Battery life!

[RedRoverJ]

People commenting that their kobo was fully charged in 30mins, or whatever, are incorrect. The light will shut off and indicate fully charged, however, this is just not the case.

If the manufacturer recommends three hours to charge, that is the minimum you should leave it for. You can leave it charging all night without worry of damaging it.

If you do not let a battery fully charge, it will deplete much quicker. That's the same for pretty much any devices I have used and I have lots.

Ignore the red light, whether it works or not, and let it charge all night. If you still have issues with fast discharge then it should be returned as defective.

[corona]

Actually, the light is supposed to go on when it's charged if I'm not mistaken. And the fact that the light doesn't come on could, IMO, mean that the battery isn't getting fully charged. I.e., if the the light is triggered by, let's say, a combination of the battery's voltage (above a certain threshold) and charging current (below a certain threshold) -- or the latter criterion alone, or some other more sophisticated measurement of the battery's charge -- then the light not coming on could mean that the battery's no good.

I think there are other conceivable issues. Is the operation of the light, whatever it does, determined by firmware? If so, the problem might lie there.

The manufacturer says you'll get 8000 page turns to a charge. Now it's likely that I (and probably most people) will only get into that situation when we go on vacation (because otherwise we'll be plugging the thing into our computer to get books, etc., and we'll be too busy with other things to turn pages so relentlessly). I don't want to find out in a year, say, that my battery's no good.

And, batteries don't get better with age. If the brand-new battery in my Kobo won't take a full charge now, it won't be better in six months.

In regard to a battery discharging more quickly if it's not fully charged, well of course that's true; the less charge it has, the less it has to discharge. However, these aren't NiCads, and there's little or no memory effect, so although a full charge is a good thing, not fully charging the battery shouldn't cause any permanent reduction in capacity.

My concern with the red light not coming on (and my own experience now that even if I leave the Kobo plugged in for many hours the battery still starts showing a reduced capacity after <200 page turns) is that the battery just isn't any good. The hardware itself is from some other manufacturer, I understand, so presumably the charging circuitry itself is tried and true. Firmware? Could be. But I think the most likely answer is that a batch of bad batteries got put into these things.

This does happen. My wife has an implanted cardioverter defibrillator, which is kind of like a super-pacemaker, and cost, I don't know (woohoo -- I'm Canadian!) umpteen-thousand dollars. It was a new model when she got it. Fortunately this didn't affect her, but they put a big batch of the things in people only to find out the batteries were bad and they had to pull them all out again.

Anyway, I called my local Chapters store; they don't have any Kobo's in stock, but when they do they said I could exchange mine. My guess is that the batteries are just bad.

[Stinger]

Here are a couple things to take note of:

Some Li-ion batteries have built-in circuitry (read below for reason) to measure the charge level accurately. With these types of batteries, as was already mentioned in before:

a full discharge/charge will reset the digital circuit of a 'smart' battery to improve the state-of-charge estimation

However, not all Li-ion batteries have this circuitry. Maybe economy versions? if that's the case, I'm sure Kobo would have opted for those to keep its price down. With these types of batteries, its just a simple voltage measurement thats used as a rough estimate of charge level:

It must be noted that utilizing voltage as a fuel gauge function is inaccurate because cells made by different manufacturers produce a slightly different voltage profile. This is due to the electrochemistry of the electrodes and electrolyte. Temperature also affects the voltage. The higher the temperature, the lower the voltage will be.

Also, here's a charge-profile graph I found for Li-ion batteries:


Most charging systems will indicate full charge when the current hits the low threshold at the end of 'Stage 2'. Some of the 'Turbo' charges will skip stage 2 and indicate full charge using a voltage measurement at the the end of stage 1 (note: The charge level at this point is about 70%).


In any case, given the fact that the Kobo was released pretty bare-bones, with plenty of little kinks and such, I don't think it's a stretch to think they didn't really care about a very accurate battery gauge meter algorithm. The red light could be explained by this as well.

[Duiker]

I powered off my Kobo this morning. The battery was at about 3/4 full. Just powered it back on this afternoon and the battery has gone down to nearly 1/2. Think I'll be exchanging.

[StealthyScribe]

I got my Kobo on Monday afternoon and charged it for the recommended 3 hours. The red light had come on by the end of the 3 hours (when exactly though I don't know, I wasn't watching it). I've since used it every single day and now today, my battery is down to just one little tick left showing its life. I'm not sure how many pages I've turned, but for it to last from Monday to Saturday is decent to me. I don't think having to charge it once a week is too bad.

[corona]

Originally Posted by Stinger

I don't think it's a stretch to think they didn't really care about a very accurate battery gauge meter algorithm. The red light could be explained by this as well.

That may well be so, and I appreciate the graph showing how it all works.

