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Old 02-24-2013, 05:21 PM   #1
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Battery Calibration

I've had several people PM me asking about battery calibration (why and how). I thought I'd create this to explain things.

The battery inside your e-reader doesn't tell the e-reader what percentage of "juice" it has left, instead your e-reader has to learn the characteristics of your particular battery. In order to help your e-reader learn about your battery you need to "calibrate" the battery, which teaches the e-reader the limits of your particular battery. This isn't unique to Kobo, any device that uses lithium-ion batteries (mobile phones, laptops, tablets, etc) can benefit from this.

For information on battery calibration please read Battery Calibration

If you would like to view a short video explaining how to calibrate a battery please view:



Ideally you should have done this as soon as you received your e-reader, but even if you've charged it several times it's still worth doing. It also might be worth doing once every 3 or 4 months too.

Note that this won't make your battery last longer, it's all to do with teaching your e-reader the characteristics of your particular battery so it can better display battery percentage figures. Why is this important? Well without it your e-reader might tell you that the battery is at 50% when in fact it's at 70%, causing you to get upset because you think the battery isn't lasting as long as it should be.

Also, the discharge curve for lithium-ion batteries isn't linear; it doesn't start at 100% and then drop x% for each time period (i.e. 5% for each hour of use). Instead what you'll probably see is it will sit at (or near) 100% for a while and then slowly drop off until it gets to a certain point where it will drop quickly. Similar to this:



If you want to learn about how to make lithium-ion batteries last longer then have a read of How to Prolong Lithium-based Batteries

Note: I'm not an expert on batteries, but this is something that I've always done with lithium-ion batteries and it has always worked well for me.
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Old 02-24-2013, 07:54 PM   #2
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While that video is not exactly wrong, I can't say I like it as advice.

The simplest reason is that there is no reason to leave the laptop off while running the charge part of the calibration. The calibration is simply two or three complete discharge and recharge cycles. It doesn't matter what else happens at that time.

The other problem is the advice to leave the charger on some extra time after the battery reads full. This is useless. When the charger determines a Li-Ion battery is full, it turns off. They cannot be trickle charged. And if someone tries to, it is bad. "Bad" as in damages the cells and could lead to an explosion. For the tiny cell in an ereader, this probably won't be that bad, but for the multiple cell laptop battery, it can be spectacular.

The complete discharge end is also a problem. The suggestion to leave the laptop in sleep for a while is a good idea. For some, a good way to do this is to start the laptop and go into the BIOS and wait for it to run out of power. But, while you are there look and see if the BIOS has a battery calibration function. A lot of laptops do.

For an ereader, it is a bit a harder. Running the battery down takes time. You can't just load a video and leave it running. You need to sit there tapping the screen to use power. Continuously running WiFi syncs would also do it. But using the browser might be the quickest way. That will run the WiFi and will use a lot of CPU downloading and drawing the screen. And if the pages are long and need a lot of scrolling, that should use a lot of power as well.

I'm not sure if calibrating the battery will do anything. I expect the battery level to be simplistic rather than the fuel gauge in a laptop battery. If it is simplistic, it will have a voltages set for the maximum and minimum charge levels and current level will just be the difference expressed as a percentage.
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Old 02-25-2013, 03:47 PM   #3
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Originally Posted by davidfor View Post
While that video is not exactly wrong, I can't say I like it as advice.
Perhaps it wasn't the greatest video to use as an example, it was just the first that I came across that seemed to cover all the bases.

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Originally Posted by davidfor View Post
The simplest reason is that there is no reason to leave the laptop off while running the charge part of the calibration.
Maybe his thinking is that it will charge faster if the laptop is off. I'm not sure if this is true, it might depend on the particular laptop.

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The other problem is the advice to leave the charger on some extra time after the battery reads full. This is useless. When the charger determines a Li-Ion battery is full, it turns off.
I've seen lots of advice that says to leave the battery charging for an hour or two after it reaches 100%. I think the thinking behind this is because the device, which shows the percentage figure, may not have yet learnt what a full charge is for your battery, so it might be saying that it's 100% when in fact it's only 98%. Remember the whole point of calibration is to teach the device the true upper and lower limits of your particular battery.

