Discovery could extend battery life by replacing tape that causes self‑discharge | Hacker News Reader

Discovery could extend battery life by replacing tape that causes self‑discharge

dal.ca

I have a personal anecdote that is maybe related?

I store some spare car/boat batteries in my garage, and you would think that batteries, in their plastic/insulated containers, should be fairly inert or impervious to odd discharge effects.

However, over years, I have noticed that if batteries are left on the bare floor of a garage, they will discharge over time. Something to do with gradual leakage via the plastic contacting ground (and maybe plus humidity) -- there is some conduction going on!

So instead, you have to store them on well-insulating platforms, say styrofoam or acrylic, and they will hold their charge far longer. But this is on the timescale of months -- I wonder how that relates to the timescale these researchers are investigating (and for often used batteries, I would imagine it matters less).

These little parasitic losses that are rarely studied...

Another hypothesis:

I think that the batteries on the floor will be colder, so are prone to lose charge / fail faster (internal discharge through plates).

Being colder (due to being on the floor) could also bring water vapor condensation on the battery surface, so that could be a path of external discharge (between the battery terminals).

That’s what I would have thought as well.

> I think that the batteries on the floor will be colder, so are prone to lose charge / fail faster (internal discharge through plates).

Cold is good, as long as the air is very dry. It will reduce self-discharge.

> Being colder (due to being on the floor) could also bring water vapor condensation on the battery surface, so that could be a path of external discharge (between the battery terminals).

Bingo. Warmer air holds more water, and as the temperature drops, because cooler air can't hold as much water, it will condensate out and form droplets. Water and moisture are bad for cells, even humidity is bad. A garage is usually not climate controlled. Some awesome folks do climate control their garage, most don't though. Whatever the %RH outside is, the garage will follow. Most US states have a surprisingly high average %RH.

whats the physical process by which water condensation discharges batteries?

Yeah I'm not sure how such low voltage can overcome the lack of any ions in the condensation in which this could occur.

There's likely contaminants on the surface of the battery which, when water is added, become conductive.

if youve ever rubbed pH paper on an auto battery youll realize there is a lot of residual sulfuric acid on the outside of the case.

That mixed with water is pretty conductive.

Yeah humidity increases the conductivity of air by reducing the breakdown voltage of air, not by conducting electricity, because it doesn't conduct electricty, because it's an insulator.

I think of it this way: when it's dry, static electricity can build up, and that's why there are static shocks, when that built up electricity is released. But when it's humid, there's never any static electricity or static shocks because electricity can't build up; it is just constantly absorbed by water vapor. Water is technically an insulator, which is why distilled water is a poor conductor and salty water is a good conductor. But water vapor, even though free of contaminants, increases the conductivity of the air by reducing the air's breakdown voltage,[1] helping to ionizing the air to form plasma. Condensation helps absorb static charges by keeping surfaces moist, increasing surface conductivity. Condensation also damages batteries by oxidizing the contacts, which are steel. Water can even condense under the cathode contact, which is vented, and get into and dilute the electrolyte, leading to capacity loss and possibly shorting the cell by causing the formation of dendrites.

[1] https://en.wikipedia.org/wiki/Breakdown_voltage

In my first job we had several UPSes for racks of equipment that had been augmented with marine batteries for longer life and all the batteries were on slats of wood to keep them off the floor.

I asked and got the same answer you did - they will last longer - but I’ve never understood why.

Either your batteries were old[1], or you're overlooking something else that might have caused increased self-discharge, such as high humidity. Some will say it was a myth, but it was true at one time.

What is a myth is that storing cylindrical cells in your freezer will slow self-discharge, and while it is proven cold storage will reduce self-discharge, the problem with a consumer freezer or refrigerator is that they are humid, so any gains the cold would provide are more than defeated by the humidity, which not only will increase self-discharge, it can damage and short a cell. The humidity in a consumer-grade freezer drastically increases to 80%-95%RH twice a day and slowly drops over several hours. The best place to store cells is in a cool, dry location. And cells are cheap and readily available, and storing cells for years in a freezer, even if it worked, would be wasting a ton of energy just to save a tiny amount of energy, which, again, wouldn't happen anyway.

[1] https://www.mcgill.ca/oss/article/general-science-you-asked/...

Sounds like you could store them in the freezer, but e.g. in a vacuum sealed bag.

