Possible Way To Extend Battery Life?

[Immerman]

So I imagine everyone here has suffered from "battery fade" on some piece of tech - you know, the way your laptop battery capacity is cut half every 6-12 months. This is a relatively well understood phenomena, at least for lithium ion batteries, and is accelerated by heat and extremes of charge level - hence the Prius being programmed to keep the battery between 40% and 60% charged - you "waste" 80% of your capacity, but the battery lasts much longer.

So what I'm thinking is, is there some way to prevent the pandora from charging all the way - i.e. an automatic cutoff circuit of some sort? It's easy enough to set the lower limit in software (critical hibernation level = 20% or something), but I'm not so sure about the upper limit. Any ideas?

 

[lulzfish]

There's no cutoff circuit, but it should be easy enough to do through the same mechanism that triggers the low battery alarm.

Or just through a program that checks acpi every minute or so, and tells you how the battery's doing.

 

[Kramy]

Why would you want to? Pandora batteries are relatively cheap.

 

[Squidge]

I don't think there's a cut off as such, but you can interrogate the battery with a background program and tell the user to remove the power cord

TBH, there's probably a way to stop the system from charging too. Have a look at this datasheet: http://focus.ti.com/docs/prod/folders/print/tps65950.html

 

[RajTakhar]

Can't see the point of extending as such - because you would in theory just have to spend $10 to $20 on replacement battery from OP, flip the back cover and replace.

Can see some logic in prolonging via app usage - but as we have a relatively cheap power source and changing is straightforward

 

[Immerman]

Well, personally unplugging it probably wouldn't work - I plan to normally recharge it overnight along with my cell phone and brain, and a 2am wake-up-and-unplug-me alarm is not acceptable. Thanks for the data sheet though - I'll have to dig through that sometime when my inner engineer wants to play.

As for why not just run it into the ground and replace it - the same reason I use cloth towels and ceramic plates instead of paper - I don't approve of the philosophy that underlies a disposable lifestyle, not to mention the waste it entails. And sure it's not terribly expensive to replace (provided OpenPandora is successful enough to stick around for as long as I want to keep using my Pandora), but why would I want to if a little preventative maintenance can extend it's lifetime significantly?

Personally I'd rather have 6 hours of battery life for 12-18 months than 8 hours that drops to 4 by the end of the year - especially since I doubt I'll often want to use it for eight hours without recharging. Maybe the difference won't be as extreme as that - unlike a laptop there won't really be the temptation to just leave it plugged in while using it around the house, but I'm still waiting for electronic gadget that will let me leave it plugged in to keep it "topped off", without giving it that last 5-10% charge that causes the worst of the damage.

 

[Klaus]

Is this really this bad with some li-ion-batteries? The one in my ThinkPad is well over two years old and the capacity only dropped from 77750 mWh to 67470 mWh. This machine is constantly on, runs quite hot and the battery is almost never taken out.

 

[Immerman]

It can be. My Dell laptop dropped from almost 8 hours to under 2 in about a year. I believe the culprit is leaving it plugged in, especially when using it. From what I've read it sounds like those last few percent worth of charge dramatically accelerate the degredation. Combined with the heat from running it for prolonged periods.... well lets just say I learned my lesson.

I also became mightily annoyed by the fact that *nobody* puts an early charging cutoff circuits in consumer electronics. Are replacement batteries really that much of a profit center? What's an engineer to do?

 

[Kramy]

I also became mightily annoyed by the fact that *nobody* puts an early charging cutoff circuits in consumer electronics. Are replacement batteries really that much of a profit center? What's an engineer to do?

LG does, but their laptops are super expensive. They also design their laptops with reinforced frames and stuff, to survive vibrations from car usage, ferries, etc.

From the sounds of it, Klaus's ThinkPad might, too.

 

[Izomiac]

LG does, but their laptops are super expensive. They also design their laptops with reinforced frames and stuff, to survive vibrations from car usage, ferries, etc.

From the sounds of it, Klaus's ThinkPad might, too.

Sony puts it in theirs I know. But I'm also kinda stumped as to why people wouldn't want this... I mean, you have a choice of an extra ~20% battery life for a few months followed by a degradation to uselessness, or you can just not use the top 20% of charge capacity and keep your ~80% for years. Needless to mention that Murphy's Law ensures that the battery will need replacing at the worst possible time. Lithium ion batteries also degrade from time of manufacture, so keeping spares isn't ideal either.

BTW, I completely agree that this is a necessary feature. Given how most of my electronics "died", I'm seriously thinking that manufacturers use lithium ion battery lifespans to ensure people upgrade to newer models after a few years (everything else probably lasts 5 or 10 times longer than the battery).

 

[WhiteBat]

all i can think of is

turn screen brightness down
use headphones instead of the internal speakers
close lid when listening to music
reduce clock speed for certain apps (maybe something that does this automatically?)
whisper sweet compliments to your pandora

 

[Izomiac]

all i can think of is

turn screen brightness down
use headphones instead of the internal speakers
close lid when listening to music
reduce clock speed for certain apps (maybe something that does this automatically?)
whisper sweet compliments to your pandora

A PowerTop like utility would probably help immensely, if one can be written for ARM processors. In any case, that's battery life, as in hours/minutes/seconds which is a function of battery charge level and load. Lithium ion "fade" is more precisely declining battery charge capacity in Watt-hours which is a function of battery age, temperature, and charge level. E.g. a 10 Watt-hour batter (just a guess) might run the Pandora for 10 hours doing the stuff you mentioned. But if you kept it at nearly 100% charge all the time, that might decline to 8 Watt-hours after a year, so you'd only get 8 hours of run time even if you didn't change what you were doing.

 

[verm71]

How about overcharge protection? For instance, say I forget it and leave it plugged in for an entire weekend and realise Monday morning when I'm leaving to hop on the bus that it was left plugged in all weekend. Did I just kill my battery by doing that? Or did the charger go to a trickle charge after a certain max %?

I've had some brand new NiCd's do that to me back in the 90's when I used a cheap charger (incidentally the charger that came with them as a bundle).

 

[lulzfish]

I think that's one of the basic requirements of any li-ion charger, the Pandora won't have a problem with that.

The duty cycle and current are lowered in the last 10% or 20% of the charge, and it stops charging at 100% and just maintains the battery there.

Even, like, car battery chargers do that. Your Ni-Cd charger must have been a timer-only charger, they don't make those anymore. They're impractical.

 

[greendots]

What ways are there to save battery with the SD cards? Is it possible to save the file and folder listing to memory or nand and then unmount the card. After when the user tries to access a file it will automatically mount? A simple way would be to have a file manager for each card slot that will mount the card when the file manager starts up and unmount when closed. For playing mp3s in a random order it would increase battery life by saving the next 25 or so songs (150mb) to ram and then unmount. Also only using one card for your most common files. Any one have other ideas?

 

[Pleng]

I can't remember where I read it but I'm pretty sure that the power use of the SD cards is negligible.