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For an ereader, it is a bit a harder. Running the battery down takes time. You can't just load a video and leave it running. You need to sit there tapping the screen to use power. Continuously running WiFi syncs would also do it. But using the browser might be the quickest way. That will run the WiFi and will use a lot of CPU downloading and drawing the screen. And if the pages are long and need a lot of scrolling, that should use a lot of power as well.
It doesn't really matter how fast you discharge the battery while you're doing the calibration, you can just use the device as normal. Of course with an e-reader this might take a few weeks or more! If you want to speed the process up then something that used WIFI and some processing would probably do the trick. I haven't played with the Kobo browser much, but if it supports Javascript then it should be pretty easy to make a web page that does something causes lots of processing and WIFI usage. Maybe some animation or a scrolling Twitter feed?
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Old 02-25-2013, 09:06 PM   #4
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Maybe his thinking is that it will charge faster if the laptop is off. I'm not sure if this is true, it might depend on the particular laptop.
True, especially when the laptop is pushed a bit and using more power.
Quote:
I've seen lots of advice that says to leave the battery charging for an hour or two after it reaches 100%. I think the thinking behind this is because the device, which shows the percentage figure, may not have yet learnt what a full charge is for your battery, so it might be saying that it's 100% when in fact it's only 98%. Remember the whole point of calibration is to teach the device the true upper and lower limits of your particular battery.
I am pretty sure it won't make a difference. Once the fuel gauge detects the battery is full, it turns the charging off. That gives the upper limit for the calibration.
Quote:
It doesn't really matter how fast you discharge the battery while you're doing the calibration, you can just use the device as normal. Of course with an e-reader this might take a few weeks or more!
That was what I was thinking of. For a laptop, you can put a movie on repeat, but the ereaders need interaction.
Quote:
If you want to speed the process up then something that used WIFI and some processing would probably do the trick. I haven't played with the Kobo browser much, but if it supports Javascript then it should be pretty easy to make a web page that does something causes lots of processing and WIFI usage. Maybe some animation or a scrolling Twitter feed?
According to http://browserspy.dk/javascript.php, the browser supports Javascript 1.7, so this idea should be possible.
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Old 02-26-2013, 04:17 AM   #5
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It doesn't really matter how fast you discharge the battery while you're doing the calibration, you can just use the device as normal. Of course with an e-reader this might take a few weeks or more!
I wish!


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If you want to speed the process up then something that used WIFI and some processing would probably do the trick. I haven't played with the Kobo browser much, but if it supports Javascript then it should be pretty easy to make a web page that does something causes lots of processing and WIFI usage. Maybe some animation or a scrolling Twitter feed?
Nice idea! Care to make us all a site where we can go and calibrate/test our battery?
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Old 02-26-2013, 02:02 PM   #6
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Nice idea! Care to make us all a site where we can go and calibrate/test our battery?
Well a quick search bought up this page. Plenty of scrolling going on there, which will use up some processing power, but I don't think it's a live feed so WIFI won't be used once you open the page.

Here's another one. This one does do an AJAX call to retrieve info every 5 seconds, so should use WIFI.
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Old 02-26-2013, 02:04 PM   #7
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I was tempted to post a link to Hamster Dance...
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Old 02-26-2013, 02:16 PM   #8
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I was tempted to post a link to Hamster Dance...
Ooo, yeah, that'll chew through the CPU quickly!

Or maybe this:

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Old 02-26-2013, 03:15 PM   #9
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Ooo, yeah, that'll chew through the CPU quickly!

Or maybe this:

[youtube video]
Oooooh battery testing suddenly became fun!
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Old 03-04-2013, 03:07 AM   #10
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Well a quick search bought up this page. Plenty of scrolling going on there, which will use up some processing power, but I don't think it's a live feed so WIFI won't be used once you open the page.

Here's another one. This one does do an AJAX call to retrieve info every 5 seconds, so should use WIFI.
Thanks, that was actually useful today
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Old 03-04-2013, 03:25 AM   #11
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Thanks, that was actually useful today
Glad I could help!
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