And really, is it such a big deal? As it is, I plug the thing in all the time. If I go on a trip for so long and to such a remote place that I'm not going to be dragging along laptops, chargers, etc. (in my dreams!) then I'm probably not going to want my silly e-book reader anyhow.

[PenelopeWeaving]

I wrote to Kobo and they suggested a reset would fix the problem of the red light not coming on when the battery is charged. However, it might delete downloaded books. Those from Kobo could, of course, be reloaded from the Kobo account for free.

[corona]

Originally Posted by PenelopeWeaving

I wrote to Kobo and they suggested a reset would fix the problem of the red light not coming on when the battery is charged. However, it might delete downloaded books. Those from Kobo could, of course, be reloaded from the Kobo account for free.

I reset mine. The books remained, and the red light is as elusive as ever.

[jimr]

I sent an email to Kobo asking about battery life and whether or not it was worth exchanging the device for another. I told them I was getting upwards of 1000 page turns per charge before it seemed ready for another charge. Here's their reply:

"In regards to the battery life you should be getting about 1000 pages turns for each charge. It is advised that you allow the device the die completly then recharge completly. You should be able to get away though with charging for twenty minutes a day and have it last over a week. Battery life also depends on how frequently you use the device. Keep an eye on it, and let us know if you have any more questions!"

The suggestion of 1000 page turns isn't all that consistent with their initial claim of 8000. Anyway, thought I'd pass this along for what it's worth....

[terifili]

Yes, sort of a piss off, when this is what they claim...

Battery Life: up to 2 weeks battery life or 8000 page turns

[PenelopeWeaving]

Well, I reset mine, lost the books, but the red light came on when it was charged.

Now, I say "Lost the books" - but when I tried to reload them, I got a message that they were already there. I looked and looked to no avail, so I chose the option to overwrite the existing file. All is well and I am happy! :-)

[corona]

I bowdlerized my Kobo's database to get rid of the free books. It worked, but the funny thing was that the red light came on again. I haven't seen it in ten days!

[Duiker]

Originally Posted by jimr

"In regards to the battery life you should be getting about 1000 pages turns for each charge. ...The suggestion of 1000 page turns isn't all that consistent with their initial claim of 8000. Anyway, thought I'd pass this along for what it's worth....

That's very inetresting. I don't have my e-mail from them anymore but when I sent them one about my battery issues they told me I should be getting 8000 page turns per charge and if I wasn't I should exchange it. I haven't yet. I wonder if they have officially changed their battery life expectancy?

[jimr]

Originally Posted by Duiker

That's very inetresting. I don't have my e-mail from them anymore but when I sent them one about my battery issues they told me I should be getting 8000 page turns per charge and if I wasn't I should exchange it. I haven't yet. I wonder if they have officially changed their battery life expectancy?

Interestingly, I sent them another email asking just about the same question. Here was their reply:

My Email:
Thanks for the reply. Although I do have one more question. How does 1000 page turns and one week worth of use fit with your initial claim of 2 weeks or 8000 page turns? Is there something wrong with the actual devices/batteries/firmware that is limiting them? (ok, that was two questions...but you get my point).

Thanks again...Jim


Their reply:
May-16 2010 17:08. Ben

Hello Jim,

Well how long the battery lasts depends as well on how frequently and for how long you use the device. That will affect how long the charge lasts.

Thanks again!

The Kobo Team


I'm not even sure what he was trying to say....lol.

[Stinger]

I always thought that the 'UPTO 2 weeks' meant something like, "If you read for an hour before bed, it'll last 2 weeks". In my experiences UPTO estimates always use numbers based on liberal usage like I mentioned, the not-so average grandma reader

The 8000 page turns is probably also a naive calculation, where they calculated how much power it takes to do a single page turn, and divided the average battery capacity.
This kind of simple calculation would ignore the fact that nobody is going to do 8000 consecutive page turns like that. Which means it doesn't account for additional drains on the battery:

• Power down, Power on (at least a couple screen updates, plenty of internal memory reads, processing, etc)
• ANY other operation besides page flips will usually include a page refresh + processing (display tab to check battery, change font, browse library, GOTO next chapter, etc)
• even powered down, the kobo has to use minimal battery power to keep the clock/date system going

Technically speaking, it can do 8000 page turns, if you ignore all that crap, so they can put it on the box without getting sued. Same goes for the 2 weeks... it can last two weeks, sure, but it won't be anywhere near 8000 pages since you also have all the battery drains I mentioned coming into the equation.

Notice specifically what they say, note the 'or' & 'approximately':
"This charge will last approximately 8000 page turns or two weeks of average reading."

Marketing people get payed a lot of money to brain-f**k you, and they do it well. Sometimes they get sued for false advertising, sure, but I think Kobo is safe by their careful wording.