Shorter Battery Life with Audible Content?

[duncman]

What kind of battery life does anyone else get with Audible content? I use my iPod to play books about 95% of the time and I guess my battery is only good for only about 6 hours between charges.

I've turned off the backlighting and the equalizer to maximize battery life. I've heard that files (books or songs) > 9MB make the iPod use the hard drive more often and drain the battery faster. Of course most audible books are much bigger than this.

I know the battery meters can be flaky too so it can be hard to judge how long the battery really lasts. I don't want my iPod to die in the middle of listening to a book so I usually recharge it before the battery meter is 'empty'.

I have a 2G 10GB iPod. I love being have to have a dozen books loaded up on it but I'm a little disappointed that I don't get the rated 10-11 hour battery life though.

[dordale]

duncman--

Like you, I mainly use my iPod for audio books. (I have a 3g 15gb.) I'm lucky to see 5 hours of play time--quite a bit less than the 8 hours apple claims for the 3g's.

I do think that a lot of this is because of the file size of the audible books, and the iPod not being able to cache the files efficiently.

I would love longer battery life between charges, but I did buy a car charger, so that I can charge my iPod while I'm commuting to and from work. In the car is where I usually listen to my iPod anyway.

dordale :)

[Moritz]

i always thought that the battery life also depended to a great amount on the data per second rate of a file.

that should give the audible files a big advantage over your everyday 128 kb/s mp3's - considering, that *.aa come at ca. 32/kb at the highest quality option (but please don't hit me, if my calculation is totally wrong, my membership with audible is only 2 days old, but i love it already).

and that should more than offset the battery drain from the hard drive usage, since the 32 mb the ipod puts into its cache should give you more than 2 hours of playtime before the hard drive would have to spin again.

but that is all theoretical and maybe just plain wrong - it's too late, i just got back from work and am tired.

so why does the ipod have to access the hard drive more often with a big file anyway? why doesn't it just load the first 32 mb and plays them? i see, i don't understand computers...

well i am sorry for not answering your question. i only brainstorm along because i hoped that the battery life would be longer with
*.aa files because of the lower data rate. i did not perform any testing as of now - to busy listening to my first audible-file: cold mountain ;)

[CarbonRods]

Five to six hours is all I get when listening to .aa files

CR

[arsolot]

Like duncman I've got a 2g 10Gb iPod. My primary iPod use is for Audible.com content. Listening to books was a major factor in my decision to acquire an iPod.

I must admit I've never noticed that my battery drains quickly from the books. I don't keep more than one or two books on the iPod at a time. I listen to the iPod in relatively short sessions, though, like 45 minutes in the morning while working out and getting ready for work, and then in my 20 to 30 minute commute to and from work. Manytimes, if I've got the time, I listen during a lunch break for 1/2 hour or so.

But, I've not noticed that the battery life is short, and it's never been an issue for me.

[duncman]

Thanks. I bought a refurbished iPod so I was beginning to wonder if it had a sub par battery. I'm glad to know that my battery is average.

[pi227]

I was under the impression that the data rate of the file didn't matter.

Doesn't it load about 20 minutes of content into memory? If this is the case it's impressive to get 5-6 hours of battery life.

[dordale]

The following is from Apple's Website:


iPod's cache works best with songs of average file sizes (less than 9 MB). If your audio files are large, or uncompressed (including AIFF format), you may want to compress them, or use a different compression method, such as MP3 or AAC, when importing them into iTunes. Also, consider breaking very long songs or tracks into shorter tracks that have smaller file sizes.

http://docs.info.apple.com/article.html?artnum=61434

So, according to this, smaller size files should work better. Unfortunately for us audible.com listeners, there is no way to break their files up into multiple smaller files.

dordale :)

[mewyn]

I have a simple answer for you on why Audible formats drain your battery more than MP3 or AAC. The CPU, as far as I know, on the iPod has hardware assisted MP3 and AAC decoding. The Audible format is done all by software. Now when a mobile processor like this needs more CPU speed for one of those formats, it usualy will be made to dynamically up it's clock frequency, therefore upping it's battery consumption.

