I know these are currently out of fashion but I’m still thankful they exist.
Let’s remind ourselves of devices that use(d) these standardized batteries:
- Toys
- Digital cameras
- Torches
- Gadgets like fans
- Wireless keyboards
- TV remotes
Thanks to having a standardized system of batteries,
- You can use the same battery across several devices. This is a no brainer but it’s very practical.
- Batteries can charge quicker thanks to being put in a dedicated charger and not being limited by USB cables. (But yes I concede that USB has been updated for faster charging over the years)
- Devices don’t have down time when their battery is charging. To charge, the battery is removed from the device and can immediately be replaced with a fresh one.
- You’ll never have to trash a device due to an expired battery. Just buy a replacement. And building on this…
- Any improvements in future battery technology can be retro-fitted into your existing devices. And there is a high incentive for future improvement, because…
- An accessible (due to easy replacement) and large (due to many devices) battery market is very attractive to competition.
If you look at the pros I listed, they all happen to be things that would be very useful for electric cars. So I think it would aid the adoption of electric cars if their batteries were standardized too.
Those batteries in your photo are NiMH batteries… which discharge on their own at a fairly rapid rate even if you’re not using them at all. They’re also pretty big and heavy for the amount of power they provide (which, due to the self-discharge issue, is effectively a lot lower than the official number on the battery).
I strongly recommend investing in devices that use 18650 batteries. They’re about the same size/weight as a AA, and they last much longer (both in terms of from full to flat and also the number of years (decades?) of use you’ll get from the battery.
A lot of “proprietary” batteries are in fact a bunch of 18650 cells wired together.
It’s worth investing in good ones - the quality varies significantly from brand to the next. With a good 18650 cell, you won’t be replacing it when the battery expires, you’ll be transferring it to a new gadget when the gadget is broken or so old that you decided to buy a new/better model.
An 18650 is way bigger than a AA
But got damn does it ever put out some insane light! My flashlights turn night into day.
While all this is true, unfortunately not many devices support swappable 18650s, either they have swappable AA/AAA or have built-in 18650s that would require disassembly to replace. However, if you CAN find a device with swappable 18650s (the only ones I’ve found so far are flashlights) they’re absolutely great!
I am not aware of many devices that use swappable 18650’s either. Off the top of my head the only ones i’m aware of are vape devices.
There are also flashlights with 18650s. There are some powerbanks with exchangeable 18650s as well.
But that’s all I know of.
I have a set of lasers powered by them as well. Love that it makes the whole thing a bit larger and durable.
My OWON portable oscilloscope does. The only device I know of.
Wait, do they not make AA-sized 18650 batteries?
18650 isn’t a specific type of battery, but a size. 18mm diameter, 65mm length, and 0 typically represents it being cylindrical in shape. 18+65+0
Heres a quick read
Besides being the wrong size by definition, AA batteries are expected to have 0.8V to 1.5V, while Lithium Ion cells (such as 18650) have a voltage range of 2V to 4.2V. That’s completely incompatible, you couldn’t even replace two AA batteries with a single Li-Ion cell.
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Couldn’t it theoretically be fixed with a voltage regulator?
Don’t they need a circuit protection to not over-discharge lithium batteries? Most AA devices would suck all the juice from the battery until it stops working.
Yes.
The other problem with lithium batteries like 18650s is that they need to be handled with care so manufacturers don’t want users swapping them in and out like AA/AAA. This is why they build them into devices and have you charge them through a regulated port.
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Well there aren’t really different sizes of 18650s, if you chance the size it’s no longer an 18650.
The flat vs button top issue can be annoying though
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The problem with those is that the device loses the ability to sense the charge status of the battery, since the voltage remains the same until it’s empty.
NiMH AA’s have the same problem.
Most 18650’s don’t go down to 2 volts. They should be considered “flat” at 3.4 volts - going any lower risks damaging the battery (unless you know what chemistry it uses, some can go lower safely).
Allowing a rechargeable AA to get down to 0.8V is also risky, if you go much lower than that you will damage the battery.
An 18650 is essentially the same voltage as three AA’s. And the amount of charge level they store is closer to five or six. The size and weight, on the other hand, is a bit more than one AA.
But the biggest advantage, by far, is a lot of devices can be powered by a single 18650 but would require multiple AA’s to have acceptable battery life (or a high enough voltage). As soon as you have multiple batteries thing start to get really complex. Your batteries will never be at exactly the same charge state and that can potentially damage the battery and the device.
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But 18650 size is manufactured at much higher scales than other sizes, and therefore it’s the cheapest, and therefore it continues to dominate.
The main barrier is when you need multiple batteries.
If you install a dozen 18650’s in a device (or thousands in a car), they will work great as long as they’re all at the same charge level and can maintain the same voltage throughout the discharge cycle. If they can’t do that, then the battery could catch fire. Yikes. So any device with multiple 18650 cells will hard wire them together so the user is forced to use and charge and discard the entire set of cells as a single battery.
AA/AAA NiMH batteries won’t catch fire if they’re uneven, but being uneven will damage the batteries. You don’t need to keep them together to be safe, but you do need to keep them together if you want the batteries to last longer than six months. Keeping them together can be a logistical nightmare and it’s the main reason I’ve stopped using them… it’s just too much work to keep all the batteries together (especially if the device is shared in a household or workplace). If you get it wrong, then they don’t last much longer than disposables.
