Battery life!

[RedRoverJ]

I am glad there are so many people having the same issues. Most likely, these issues are high priority items and will be resolved much sooner than if it was an intermittent problem that only affected a few.

Of course, their product testing team should have caught most of these before it was even released, but that's a whole different topic.

[corona]

Originally Posted by Roy Hinkley

The specs on the EB-600, which, I have read that Kobo is based upon, shows battery information:

Battery: Li-Ion 3.7V, 1000 mAh, 8000 screen refresh.
Battery Charge Time: AC Adapter 4 hours, USB cable 6 hours.

I am guessing that they measured a page turn (blank the page, fetch the new page and redraw) would consue 0.125 mA.

I think you mean 0.125 mAh, for 1/8000 of the battery's charge. But I think it's easier to think of the charged battery having 1hr x 1A x 3.7v = 3.7 WHrs of energy available from a full charge. So each page turn requires .4625 mWHrs of energy. In theory.

I find a specification for a Li-Ion battery of similar capacity, that says initial charging current should be simply be the current value of the capacity. http://www.batteryspace.com/ProductI...-E%28A1%29.pdf

I find another recommendation that Li-Ion batteries should be charged initially at 0.7 x current value of the capacity. http://www.electronics-lab.com/artic...n_reconstruct/

In the first case that would be 1000 mA; in the second, 700 mA. Both of these would be more than the 500 mA USB port spec. Hmm. The Kobo isn't the only peripheral to charge a Li-Ion battery from a USB port. Is the charging circuitry dumber, i.e. by asking for too much current is it pulling down the voltage? (Li-Ion batteries should be charged, generally speaking, at a constant voltage -- see the second link above for more info.) If so, this might support the notion that charging performance could be degraded depending on the current available at the USB port, which would depend on manufacturer/design. And, therefore, a wall charger or whatever with more available current would provide a fuller charge.

If not, i.e. if you provided less than those desired maximum currents and the voltage stayed where it should be, the battery would still charge fully -- it would just take longer. Which doesn't seem to be an issue here, because lots of us seem to be getting poor performance even when we leave the Kobo plugged in for hours.

I don't have access to any of the required bits and pieces at the moment, but this would be pretty easy to measure -- voltage at and current from the port when charging a fully-discharged Kobo (in a computer/Kobo configuration where the Kobo's battery isn't performing up to spec).

(Sorry to muddy the water, but now I'm confused.)

[StealthyScribe]

Originally Posted by StealthyScribe

Well I left it charged for a full 9 hours while at work today using a Blackberry wall charger, just like the woman suggested to me, and the red light never came on at all. When I disconnected it the battery shows a full charge though, so I'll see how long this one keeps and update later on. I'm still really annoyed with this whole battery business and wish they weren't behaving like this for so many of us.

I knew I had posted about this...so to update (although I have in another thread), the battery was showing 100% from Thursday night until last night. I was not turning the unit off at all. I finished a 300ish page book, decided to power it down last night, turned it on earlier this afternoon and it's down from 100% last night to one little tick left. I've already contaced Kobo about exchanging the unit through them since there aren't any available in my area.

[RedRoverJ]

It seems that the Kobo reader only updates the battery indicator during the boot cycle. You need to actually turn it off and back on to get an accurate reading.

Unfortunately, this has led to many people incorrectly ruling the unit as defective since it was "at 100% yesterday and down to one bar today."

I hope this is something they are working to rectify.

[artificial]

Originally Posted by RedRoverJ

It seems that the Kobo reader only updates the battery indicator during the boot cycle. You need to actually turn it off and back on to get an accurate reading.

Thanks for that explanation! I've personally been happy with my battery life so far (~60% after 6 days use, and I've been using it quite a lot), but I did notice a big drop in my battery status after loading new content to the Reader. Armed with your explanation that now makes perfect sense!

[StealthyScribe]

Well I've turned it off and back on again and it's still showing one bar left.

[TallMomof2]

I charged my Kobo about a week ago and I still have 50% battery left and I've probably made close to 4000 page turns.

Since the problems after the first charge, my battery has been fine.