[Jim Reese]

As previously stated here, the iPod's memory buffer is 32MB. Assuming all of that is available for audiobook content, I did some simple calculations with several audiobook titles I have and consistently reached the same results for a given bitrate, so I'm pretty sure it's accurate. This was simpler than going into bits and bytes and trying to figure out whether 1K = 1000 or 1024 bytes, etc.

Assuming you're using Type 4 content (32 kbps) as I am, a typical audiobook such as "The Second Coming of Steve Jobs" that is 108.2MB in size and 7 Hrs 54 Min in length would yield:

474 minutes / 108.2MB * 32MB = 140 minutes

So, that 32MB of buffer should play for about 140 minutes (2.33 hours) before the hard drive needs to spin up to refresh it, assuming you let it play continuously. Using files of lower quality, this would extend the time even further. For example, Lonesome Dove Part 1 (8 kbps) would play for:

370 minutes / 22.4MB * 32MB = 528 minutes (8.8 hours)

I have a 2nd generation 20GB ipod with a battery that lasts 10-12 hours on a full charge. On a recent trip from SC to NY, I obtained 13 hours of Audible playback from full charge to dead battery listening to Timeline (15.2 hours). I paused playback a number of times, even let it shut itself off when I stopped for gas and food, but otherwise it played continuously, and I didn't use an automobile charger, just the iPod built-in battery. I actually obtained longer playback times than I could achieve with just music playing, and I believe it's because the hard drive doesn't have to spin up every 15-20 minutes to refresh the buffer (more if you bounce around songs a lot). I'm not sure why others are experiencing shorter battery life with Audible titles, since my experience is that I get longer battery life listening to audiobooks than I do with music.

[Moritz]

Originally posted by Jim Reese
Assuming you're using Type 4 content (32 kbps) as I am, a typical audiobook such as "The Second Coming of Steve Jobs" that is 108.2MB in size and 7 Hrs 54 Min in length would yield:

474 minutes / 108.2MB * 32MB = 140 minutes

So, that 32MB of buffer should play for about 140 minutes (2.33 hours) before the hard drive needs to spin up to refresh it, assuming you let it play continuously. .

I assumed the same (see my post above) and up until now, i did not notice any substantial shortage in battery time when listening to *.aa files compared to mp3s.

[robert]

Yesterday began an Audible book immediately after removing my fully-charged 3G iPod from Charging connection. Over two days listened to 7 hours 49 minutes of the Audible book before losing battery power.

So, pretty close to the advertised 8 hour battery charge life in spite of my hardly ever running the battery all the way down before recharging. Usually find myself recharging iPod with a quarter or more charge. Pretty consistent use and recharging of iPod since July '03. Often listen in automobile connected to cigarette lighter power source, regardless of the charge level. Point being that my erratic charging habits don't seem to have reduced the life of the battery charge.

Rarely have an opportunity to listen to this much over so short a time, so I thought, may as well benchmark it. :D

Went back to the last bookmark at 7:32 (did not bookmark at power loss at 7:49), and iPod reset.

[Jim Reese]

Originally posted by robert
So, pretty close to the advertised 8 hour battery charge life in spite of my hardly ever running the battery all the way down before recharging. Usually find myself recharging iPod with a quarter or more charge. Pretty consistent use and recharging of iPod since July '03.

Did lose the bookmark, and iPod reset.

The Lithium Polymer battery in the iPod doesn't have any of the characteristics of other rechargeables, so the practice of fully discharging and recharging occasionally to get the maximum performance doesn't do anything to boost performance of this battery, as it has no adverse memory effects of previous rechargeable types. It does, however, have an expected life of 300-500 recharge cycles, so I try to keep it on the charger as often as I can, including in my car. I do love having the 12 hour model, and won't consider going to one of the newer models anytime soon. Hopefully, future iPods will have better battery life. Gotta love that Dell player with the 16 hour battery, at least in concept.

I have been burned a few times myself with the iPod resetting and losing the bookmark, or more often than not, myself hitting the BACK button inadvertently and restarting at the beginning of the title. I've learned the advantages of occasionally making a mental note of the current location in the book, so that I can find my place again without much trouble if these things happen.

[robert]

Originally posted by Jim Reese
... It does, however, have an expected life of 300-500 recharge cycles, so I try to keep it on the charger as often as I can, including in my car. ...

