Last edited by malow; 12-01-2009 at 08:05 PM.
UniqueFire AA-S1 and a Aurora SH0032!!!!
Two cheap flashlights make me a "flashaholic"?
It can still happen when the manufacturer have full control over both batteries and charger (and yes they will be recalled if they explode). It would be thousands of times more common with random chargers and random loose cells in them.
if we consider that every user will do stupid things with a product, nothing is safe. we must rely on "user brain" to use it correctly.
anyone can put ni-mh on a ni-zn charger. anyone can drop a quality li-ion cell on the floor. anyone can put a 14500 cell on something and forget it is 3x more voltage than a "normal AA". anyone can put a li-ion cell in the pocket and forget that a metal key-chain can cause a short-circuit. a li-ion cell does not come with a 3 sheet manual with everything that you should "not do". "don't wash it - don't trow on fire - don't eat it".
any crap manufacturer can make this battery and say: "use specific charger - don't trow away - don't short circuit". them, sell together with a charger for it. that's it. if it catch on fire wile charging, and blow up your house, "sorry". if you use incorrectly and also blow up your house, "sorry". this is the kind of safety we already have on most generic brand products.
if you can get something with quality, good. if you get a cheapo product, good luck and better you be smart on how to use it.
UniqueFire AA-S1 and a Aurora SH0032!!!!
Two cheap flashlights make me a "flashaholic"?
I realize this is an old thread. But I thought I would throw in my two cents worth here. It is entirely possible that a lithium chemistry could be found that would allow for a 1.5 volt rechargeable battery. But the BIG question is whether such a battery would REALLY be better than what we already have (ie NiMH). Consider the Energizer L91/L92 lithium primaries. These exist because they serve a definite purpose. Namely, they give consumers the option of a primary battery that remedies many of the shortcomings of alkaline batteries. These shortcomings include low current capability, excessive voltage sag under a load, terminal voltage which drops drastically as the battery is discharged, and drastically reduced capacity at higher loads. When you consider these things, the advantage of L91/L92 primaries is that they behave more like NiMH batteries compared to alkalines.
The issue is therefore how a 1.5 volt rechargeable lithium battery could be better enough than NiMH batteries to justify their development. And I can't see how you could improve much on NiMH. NiMH already has the ability to deliver high current with little voltage sag, and deliver a very constant voltage during discharge. Capacity also drops little as discharg current increases. And because the elctrolyte is aqueous, NiMH is a very safe chemistry. Some make an issue of the 1.2 volt nominal voltage. But this is FAR less of an issue in practice. And if this is REALLY a problem, further development of existing technologies like Ni-Zn would be FAR more cost effective. Of course, if a rechargeable lithium battery with all the virtues of NiMH could be developed which has drastically greater capacity than NiMH, that might be another story. But I don't see this as likely.
In the end, NiMH is awfully hard to beat, especially given the REALLY good, low cost LSD options available today. Any rechargeable lithium batteries of similar nominal voltage would have to be FAR superior to existing NiMH and cost effective in ordr to be successful. And THAT'S a tall order.
I realize that this is an old thread, but it addresses a question that I've been wondering about. It's said here that the 3.7 volt batteries are Lithium ION types and the non rechargable types are just Lithium, and the chemical listing was very nice, but doesn't list what is in the 1.5 volt lithium types?
For now, the PowerGenix nickel-zinc AA cell comes closest to your 1.5V ideal rechargeable: 1.6 to 1.8V under load, outstanding safety, great cold-weather performance, and cheap. The main drawbacks are: fickleness (failing at an unusually high rate when overdischarged), a self-discharge rate that's higher than most of us would like; lowish amp-hour capacity (better than 14500, but worse than NiMH); and they require their own charger. Oh, and they're no longer made; when they're gone, they're gone.
My lights, all AA, neutral or warm: 3 Fenix TK20s; 2 Malkoff M30WFs; 2 Shiningbeam Romisens (5A); Dereelight XP-G R5 (close enough); UK 4AA incan.
I have been waiting for a battery like this too!!!
I've seen those batteries too, and while the idea is exciting I'm not going to go out and buy those particular ones. I don't exactly trust a manufacturer who prints "mWh" on their batteries when they mean "mAh". If they can't keep that straight, what other corners are they cutting? That said, if someone braver than me wanted to buy these and run some tests on them that would be wonderful.