[StealthyScribe]

Originally Posted by TallMomof2

I charged my Kobo about a week ago and I still have 50% battery left and I've probably made close to 4000 page turns.

Since the problems after the first charge, my battery has been fine.

Are you just using your computer to charge it or are you using a wall charger now? I sure wish I knew what I was doing wrong...are you powering the unit down at all or just leaving it on?

[Ghoda]

Originally Posted by StealthyScribe

Are you just using your computer to charge it or are you using a wall charger now? I sure wish I knew what I was doing wrong...are you powering the unit down at all or just leaving it on?

Make sure that your wall charger is not rated higher than the Kobo is designed to receive - I believe standard USB pushes up to 500mA at 5V and the label on the Kobo says it will accept 750mA at 5V. Using a charger that is 'too strong' will cause the battery to think it's fully charged long before it really is. I use a wall charger that is rated at 350mA at 5V - takes a couple of hours to charge and the charge lasts a few weeks.

For the record I also see this same behavior on my cell phone and wireless headphones (low amps on a long charge = awesome).

Bottom line - if you've got the time a trickle charge at low amperage is always better than a quick charge at higher amperage.

[corona]

Hmm. I think that it's the charging circuit in the Kobo that regulates the charging current. The supply has to be able to provide adequate current, without a drop in voltage. Thus I think that the opposite to what you've said here is true, and that as some people here have suggested, maybe some computer's USB ports aren't capable of providing the required current without exhibiting a drop in voltage. This is all pretty speculative, but generally I think having a supply able to provide adequate current is better than one that can't. I didn't start out with this point of view, but I'm starting to think the wall-wart/blackberry/paralleled-USB advocates have a point.

[Solicitous]

Originally Posted by Ghoda

Make sure that your wall charger is not rated higher than the Kobo is designed to receive - I believe standard USB pushes up to 500mA at 5V and the label on the Kobo says it will accept 750mA at 5V. Using a charger that is 'too strong' will cause the battery to think it's fully charged long before it really is. I use a wall charger that is rated at 350mA at 5V - takes a couple of hours to charge and the charge lasts a few weeks.

For the record I also see this same behavior on my cell phone and wireless headphones (low amps on a long charge = awesome).

Bottom line - if you've got the time a trickle charge at low amperage is always better than a quick charge at higher amperage.

I always thought with mA rating was the maximum the charger can put out, not what it does put out consistently. What I mean by this is if a wall charger is rated 5v 1A and the device charges at 5v 750mA, then all the device will pull from the charger will be 5v at 750mA. Same goes if the device is say 5v 1.5A, because the charger has a maximum output of 1A, that is all the device will receive.

[corona]

Originally Posted by Solicitous

I always thought with mA rating was the maximum the charger can put out, not what it does put out consistently. What I mean by this is if a wall charger is rated 5v 1A and the device charges at 5v 750mA, then all the device will pull from the charger will be 5v at 750mA. Same goes if the device is say 5v 1.5A, because the charger has a maximum output of 1A, that is all the device will receive.

Yeah I think that's correct.

[terifili]

Well, not sure if this has been mentioned yet, but if you don't power down your kobo, the battery lasts much much longer!! Just leave it on....

[zoran]

still have no kobo reader, but wonna clear some issues regarding proper device charging. let me show you 3 chargers I could get at this moment:
1) http://www.vivanco.de/cgi-bin/vivanc...=9816&todo=add
2) http://www.speed-link.com/?p=2&cat=511&pid=21913&paus=1
3) http://www.amazon.com/Logitech-Premi.../dp/B000RZUV9S
I would appreciate if I could have the answer at time I get my reader.

[juiceless]

Originally Posted by zoran

still have no kobo reader, but wonna clear some issues regarding proper device charging. let me show you 3 chargers I could get at this moment:
1) http://www.vivanco.de/cgi-bin/vivanc...=9816&todo=add
2) http://www.speed-link.com/?p=2&cat=511&pid=21913&paus=1
3) http://www.amazon.com/Logitech-Premi.../dp/B000RZUV9S
I would appreciate if I could have the answer at time I get my reader.

What is your question?