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reppans
Jun 16, 2012, 10:05 AM
I've heard that Thinkpad laptops allow you set when the battery charger starts and ends charging (eg, charge at 30%, terminate at 80%), when the device is plugged in. Was wondering if there was a battery management app like that for our iPads.

I'm pretty well versed on Li-ions, and am interested in terminating charging at levels less than 100% to increase cycle life.

Thanks.



Night Spring
Jun 16, 2012, 11:25 AM
I've never heard of an app like that, I don't know if it's possible, and if it were I'm pretty sure it wouldn't be allowed in the app store, it'd have to be a jailbreak app. In any case, I doubt you need such a thing, iPad battery is insanely great, you can't compare it to a Thinkpad battery. You really don't need to manage the iPad battery, just charge it while you sleep every night and it'll last you until you are ready to upgrade to the latest iPad.

reppans
Jun 16, 2012, 12:09 PM
Your probably right about the Apple big brother thing.

I just get concerned with these non-removeable batteries that the batteries ultimately determine the useful lives of the products. I like to hold onto devices well after they're obsolete and a lot longer than the manufacturers expect, or would like (going on yr 4 with my 3G iPhone). Also, I got kids I can hand these devices down to.

If you consistently charge a Li-ion to 90% (4.10v) instead of 100% (4.20V) you can double the number of charge cycles, for example. Seems worth it to me. There's a bunch of other battery care tips, but this seems to be the biggest bang for the buck.

Night Spring
Jun 16, 2012, 12:58 PM
If you consistently charge a Li-ion to 90% (4.10v) instead of 100% (4.20V) you can double the number of charge cycles, for example. Seems worth it to me. There's a bunch of other battery care tips, but this seems to be the biggest bang for the buck.

Double the number of cycles? How does that work? I'm afraid I don't know much about batteries, but the way it was explained to me was that with the latest battery technology, it didn't matter what percentage you charged the battery to. That is, say you charged from 0-50% twice, that is the same as charging from 0-100% once, and there is no way to shorten or lengthen the number of life cycles. I may have misunderstood, of course.

reppans
Jun 16, 2012, 04:52 PM
Might be worth reading THIS (http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries).

High voltage is one of the stress factors that wears Li-ions. So charging to its 4.2V max, as well as letting sit there at 100%, wears it out faster. So does heat and depth of discharge (DoD). Even age.... but there's not much you can about that.

To help prolong my batteries, I charge off a light timer so I can charge it short of 100% and also have it reach my max charge just before I'm ready to use it (so its not sitting idle at a high voltage while I'm sleeping).

For DoD, I typically use 40% capacity per day. So I can go 100%>60%>20%>Full Charge every other night - OR much better for the battery from a DoD and SoC POV - 80%>40%>Partial Charge (40%) every night.

FWIW, I'm on candlepowerforums and there some battery gurus there that have forgotten more about batteries (any chemistry) than I'll ever know.... their thoughts are very consistent with the link above.

Night Spring
Jun 16, 2012, 07:18 PM
To help prolong my batteries, I charge off a light timer so I can charge it short of 100% and also have it reach my max charge just before I'm ready to use it (so its not sitting idle at a high voltage while I'm sleeping).


Thanks for the link. Going to take me a while to digest all that info, but the following kind of leapt out at me.

“Should I disconnect my laptop from the power grid when not in use?” many ask. Under normal circumstances this should not be necessary because once the lithium-ion battery is full the charger discontinues charge and only engages when the battery voltage drops. Most users do not remove the AC power and I like to believe that this practice is safe.

That sounds like it's ok to leave devices plugged in after they reach 100% charge, and not worry about the timing of when it reaches max charge, like you seem to be concerned about. Am I wrong?

reppans
Jun 16, 2012, 09:26 PM
Thanks for the link. Going to take me a while to digest all that info, but the following kind of leapt out at me.