Help me on this one, what does keeping it on the charger do? If there are 300-500 recharge cycles seems keeping it constantly recharging would reduce the calendar life of the battery. What am I missing here?

Thanks.

[Jim Reese]

The 300-500 recharge specification assumes each cycle is from fully discharged to fully charged. Or, if you only let the iPod discharge half-way each time before recharging, you would expect a lifetime of 600-1000 recharges.

By keeping the battery charged up as much as possible, you effectively extend the life of the battery. This goes against what most people have been taught about rechargeables, but as I pointed out in my previous post, Li Ion and Li Polymer batteries are different animals.

Just think, in another year or two, we will probably see iPods powered by fuel cells running on Methanol, and you'll be able to probably get 40-60 hours or more on a refill. Just think of what this will do for laptops.

[robert]

Originally posted by Jim Reese
The 300-500 recharge specification assumes each cycle is from fully discharged to fully charged. Or, if you only let the iPod discharge half-way each time before recharging, you would expect a lifetime of 600-1000 recharges.

By keeping the battery charged up as much as possible, you effectively extend the life of the battery. This goes against what most people have been taught about rechargeables, but as I pointed out in my previous post, Li Ion and Li Polymer batteries are different animals.

Just think, in another year or two, we will probably see iPods powered by fuel cells running on Methanol, and you'll be able to probably get 40-60 hours or more on a refill. Just think of what this will do for laptops.

Help me with this, please. For simplicity, assume the lower number for both cases. Assume the iPod runs four hours a day.

If I charge it every day, allowing only a half-way discharge, then the battery will last 600 days.
If I charge it every other day, allowing the 3G iPod to fully discharge, then the battery will last for 300 charges X 2 (for every other day) = 600 days.
Sort of intuitively, I accept your recommendation to keep the iPod charged, but the numbers don't seem to bear it out. What am I missing? Are you saying, keep the iPod drawing power from, say a cigarette lighter adapter, to reduce the need for charging and thereby the wear and tear on battery life?

I don't want to know where we will plug in the iPod if we run it off methanol. (Just trying to keep up with the responses to my suggestion to suck on an ear bud to fix an ear bud that is buzzing. :cool: )

Thanks for the post. I had no idea about the difference in batteries, assuming the traditional wisdom about let it run down was best. It is nice that your recommendation coincides with my charging habits.

[Jim Reese]

Don't think of it as number of days, think of it as number of cycles... if the specs for the iPod battery stated that it would last exactly 500 full-cycle charges, then discharging it halfway and recharging it would use up 1/2 of one cycle, so you would then have 499.5 cycles left. If you then discharged it fully and recharged it to full, you would then have 498.5 cycles left. It's like a counter for number of charge cycles remaining in it's useful life. So, if you want to extend your battery life as long as possible, you should listen to it using the AC adapter as much as possible. When I drive, or when I listen in bed, I have mine plugged into the charger to minimize any unnecessary drain on the battery. Basically any use of the battery takes a little away from it's useful life. That's not to say that you should keep yourself tethered to the AC adapter... the iPod is designed to be mobile. It just makes sense to utilize the charger whenever you can to help your battery last as long as possible.

In previous rechargeable battery technology, this approach wasn't recommended, because the batteries had memory effects, and keeping the batteries fully charged most of the time tended to shorten their output for a given discharge cycle. The only way to restore the full capacity of a charge was to occasionally fully discharge the battery and then recharge it. Li-Ion batteries are much less susceptable to that characteristic.

As far as recharging a methanol fuel cell, it will be no more difficult than refilling a cigarette lighter with fluid. And methanol is fairly inexpensive, so it should be a good thing.

[DylPod]

Originally posted by mewyn
I have a simple answer for you on why Audible formats drain your battery more than MP3 or AAC. The CPU, as far as I know, on the iPod has hardware assisted MP3 and AAC decoding.

That's interesting. I was wondering if that was the case.

Format 4 is mp3 encoded inside of some Audible wrapper. The others are a different codec. It would be interesting to test whether the different Audible formats cause differences in battery life.

[DylPod]

I looked this up and the Portal Player chips used by the iPod and mini to decode mp3 and aac also do Audible's codec - ACELP.net - in hardware.

