Ni-MH vs Li-Ion cells

moldyoldy

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Not sure if I have this entry in the correct forum. Moderators please move it to whereever more appropriate.

In the special issue of Forbes regarding "energy + genius", there is an article on "The Saudia Arabia of Lithium" - a Chilean lake bed at 1.4 miles above sea level some 700 miles north of Santiago, annual rainfall of a few millimeters. bad climate for bare skin... At any rate, this single location is where 27% of the world's lithium supply comes from. As the consumer demand for higher density batteries sharply increased to include especially Li-Ion batteries, the demand for the metal has skyrocketed and predictions are for a double digit annual sales growth for lithium carbonate at least thru 2012. China has another 23% of the lithium carbonate production. The original source of lithium was from a mine in the town of Kings Mountain in N.Carolina and was developed for the US H-bomb program. By the mid-1970s, that location was producing 2900 tons of lithium per year. lots of bombs.... hmmmm.

Attempting to ignore the increasing politics over any source of lithium carbonate, both Honda and Toyota declined to convert their respective hybrid cars from a Ni-MH battery system to the Li-Ion battery system claiming that the world's supply of lithium was insufficient for cars. The production Tesla and the new planned Chevrolet Volt use Li-Ion cells, as do just about any laptop computer.

Getting to the point of my entry for CPF: After a long initial "get acquainted" time period with CR123 and RCR123 cells during which I spent far too much money on various brands of RCR123 cells and chargers, I am moving away from the CR123 format back to the AA/AAA Ni-MH format. In doing so, I am also progressively moving over a couple dozen flashlight users in several institutions back to AA/AAA celled flashlights as well. When I am asked for my advice on flashlights by a tradesman or emergency worker, the request nearly always begins with an AA/AAA format flashlight. Sometimes the user likes the small size and goes with the CR123 size - until it comes to battery replacement time. Even if I give them the website address of a good CR123 source, they do not want to purchase in any bulk, and the shipping costs for a couple batteries are prohibitive. Ergo the user might actually purchase a retail CR123 package once or twice, and then the flashlight sits unused. Eventually I see them carrying around a mini-mag AA light or something AA/AAA-based from Walmart or Target. The CR123 system is really questionable for non-flashaholics.

Yes, the energy density and voltage output of a lithium-something cell provides a bright flashlight in a small package. But there are simply too many conditions for rechargeable lithium-ion cells to be recharged and used correctly - and too many incidents are still being reported. And, there are far too many variations on lithium-xxxxx cells in an attempt to develop a "safe" rechargeable lithium-something cell. Lithium batteries had a very bad reputation in the flight industry for starting fires in the emergency radio beacon were they were used. All of this leads to why individual rechargeable lithium cells with rechargers are not carried in any retail consumer stores. Compare that with the glut of Ni-MH cells and rechargers on the market.

Regarding the AA/AAA format: Now that Ni-MH cells are generally available in the low-self-discharge formulation, the primary usage difficulty for use of Ni-MH cells seems to have been addressed. no more dead flashlights or toys when needed. Not only that, but over time, and especially noticeable with the latest LED-Q4/5 lights such as the Eagletac LED flashlights, the output of an AA-based light is really not all that different from a comparable CR123-based light. Example: for a tradesman yesterday I compared an Eagletac P10A 1xAA light to a Fenix P1D-Q5 1xCR123 cell (both on highest output with fresh batteries) and illuminated a heating fixture on the ceiling of an industrial "high bay". There was not much difference in illumination on the heating fixture. His Mini-mag AA flashlight did not have a chance in that competition.

Yes, flashlights on the CR123 format do have their niche, but only for "afficiandos" and flashaholics, or emergency workers and spec-op types....
 

JackJ

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Interesting, thoughtful post. Thanks! I find myself going back on forth on this issue. I dabbled with CR123 and CR2 cells for a while, but eventually gave up on them for the reasons you cite--safety concerns with both primaries and rechargeables, cost/availability of primaries, and general satisfaction with LSD NiMH.

