Maximizing battery life on your device

[j.p.s]

Originally Posted by Tarana

Yes, but knowing that these options all use power means that you can make some decisions, based on YOUR personal usage, what to disable and what not to.

I completely agree.

Originally Posted by Tarana

My late sister used the dictionary maybe twice in the year she had my ereader, so for her, that would have made sense to disable it.

What evidence is there that disabling the dictionary saves any power whatsoever?

[DuckieTigger]

Originally Posted by j.p.s

What evidence is there that disabling the dictionary saves any power whatsoever?

By disabling touch screen, possibly, and avoiding accidental looking up words or unwanted highlighting.

[sjfan]

Originally Posted by Tarana

Yes, but knowing that these options all use power means that you can make some decisions, based on YOUR personal usage, what to disable and what not to.

My Mom has a tablet and never uses the SD card that we bought her, so if that is using up battery power, I'm just going to disable it unless she needs it. I have an SD card in my Nook that I rarely use, so may choose to disable it.

This is why the OP is a bit misleading; while the SD card does draw some power, it's tiny in the grand scheme of things. Virtually negligible. As I said above, it's like taking out your car's headrests to increase gas mileage: yeah, theoretically that would decrease the car's weight and make it more fuel efficient, but the actual impact is so small as to be irrelevant.

A micro SD card's sleep current is typically in the range of 0.2 mA drawn. If a Kindle with a typical 1420 mAH battery has 30 hours of continuous reading life, that's 47.333 mA of average draw; removing the SD card would decrease that to about 47.1 mA, saving you less than half a percent. Instead of 30 hours, you might get 30 hours and 7 minutes; it's not really going to be noticeable, and certainly isn't enough to impact how often you need to charge the battery.

On a non e-ink device like a tablet, the SD card will represent an even lower proportion of the power used—if you have a tablet with a 4000 mAH battery and 12 hour charge life, then it's normally drawing 416.67 mA. Knocking 0.2 off that is a saving of about 1/20 of 1%; instead of 12 hours, you might get 12 hours and 20 seconds of battery life from a charge.

All of these numbers are order-of-magnitude: maybe your SD card draws more like a 0.3 mA sleep current. But the basic story is the same: while there is a theoretical power draw there, there's not a big real-wold impact on reader battery lifespan (unlike with wifi or backlights, which can have a significant impact on battery life).

[JSWolf]

How does one disable the dictionary?

[ZodWallop]

Originally Posted by sjfan

...while the SD card does draw some power, it's tiny in the grand scheme of things...

That, right there is what I was getting at.

If battery performance on your device is so poor you find yourself having to hack it to disable SD cards, touch screen and dictionaries, you likely should get a new device.

[j.p.s]

Originally Posted by DuckieTigger

By disabling touch screen, possibly, and avoiding accidental looking up words or unwanted highlighting.

I hope that you do not see this a quibbling, because I see it as key to exchanging information and thinking clearly.

Being unable to access the dictionary from a book is a secondary effect of disabling the touch screen, which as you point out also disables highlighting. The advice to save power by disabling the dictionary is invalid (and silly) and does not merit entry in a list of power saving measures.

[Katsunami]

Never had to pay attention to battery life short of disabling wifi, which I do anyway, because I don't want the reader to auto-update firmware or to send user statistics to the manufacturer.

My 5 year old Kindle Paperwhite 1 doesn't have the battery life anymore that it once had, but it can still go for about 10-14 days with normal usage, which is good enough for me. Maybe, at some point, I'll replace the battery so it can go for another 5 years. It seems the KPW1 is one of the last readers not glued shut, with a glued down battery... it's one of the reasons I haven't sold it when I got the KA1. It's a good backup device.

The Kobo Aura ONE I have can go for about 2-3 weeks as well (since I've had it, which is about 17 months now), but it obviously uses more power because it has a bigger screen.

[DuckieTigger]

Originally Posted by j.p.s

I hope that you do not see this a quibbling, because I see it as key to exchanging information and thinking clearly.

Being unable to access the dictionary from a book is a secondary effect of disabling the touch screen, which as you point out also disables highlighting. The advice to save power by disabling the dictionary is invalid (and silly) and does not merit entry in a list of power saving measures.

Correct. It is a secondary effect. It is pretty much not saving any battery at all. It is as useful as disabling access to the aA menu - cannot open menu to change fonts, hence it saves energy by not having to screen refresh and draw the menu.

Hey, it wasn't my idea, just trying to think my way out of someone elses paper bag. No offence prodigit, but disabling unused software features that only cost processing time and screen time when used is not going to do anything. Not sure how others handle dictionaries, but on a Kindle the dictionary is not being indexed - so downloading it is the only drain on the battery it is causing.

[cfrizz]

All three of my phones and one tablet stay in airplane mode. The batteries last at least a week and a half if not longer. One phone is used as an mp3 player hooked up to my audio system. I can play it all day long, and still over half the battery still left.

But for my main phone that gets used every day for calls (when needed on my end), ereader & mp3 player gets plugged in every night automatically. Even still it has over 80% of the charge left by the time I plug it in.

But honestly, battery life isn't something I'm overly concerned with since I have chargers all over the place, including at work. And if need be, all of my phones have batteries that I can replace myself, which I only have to do maybe once every two years if that.

[4691mls]

I keep wifi turned off on my T3 unless I am going to use it to download a book. Wifi does cause noticably faster battery drain.
I assume someone who reads on a phone or tablet would be more likely to leave wifi on if they are using it for other purposes such as email or Internet.