As long as it is vacuum sealed from moisture, with all the air evacuated, and not just a ZipLoc bag out of which you "pressed all the air." Otherwise, the air inside the bag is the same air as where it was sealed, maybe the 50%RH of the air in a climate controlled home and kitchen, and temperature changes will cause the vapor in the air to precipitate out into moisture, and back to vapor, and this repeats every time the temperature fluctuates, which usually is twice a day as part of a freezer's frost cycle.

But then you are still using far more energy, and money, to save a minuscule amount lost from self-discharge. Li-ion cells have low self-discharge and only lose about 15% capacity per year. LSD NiMH cells like Eneloop lose about 30% capacity after 5 years. Alkaline cells, surprisingly, lose only 2-3% per year in self-discharge. LiFeS2 cells, like Energizer Ultimate Lithium, have an extremely low self-discharge rate, well under 1% per year, and have more than a 10 year shelf life, though they'll probably hold charge for at least 20 years of dry storage.

I wonder what it would amount to in mAh to lower the temperature of cells to below freezing and maintain that temperature for a year. You'd probably lose in a contest with someone panning gold out of a bottle of Goldschläger.

The latest episode of HBO's "The Last of Us" shows a prepper with this freezer setup for a car battery

https://static1.colliderimages.com/wordpress/wp-content/uplo...

Episode 3. Awesome, and I'm not even a fan of the game. I don't game, but I actually enjoy watching others play games. I tried to watch a play through on YouTube. Amazing, incredible graphics. But booooriiing. Reminded me a lot of Myst, but far less primitive.

FWIW, there's no battery in that screen grab, for a car or otherwise. I'm not sure what is in that refrigerator (freezers rarely have grated shelves, at least, I've only seen them in floor freezers), but it isn't a car battery. Maybe it's components for a battery, though. I wondered at why they chose to show that shot.

> FWIW, there's no battery in that screen grab, for a car or otherwise

All the components of a car battery. You can see the lead on the right.

Where's the case?[0] I also don't see the point of lowering the temperature of a plastic battery lid. It's an insulator. I guess it would keep dust off it, though.

[0] https://d3as1itr0z6zbr.cloudfront.net/assets/marketingConten...

The lid was so they can concisely communicate to the average viewer that we're looking at components for a battery.

(spoilers, and partly replying to your earlier comment above): It's shown here because part of the storyline requires getting a car. The story specifically has him with a car available, but no battery which he has trouble getting. Just before this scene, he is told there is a car he can use, but of course he opens the bonnet and there is no battery installed (or, it's just the case, I can't remember).

As to why the lid should be in the fridge? My real-world guess is so all the bits are in one place, but the real reason is likely because the audience will more easily recognize the top of a battery over just seeing the chemicals.

Fair enough. And nice explanation. Thanks.

The top of the case is right there. The rest of it is just a plastic container and doesn't need to be in a fridge.

I pulled this image from a random blog about the episode. The episode itself has better shots of the components

Speaking of TLoU, I've tried watching it but it's so overwrought and sentimental. I feel nothing for the characters at all, it's like they're cardboard or the creators set out to create something but had nothing to say. Can't say I liked EP3, started out great but jesus they might as well have had cue cards for feelings.

The fans sure don't like you saying that though.

> The fans sure don't like you saying that though.

Worth it.

> The humidity in a consumer-grade freezer drastically increases to 80%-95%RH twice a day and slowly drops over several hours

I guess you are talking about the frost-free function? https://home.howstuffworks.com/question144.htm

Do you have any references - I can’t imagine why the RH would stay so high for hours (rather than a shorter period).

I've heard this, I have a friend whose father was in the auto industry all his life, owned a body shop so they would constantly have a bunch of cars in various stages of disassembly in their shop. He was adamant about not leaving batteries on the concrete floor. There might be something to it.

The problem is that PET plastic leaches chemicals at sub-boiling temperatures.

PET plastic bottles are frequently used to hold food and beverages, and considered "safe" by the industry, despite research that suggests they leach endocrine disruptors into food.

PET containers are so widely used that if there were an actual problem with them, people would be dying--or at least ill--in millions.

I think you’re over-exaggerating the impact to dismiss the premise. Endocrine disrupters don’t generally lead to death, they lead to developmental and hormone disorders, ADHD, etc. All of these things are on the uptick.

Our ability to diagnose those things is also improving yearly...

Our ability to count sperm cells, for instance, isn't decreasing yearly.

Talk about lacking nuance.

Health isn't binary: alive or dead.

Something like one in three people will get cancer at some point.

