Touch Should I let the battery drain before recharging?

[Airlane1979]

I have a used Kobo N905 Touch which is, I've read, powered by a Lithium-ion Polymer battery. I'd like to keep the battery life as long as possible, as replacing it is far from easy. Should I wait until the Touch displays a 'Low Battery' message before recharging, or does this kind of battery not have a memory effect (which significantly reduces long-term battery life if you repeatedly recharge it before it is drained)?

[davidfor]

Short answer: Don't worry about it. Use the device when you want to, charge it when you can.

Longer answer:
Li-Ion batteries do not suffer from any memory affects like NiCads. Partial charge cycles are safe. Last I looked, they were considered to last about 500 charge cycles. Partial cycles add up to a full cycle (ten 10% discharge and recharge cycles is roughly the same as a full discharge/recharge cycle). As soon as they are made, they start losing capacity. They are likely to be at 50% after two or three years.

You can extend the life of Li-Ion battery by charging to about 40% and storing in a fridge. Or, keeping the charge level in the 30%-70% range. Exposing them to high temperatures will reduce their life. Letting them completely discharge and stay there for a while, is bad and the natural self-discharge could drop the charge level below the safe recharge point. But, "a while" is probably weeks, not hours.

Overall, anything you can do to extend the life of a Li-Ion battery is inconvenient and means you don't actually use the battery. And they don't have enough effect to make them worthwhile.

As you have an N905 Touch, the battery has probably already aged a lot. They haven't been made for at least six years. Mine, bought in November 2011, still has some life, but, I doubt if it would last more than a couple of hours of reading. But, my wife's Touch battery died a year or so ago.

[Uschiekid]

And my Kobo Glo was bought 6 years ago and still keeps a charge well (although I read with it less since getting my aura one earlier this year). It is a bit of luck how long a battery will stand up. I expected to have the battery last noticeably shorter after 3 years at most, but although I'm sure it's not the same as day one, it's not noticeably shorter even now.

[Tarana]

So long as you immediately put your device on the charger as soon as it says Low Battery, your battery will last a long, long time. My brother and I had several identical gadgets and in every case, my item had much more battery life than his because I regularly charged before it was out of charge. My Itouch has been in continual daily use since I bought it in November 2012. I get about 18 hours out of a charge now, so have to remember to dock it every night now.

[Airlane1979]

Thanks for the useful and thoughtful replies. It seems that, if I charge it every day, it will not induce a memory effect, so I'll no longer wait for the Low Battery message. I've not been able to discover online if the Touch's Li-Ion Polymer battery works differently in this respect to a normal Li-Ion battery.

[Ozymango]

Originally Posted by Airlane1979

It seems that, if I charge it every day, it will not induce a memory effect, so I'll no longer wait for the Low Battery message. I've not been able to discover online if the Touch's Li-Ion Polymer battery works differently in this respect to a normal Li-Ion battery.

The one thing all Li-Ion batteries have in common is:

1) They perform better if kept charged, e.g. you'll get better response and life out of your li battery if you keep it mostly charged, don't let it get too low before you recharge it.

2) If the voltage gets too low (i.e. if the battery is discharged below normal use, like if there's something actively draining the battery even if the device is not powered on) your battery can "sleep" to the point where it'll basically need a jump-start to get going again.

So short version: It's much better to keep an Li-Ion battery charged, than to let it go too long between charges, don't worry about any memory effect, keep it charged! :-)

[davidfor]

Originally Posted by Ozymango

The one thing all Li-Ion batteries have in common is:

1) They perform better if kept charged, e.g. you'll get better response and life out of your li battery if you keep it mostly charged, don't let it get too low before you recharge it.

That isn't really correct. The overall life is actually better if the charge level is kept closer to the middle of the range. The maximum charge level (where the charger turns off) is a tradeoff between runtime for each recharge and overall life. The higher the charge, the shorter the overall life, but the longer the device will run. A lot of laptops had (still have?) a "battery saver mode" that was simply changing the charging to not go past 80%. There is also an absolute maximum charge level beyond which the battery will be damaged.