[ProDigit]

Originally Posted by j.p.s

To be a bit more specific, with the light off, the 7.8" reader uses 69% more power per page turn because it has 69% more pixels, but it needs 1/1.69 as many page turns, because it has 69% characters per page. Justification, paragraph length, and chapter length will cause these ratios to vary. That is, the cost per page turn ratio is pretty much fixed, but the total number of page turns per book for each reader will vary.

So, as DuckieTigger writes, on average, it is a wash, but YMMV.

You're forgetting the time it takes for a cpu to up and down throttle.
Basically, after every execution, the CPU goes into a sleep state, and disables cores. Every time you execute something, it goes out of this sleep state, which probably consumes just about as much battery, as the calculations it needs to make to render the new page.
Reducing font size may prolong your battery life by a few seconds, to 1 minute, over the course of several days use; but it's a valid argument nevertheless!

[ProDigit]

Originally Posted by DuckieTigger

By disabling touch screen, possibly, and avoiding accidental looking up words or unwanted highlighting.

Background dictionary loading in RAM.
Same thing with X-ray.
We're talking about saving seconds off of a device with days worth of battery life, and possibly even more of an effect on tablets that will keep the dictionary loaded in RAM, for instant search results.

[ProDigit]

Originally Posted by sjfan

This is why the OP is a bit misleading; while the SD card does draw some power, it's tiny in the grand scheme of things. Virtually negligible. As I said above, it's like taking out your car's headrests to increase gas mileage: yeah, theoretically that would decrease the car's weight and make it more fuel efficient, but the actual impact is so small as to be irrelevant.

A micro SD card's sleep current is typically in the range of 0.2 mA drawn. If a Kindle with a typical 1420 mAH battery has 30 hours of continuous reading life, that's 47.333 mA of average draw; removing the SD card would decrease that to about 47.1 mA, saving you less than half a percent. Instead of 30 hours, you might get 30 hours and 7 minutes; it's not really going to be noticeable, and certainly isn't enough to impact how often you need to charge the battery.

On a non e-ink device like a tablet, the SD card will represent an even lower proportion of the power used—if you have a tablet with a 4000 mAH battery and 12 hour charge life, then it's normally drawing 416.67 mA. Knocking 0.2 off that is a saving of about 1/20 of 1%; instead of 12 hours, you might get 12 hours and 20 seconds of battery life from a charge.

All of these numbers are order-of-magnitude: maybe your SD card draws more like a 0.3 mA sleep current. But the basic story is the same: while there is a theoretical power draw there, there's not a big real-wold impact on reader battery lifespan (unlike with wifi or backlights, which can have a significant impact on battery life).

..Which is why you'll find it at the bottom of the list.
However, if you have a device where you play games, watch video on, it makes sense to run it off of the internal drive. Not only for performance reasons, but also the power draw on data transfer on an SD card is much higher than it's idle draw. SD card slots on Ebook readers should mostly remain passive though...
Still, removing the card, is a power saving nonetheless.

Originally Posted by ZodWallop

That, right there is what I was getting at.

If battery performance on your device is so poor you find yourself having to hack it to disable SD cards, touch screen and dictionaries, you likely should get a new device.

From another perspective,
If you don't need the SD card slot, and can fit your library in internal memory, you could be saving battery by doing so.
If you're unaware of this, you may be using up more battery, paying for an SD card that can get lost, stolen with your device, or break down.
Internal SSDs last longer, and if your device is stolen, you might already have $15-25 available for a new one (if you didn't invest it in an SD card).

[DuckieTigger]

Originally Posted by ProDigit

Background dictionary loading in RAM.
Same thing with X-ray.
We're talking about saving seconds off of a device with days worth of battery life, and possibly even more of an effect on tablets that will keep the dictionary loaded in RAM, for instant search results.

Background dictionary loading into RAM? Are you kidding me? That is what - 20-30 MB. It costs the same amount of energy to keep a 0 or a 1 alive in your RAM regardless of content.

I thought your list only had practical and real life noticeable savings in it.

Since it is mostly of academic value, here is the biggest energy saving of them all that you missed:
0) disconnect the battery.

[davidfor]

Originally Posted by DuckieTigger

Since it is mostly of academic value, here is the biggest energy saving of them all that you missed:
0) disconnect the battery.

I used to hang out in a notebook forum where one of the most common questions was how to extend the life of the battery. They were more talking about overall life rather than runtime, but, all the suggestions really come down: don't use it. With the most common being to take it out of the laptop.

And that always seemed pointless to me. You are spending a lot of money on a portable computer, and then you are making not portable.

After a bit of research, and my own use over the years, my advice became:

Just use it. Anything you can do to extend the life of the battery is inconvenient, means you can't use it or doesn't have that much affect. Charge it when you can, run on battery when you want to and enjoy the freedom of not worrying about it.

And that's basically the case here. There is absolutely nothing in the first post that I want to do. I use the WiFi, so I want it on. The point of getting a frontlit ereader was to have a built-in light. And I adjust the level frequently based on what feels right at the time. Touch screens are wonderful (but I haven't used an ereader with button outside a shop). I use the dictionary, but not as much as I use the annotations. I suppose I do use simple epubs, but that's because I want to make sure they work and clean the code up while still trying to keep the style the creator was after.

To me, the instructions in the first post are: "Buy an expensive device and then don't use any of its best features."

And thinking about point 5, if the compressed formats are so bad, why wasn't the suggestion to rezip them with zero compression? That should be a faster, use less CPU and hence less battery.