But I just purchased two new lights designed specifically for Lithium: An Eagletac T10L and a Dereelight CL1H. Unfortunately, I'm still waiting for the cells to arrive from Hong Kong, though they should be here today.

My feeling is that the 18650 form factor (size/performance ratio) is close to ideal for outside activities, offering better performance than 2AA models. Inside, I'm very happy with single AA offerings, e.g., the Nitecore D10.

I'm wondering if I'd be better served by a new NiMH cell shape, something about the size of an 18650, or perhaps even a little larger. What would the mAh rating be? I guess I could even consider 2 C cells, but not many high quality lights are designed for that, and I'd prefer just one cell.

It's not like I'm excited about yet another charger and cell format coming along, but I do think current NiMH (and Alkaline, though I hardly ever use those) sizes are not ideal for hand held flashlights (the exception being pocket lights).

Jack
 

moldyoldy

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Hi JackJ,

To assist with the delay in arrival of the 18650, why not try a dummy CR123 cell (conductive) and a normal CR123 cell in your Eagletac T10L light? Normal CR123 cell next to the head. Either that or a couple 15mm spacers works also. That was my solution to roughly the same input condition. The Eagletac T10L is at least functional, although certainly not at optimum.
 

JackJ

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I've got a couple of dummy cells on order from AW, too, but they'll come with the 18650s. If for some reason they don't arrive today, I may have to look at improvising spacers. Though it's not like I don't have other flashlight options at my disposal! I guess I should point out that it's not taking a long time for the cells to arrive; I'm just impatient.

Back to the topic, I am looking forward to newer, safer, more abuse-tolerant Lithium rechargeables. Given that most users employ this chemistry in battery packs, as opposed to individual cells, it's nice that the manufacturers feel free to produce lots of cell shapes. NiMH cells are much easier to obtain, but there are only two cell shapes, both quite small, available to me locally (AA and AAA).

I'm now curious what the ideal dimension for a flashlight cell is. 14mm x 50mm comes pretty close for me for an EDC, and it's nice that I can get cells with that dimension in many different chemistries. But for a larger, outdoor light (what for many amounts to a "duty" light) I'm not sure. Maybe 20mm x 80mm? I'd still want to be able to put the light in a pocket; anything that truly requires a holster is too large.

Jack
 

Mr Happy

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For NiMH cells the ideal dimension is short and fat, say like 1/2D or 2/3C rather than AA. The benefits are that

  1. They will fit end to end in a tube of reasonable diameter
  2. You can put more of them in series for higher voltages
  3. Short fat cells seem to have higher current capabilities than long thin ones
I think there is a huge mountain to climb before a different cell format would get into the mainstream consumer market though.
 

linterno

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How good would be to have 1/3 18650 NiMh batteries?

Current AA NiMh are ~11 x 50 mm (550 squared millimeters). A 1/3 18650 would be 18 x ~22 ( 396 squared millimeters). If we consider ~2200 mAh per AA NiMh then this 1/3 18650 would be 72% of AA batteries or ~1584 mAh.

Like this we would have a near replacement for 18650 Li-Ion (1.2 * 3 NiMh = 3.6V or ~4.2 fully charged) with a reduced capacity but safer operating conditions.

PRETTY LATE EDITED:

In fact the volume of a cylinder
f4158dab7968d0898a95f83495604c73.png

A AA NiMh volume is 3.141592654 x 7 ^2 x 50 = 7696.90 cubic millimeters and 1/3 of 18650 Li-Ion is 3.141592654 x 9 ^ 2 x 22 = 5598.32 cubic millimeters. a 1/3 18650 would be 5598.32 / 7696.90 * 100 = 72.73 % of NiMh. The same result in terms of percentage but done the correct way.
 
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mdocod

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MoldyOldy

great well thought out post!
I find myself avoiding the discussion of lithium/li-ion powered flashlights all-together when asked by friends or family what flashlight to buy. They have their place in the hands of certain professionals and enthusiasts. (And it requires a certain level of enthusiasm from anyone who might be interested to really take on the lithium powered world of flashlights).


