Li-ion AA, rechargeable
- Thread starter kmjelle
- Start date
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yes it exists, its called 14500 and is available here
http://www.cpfmarketplace.com/mp/showthread.php?t=184670
http://www.cpfmarketplace.com/mp/showthread.php?t=184670
mdocod
Flashaholic
kmjelle,
Make sure whatever you are planning on using such a cell in is compatible with the 3.7V, and that you have the proper means to recharge the cell safely before using one. Very few devices are compatible right out of the box, the only ones I am aware of are a limited number of 1xAA LED flashlights. Modifications can be done to a number of 2xAA lights to make them compatible with 3.7V cells. Any device that uses 3AA cells in series could use 3 3.7V 14500 cells wired in parallel.... There's all sorts of possible uses for the cell, I'd just hate to hear about anyone destroying an expensive device using these cells.
Make sure whatever you are planning on using such a cell in is compatible with the 3.7V, and that you have the proper means to recharge the cell safely before using one. Very few devices are compatible right out of the box, the only ones I am aware of are a limited number of 1xAA LED flashlights. Modifications can be done to a number of 2xAA lights to make them compatible with 3.7V cells. Any device that uses 3AA cells in series could use 3 3.7V 14500 cells wired in parallel.... There's all sorts of possible uses for the cell, I'd just hate to hear about anyone destroying an expensive device using these cells.
I was looking for AA`s with NiMH/Alkaline voltage, and the advantages of Li-ion (high energy density, low self discharge rate). I am missing some straight forward reason wy these haven`t been made yet? I guess they would have been pretty compatible with AA size and the low voltage many of todays gagdets are designed for.
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There are lithium rechargables, but they are not drop-in. Much higher Voltage. They are expensive, they are dangerous without significant care in use. Many Li ion cells don't give you 1.5 V, the electrochemistry of the half cell reaction yields a higher Voltage. I can't conclusively answer the why question. One can chain "whys" together to reach a point of no answer pretty quickly anyway.
There are commonly available 1.5 V lithium primary AA's. They are expensive, but have some great characteristics. I say get some of those, too.
If you look briefly here, you will find many, many discussions about this subject.
My answer to you is that if you are looking for AA's with NiMH voltage, rechargability, and low self discharge, the Sanyo Eneloop is a great solution, and it has good energy density. Most see few if any downside to this choice. They are robust batteries that can be recharged as many as 1,000 times, and most users here swear by them.
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mdocod
Flashaholic
The straight forward reason has to do with chemistry. It's straight forward only in the sense that when you design a new better battery chemistry, your goals are rarely to be compatible with a previous generation, as devices can be redesigned around the new chemistry, especially when the battery type you are working on is intended for permanent installation into consumer devices, and never originally intended to be sold as loose cells to consumers. Lithium cobalt originally was developed for laptops and portable devices. It has been more recently that the chemistry has found it's way into flashlights that have been designed around those cells.
As far as the simple reason "why" there is no 1.2V li-ion rechargeable cell. There is no *known* combination of lithium metal, anode and cathode materials, that would result in a 1.2V cell that is stable, safe, reliable, energy dense and cost effective. The voltage of a cell is a byproduct of the laws of the universe. If scientists set out with the intention of building better cells with a particular voltage goal in mind, they would never make any big breakthroughs. The better method is to ignore voltage goals and shoot for every other attribute that makes a cell good, and deal with whatever voltage the happens to end up as after the fact.
In the 14500 size, currently, the energy density of a lithium cobalt cell isn't really much different than a NIMH cell. For low-self-discharge, high cycle life 1.2V AA cells, go with Sanyo Eneloops.
Eric
Well if you take the word density literally then that is not quite true. The LiIon weighs half as much therefore there is more watt-hours per gram.
Total energy capacity in the AA size (14500) though is very similar.
AA NiMh: 1.2v x 2650mAh = 3180mWh
cost about: $10 for 4 at your local store
14500(AA sized) LiIon: 3.6v x 750mAh = 2700mWh
cost: $9 ea + shipping from AW
There are all sorts of reasons that the above calcs don't quite work in the real world due to efficiencies of driving circuits, voltage under load and actual capacities vs printed capacities. But even in the real world they are close enough that one shouldn't chose LiIon for capacity.
