Molicels: battery of the future?

[MCPeePants]

Note: All knowledge in this post is based on what I remember from grade 10 circuitry. As such, there's a good chance that it's a bunch of lies. By all means, correct any of my errors.

Over the last week I did some work experience at Moli Energy (Maple Ridge, BC), which is among the largest manufacturers of lithium-ion cells in North America. After a few days working with the cell production line, I discovered that each cell is charged to 4.2V, with a 2200mAh and a 3000mAh size. Now, if what I recall is true, cells connected in series will have additive voltages, which means it would only take two of these cells to achieve a voltage rating of 8.4. Of the two cells, the smaller is 18mm in diameter and 65mm tall, and the larger is 26mm in diameter and 70 mm tall.

Again, my knowledge could generally considered to be bad, but this seems to me an excellent way to make small, high capacity batteries. In all my searching, I've never come across a mini battery with a mAh rating of more than 1000, so it seems to me that a battery consisting of only 2 cells could open a lot of options for smaller guns (most batteries are 7 to a pack, yes?). My sad lack of a gun, however, means I really have no idea as to the specific dimensions of the battery compartments in most guns. I'll have to ask my buddies that actually do more than read forums.

One thing to consider while reading this is my complete ignorance to any of the more complicated aspects of current discharge. I don't know their tolerance, I don't know their discharge rate, I don't even know if they follow the same charging procedures. They are, however, used in Milwaukee's cordless line of power tools (which I understand are pretty sexy, as far as those things go), so they must be moderately good at things in general.

Alas, they don't just retail their cells. They sell directly to battery pack manufacturers, so getting hold of some might prove difficult. I also have no idea what price range it would be. And those of you who want 9.6V are out of luck: you'd have to try 12.8V, which I can't imagine being good for a gun.

But anyways, if any of you people that know things could come in and clarify any erronious points here, I would much appreciate it.


Edit: this may well be in the wrong section, but I don't feel it's partcularily fitting in accessories or gear, so here it went. By all means, move it if you disagree.

[Regan]

Hmmm well I'm no big city chicken lawyer, but I think you may be on to something. The only thing I can see is that the max discharge rate is kind of low @ 4A, but otherwise it could probably work, but I'm no expert either.

http://www.molienergy.com/specs/ICR-18650J.pdf

[Digital_Assasin]

Li-ion batteries are nice and dandy for their energy storage density, but are lacking in several other departments. Cost, life, durability and current delivering ability.

At a 100% charge level, a typical Li-ion laptop battery that's full most of the time at 25 degrees Celsius, will irreversibly lose approximately 20% capacity per year. This capacity loss begins from the time it was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 °C, 20% at 25 °C, and 35% at 40 °C. When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively. Every deep discharge cycle (Using your battery till it's empty.) decreases its capacity, and the degradation is sloped such that 100 cycles leave the battery with about 75% to 85% of the original.

I don't know about you but I sure as hell don't want to shell out a lot of cash for a battery that will be effectively dead in 2 years or sooner if it is kept warmer (from high current discharge, fast charging, of those hot summer days.)

Li-Ion:
- Specific energy density: 150 to 200 W•h/kg (540 to 720 kJ/kg)
- Best Capacity
- Most Sensitive to Abuse

NICAD
- Specific energy density: 40-60 W•h/kg
- Best for High Current Applications (Airsoft Guns)
- Least Sensitive to Abuse

NIMH
- Specific energy density: 60 W•h/kg (220 kJ/kg)
- Best Compromise Between Capacity and Current Delivery

More Info:
http://en.wikipedia.org/wiki/Lithium_ion_battery
http://en.wikipedia.org/wiki/Nickel_...ydride_battery
http://en.wikipedia.org/wiki/Nickel-cadmium_battery

[MCPeePants]

And there you have it.
Still, if some could be found for anything resembling a reasonable price it'd make for a decent power source for mini/stick battery guns. After all, the standard 600mAh mini has only 20% the capacity of a 3000mAh Li-Ion. So you benefit for most of those theoretical two years. At their price though...
Too bad I didn't smuggle any out.

[MadMax]

I'm running twin parallal Kokam 11.1v 3Ah (1.5Ah ea) packs in my P90. Absurd ROF.

These cells are marketed to the RC car and airplane market so they're designed for high current application. So far I'm very happy with them, but I haven't made a self protection cct yet. I have to be careful not to run them down completely (no cutoff circuit) but that's not a huge deal with 3Ah of capacity and my use of locaps (P90 hicaps suck).

You also need a proper charger for Lion cells.

The Kokam cell has made a big difference in my battery collection. I see myself using only NiCd (cold weather battery) and Lion now. I've never liked the NiMH internal resistance issues of NiMH and they perform very poorly in the cold so I use Lion in the warm weather for it's very high energy density and NiCd for the cold weather performance. At 3Ah, there's no need for me to fast charge. I'm happy with slow charging the night before. They're rated for 8C discharge which means that individually each can supply 12A for a total of 24A in the parallel arrangement.

Did you know NiCd cells are still launched in sattelites? They're robust and can provide power on the cold dark side of the earth.

Check: towerhobbies.com for Kokam cells. they're not that expensive.

[Tom_Keeler]

Lithium Ions are supposedly getting more and more reliable as time goes on... you'll notice that all power tool manufacturers are in the process of switching over to Lithium Ion, just because of weight.

[aftica]

a few guys i have read about, have been using the emoli stuff with great results! ( RC ). i think the only reliable source ( at this point ) though, is taking apart the new power tool packs! lipos are great too...just follow the rules, and be careful with em'

[DJ_Mittens]

The advantage of the power tool packs is that if you fabricate a connector to the old battery casing, you get a convenient, reliable charger too by using the battery's original charger.

But I agree with some sentiments offered here, that LiIon batteries are continuously becoming more and more reliable and affordable, and we can all maintain hope that they can reliably replace NiMH in airsoft applications.