-----------------------------------------------

JackJ said:
I'm wondering if I'd be better served by a new NiMH cell shape, something about the size of an 18650, or perhaps even a little larger. What would the mAh rating be? I guess I could even consider 2 C cells, but not many high quality lights are designed for that, and I'd prefer just one cell.

It's called a 4/3AF cell, and they are available with label capacity up to around 4200mAH. Total stored energy is still about 30% less than the same size cell in Lithium Cobalt chemistry. Well, technically speaking, there can be a slight difference in sizing between an 18650 and a 4/3AF, but not much more than the variations then we see from 18650 to 18650 in the market anyways. Most 4/3AF cells are ~18mm x ~65mm.

-----------------------------------------------

linterno said:
How good would be to have 1/3 18650 NiMh batteries?

Current AA NiMh are ~11 x 50 mm (550 squared millimeters). A 1/3 18650 would be 18 x ~22 ( 396 squared millimeters). If we consider ~2200 mAh per AA NiMh then this 1/3 18650 would be 72% of AA batteries or ~1584 mAh.


Think in terms of cubic millimeters instead. And use the right dimensions for AA cells :)

AA cell is (pi x 7^2)50 = 7697 mm^2
1/2AF cell is (pi x 9^2)22 = 5598 mm^2

You may have noticed, I used the term "1/2AF" there for the cell size you have described... guess what, that cell size already exists :) I have never seen a 1/2AF cell even close to the theoretical ~1400-1600mAH that might be possible based on looking at the energy density of an AA NIMH cell, and there are numerous reasons for this. A lot of it has to do with the popularity of the cell size. More popular cells see more research and development, and a lot of these odd ball cell sizes are not designed to have the highest possible capacity, but instead, have reliable consistent performance for use in permanent installation in things like cordless phones. Also, as you make a cell smaller, there is a smaller percentage of available internal space available to dedicate to electrolyte, there are certain things that remain pretty constant in size and thickness across a wide range of cell sizes, such that as the cell gets smaller, there is more "wasted" space.....

[edit in] just noticed that most 1/2AF cells are actually 17 x 22mm... so an 18mm x 22mm would have slightly better potential if the size were focused on...
In the end, I think anything that a stack of small NIMH cells can do, a single LiMn cell can do just about as well or better.

Eric
 
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drmaxx

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In the special issue of Forbes regarding "energy + genius", there is an article on "The Saudia Arabia of Lithium" - a Chilean lake bed at 1.4 miles above sea level some 700 miles north of Santiago, annual rainfall of a few millimeters. bad climate for bare skin... At any rate, this single location is where 27% of the world's lithium supply comes from. As the consumer demand for higher density batteries sharply increased to include especially Li-Ion batteries, the demand for the metal has skyrocketed and predictions are for a double digit annual sales growth for lithium carbonate at least thru 2012. China has another 23% of the lithium carbonate production.

Attempting to ignore the increasing politics over any source of lithium carbonate, both Honda and Toyota declined to convert their respective hybrid cars from a Ni-MH battery system to the Li-Ion battery system claiming that the world's supply of lithium was insufficient for cars. The production Tesla and the new planned Chevrolet Volt use Li-Ion cells, as do just about any laptop computer.

Lithium reserves were not quite the main topic of the post, but here some additional info
I've got an other source that says: "Safety issues are still a concern with automakers Honda Motor Co., Ltd. and Toyota Motor Corp., that have delayed launching lithium-ion hybrid vehicles into the market over concerns of continued lithium-ion battery instability, although their research continues." Source: http://minerals.usgs.gov/minerals/pubs/commodity/lithium/myb1-2007-lithi.pdf