Similarly, there is minimum level where the battery will be damaged if you let the charge level drop below this. And the zero charge point is sufficiently above this that if the battery hits this, the device won't push it to much further down while shutting down. And that the natural self-discharge of the battery won't drop it down below the safe recharge point if you don't recharge it immediately.

2) If the voltage gets too low (i.e. if the battery is discharged below normal use, like if there's something actively draining the battery even if the device is not powered on) your battery can "sleep" to the point where it'll basically need a jump-start to get going again.

Which could be a really bad idea. If the charge level drops to low, or is charge to high, the battery could be damaged and become dangerous. And in this case, dangerous means "could explode".

So short version: It's much better to keep an Li-Ion battery charged, than to let it go too long between charges, don't worry about any memory effect, keep it charged! :-)

Well, the reason not to worry about a memory effect is that there isn't one. But, just use it and charge it when you can is a good way to use them.

[the.Mtn.Man]

Originally Posted by davidfor

Longer answer:
Li-Ion batteries do not suffer from any memory affects like NiCads.

Even NiCads don't suffer from "memory" issues like people think. The problem is that back when NiCad was the most popular rechargeable battery type, we didn't have "smart chargers" and built in protection circuitry like we have today, so it was very easy to overcharge and over-discharge a battery which would damage the cells and reduce their capacity. Ironically, it was the conventional wisdom that a NiCad should be drained completely before recharging that often caused rather than prevented the "memory effect".

Modern technology has solved all these problems, so it is always safe to "top off" the battery.

[Ozymango]

Originally Posted by davidfor

That isn't really correct. The overall life is actually better if the charge level is kept closer to the middle of the range.

Then actually what I said was correct -- better to keep the battery charged than let it get too low.

I mean I do grok your technical points about maximizing li-ion battery life and all that stuff, the nitty-gritty physics of the deal, but really c'mon -- your average normal human user (like the perfectly nice person who asked the question in the first place) will get by just fine if they use their li-ion devices like normal people, if the battery gets so low that your device shuts down or starts beeping and warns you to plug it in or replace battery immediately, then plug it in or replace battery immediately. Conversely if you use it for half an hour and the charge is at 75% and you plug it back in to the charger, the mechanics and technicians who designed and built your favorite device pretty much took into account the realization that your average normal human user is gonna plug and unplug their devices under all sorts of conditions and, frankly, it's just not gonna make that big a difference in the real world.

So I'll try again: If your battery shows low, plug it in, ideally until it says "charged." Use it for what you need it for, and plug it back in when it says "battery low." In between you can leave it on the charger and that's okay. Now enjoy your devices and go play.

[the.Mtn.Man]

Lithium ion battery lifetimes are rated in charge "cycles", meaning one full charge and one full discharge. So if you discharge your battery to 75% and then top it up, that's 1/4 of a cycle. The average life is 500 cycles before the battery begins to exhibit a reduced capacity, and it's almost impossible to significantly change the lifespan with normal use.

Long story short, don't worry about it. Just use your device and charge when needed.

[Ozymango]

Originally Posted by the.Mtn.Man

The average life is 500 cycles before the battery begins to exhibit a reduced capacity, and it's almost impossible to significantly change the lifespan with normal use.
.

Kinda along those lines, no matter how good you treat your li-ion battery, they just don't live longer than 2-3 years due to [complex chemistry/physics I don't really understand]. That is, even if you completely baby your battery, and/or if you buy a brand-new battery and leave it on the shelf untouched (well, charge it occasionally but don't really use it) for 3 years, it'll still slowly get weaker and weaker over time, it won't hold a charge. I work tech support and we had a customer who bought a couple of spare batteries for her laptop at the same time she bought her laptop, and she found out the hard way that it's a much better idea to just use one battery as long as possible, then replace it with a new and I mean NEW battery when you need to [she didn't rotate the batteries in her laptop, she just used the same one for a couple years, and thought she'd just use one of the other batteries in a couple years when the first went dead, i.e. she thought she wouldn't need to buy another battery in the next six years]

Basically she ended up with three dead batteries at the same time. And those puppies weren't cheap, so she was a bit put-off. So we try to warn people not to buy a bunch of extra batteries unless they're swapping them out concurrently and just always want to have a spare ready for today.