“Should I disconnect my laptop from the power grid when not in use?” many ask. Under normal circumstances this should not be necessary because once the lithium-ion battery is full the charger discontinues charge and only engages when the battery voltage drops. Most users do not remove the AC power and I like to believe that this practice is safe.

That sounds like it's ok to leave devices plugged in after they reach 100% charge, and not worry about the timing of when it reaches max charge, like you seem to be concerned about. Am I wrong?

i believe this statement refers to the fact that a laptop will not overcharge a Li-ion. If a Li-ion is overcharged >4.3V or over discharged ~ 2.9V? the chemistry becomes unstable and battery can explode when charged again. Not much of a risk with laptops, phones and cameras since these have dedicated batts and the devices have electronics to ensure the batts stay within the safe voltage parameters.

That statement is not really addressing what is best for the battery.... however, these do:

the worst situation is keeping a fully charged battery at elevated temperatures. This is the case when running a laptop off the power grid. Under these conditions, a battery will typically last for about two years, whether cycled or not. The pack does not die suddenly but will give lower runtimes with aging.

and

Commercial chargers do not allow changing the charge voltage limit. Adding this feature would have advantages, especially for laptops as a means to prolong battery life. When running on extended AC mode, the user could select the “long life” mode and the battery would charge to 4.00V/cell for a standby capacity of about 70 percent. Before traveling, the user would apply the “full charge mode” to bring the charge to 100%. Some laptop manufacturers may offer this feature but often only computer geeks discover them.

Another way to extend battery life is to remove the pack from the laptop when running off the power grid. The Consumer Product Safety Commissionadvises to do this out of concern for overheating and causing a fire.


All that said, the battery management I'm talking about is probably not worth doing for the average user. 300-500 charge cycles is a lot and most are fine with upgrading the equipment every two years or so anyway. I figure that if terminate charging a bit earlier, say averaging at around 90%, I can get 600-1000 charge cycles, and 4-5 yrs of use and without significantly declining runtimes that many experience as the battery nears EOL.

(note: I know Apple quotes 1000 cycles, but there's nothing special about their Li-ion chemistry, except perhaps if their internal charger is already set to terminate a 4.10V instead of 4.20V... in that case, you can again double charge cycles by terminating at 4.00V.)

Night Spring
Jun 17, 2012, 12:57 AM
All that said, the battery management I'm talking about is probably not worth doing for the average user. 300-500 charge cycles is a lot and most are fine with upgrading the equipment every two years or so anyway.

That's exactly it, I don't plan on using any iDevice for more than two years. But this has been very informative, thanks.

BTW, the passages you quote seems to be advising against using laptops plugged in with the battery attached -- I'm guessing with non-detachable batteries like the ones in recent MacBooks, the best practice is to unplug them when in use? In any case, it didn't strike me as relevant to my usage of iPads, which I almost never use while plugged in to a power source.

thewitt
Jun 17, 2012, 01:13 AM
There is no risk of over charging iOS devices.

The charging circuitry stops drawing current at full charge and then trickle charges as needed as long as the device is plugged in.

It will not change the duty cycles and is actually healthier on the battery than letting it drop to 10% and charging again.

reppans
Jun 17, 2012, 08:13 AM
BTW, the passages you quote seems to be advising against using laptops plugged in with the battery attached -- I'm guessing with non-detachable batteries like the ones in recent MacBooks, the best practice is to unplug them when in use? In any case, it didn't strike me as relevant to my usage of iPads, which I almost never use while plugged in to a power source.

Laptops are a relatively extreme example (hot, high drain, relatively low capacity batts) as opposed to the iPad or iPhone (cool, low drain, relatively high capacity batts) as a result they are used differently. Laptops - usually plugged in, iPhone/iPad - usually unplugged. However, the things that wear the battery still apply to both types.... for the purposes of this thread that is 1) charging to a full 100%/4.2V, 2) the amount of time the battery sits at full or near full charge, and 3) the number of charge cycles the device uses.