[Virduk]

Originally posted by duncman
What kind of battery life does anyone else get with Audible content? I use my iPod to play books about 95% of the time and I guess my battery is only good for only about 6 hours between charges.

I've turned off the backlighting and the equalizer to maximize battery life. I've heard that files (books or songs) > 9MB make the iPod use the hard drive more often and drain the battery faster. Of course most audible books are much bigger than this.

I was wondering about that, and whether it would be worth my time to break up some of the audiobooks of mine I have in MP3 into a multitude of sub-9MB files.

[robert]

As I said in earlier post, I got very nearly the 3G 8 hour rated battery life with 7:49 playing all Audible content over a two day peroid. That makes me guess that shorter battery life is a function of a particular battery, not file content.

[pax]

As one who uses an ipod almost exclusively for listening to books I have to tout the Dension ice-link for listening in the car. The ice-link lets you charge while listening and *no more cd's or tapes*. Pure heaven!

[Tom@densionusa]

Originally posted by pax
As one who uses an ipod almost exclusively for listening to books I have to tout the Dension ice-link for listening in the car. The ice-link lets you charge while listening and *no more cd's or tapes*. Pure heaven!

Not to mention the ICE>Link cradle automatically charges the iPOD while in the car! :D

[davidctaylor]

I have a new 2G mini and seem to be experiencing less battery life with Audible content. It doesn't seem like there is a definitive answer out there. I suppose when I have some time on my hands I'm going to have to play it from a full charge until dead on both music and audiobooks and measure the difference.

Has anyone else done this? I know one posted got almost the full 8 hrs for his version of the ipod, but what would he get with music? More? Or the same?

I guess I'm just curious if anyone has done a test like this, because there IS a quote from Apple saying that larger files will consume more battery due to caching issues.

[Jim Reese]

David, congrats on the new 2G iPod mini. I'm sure you're loving it.

While some have claimed to observe differences in playback times for Audible content vs. music, I still believe the differences are mainly the result of other factors. I have observed at various times that my iPod, when playing strictly music, will tend to exhibit better battery life at some times, and shorter battery life at other times. I generally don't hunt around a great deal, often just letting it fly on random play for hours. I have observed better overall times playing Audible content than in playing music.

To briefly restate how the iPod operates: The iPod has a 32MB RAM module, which is filled initially, and then the hard drive spins down to save power. As the files stored in RAM are decoded and played, at some point the hard drive will spin back up to refresh the RAM with new content, and then spin down again. The vast majority of the time your iPod is playing, the hard drive is at rest. The cycling of the hard drive is the biggest drain on the battery. If you've ever loaned your iPod to someone who has never used it, watch them as they sample songs, constantly selecting new songs, and keeping the hard drive spinning. After an hour or two, you can see a drastic reduction in battery charge remaining.

For comparison, I will assume you are listening to Audible content of Format 4 (MP3), which is encoded at 32 kbps. And, I'm assuming your music content is at a minimum rate of 128 kbps.

Streaming music at 128,000 bits/sec (16,000 bytes/sec) will deplete the contents of RAM in about 2000 seconds (33 minutes). Streaming Audible content at 32,000 bits/sec (4,000 bytes/sec) will deplete the contents of RAM in about 8000 seconds (133 minutes). As you can see, playing Audible content would result in the hard drive having to spin up only 1/4 the number of times required for streaming music, assuming continuous play with no operator interaction. During the 15 hour battery life, streaming music continuously would result in the RAM being refreshed a total of about 27 times, while only about 7 times for Audible playback. Theoretically, in a controlled test where all other conditions (same volume setting, full charge), the Audible playback should be longer than music playback. For music encoded at higher than 128 kbps, the playback time should be a bit less as the hard drive spins up even more to refresh the RAM.

There are some who claim that decoding the data stream for Audible content requires more power than that for music. Without seeing any published information from Apple on this, there's no way to be sure. Conducting your own tests might prove interesting and I would suggest you post your results here if you do perform the tests.

In my own tests, I have observed Audible content playing for about an hour longer than music content, given the same conditions, and no interaction on my part. Your results may vary. In everyday playback, I do believe the hard disk spinup has a far greater effect than decoding power requirements, but in a controlled test with no interaction, the hard disk effect would be minimized, and the decoding effect would be more of a factor.

[zerock]

this is quite a dilemma.