A AA-sized LiPo rechargeable with a step-down circuit to 1.5V would be a really neat thing though, and those batteries seem to imply that it's on the horizon. If the idea is a feasible one then hopefully we'll see better manufacturers coming out with batteries like that in the near future. If they can keep the energy density higher than LSD NiMH while fitting in the step-down and protection circuit, and if they can manage to keep the current capacity reasonably high, they could be a real step forward. It's probably a matter of technology rather than physics – packing a step-down-and-protection circuit in there that is robust, efficient, small, and has high current-carrying capacity is no trivial thing but with the right electronics it sounds doable.
They'll probably always be a bit more expensive and lower energy-density than normal 3.6V LiPos because that step-down circuit is going to take up space and increase the price, but there's just so much gear out there designed for 1.5V AAs, and AAs are so easy to come by (you can always find a crappy Alkaline at the corner store in a pinch) that I would love it if something like this became common and high-quality. Another advantage I could see is that the step-down circuit would work as a built-in voltage regulator, so that you would have a nice 1.5V output right up until the end (followed of course by a very sharp cutoff, but that's why we carry spares for critical applications, right?).
1.5V rechargeable AA lithium batteries may well be the next step forward in the evolution of rechargeables. If you ask me we're probably not quite there yet (unless somebody knows of a source of high-quality ones that's already out there) but maybe we will be soon.
I saw a chart outlining the discharge current and voltage and the plot is rather interesting. (Image re-hosted from my personal blog)
EDIT: Note how there is no real current data as for each load line. Without any data to correlate current and voltage, this graph isn't exactly helpful...
My whole blog post talking about this cell is available here: http://ripitapart.wordpress.com/2013...rcery-is-this/
Last edited by ginbot86; 11-25-2013 at 10:33 PM. Reason: Added line about how the graph has little value
My blog post talks about the graph in a bit more depth. That said, the forum and blog posts were done in the early hours of the morning, so my apologies if the postings are a little rough around the edges.
Last edited by ginbot86; 11-25-2013 at 10:38 PM.
My website with flashlight, battery and charger information: lygte-info.
More than 200 battery reviews and 80 charger reviews.
Compare 18650 LiIon batteries or smaller (RCR123, 16340, 14500, 10450) LiIon batteries.
A TPS54719 could draw some current and still be efficient at light loads.
But it would be strange to put 2-3-4 AA in series that, each, downs to 1.5V from 3.7V...
Or only one down to 1.5V then pushed to ~3.2V to drive a LED.
IMHO the question is not "why not rechargeable 1.5V AA" but "why is still AA alive at 1.5V" ?
HMDI replaced old fashion video connections thanks to industry agreements. I wish the same for cells, a standard prismatic cell of about 50x20x8mm embedding 5Wh of energy at least would be nice.
Well I think it's just because 1.5V AAs are so damn ubiquitous and so much pre-existing gear runs on them, and devices that run off of other battery types are not backwards-compatible. With HDMI it was only a matter of replacing one or two pieces of equipment, and for a long time televisions and the like were backwards-compatible and would work with either the old connectors or the new (and some still do).
If 1.5V AAs disappeared a lot of people (including a lot of hardcore battery nerds, even) would suddenly have a lot of non-functioning gear that would need to be replaced, which would be annoying to say the least. And 1.5V AAs are perfectly fine for many applications (my wireless mouse will run for about a month on a pair of them, for instance) so that would mean that people would have to replace a lot of equipment that was otherwise perfectly good, just because the batteries to power it had become unavailable.
That said, better batteries (and gear that runs from them) are becoming gradually more common. 3.6V 18650s and the like have already mostly replaced AAs (or maybe it would be more appropriate to say that they've replaced C and D cells, which were what we used to use when we needed more capacity) in high performance applications like powerful flashlights and electronic cigarettes. And various custom-form-factor LiPo batteries are ubiquitous in stuff like cameras and phones where space and power are at a real premium.
1.5V AAs are probably here to stay for the foreseeable future, though. Perhaps something like a 14500 or a standardized prismatic will eventually replace them, but it will be a slow phase-out and AAs will stick around for a long time so that people can continue to run low-performance gear that works perfectly satisfactorily on 1.5V AAs. In the meantime, it will only be a good thing if manufacturers can continue to push the capacity and performance envelope for that battery type -- a lot of that technology (not all of it, but a lot) will carry over to other types of batteries, improving things across the board.
A look at future battery chemistries is a nice glimpse into the design decisions involved in constructing a rechargeable battery. It explains briefly how anode/cathode elements are chosen from the periodic table to meet various design constraints (including voltage). The author Yevgen Barsukov is a leading expert in battery technology at Texas Instruments (who did much of the work on TI's widely-used Impedance Tracking battery fuel gauge). The article is part of TI's Fully Charged blog, which contain many interesting, informative entries.
Last edited by Gauss163; 11-27-2013 at 12:29 PM.