Topping off: A major advantages of rechargeable batts. How often do you top off?

[night.hoodie]

I do think those lipo packs used in cell phones probably do age a lot in 2 years. I don't think they're as robust as cylindrical cells, and they're likely abused a lot more since people use their phones all day long. So, 50% after 2 years doesn't sound unreasonable. (Especially if it's an Apple product trying to make you buy a new phone.)

At the risk of skirting topic, smart cell phones do seem to spontaneously combust more often than other Li-ion powered devices. Apple most certainly does seem to force a hardware update, but I believe they only do this with software updates, feature creep, very often successfully tempting users of older devices to update the software, which invariably slows the device to the point of frustration and uselessness.

That said, regarding cell performance specifically, I do not believe Apple is intentionally crippling their devices with the intent to force a hardware refresh for its user. Rather, I know Apple realizes just how many of these older devices are out in the wild. I think it is more reasonable to assume that Apple takes a very conservative approach to the batteries in older devices, and the "crippling," the change in cell performance, reduced runtime, is intentional only to make use of an older cell safer. It would be devastating even for Apple if suddenly all the cells in their 4+ year old devices in the wild started to fail, en mass. Apple is being smart here, not to force new hardware purchases, but to prevent fires, injuries, deaths and expensive lawsuits. They are taking the correct approach to the real danger inherent in Li-ion cell use, and because of their philosophy, removing any responsibility from the user as far as how to properly care for the cell. IOW, this is not sabotage, but instead conservatism to prevent as long as possible cell failure, even if a particular cell in a particular device is in good shape, there are millions of these things out there, and profiles must be applied as simply as possible, thus across all older devices, just to make as certain as possible no one gets -- and it does happen anyway! I cannot say the same for other smart phone manufacturers that definitely seem to push the envelop, regarding cell performance, and therefor safety.

So I think our paranoia is only half justified, there is definitely a rational benevolent method behind Apple's treatment of older Li-ion cells: preventing never ending legal bills, which does benefit our health.

 

[archimedes]

My point was that, since using a more active battery management style, I have found noticeable real-world benefits.

This has been more evident to me with LiPo in (yes, integrated and monitored, but also more heavily used) electronics, on the order of a ~ 50+ % performance differential, over the course of as little as ~ 2 years.

With a timed charger, it is not too inconvenient to avoid charging over, say, 70%

Whether or not this is "relevant" or "significant" or "worth" the effort, may vary. I know some upgrade their mobile phones every year, while others keep using these devices for much longer.

 

[night.hoodie]

I know some upgrade their mobile phones every year, while others keep using these devices for much longer.

:wave: iPhone 4 here since Summer 2010, original battery.

 

[archimedes]

:wave: iPhone 4 here since Summer 2010, original battery.

Do you "actively manage" your charging, and how much (if any) noticable decrease in battery performance over ~ 8 years ?

 

[Warp]

One of the great things about flashlights that take removable batteries, is you don't have to handicap their available performance for years and years, you can just spend a few bucks on a new battery after several years if need be.

Same thing for a lot of older non-Apple phones.

 

[night.hoodie]

Do you "actively manage" your charging, and how much (if any) noticable decrease in battery performance over ~ 8 years ?

No, I really haven't, I've been bad. I only started learning about Li-ion cells years later. Battery performance in it is abysmal, but consistent, so I know what to expect, and knowing remaining capacity is not something I must look at the battery indicator for, I just know... depending on what I am doing, which is almost never talking on it or calling, that I need to plug it in and charge it, many times a day under heavy use. I can still watch a full length movie streamed over wifi from a local media server, or from a local movie synced to play it on an external display. That's about the limits of the capacity. Its just fine as an iPod still, as the screen doesn't get used much while listening in a car, where I usually, but not always, simultaneously charge it. Also, I'll turn off wifi, or go with airport mode. I keep meaning to get the battery replaced... but these things sometimes sell on eBay for $18. I mean the whole device, not just the battery. $50 is a median price for it, so replacing the battery isn't happening.

 

[archimedes]

One of the great things about flashlights that take removable batteries, is you don't have to handicap their available performance for years and years, you can just spend a few bucks on a new battery after several years if need be....

Clearly there are differing approaches to this issue, as would be expected, but personally I don't consider using rechargeable cells at submaximal SoC to be a "handicap"

I can, and sometimes do, quickly and easily charge these up fully when needed.

But leaving LiIon cells for extended duration at maximal charge will lead to irreversible degradation in performance.

I agree that whether that is considered relevant or not, apart from or despite the cost(s) of replacement, depends on the specific circumstances and situation.

Also of note, given continued improvement in battery tech over a several year time frame, newer cells may have substantially better performance than the cells they are replacing would have had even when new.

 

[WalkIntoTheLight]

A lot of high-powered lights, especially in the "budget" category, use FET drivers to achieve maximum brightness out of the LED. In those lights, if you want the high output, you have to use fully-charged batteries. Performance from a FET driver really sucks when it's down to about 50% charged. (Still better than a linear driver, but not as good as what you expect from a FET driver.)

 

[IonicBond]

For most battery chemistry, especially Li-Ion types, time spent at max SoC is one of the most taxing factors in terms of maintaining service life and function.

Yes! Time at max soc is the killer, mostly from lithium plating of the positive cathode. Inorganic materials also clog the pores of the SEI layer too. So spending the least amount of time to get the job done is the keyword.

Thing is, many chargers are not "adaptive", that is they treat old cells just like new ones and can add to the problem.

Ie, a charger may spend too much *time* trying to bring an old cell to 4.2v (as an example, the whole voltage thing has been covered elsewhere here), and if using a typical cc/cv algo, spend a lot of time in absorb at that voltage.

