before I top off my misbehaving Nook, it will drop to 89% over ONE night. So it almost sounds as though your Nook may be OK once you have it for awhile.

See what it is tomorrow. If it's down to like 79 or 80, I'd return it. If it's say 85, I think I'd keep it (I suppose it will be 83! )

[RAH]

Want to mention one other thing. From what I have read on this forum and other places, having your Nook Touch, with its e-ink screen, turned on or sleeping is much the same thing. What causes the significant battery usage is PAGE TURNS and other screen-change operations.

So if you are a slow reader and have it turned on and are reading along slowly, you are not using much battery power. In fact, someone who is reading fast and doing more page turns would actually use MORE battery power. Also, having a larger font will almost surely use more battery power, since it requires more page turns.

This, of course, is only true with e-ink devices. Back-lit Nooks like the Color and Tablet use a lot of power just by being turned on.

[azazel1024]

Backlit devices will also still use more power when turning pages than with not as the processor and display processor and probably GPU have to render the next page and display it on the screen. However, the backlit and idle CPU usage and main board power consumption, let alone wifi, etc on a backlit device is going to consume orders of magnitude more power than the page turn operation is likely to agregate out to.

Reading 10 pages an hour on a tablet is probably only going to use in the single digits of percent less power than reading at 50 pages per minute.

If the nook is awake it is using markedly more power than if it is asleep. The CPU has to be powered on, if in "idle" state, the IR emitter(s) for the touch screen have to be running the main memory likely has to be in a higher power state, etc. That said, idle power consumption is pretty low.

Actually we could come out to a rough number of actual power draw rate. 30 minutes per day for 2 months is an average power draw from a 5.66wh battery of 94.3mw of power. From what I know of DDR memory, the ARM8 CPU and some other stuff, and idle power draw of roughly 50mw actually seems probably close to spot on. That would leave about 44.3mw left over for page turns, averaged. That gets you 2.65wh used by page turns in the 60hrs/2 months of usage. Lets say 2,000 pages turns in that time (seems resonable that they used that measuring stick, that is 33.3 pages per hour) you get 1.325mwh of energy per page turn, or about 10w used for half a second, which is WAY too high for what the CPU, screen rendering engine and the eink screen must use to redraw the screen, even with a full refresh. A more likely "target" power consumption is probably in the 2-4w realm for "system" power consumption during a page refresh before it falls back to idle power consumption. To get even on the high end of 4w for a 500ms page redraw you come out to about 15mw average power consumption over those 2 months of reading, leaving you with an idle power consumption of about 80mw.

Of course that doesn't take in to account power lost during sleep, but in sleep all you have to do is maintain a watch on the power/n button to wake the system and low power mode for the DDR memory to keep things in memory. 80mw is already pretty gosh darn low, but I'd bet (if nothing untoward is going on) sleep power use is probably on the order of 1-3mw, otherwise there would be absolutely no reason for the nook to go to sleep if it didn't save power.

So going back to the usage model for a minute, if we said the nook used 4w during page turns, if you read at 66 pages an hour instead of 33 pages an hour, you'd up your power envelope from ~95mw average to 110mw average, reducing battery life by 15% by doubling your page turn rate.

Now one other thing to consider that I didn't take in to account is that partial page redraws likely use less power than a full refresh. Also just because a page turn (under 1.1) supposedly take 450ms (lets round to half a second), that doesn't mean that system power actually returns to idle istantly at the end of that time. I'd bet that the system agent keeps the CPU above idle for a period of time after a page turn to facilitate fast page turns by keeping CPU clocks up, maybe pre-rendering a page or so in advance at that time as well keeping the screen renderer power up and whatever that needs to do to remain primed, etc, all waiting to see if there is going to be another screen touch event or button page turn.

Now, I'd imagine the system really does return to an idle monitoring state pretty quickly, but it probably takes anything from an additional 250-2000ms to return to this state after the screen redraw occurs. So the idle power consumption could well be below 80mw if you, say, assume 2-4w for the half second to redraw a page for 500ms, dropping to maybe 500-2000mw for anything from 250-2000ms after the page draw.

