Comment by alnwlsn
8 hours ago
Designers have a choice in lithium-ion though. 18650 is is pretty large cell but there's 14500 which is AA sized or 10440 which is AAA sized. They make versions with the usual battery "nub" rather than the flat faces for spot welding, and built-in protection circuitry to prevent over-discharging. You probably would want to use ones of a different size than normal 1.5v cells though. A personal favorite of mine is RCR123A/16340.
Even many of the pouch cells come in "standard"-ish sizes. An 803860 is nominally 8.0mm x 38mm x 60mm, but I am seeing more custom sizes recently.
Meanwhile, alkaline batteries can go to hell. You might as well plan on one leaking in the battery compartment. My favorite non-rechargable 1.5V AAs are Li-FeS2, which never leak and have spectacularly low self discharge (especially good for multi-year ultra-low-power projects), but are dammed expensive.
> Designers have a choice in lithium-ion though. 18650 is is pretty large cell but there's 14500 which is AA sized or 10440 which is AAA sized. They make versions with the usual battery "nub" rather than the flat faces for spot welding, and built-in protection circuitry to prevent over-discharging. You probably would want to use ones of a different size than normal 1.5v cells though. A personal favorite of mine is RCR123A/16340.
But other than 18650 you can't expect to find a lot of devices using any particular size.
We should strive for a couple blessed sizes that a lot of devices will stick with, where all cells include a nub and protection circuitry.
The form factor I'd like to see standardized would be a flat pack like the Nokia phone battery.
Not saying the cylinder doesn't have it's place, but so many of my devices would like a flat pack.
If that happened, it'd have the added benefit of being able to standardized a bms protocol for the packs. Hard to have control pins with a cylinder.
And if you were super clever, you'd make those packs stackable so they could be charged and discharged together.
There's some flashlights which take either 14500s or AAs. Seems like it'd be pretty handy as a backup (iirc the AAs can't put out quite as much instantaneous juice)
>Meanwhile, alkaline batteries can go to hell. You might as well plan on one leaking in the battery compartment.
On the other hand, alkaline batteries never burn your house down.
I also feel like they serve different purposes. Needed for long-term storage and only used in an emergency? (eg, a flashlight for power outages) You're probably better off going with old-fashioned alkaline batteries. Duracell claims they're good for 10 years. Needed for day-to-day usage? Lithium might be better: you can monitor for swelling, the battery recharge-ability is probably more important than any of the downsides that come with lithium ion batteries.
No, there's basically no reason you'd ever want an alkaline battery except cost. For your use case of long-term storage or a rarely used flashlight (e.g. in a car emergency kit), you'd want a Li/FeS2 as the parent poster recommended, also called just a "Lithium" primary (i.e. non-rechargable) cell. They have a longer shelf life, don't leak, hold more energy, can provide a higher discharge current, work over a wider temperature range, and have safety characteristics very similar to alkaline.
There is one very good reason: the discharge curve. An alcaline battery loses voltage when it discharges, the lithium ones discharge with the max voltage until they suddenly stop working.
This is a reason insulin pumps require specifically high quality alkaline and lithium is considered a risk.
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Main disadvantage is cost. Looking on Amazon, it's $1.61/ea AA lithium vs $0.62/ea akalaline. That's Energizer vs Energizer. Amazon Basics AA alkaline are $0.32/ea. (Unlike alkaline, knock-off lithium aren't much cheaper than Energizer.)
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Great point.
I was going to say cost is a really significant factor there, but I was thinking convenience retail where they are marked up. They are only 3x more on Amazon. Now you're guaranteed to damage equipment as the current alkaline formulations leak.
There are a handful of applications where alkalines are better. IR TV remotes run effectively forever on a couple of batteries and the slow self discharge on the alkalines makes them ideal for the task.
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That's an interesting counterpoint, thanks for letting me know. I was really under the impression that lithium ion batters discharged more aggressively. Maybe that's just more reflective of how they lose capacity over time? Can you speak to the fire risk?
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Lithium primaries are great. I use them in my weather station. 2AAs have lasted at least 4 years, and still work well when it's 0F out.