Disposable batteries have the same issue - but since they’re disposable you’re probably pulling four brand new batteries from a packet.
An 19650 cell holds about the same amount of energy as five AA batteries. So there are a lot of devices that can run well off a single battery, and those tend to be the ones that are user replaceable.
Low self discharge NiMH batteries have been available for a long time now. They hold a charge for several years.
@abhibeckert I have those from Eneloop. They do not discharge that fast as the old generation of rechargeable batteries. Yes they do, but the rate is quiet slow.
Same. People used low quality Ni-Mh batteries and got what they paid for. Eneloops have worked great for me. Believe it or not, Duracell has been great too. It’s the energizers that have all been awful for me.
I second that. Have been migrating devices over to eneloop batteries successfully. (other NiMH batteries go flat after a month even if not used.)
18650s are in no way close to the same size as AA batteries. Your other points ring true and I generally agree with them though.
For example, basically all power tool batteries.
If they advertise ~12V, it usually means it is 3 ‘cells’ of 18650s in series. Crack open the case on such a tool battery and you’ll find just that – 3 18650 batteries for a little one. A high capacity battery might instead of 6, with 3 pairs of 2 parallel batteries, doubling the capacity. And nothing but weight and size stops them from just making them ever-larger.
18-20v tools are 6 cells (18v is the nominal voltage, 20v is the ‘max’ voltage at full charge). For higher cap, add more batteries in parallel in each series cell.
It is RARE to be able to service these unless you have some specialized skills. Typically, they are spot welded together, which can be dangerous to attempt to DIY. That said, often when a battery ‘fails’, it’s actually just one 18650 that has failed and taken the others down with it.
These days you do see other sizes. 21700s or even pouch batteries are starting to be more common when tools need more stored joules per unit volume.
There are some clever innovations from some tool manufacturers too.
DeWalt has launched batteries that work with both 18v and 54v systems, by having different pins on the output wired to different points in the battery chain.
(3 sets of 3 in series for 18v, or 9 in parallel for 54v, I’m assuming)
20V tools are 5S rather than 6S
That’s not my experience - my preferred brand* offers 18V batteries at 3Ah, 6Ah and 9Ah. They also have higher end tools that take 56V batteries - either 4Ah or 8Ah.
I haven’t opened them up to check, but surely the higher capacity batteries have more cells.
(* preferred brand because it’s the one I already have a bunch of batteries for… I actually regret choosing that brand)
Sure… but if you replace that one “bad” cell before it takes down the others, the battery might spontaneously combust and burn down your house while you’re (hopefully?) not home. 18650’s in series have to be the same voltage throughout the charge cycle.
The charger for the tool batteries has to have circuits to get all individual cells to the same voltage. They are not simply charging them all at once in series. More complex than that, but there is a second circuit for an alternate config that the charger can make use of to charge.
If one cell is dying/dead, it stops the whole battery from working. Replacing that individual cell would allow the others that are still performing nominally to continue to do so. If it were practical to change one cell. Which it really isn’t. But old tool batteries can be a good place to cannibalize 18650s from if you need them for other uses because a “dead” battery likely still has at least some OK 18650s in it.
The 56-60V tools just has triples of all the batteries with an additional circuit path to let them either function in the 18V 5s or 56v 15s configuration, depending on what it is plugged into. Similar story with the brands advertising 40V tools. There’s a reason they’re all staying on multiples of the 18-20V base.
I literally said there can be more 18650s for each series cell. The “not your experience” you referenced is… exactly the same thing I said. Though it is actually 5 18650s for a base battery, not 6, I misremembered that. 3.7V x 5 cells = 18.5V (which some brands advertise as a max 20V to make the number bigger while others just call it 18V). Each cell is 2.4 Ah, which gets you the base battery capacity. The even-smaller cells are either using pouch batteries or something else that isn’t an 18650.
Oh I see, I’ll look into them. Yeah these are at least 10yrs old so I wouldn’t be surprised if the technology was quite bad for today’s standards
They make USB rechargeable lithium ion batteries in every common form factor. I use lithium rechargeable AAA batteries in my mouse and they work great. You don’t even need a charger, they are USB-C. Highly recommend.
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I mean I can’t really blame them for being smaller, the USB port is a lot of value added but is also pretty huge.
It infuriates me that we use Wh/Ah instead of Joules for this.
It’s like measuring distances with time – “NYC is 3.4 highway hours from DC” – except doing it in a world where no one has any idea what speed people drive on the highway.
Oh I see, I’ll look into them. Yeah these are at least 10yrs old so I wouldn’t be surprised if the technology was quite bad for today’s standards
I had some Molicel (I want to say, P26s) 18650s in regular rotation that lasted only three years. I went through Mooch’s battery reviews ahead of selecting them, purchsed them at Liionwholesale, and they started heating up in my Nitecore one by one after maybe 1,200 full discharge (e-cig) cycles. Meanwhile, I have vape-shop NCRs from 2016 still humming along (though rarely used).
At this point, I’m not really sure what to make of battery reviews. And the economics work fine for three years of consistent use. I just wish that was how they were sold, not like some absurd number you’ll never hit.