The world production in 2007 was 25,000 t of Lithium, with estimated Reserves 4,100,000 and a Reserve base of 11,000,000. Sounds like there is quite some room to produce a few more batteries - especially considering that the Li from batteries can be recycled. Source:
http://minerals.usgs.gov/minerals/pubs/mcs/2008/mcs2008.pdf
 

uk_caver

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It's called a 4/3AF cell, and they are available with label capacity up to around 4200mAH. Total stored energy is still about 30% less than the same size cell in Lithium Cobalt chemistry. Well, technically speaking, there can be a slight difference in sizing between an 18650 and a 4/3AF, but not much more than the variations then we see from 18650 to 18650 in the market anyways. Most 4/3AF cells are ~18mm x ~65mm.
I'm interested in how many different NiMH cells there are in that size ballpark - 4/3A, 7/5AF (17.5*67 or 17*66, depending on manufacturer), 18650, 18670, etc.
Seems odd that there wasn't a bit more standardisation, but I'm sure there must have been reasons.
 

moldyoldy

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Lithium reserves were not quite the main topic of the post, but here some additional info
I've got an other source that says: "Safety issues are still a concern with automakers Honda Motor Co., Ltd. and Toyota Motor Corp., that have delayed launching lithium-ion hybrid vehicles into the market over concerns of continued lithium-ion battery instability, although their research continues." Source: http://minerals.usgs.gov/minerals/pubs/commodity/lithium/myb1-2007-lithi.pdf

The world production in 2007 was 25,000 t of Lithium, with estimated Reserves 4,100,000 and a Reserve base of 11,000,000. Sounds like there is quite some room to produce a few more batteries - especially considering that the Li from batteries can be recycled. Source:
http://minerals.usgs.gov/minerals/pubs/mcs/2008/mcs2008.pdf

Interesting data! Thanks!

As for the significance of the reserves cited, here is a quote from the Forbes article: ""Bill N. Reinert, national manager for Toyota's advanced technology group, predicts that lithium-ion batteries will be in vogue for only about a decade, after with the auto industry will switch to a lighter, more affordable solution...If people want an electric vehicle that goes 200 miles but doesn't cost $100,000, that's not lithium, that's something else".

Umm, well, perhaps a different perspective and apologies for being way off topic: it took a perceived need to build H-Bombs that eventually led to the lithium-something cells that we carry around today. What will have to happen to give us the "something else" chemistry anticipated by Mr. Reinert? As an ex-mil from the 60's and also having grown up in the 50's during the early Cold War by practicing diving under school-room desks "in case of", I am not sure I want to find out! I watched in-person as the __second__ shock wave that traveled around this planet from the largest nuclear weapon ever detonated (Soviet) pass across the recording barograph at my school. sobering!

back on topic: I believe that developments in LED technology will far outstrip developments in battery technology, as evinced by even the last 5 years of history.
 

moldyoldy

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Bolivia has a boatload -- 50% of the world's Li reserves. Now we just need another CIA sponsored revolution. LOL!

Impressive on the new source of Lithium - in the wrong part of the world again! The CIA does not have a lot of success in sponsoring revolutions, or conducting wars. Remember Air America.....

Instead of a revolution, I can contrain my use of Lithium cells! :)

In my view, the interest in how to store or conserve energy is far better than focusing on the production side. CPF serves a proper and useful service in educating the public about both storage and conservation. Storage by promulgating information about better cells and chargers. Conservation by causing so many of us to upgrade to the latest LED technology, which creates the incentive for more research and to push production of the better LEDs up and therefore the price down!
 
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moldyoldy

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Curious comment. Where would you consider the correct place in the world?

chuckle - there is a loaded question! :) Before I answer, I probably should state that I lived in Germany for 3 years and some other locations outside of the US and speak a couple other languages besides English.

The "correct" location for a natural resource to be developed is preferably close the to consumption location. IOW, the source should be close to the sink. An example would be electric power plants - generate the electric power in smaller units closer to where that power is consumed. Yes, I am an engineer... An example of a bad case of ruining a useful resource is to burn the Amazon jungle just to grow some energy crop so the product can be shipped somewhere else in the world.
 