[John F]

Originally Posted by Ozymango

Kinda along those lines, no matter how good you treat your li-ion battery, they just don't live longer than 2-3 years due to [complex chemistry/physics I don't really understand]. That is, even if you completely baby your battery, and/or if you buy a brand-new battery and leave it on the shelf untouched (well, charge it occasionally but don't really use it) for 3 years, it'll still slowly get weaker and weaker over time, it won't hold a charge. I work tech support and we had a customer who bought a couple of spare batteries for her laptop at the same time she bought her laptop, and she found out the hard way that it's a much better idea to just use one battery as long as possible, then replace it with a new and I mean NEW battery when you need to [she didn't rotate the batteries in her laptop, she just used the same one for a couple years, and thought she'd just use one of the other batteries in a couple years when the first went dead, i.e. she thought she wouldn't need to buy another battery in the next six years]

Basically she ended up with three dead batteries at the same time. And those puppies weren't cheap, so she was a bit put-off. So we try to warn people not to buy a bunch of extra batteries unless they're swapping them out concurrently and just always want to have a spare ready for today.

And yet I have multiple Li-on devices that are >3 years. My last laptop was +5 years, and seemed fine. I'm using a Glo HD, a device released late 2012, and the battery continues to work well.

Edit:. Oops, the Glo HD was released spring of 2015.

[John F]

I'm going to use my Glo for my next read to see how it does.

[davidfor]

Originally Posted by Ozymango

Then actually what I said was correct -- better to keep the battery charged than let it get too low.

To me, your statement read as "keep the charge as high as possible". That's what I intended.

I mean I do grok your technical points about maximizing li-ion battery life and all that stuff, the nitty-gritty physics of the deal, but really c'mon -- your average normal human user (like the perfectly nice person who asked the question in the first place) will get by just fine if they use their li-ion devices like normal people, if the battery gets so low that your device shuts down or starts beeping and warns you to plug it in or replace battery immediately, then plug it in or replace battery immediately. Conversely if you use it for half an hour and the charge is at 75% and you plug it back in to the charger, the mechanics and technicians who designed and built your favorite device pretty much took into account the realization that your average normal human user is gonna plug and unplug their devices under all sorts of conditions and, frankly, it's just not gonna make that big a difference in the real world.

So I'll try again: If your battery shows low, plug it in, ideally until it says "charged." Use it for what you need it for, and plug it back in when it says "battery low." In between you can leave it on the charger and that's okay. Now enjoy your devices and go play.

Sorry, but that makes it sound like it is better to follow that pattern. It implies that charging before the battery hits the low level is a bad idea. It implies that not charging to the full level is not a good idea. I'll stand by my statement in the first line of my first post in this thread:

Don't worry about it. Use the device when you want to, charge it when you can.

[davidfor]

Originally Posted by the.Mtn.Man

Even NiCads don't suffer from "memory" issues like people think. The problem is that back when NiCad was the most popular rechargeable battery type, we didn't have "smart chargers" and built in protection circuitry like we have today, so it was very easy to overcharge and over-discharge a battery which would damage the cells and reduce their capacity. Ironically, it was the conventional wisdom that a NiCad should be drained completely before recharging that often caused rather than prevented the "memory effect".

Modern technology has solved all these problems, so it is always safe to "top off" the battery.

I have to admit to not having used NiCads for a long time and not looking into them. Most of my knowledge came from the '70s and '80s with radio controlled planes and cars. I had a look when my first laptop battery died and discovered that LiIon should be treated differently. But, the rules for NiCads seemed to be the same. Since then, I've checked the LiIon info occasionally, but don't use NiCads so have never rechecked that.