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Dec 08, 2001, 11:01 AM
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Smallest Li-ion Cells for Low-Voltage Motors?


Reading some of the talk about small, low-voltage motors such as the N20 made me wonder how one of these might work with a single 3.6V Li-ion cell. So far, the lightest Li-ion cell I've seen that might work is the 600mAh Neopoint 1000 discussed in the thread below. The 2-cell pack weighs 39 grams, so a single cell would weigh ~ 20 grams (~ 3/4 oz.). That's about double the weight of a 3-cell 50 mAh NiCd pack, but with about 12 times the capacity. Has anyone seen any smaller, lighter Li-ion cells available at the same kind of low prices as other surplus cell phone packs?

https://www.rcgroups.com/forums/show...light=Neopoint
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Dec 08, 2001, 03:19 PM
"Simplify, then add lightness"
Dave,
I have looked at both the Sony, and Panasonic lithium ion data, and I think that is about the lightest you are likely to find. Sony has a cylindrical 570mah cell that is 16g but I don't know if it was used in any cell packs. If you want lighter than that you will probably have to go to lithium polymer.

Jeff
Dec 08, 2001, 03:56 PM
Registered User
I was thinking Li-ion because it is an older technology and there is more likelihood of finding cheap, surplus Li-ion cell phone batteries. I hadn't really thought about lithium-polymer (Li-poly?) because I don't know much about it other than it is a newer technology and probably better than Li-ion. So there's a new question to ask: Anyone seen any small, cheap, surplus Li-poly cells for sale?
Dec 08, 2001, 05:21 PM
F5D father
Tuomas Pietinen's Avatar

li-ions


I have a 12 grams 570 mA cell. Where it came from I canīt say. I tested it and it gives 25 min with 1.5 A load. Not bad. Gonna try a 2-pack of these in my Tiny with Wes Tecnik motor. The source of these cells will provide soon? polymer cells with double capacity but they are yet less reliable and lot of tolerance occurs in different producing stocks. Look at your mobile phone...the truth is out there!
tuomas
Dec 08, 2001, 10:11 PM
"Simplify, then add lightness"
Dave,
Since the Li-poly is such a new technology, I doubt that you will find the kind of deals we have been getting on Li-ion. The only cell phone packs I have seen are the single cell packs for the Nokia 6100. Nokia has a 600mah and Ultra-life has a 750mah pack. The prices are in the $29-$39 range. I would expect the stripped weight of these cells is around 15 grams. Here is a link to the Ultra-life site. They have standard cell sizes down to 30mah at 1.5 grams, but I don't think you can buy the raw cells unless you are a manufacturer.

Jeff

http://www.ulbi.com/product-display.asp?ID=39

PS
I just weighed the Neopoint 1000 cells and they are just a hair under 19 grams each.
Dec 09, 2001, 01:43 PM
Registered User
Bill Glover's Avatar
Out of interest, WES Technik do a 450 mAh Li Ion cell that weighs 14g. Not cheap though!

http://www.wes-technik.de/English/news.htm
Dec 13, 2001, 01:14 PM
Senior Member
CR2 primary cells (3v 800mah) weigh about 11g... they can be found for $2-3
Dec 17, 2001, 09:30 AM
FASST flyer
KatManDEW's Avatar
Are those CR2 cells rechargable?
Dec 17, 2001, 09:46 AM
Just an average RC'er
Jim McPherson's Avatar
The CR2 cells are "not" rechargeable. Having said that, there was quite a discussion a while back about an article in RCmicroflight about a charger for li-ion, that just happened to charger CR2 type primary cells as well. The schematics for the charger were quickly removed from the RCmicroflight web page because of the dangers associated with charging non-rechargeable cells. The author of the RCmicroflight artical said that he had (if memory serves me) averaged about 10-30 cycles before the batteries would no longer recharge. I'll see if I can find a link for the charger, (any li-ion/metal charger should do as long as the voltage cut off is set right), if you want to search for the info, I'd suggest looking under "banned charger". I've got some CR2's that I eventually plan to try to recharge, I just don't have a plane to discharge them with yet. You can pick up CR2's DIRT cheap on ebay.
Dec 17, 2001, 08:20 PM
Registered User
JoeyC's Avatar
The smallest commercial Li-ion cell is NEC's 3.8V, 150 mAh prismatic cell that weighs 5 g. NEC also has a 300 mAh that weighs 8.5 g. I don't know if these are available as surplus (I doubt it).

http://www.necel.com/battery/laminate.cfm
Dec 18, 2001, 02:24 PM
Our Daddy and Heli Junkie
Fred Bronk's Avatar
Just remember, I will delete posts that show how to charge non-rechargeable L-I cells.
There are dangers involved that some may not head. If you wish to exchange info yourselves, that is up to you.
Feb 14, 2002, 02:21 PM
No Dear its not a new one
hotairflyer's Avatar

Tuomas Pietinen


Did you ever find the source of the 12g battery you have mentioned? I am interested in trying one in a MICRO IFO that I am building.
THanks
Feb 14, 2002, 06:22 PM
Senior to who? Member
crossup's Avatar

Small Li-Ion


Went to my local (500') electronic supply store and WOOHOO!!! Li-Ion batteries out the wazoo. They had about a dozen Tadirans in 2or3 sizes, and various Li-Ions from button cell to about 3K mah. Only bad part is the prices are astronomical when you 're used to Mark Hacketts prices.
Anyway, Im suggesting those of you who lust after these, check your non-chain( not Radio Shack, in other word) electronics store- hopefully you will get the same surprise I did

crossup
Feb 14, 2002, 06:33 PM
Registered User
JoeyC's Avatar
crossup,

Are you sure these are rechargeable Li-ion? As far as I know Tadiran only makes primary, non-rechargeable Lithium batteries (Lithium Thionyl Chloride). DO NOT CHARGE THESE BATTERIES!
Feb 14, 2002, 06:58 PM
High Exalted Poohbah
planeman's Avatar
For cheap Li-ion and Li-poly batteries go to eBay and search on these terms or by the cell phone battery pack manufacturer and the above terms.

I just bought two Li-poly Qualcomm battery packs containing two 3.5 volt batteries for $12.00 each (normally $60.00). You have to break open the molded plastic from around the batteries to get the batteries out and you will have to solder and set them up...but its cheap!

I also got 20 Li-ion 830mah batteries for about $1.50 each.

Planeman


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