A manufacture could make a 1.5v LiIon AA by using a shorter battery and a buck regulator built into the cell. Because of the circuit inefficiency and the cell would be shorter the capacity with todays technology would actually be less than an eneloop though, so why bother?
Don't expect to see an AA LiIon in stores anytime soon mainly for liability reasons. If a consumer mixed and matched or inserted them in devices not designed for them:
At best it would destroy the device and at worse it would burn down the house. A commercial LiIon AA would have to be idiot proof as there are lots of idiots!
mdocod
Flashaholic
good point, I was thinking volume 
I didn't even consider weight, lol....
As you say, in the real world, estimated numbers don't add up. Totally agree 100% with that.
I didn't even consider weight, lol....
As you say, in the real world, estimated numbers don't add up. Totally agree 100% with that.
Well if you take the word density literally then that is not quite true. The LiIon weighs half as much therefore there is more watt-hours per gram.
Total energy capacity in the AA size (14500) though is very similar.
AA NiMh: 1.2v x 2650mAh = 3180mWh
cost about: $10 for 4 at your local store
14500(AA sized) LiIon: 3.6v x 750mAh = 2700mWh
cost: $9 ea + shipping from AW
There are all sorts of reasons that the above calcs don't quite work in the real world due to efficiencies of driving circuits, voltage under load and actual capacities vs printed capacities. But even in the real world they are close enough that one shouldn't chose LiIon for capacity.
A manufacture could make a 1.5v LiIon AA by using a shorter battery and a buck regulator built into the cell. Because of the circuit inefficiency and the cell would be shorter the capacity with todays technology would actually be less than an eneloop though, so why bother?
Don't expect to see an AA LiIon in stores anytime soon mainly for liability reasons. If a consumer mixed and matched or inserted them in devices not designed for them:
I'm trying to find some real world numbers and this is the best I could come up with:
Eneloop at 3amp load: 2.039 Wh
Duracell 2650 at 3A load: 2.576 Wh
AW RCR123, 750mah LiIon under 1A load: 1.363 Wh
(same rated capacity as 14500)
Source:
http://www.candlepowerforums.com/vb/showpost.php?p=920843&postcount=1
http://www.candlepowerforums.com/vb/showthread.php?t=117117
Note: I used a higher discharge rate (amps) for Nimh because a boost regulator would require ~ triple the current to boost voltage to that required from the LED.
Mr Happy
Flashlight Enthusiast
I think that if you take the word density really, really literally, then it means quantity per unit volume. So energy density would be measured in units of mWh/cm³ or something like that.
The term for energy per unit mass is specific energy. So the specific energy of a cell could be measured in mWh/g for example.
As to why these particular terms got chosen to be used I couldn't really tell you; it's something that goes way back in the mists of time...
mdocod
Flashaholic
IIRC the AW RCR123 performs quite a bit worse than the 14500, for various reasons. I think the 14500 is a lot closer to the 750mAH label rating.
Eric
Eric
Got any data for that? I couldn't find it.
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Best real world data I found was L1D on 14500 vs P1D on RCR123. 14500 wins but the circuits might be different in each light though.
http://lights.chevrofreak.com/runtimes/Fenix L1D CE/Fenix L1D CE vs P1D CE.png
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Thanks for the answers so far. What`s the difference in chemistry between lithium primaries and li-ion? How can primaries be made with 1,5V, and Li-ion only at 3,7V? So far I have used Tenergy NiMH AA. How are they, compared to the recommended Sanyo Eneloops? My impression is that they have a high self discharge, but I have not done any measurements.
There are about 22 different kinds of Lithium primary batteries and over 6 kinds of rechargeable Lithium chemistries.
Check out wikipedia:
http://en.wikipedia.org/wiki/Lithium_battery
http://en.wikipedia.org/wiki/Lithium_ion_battery
Check out the Nimh battery shootout I linked to above. No better info than that. Try the search feature too.