LuxLuthor

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Without going too political, review the positions of the current socialistic leadership of Bolivia vis-a-vis natural resource industrial development. It is abundantly clear that gaining access to their supply of lithium is very unlikely.

Hence the growing interest in hyrdrogen fuel cells.
 

drmaxx

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Just to throw in an other thought: I bluntly claim, that most flashlight users do not need the energy density of a (rechargable) lithium battery. I look at my light use and I rarely run batteries down. Usually, you have the possibilty to recharge the light - and with frequently used lights you also do.
So, increase the capacity of supercapacitors by about a 5 (from 6 Wh/kg to 30 Wh/kg; see also http://lees.mit.edu/lees/posters/RU13_signorelli.pdf) and I would have the perfect energy storage for my flashlights 80% of the time. Charged in seconds and last as long as my LED...

All I try to say is: it's not always about the most energy in the smallest package - sometimes convinience and longetivity is a good argument too.
I stopped buying 2700 mAh NiMH and go almost exclusively for 2000 mAh eneloops. Just way more robust -even if I do not need the LSD most of the time.
 

moldyoldy

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Just to throw in an other thought: I bluntly claim, that most flashlight users do not need the energy density of a (rechargable) lithium battery. I look at my light use and I rarely run batteries down. Usually, you have the possibilty to recharge the light - and with frequently used lights you also do.
So, increase the capacity of supercapacitors by about a 5 (from 6 Wh/kg to 30 Wh/kg; see also http://lees.mit.edu/lees/posters/RU13_signorelli.pdf) and I would have the perfect energy storage for my flashlights 80% of the time. Charged in seconds and last as long as my LED...

All I try to say is: it's not always about the most energy in the smallest package - sometimes convinience and longetivity is a good argument too.
I stopped buying 2700 mAh NiMH and go almost exclusively for 2000 mAh eneloops. Just way more robust -even if I do not need the LSD most of the time.

Interesting comment! and sequeing back into the topic of batteries, I certainly agree that the LSD form of Ni-Mh provides adequate power and voltage for most flashlight usage, or toys, etc. The only reason the camera and portable electronic designers dropped the AA/AAA cell form was because of packaging considerations. The consumer wanted super slim and light electronics to carry.

Back to batteries and flashlights. Now that my girls have grown and flown the nest, my primary usage for batteries and flashlights is avoidance of using the mains, or when the mains simply were not active. I have worked very assiduously to drive down the KWH consumption of electricity and gas in the one-story single-family dwelling that we live in. Example: I use a flashlight in a ceiling bounce mode when I am just on the computer and not reading anything on the desk - all room lights are off. Yes, my Hungarian wife thinks I am crazy, but we have survived each other for almost 34 years now....

As a kid, I have many memories of almost every major storm causing electric power loss for many hours if not days. Kerosine lanterns and flashlights gave light at night, the kerosine stove cooked flapjacks/pancakes. A couple years in the US Forest Service in northern Idaho in the St.Joe National Forest on the Bitterroot Divide sharply increased the reliance on batteries for flashlights and for radios. Electric power was generated onsite for the day from about 0500-2100 and turned off. In the military at locations around the world, well, electric power was generated onsite/on-location as needed, and then shut off except near large cities. however in a remote part of Japan, having 100VAC at 50hz was not particularly conducive to running electronics designed for the US electric power grid. As an electrical engineer, I discovered the hard way that power up/down causes problems when the electronics are not designed for a "soft start".

In short, I strongly advocate conservation of resources rather than generating or drilling for more resources. Lithium batteries were developed in an era when the alternate was Ni-Cd - pocket plate, sintered electrode, made no difference - any operating time was short. I consider the LSD form of Ni-Mh to be good competition to the Lithium-something cells. LSD Ni-Mh cells are one of the many reasons why I am slowly converting back to Ni-Mh cells. Batteries of any form provide a bridge between the times when mains voltage/current is available, or simply that from an automotive alternator. Just do not assume that the main electric supply is normally available!
 
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