If something like that were occuring, instead of 15% faster battery usage by doubling your page turn rate, it might be more like 20-50% faster battery usage.

With my limited experience with the nook ST, but based on what I went through and my knowledge of tablets, computers and low power processing I'd suspect (at least with a baseline 33pph reading rate) doubling your page turn rate while reading is going to use the battery probably closer to a 25-35% faster rate than either 15% or 50%.

Of course total number of pages on a battery charge will go up as you read faster as less power is used for idle/sleep, though with diminishing returns. You might get 60hrs of use at 33pph and 2000 total pages. You might get 48hrs of use at 66pph and roughly 3,200 total page turns. At 132pph you might get 40hrs of use and roughly 5,300 total page turns and so on.

So really, idle uses quite a bit of power as a function of overall battery usage. Page turns use orders of magnitude more power than what idle does, but energy wise, you are at idle for dozens of times longer than it takes to turn the page so the amount of energy consumed by turning pages is relatively little (at 33pph you spend .46% of your time turning the pages and 99.54% of your time at idle or doing something other than "turning the page").

Now a tablet at idle with its active screen uses a boat load of power. An idle ARM9 CPU (which I think has a higher idle power than an ARM8 does, though maybe it is the other way around) uses roughly 10mw (absolutely lowest power ARM9, most use somewhat more than that, but lower than 50mw in general). However, other systems resources, such as the wifi chipset, memory subsystem and especially the backlight/screen use substantially more. Even with wifi off, you are looking at a total system idle draw of roughly 1.5w for some of the better tablets with the screen brightness settings in the lower range. Compared to almost absolutely no more than 100mw of power consumption averaged for something like the nook simple touch, that is more than an order of magnitude more idle power consumption than a nook ST uses on average!

Sorry, long post, but I thought I'd go through some of the math and at least my madness to my method of coming up with why idle power consumption on an ebook reader is actually resonably substantial (though by no means exhorbitant) in comparison to how much power you are using while turning pages.

This is of course not taking in to account that BN, Amazon, etc may actually be taking in to account sleep power usage in those 2 months, 1/2hr a day and whatever hidden standard of pages per hour they are using to get those 2 months. And sleep power consumption is SOMETHING, even if really stupid low (it might well be low single digit miliwatts). Heck 5mw over 23hrs is the same as 1hr of reading might be assuming ~95mw of average on/reading power consumption (course sleep power consumption is possibly/probably lower than that). So sleep power use is probably more like 1-2mw just to keep the DDR powered up enough not to lose memory and to monitor those two buttons.

Of course at 1mw power usage numbers, we start getting in to self discharge rates of lithium ion batteries. IIRC a lithium ion battery (depending on the chemistry) will self discharge at roughly 5-10% per month. Voltage monitoring circuit uses some power, they don't self discharge in a classical sense, and dumb lithium ion batteries (which is not what is in most devices) don't really self discharge, it is actual capacity loss...but they "lose this" much slower, takes about 7 years depending on storage conditions for a lithium ion battery to go dead in that it has no rechargable capacity left (or effectively none). At 1mw in sleep (if we say it is that high), you get about 7-8% of battery capacity used per month by sleep power consumption plus 5-10% from self discharge of the battery. Doubling to 2mw gets you 14-16% per month from sleep.

Sorry, long post, I tend to fixate.

[azazel1024]

As an add-on/interesting note, if you didn't mind a little more bulk, or if useage was going to be less, it would actually make sense to use a low self-discharge NiMh battery. The "best of the best" discharge at about 1.5% per month and even most consumer grade chemistries (like Eneloop) discharge at more like 3-4% per month.

So if you wanted a battery with a rechargable chemistry, a lithium Ion battery is likely to use between 10-20% of its battery charge through self discharge in 2 months of ereader use if expected use cycle was going to do that. A really good low discharge NiMh battery with a similar capacity (which yes, would be larger/bulkier for the same capacity) would only use about 3-6% in those same 2 months, actually giving you about 4-8 days more use out of the device.