> You're probably better off going with old-fashioned alkaline batteries.
Never. They will leak and die. Alkaline cells always end up leaking and dying in my experience, given enough time.
In fact, I do the reverse: If it's something I think will sit for a long time, I make sure to put a rechargeable battery in it. That way, worst case, it's dead—but it won't be destroyed by a leak.
It's gotten worse over the course of my life, IMHO. Costco's Kirkland batteries 15 years ago rarely leaked - now they do it in months sometimes. We had leakage a bit back when I was a kid (80s) but I honestly don't remember it happening as often.
It's one of the things that pushed me all-in on Eneloop. We were throwing away 10-20 AAs/month at one point (wife likes electric candles). Recently, it's been 2 or 4 as we discover old remotes or something we hadn't replaced yet. And we have 8-20 AAs and 2-4 AAAs charged and ready to go at any point. Swap, and put the empty ones in the charger is now the standard process at our house.
I have seen panasonic cells around my area advertised as leak-proof (or was it leak resistant?). I wonder the effectiveness.
Alkaline has a tendency to leak electrolyte when stored in devices long-term, especially if used intermittently, even more so if the loads are at the upper end of what alkaline can handle as they are in many modern flashlights. The electrolyte is corrosive and often results in a broken device, which is exactly what you don't want in an emergency.
Li-ion's self-discharge is pretty low for a bare unprotected cell, and a flashlight with a mechanical switch consumes no power when off. One must take care to avoid short circuits when handling such a cell, but modern Li-ion flashlights have over-discharge protection, so that's the main safety concern with a single-cell design.
> My favorite non-rechargable AAs are Li-FeS2
Lithium Iron Disulfide. For those looking for a brand name, that's what these are:
https://energizer.com/batteries/energizer-ultimate-lithium-b...
I just worry that the voltage of these is a bit too high, if the device takes 3 or 4 in series. They tend to be around 1.8 volts per cell, significantly higher than a fresh alkaline AA at around 1.6 volts, and even after half the energy is discharged, if the device is off for a long while, the initial voltage for next turn-on creeps all the way back up.
(The price doesn't bother me ... it's worth the much lower chance of leaking than alkaline, if you leave it in a remote or gadget for years. But I've come to think that rechargeable NiMH like eneloops are a better idea due to the voltage.)
I love the 14500 except for its footgun shape. 6 x 14500 is at least 21 volts, which won't play nice with a device that wanted 9 volts. I used to try to keep the 14500s far away from the AAs, but there's no stopping a kid in a hurry who wants to play with a toy or musical instrument.
I've taken the approach of electrical-taping my USB-chargeable 14500s each to a dummy-battery, since the things I put them in have 2 adjacent slots for series AAs. The voltage is still high (3.somethingV instead of 3V) but they seem to work.
That's smart. It's not perfect, as you say, but at least it's trying to play nicely with the other kids.
Are those LiFePO4 batteries that cap around 3.6V, or normal lithium ion that cap around 4.2V? I'd be cautious with either kind but especially with the latter.
I’m visiting some family and I’m a hero for fixing a couple devices that stopped working from alkaline batteries by using a bit of foil paper to overcome the corroded contacts.
Maybe not great in the long run (steel and aluminum don’t like eachother)… maybe I should have put on some grease…
I swab the corroded contacts with white vinegar from the kitchen. It turns the white gunk into a foamy blob, and I assume it etches off enough of the corrosion to restore conductivity. I wipe the foamy part with the dry side of the cotton swab, and the device usually works again.
I started doing this as a kid, reasoning that the white gunk looked like baking soda, which is fun to combine with vinegar, so let's see what happens. I just looked it up, and it appears that the process is legitimate and safe. The vinegar turns potassium carbonate into potassium acetate, also producing carbon dioxide.
That is step one. However that is rarely enough: the corrosion eats through the chrome plating on the steel (chrome is a good conductor, steel makes a great spring), and that rusty steel is a poor conductor. Even if you polish the steel, it will rust again soon. (chrome plating requires nasty chemicals, not something to attempt at home - I suspect you could silver plate at home for cheap enough but I haven't tried it)