It's possible endocrine disruptors contribute to that rare.

Something kills us eventually. Heart attacks, accidents, violence, disease, cancer, etc.

Reduce one major cause (violence) or two or three (accidents, disease), and voila - the other elements take over their portions of the pie.

That an all the nuke testing fallout, tire dust, random nasty crap, etc.

I don’t know about you, but I’d rather die healthy at a ripe old age than at 40 from some stupid plastic.

That’s the opposite of what is going on.

Would you rather die at 40 from a poorly designed car steering wheel that impales you in a 20mph accident, or get machine gunned in a trench when you’re 19, or live to 80 and die from an old age disease - like cancer, heart disease, or Alzheimer’s?

Because the only thing that’s inevitable is it will eventually be something.

And the stats show the current set of active ‘somethings’ at play.

Plastic or not may move one of the needles a few percent one way or another, but unless there is an epidemic of choking-on-plastic-bottles, it’s in the noise.

I wouldn’t put it past the next generation to come up with a bottle swallowing challenge…

It will be something, I’m not arguing that. It comes down to preferences and our collective ability to pick one to stop from happening. Eventually, we will all die from old age or accidents. I don’t see that happening in anyone’s current lifetime though.

People have dealt with far worse than what we’ve got going on now, and most of them still died of old age and accidents - depending on what you define old age and accidents being of course.

Cancer survival rates and overall incidence rates are pretty good in the US, and frankly seem to have zero correspondence with use of plastic.

It’s also predominantly older folks. I’ve seen data that indicates it’s nearly certain for a man to get prostate cancer if he gets old enough, for instance.

Denmark and Hungary being near the top of the list - https://www.wcrf.org/cancer-trends/global-cancer-data-by-cou...

You sound like saying we shouldn't care about any of those factors because other factors exist. I feel like that attitude is exactly why most of those factors exist in the first place. Just because there is a chance you might not suffer from the consequences doesn't mean there aren't any for other people (or animals, plants etc)

Nope!

We tackle what we can, and we end up with the rest.

And there is always something left, fundamentally.

Some kinds of disease are more prevalent since the introduction of PET ...

Not saying there is causation, but denying it is equally problematic.

We’ve also generally become incredible sedentary during almost the exact same time frame.

There's nothing to suggest there's a casual relationship there. It could be the case that these illnesses lead to sedentary lifestyles for all we know. Turns out depressed people don't like to do stuff.

Haha, we were getting stupid sedentary beforehand.

40% of us are obese. Lots of chronic illnesses going on as well.

This sounds like a small tweak in the manufacturing process that could lead to potentially very large gains down the road. Fantastic work!

Yes exactly why I posted it. A little improvement that can be real in few time, instead of some groundbreaking researches that will never be used in daily life (in the next few years).

You weren't kidding. Just switching out the tape material is all it takes? I wonder how frequently PET based tapes are used. I'd assume any of the pouch type batteries could be impacted, so phones/laptops/etc. Fascinating that it wasn't noticed until now.

We shouldn't rush to the conclusion of large gains; this plugs a tiny leak which affects equipment that is used sporadically between long idle times, which is a specific use case.

This could reduce the number of service visits to battery-powered, low-current-draw remote sensing equipment and such. In that sort of use case, it could be a big deal.

Exactly.

This is not going to make a meaningful difference in devices that you charge on a daily / weekly basis (cell phones, laptops, smart watches).

Additionally, there's a significant portion of "self discharge" of lithium packs that is actually the battery protection circuitry (BMS).

That's not to say this isn't a good catch; like you mention, low power devices that you want to go months between charges may benefit significantly.

I wonder if they'll switch to polyacrylamide (kapton) tape. It's already used on packs pretty frequently just not on the tabs. Heat shouldn't damage this material.

Kapton tape is also quite expensive and overqualified for this task. I think the engineers will be able to squeeze out a lot cost by using something more “barely-capable”

Cellulose tape?

That would be among the worst choices for tape. Gets damaged above 50C, decomposes above 100C, biodegradable and flammable: https://s3-ap-southeast-2.amazonaws.com/wc-prod-pim/Asset_Do...

Might as well seal it with the yellow adhesive Cyberpower uses on their UPS's which decomposes into flammable and conductive substances.

I was actually just reading about Kapton yesterday, and stumbled upon some info about its deterioration being hastened by heat. See https://en.m.wikipedia.org/wiki/Kapton#Characteristics

Kapton tape is polyimide, not polyacrylamide, isn't it?