The a plugged in laptop is primarily worn through 1) and 2) and the iPad/iPhone through 1) and 3). To some extent 2) as well - ie. if you plug in an iPhone before you go to bed at 10pm, it will hit full charge by midnight.... then it just sits at 100%, or a reasonably high state of charge, for a third of day until you start using it.

Unplugging a laptop when not in use will only save the battery if it is not in a high state of charge - the article discusses 3.92V, about 50% capacity as being the level the batt is free from voltage stress. Unplugging the laptop when the batt is fully charged does nothing.... the battery is still in a high state of charge.

For the Apple laptops with immoveable batts, I think the best practice would be to (assuming 9-5 usage) keep it plugged in from 9-2, run it off batt 2-5, then let it sit 5pm-9am at 50-60% charge. Without a specific app or program (as I mentioned at top) It's too difficult to manage less than 100% charges on a laptop.

reppans
Jun 17, 2012, 08:30 AM
There is no risk of over charging iOS devices.

The charging circuitry stops drawing current at full charge and then trickle charges as needed as long as the device is plugged in.

It will not change the duty cycles and is actually healthier on the battery than letting it drop to 10% and charging again.

Agree these devices will not overcharge... to do so with a Li-ion would result in an explosion or flame venting, something a manufacturer will avoid at all costs.

With regard to leaving the device plugged in vs using charge cycles up... it depends.

If we're talking about a 2 hr laptop battery used 10 hrs a day, yeah, I rather burn my battery letting constantly sit at 100%, then use up 5 charge cycles. If we're talking Apple's 7 hr batteries in laptops used 5 hours a day, I'd rather use up charge cycles by charging 2.5 hr (say to 80%) and then unplugging and using 2.5 hrs (to around 40-50%), then repeat the next day.

thewitt
Jun 17, 2012, 10:07 AM
A charge cycle is full depletion followed by full charge. Anything less is a partial charge not a full cycle.

Here's the rub.

When you let your battery go flat then charge, it gets shocked and actually loses some of its ability to hold a charge.

This means it's better to charge to 50% and recharge to full four times than it is to go flat to full twice.

xraytech
Jun 17, 2012, 10:33 AM
I've heard that Thinkpad laptops allow you set when the battery charger starts and ends charging (eg, charge at 30%, terminate at 80%), when the device is plugged in. Was wondering if there was a battery management app like that for our iPads.

I'm pretty well versed on Li-ions, and am interested in terminating charging at levels less than 100% to increase cycle life.

Thanks.

I've read all the literature and heard all the myths about these batteries.

Here's my advice...

"Plug In Before Sleep"

Just plug in your iDevice before you go to sleep. I've handed down numerous generations of iDevices to my Sister and she would then hand them down to our Mom. Same charging routine "Plug In Before Sleep" and battery run times have been stellar considering the age and use of the batteries in these iDevices.

To answer your question about an App that will "Control Charger On/Off" I don't think there is one in the native iOS environment. There are a couple of Apps that will Alarm when the battery has achieved Full Charge but these apps are basically egg timers. Beside, iDevices have their own power management.

xraydoc
Jun 17, 2012, 01:48 PM
I have two original iPads that are still both going strong at get charged repeatedly to full capacity and I've yet to notice any significant drop in battery life. My kids use these pretty hard and they're still as good as new as far as I can tell.

Q-Dog
Jun 18, 2012, 10:01 AM
If Apple claims 1000 charge cycles on the battery, you will get a little over 3 years of useful battery use if you fully charge and discharge your device once every day. If you fully charge and discharge your device once every two days, that's 6 years of useful battery life. I think you don't have anything to worry about.

My original iPad 1 gets plugged in almost every night, otherwise I pretty much don't think about the battery. I have not noticed any significant degradation in battery performance and I regularly leave both the 3G and WiFi turned on.