But, due to use / aging, an adaptive approach like bringing the cell to only 4.1v and allowing for absorb to take place might be the better option timewise. Perhaps cut that absorb current value in half as compared to new as the signal to stop the charge.

Obviously this means programmable chargers, and the time and energy willing to go that far, rather than just simply replace a consumable item a little more often.

 

[Gauss163]

Yes! Time at max soc is the killer, mostly from lithium plating of the positive cathode [...]

Lithium plating is not due to high SOC. Rather it is primarily due to charging at too high current (esp. at lower temps). High SOC greatly accelerates other degradation processes, e.g. see the list below, summarized from this post.

Anode degradation effects due to high SOC
Intercalation of solvent / peeling of graphite/cracking (⇒ loss of capacity [loss of active material / lithium])
Dissolution of electrolyte (cathodic oxidation / anodic reduction) / dissolution of binder (⇒ loss of capacity / power capability)
Decrease of active surface (continuous growth of SEI) (⇒ growth of impedance, loss of power capability)

Cathode degradation effects due to high SOC
Migration of soluble species (⇒ loss of capacity by film formation on anode)
Electrolyte decomposition (⇒ loss of power capability)

 

[Mr. LED]

How long is considered too long to degrade the battery, at maximum SoC?

Some years ago I read on Apple website, they recommended leaving the laptop or other device always charged, and discharging a full cycle every 30 days, to keep the electrons moving. I've done that and been very successful with my lithium batteries. My MacBook is 2 years old, only around 25 cycles, and battery is 96% of health.

My stocked 18650 at home, I discharge/charge fully once a month, then keep them charged for emergencies.

 

[WalkIntoTheLight]

How long is considered too long to degrade the battery, at maximum SoC?

That depends on what you consider degraded.

Some information says that if you leave a lithium-ion battery at full charge, after 1 year the battery will permanently lose 20% of its original capacity.

However, I think that was based on lithium-ion batteries from several years ago. Modern batteries may be better. The real killer is full charge + high heat, like you get in laptops. It's tough to know if your Mac is accurately reporting the battery's health, but it's probably in the right ballpark. In that case, it's likely well-designed to keep the battery cooler than most laptops.

There's also some evidence that suggests once you lose that first 20% of capacity, degradation slows down a lot. So, it might take a year or two to lose 20%, but another 10 years to lose another 20%. Something like that. Of course, internal resistance continues to rise, so capacity at high drain may not be as good.

 

[markr6]

I had a new cell in a flashlight kept in my car. I forget exact numbers but it started at something like 4.17v. Over a year later with no use, it was maybe 4.15v. I said to myself "these people are blowing smoke!"...until I tested the internal resistance, which went from about 50 mOhm to 240!

 

[Mr. LED]

Maybe one month is OK for a constantly charged cell in good temperature.

A cell in a car goes to the extremes of heat over one year, that certainly helped to higher the resistance.

 

[rjhooper]

Great topic!
Many real life examples here expressing practical knowledge!
What about this practical knowledge crossing over to the battery powered car? :thinking:
Maybe a topic for another Thread? or is it, same technology right?

Do you top off your car (battery pack) when you get home, is it topped off while on an extended vacation? Shouldn't they be charged to 90% too? Shouldn't they "rest" after a long commute before charging? and more importantly, aren't they considered a "fire risk" when abused over time? I never here much about this area of lion battery usage although it is the same as my flashlight battery...I guess it's PC not to talk about the similarities of the lion car battery.
Never mind, I figured it out! none of you own one of those battery pack cars...
Those battery packs are going to be an issue in the near future, to be sure. They are expensive to replace too!

 

[marinemaster]

You know reading all these we just got to get something better than battery technology.
I don't have the answer but batteries in general have shortcomings.

 

[Grijon]

>>Questions:
1). Do you top off your batteries, and how frequently?

LSD NiMH is the only NiMH I use, and I top off whenever I want full capacity available, super simple.
Li-ion I try to rotate, so I don't really "top off" so much as charge a cell when I'm ready to put it into use; I try to store the not-currently-being-used cells around 3.8v. That being said, though, I do not hesitate to top off if for some reason I want that particular cell at full capacity.

2). Will you top off a battery that you know only lost 10 - 50mAh when used last?

10-50mAh? Very unlikely would I top off after that little use: even on a 16340 or AAA that's less than 10% used, and I carry backups when I expect to use a light (and usually even when I don't)

3). If topping off leads to exceeding max cycle numbers, what happens to the battery after that number is exceeded?

Battery cycles are referring to the total amount of energy in and out, so topping off makes almost no impact on cycles, especially on NiMH. As has been discussed, internal resistance from sustained high voltage would wear out a li-ion before topping off would reach the cycle limit.

4). Do you still use disposable primary batteries, and in which applications?

I do! I use primaries in lights that get used rarely and/or in harsh conditions like a car's glovebox or trunk. As I type this I have numerous lights stashed and stowed and simply left around the house that have primaries in them; I know that when I get around to playing with them that I won't have to wonder about their state of charge, nor do I have to give a thought to their batteries' health like I would if they had rechargeables in them.
Rarely are my lights critical to my safety, but when in such a situation I will have at least two light sources that are powered by lithium primaries. All true emergency lights (in my vehicles) have lithium primaries.


I try to split the difference between the philosophies of maximizing life and minimizing maintenance.
I would like to share to the users of LSD NiMH that it seems to me that they are truly a no-fuss chemistry so long as you have a good charger: charge them when they're empty, charge them when you want them full, charge them when you're not sure, and just don't worry about them the rest of the time.

 

[Grijon]

I should add that the only primaries I use are lithium: CR123As are lithium by default, and I don't use alkaline AA or AAA because I don't like their liability to leak.