Thanks you're correct, polyacrylamide is a cool unrelated material.

Previously discussed: https://news.ycombinator.com/item?id=34582931

Honest and tangentially related question…has anyone else noticed that Apple devices hold their battery life in suspend mode way better than Windows, Android, or Linux ones do?

My kids mostly only use their Kindle Fire tablets on the weekends and even if they get fully charged Sunday night, they’re running on fumes by Friday, even if they’ve been completely unused in the interim.

Meanwhile, I have an iPhone from my employer that I usually top off once a week, but it’s still well over 80% most of the time during the same period.

What magic is Apple using here?

It's the magic of "not being allowed to run anything".

If you kill -9 all your Linux processes then you'll be great at idle use as well.

Now hunting down all the processes that might be turning on your radios, CPUs and I/O devices is the hard part on OSes where you can actually run things in the background, since you easily get into tragedy of the commons situations.

For comparison, consider a Kindle (linux device, battery lasts for weeks) or a Garmin watch (battery life is about 3-10x better than Apple watch) to see how different can outcomes be if you control what processes run.

Processes don't run while a computer is in suspend mode.

Of course they do on modern computers (so do peripheral microcontrollers).

Most modern laptops and devices don't go into full suspend states anymore, they just do a much lighter standby similar to phones and tablets. Windows calls this "Modern Standby" while Apple just does it since Apple Sillicon.

Even so, periodically they will wake up and run tasks just like phones (e.g. Power Nap on Apples, no idea what Windows calls it). Linux has a headache here because it's mostly not prepared to disable all their processes and peripherals correctly during those states so something keeps waking up and running.

Linux assuredly does not periodically wake from standby to run random background tasks. I welcome a reference to the contrary. (Android notwithstanding -- I know phones and tablets do not truly suspend -- I am responding to the suggestion of manually managing background tasks which generally implies a non-handheld OS.)

I wasn't aware macOS enables Power Nap permanently on Apple silicon, interesting.

I have quite an old samsung tablet that, when I keep wifi and bluetooth turned off in LineageOS, has just this week surprised me as I had fully charged it and hadn't used it in about a month or so, it still had 70% battery life left. It may have even been closer to two months, I can't be sure.

But if I leave the wifi on, even with syncthing/etc not running at all, it will last about as long as you'd expect an unused android tablet to.

I'm sure it's many tricks adding to one great feat, but I've always guessed that many of these devices could probably be better optimized for what is ironically their primary use case: using low amounts of power in standby while still able to relay important information as needed.

But if that's any part of the apple magic, how does the trick work, and why aren't more devices doing similar things?

For Android just leave battery saver permanently enabled at 100% charge. You lose animations and haptic feedback but it cuts down on radio usage and extends battery life.

A couple things:

1. On Windows and Linux, devices have to handle a huge number of hardware configurations. Not everything can go into the same "deep sleep" mode with the same instructions, so developers implement different "idle" states that may or may not discharge the battery quickly. Too many sales efforts focus on making a laptop 'boot' from idle in seconds, and too few focus on making it usable after being off for days. Look up "S3 Deep Sleep", "Modern Standby", and the bevy of options described at https://learn.microsoft.com/en-us/windows-hardware/drivers/k... to learn more. Apple only supports a small list of hardware platforms, and can make deep sleep work and resume quickly and reliably on just that list. Even the Kindle Fire is not totally vertically integrated between the MediaTek processor and Android OS and Amazon UI, there's bound to have been a lot of finger-pointing and little leadership pushing for microamp-level sleep capabilities.

2. Android/Windows/Linux allow users to install applications that do things that consume battery in the background - for example, my Tile bluetooth locators and Garmin smartwatch work great with my Android phones. They wake up a sleeping phone and force it to use a little power to grab a location data point or send my watch an updated weather forecast. Apple doesn't let third-party developers do the same.

I'd bet that if you pushed and held the power button on your Kindle tablet on Sunday night for 3 seconds and chose a full "Shut Down", and then held the button again Friday for 2 seconds, it would have the same battery level as it had when you turned it off. It's just because it's been checking for system/app updates and otherwise running code while 'sleeping' unused that the batteries are low, in spite of the fact that no humans were using it.

I always just shut down my Windows/Linux machines, sleep in all its forms has never worked properly. It's far better for my sanity to just turn it off knowing I can just turn it back on.