If you had a device that had an expected duty cycle of say 4 months, suddenly you are now talking 20-40% lost through self discharge of the lithium ion battery and only 6-12% from that low self discharge NiMh, and now you are in to 2-4 weeks of extra use (14-28% longer).

Supposing the extra bulk of the NiMh battery was worth while it really starts to pay off in longer battery life due to lower self discharge (and rechargability was desirable, that dumb lithium ion battery, for example like they type you see in key fobs/remotes, LED book reading lights, etc don't have a voltage monitoring cicuit as they are not considered rechargable batteries, so they have effectively no self discharge).

[RAH]

Your posts are interesting, but I think you need to clarify one thing, especially regarding the first - are you talking about backlit nooks, or e-ink? You start out talking about backlit ones, but I kept expecting you to go on to discuss the Touch, but never seem to, or maybe I just misread it. So, all those calculations, etc - are they for the Color and Tablet?

[Dopedangel]

The calculations that show up are just that calculations I never look at the battery percentage but my battery easily lasts between 10-15 days with wifi always on and I read about 2-3 hours a day apart from reading and replying to email.
Forget the battery % just use and see does the battery really die on you in 2-3 days if it does then their is something wrong. This is my 2nd nook the screen of the first one cracked but the battery life seems the same.
I am using a rooted nook touch and am running more apps than that run on a non rooted nook touch and 10-15 days battery life seems great to me.

[azazel1024]

Most of the calculations are for the nook simple touch and by association would apply to the kobo touch and kindle touch since they use similar/the same processor, IR touch emitters/processors and eink pearl screen.

The bit about backlit is in general refering to full tablets like the ipad, fire, nook color and nook tab.

An eink reader (obviously varies some) is going to burn somewhere roughly 100mw while "on" and reading averaged out. A tablet is going to burn roughly 1.2-3w while on and reading depending on the screen brightness (supposing nothing is running in the background). Eink based ereaders have batteries ranging from I think around 3-4wh (I think about what the new Kindle 4th gen uses) up to around 5-6wh (5.5 for the nook simple touch, not sure on the kindle touch, but probably 5-6wh). Those tablets use batteries ranging from roughly 12wh up to about 26wh (the 7in tabs use a bit less power because of the smaller screen, but their batteries also tend to be around 12-16wh and the bigger 9.7-10.1 tabs use more power because of the bigger screen, but also have the larger 22-26wh batteries).

So despite basically a cell phone capacity battery (5-6wh) eink readers use radically less power (as I mentioned, roughly 100mw). Since I don't really know exactly how the processor, screen renderer, memory and other systems are operated during a touch event and afterward, I couldn't tell you if everything stays "powered up" to a higher power state for a prolonged period of time, or if it is short. However, without any real testing, based on pure observation during normal use, it seems like screen refreshes take roughly half a second under normal reading, but if I hit the screen by accident (or on purpose) or a paging button within at least 1-2 seconds of the previous page turn, the action causes a page turn much faster which suggests everything remains powered up and doesn't need render a new page (just draw it to the screen) or power up the eink screen (if there is even a state other than "drawing" and "off") and what have you. Longer than that, there is some cut-off where screen redraws/refreshes take longer, but I don't know where that happens. More than 15-20s and it takes that half second to redraw (instead of maybe 200-300ms that an immediate follow on touch seems to take), 4-5s? Not sure.

So all that being said, I really don't know exactly how much power a page turn will result in, overall. I can tell you based on expected usage case and amount of time BN and Amazon claim for their devices, and empirical evidence seems to suggest that average power consumption during relatively normal reading is about 100mw. My guess is at around 30pph reading rate, about 15-30% of the power is used by page turns and the higher power state that it incurrs and 70-85% of it is used by system idle.

So if you read faster, the amount of power used by page turns and the resulting higher system power state immediately following a page turn will be higher, however, at a "normal" reading rate, the "doing nothing but on" state likely consumes a large majority of the power used by the nook ST; however, that is still a pretty tiny amount of power being used.

[RAH]

Thanks for the clarification.