Especially in this day and age of blazing fast (read: several gigabytes per second) SSDs, cold boot speed for most people is a non-issue.

I set my laptops to hibernate when the lid closes. Entire RAM written to disk, then a full powerdown. Do turn off wake timers and wake on USB (sometimes disabled in true hibernation but not always).

I don't use hibernate either: /Usually/ it works fine, but once in a while Windows just derps getting back up necessitating a full reboot. I don't want to deal with inconsistent shit like that, I'd rather just go for a proper shut down and cold boot so I can expect consistency and therefore reliability.

Is it even possible to fully turn off a Kindle anymore? I want to do exactly what you’re saying to prevent the draining of the battery, but the only options that appear after holding the power button are “Cancel” “Restart” and “Screen Off”. Holding the power button longer just seems to restart the device :/

I they need them always on so that they can gather up data from Amazon smart TVs that were never connected to the internet (project Sidewalk).

Kindles have an airplane mode. I use mine only for sideloading so it hasn't connected to the internet in years.

The "magic" is no features. For example All day events can have a notification at 9:00AM and that's it. You can't change it. You can't have 100 events with different notification times. The phone only has to wake up at 9:00, check the events and that"s it. There are many, many examples like this on the iPhone.

> For example All day events can have a notification at 9:00AM and that's it.

That's a bizarre limitation that they should fix, but I don't think it implies anything about how iPhones work in standby. Alarms, timers, reminders, push notifications, etc. seem to work fine in standby (although I'm sure standby battery life is affected by how often those are happening).

That's just a stupid limitation of the UI on the iPhone. On a Mac you can set a custom time, which triggers just fine on an iPhone.

My experience is the opposite. My company gave me an M1 mac that I leave plugged while I work. It is at 100% when I shut it down Friday afternoon, and its at around 40% when I boot it up on Monday morning.

I suspect the battery is defective, but like I said I leave it docked when I work anyway so I don't really care.

That sounds like a software config issue. Any chance you have "Wake for network access" set to "Always" instead of "Only on Power Adapter?"

Even if it shows as set to "Only on Power Adapter" change it to something else and then change it back. I once had a case where the UI state for a setting was inconsistent with the underlying system state.

I have an android tablet that I use every couple of weeks. There's no noticeable battery discharge between uses. I think I've maybe charged it once ever.

I believe Macs readily hibernate, moreso than Windows or Linux laptops do (if at all). macOS has a few tricks to make it seem more responsive coming out of hibernation (such as showing a fake image of the desktop before it becomes responsive) which lets it get away with this. (I can't find anything to back this up right now, but I remember reading this somewhere, and my experience with at least some versions of macOS match this.)

On the other hand, my Linux laptop (Dell XPS 15) lasts much longer while awake and runs far cooler than any other device I own. There simply is less crud running in the background keeping it active. (Disabling off-chip graphics, disabling full-disk indexing, and applying all suggestions from Intel PowerTOP play a big part here. vs. on my Mac, I'm forced to force-enable off-chip graphics, else input lag is horrendous.)

No magic whatsoever and this is not an Apple-thing. Tune your device well and you can achieve this on not just Android but old Android devices. Just like your employer-provided iPhone I have some devices which are rarely used but still kept charged for when they're needed. Unlike your employer-provided iPhone these devices are old in gadget-terms, e.g. a Samsung Galaxy Tab 3 10.1" from 2013 which is used occasionally but mostly just dozes its way through "life". I just checked its battery, it tells me the last charge was 5 days ago and the battery is at 73%. This is the original battery, 10 years old. I did an experiment with a Motorola Defy+ some years ago to see how long the thing would last on a single charge, doing absolutely nothing which turned out to be 26 days The key here is that all my devices run either AOSP-derived distributions like CyanogenMod (the Defy's - I have 5 of them, 3 in regular use) or LineageOS (the Galaxy's). They do not have any Google apps installed, some of them use microG as a substitute for those few apps which need it. They mostly run free software except for the few commercial/proprietary things needed - mostly banking and electronic-ID related - which also means there is no background traffic to commercial entities who desire to profit from my data.

If you think a bit about this it isn't that strange, really. Compared to iThings most Android devices have relatively high-capacity batteries while the rest of the hardware is quite similar. The higher battery capacities tend to be (ab)used to enable a host of data-hungry apps to run on the things, sending their spoils off to their masters. If you kill those apps and their means of subsistence you're left with a device with a lot of battery to spare.

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