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Old Sep 11, 2001, 06:42 AM
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Qualcomm Lithium Ion Pack

I can't seem to find the most recent posts on Qualcomm Lithium Ion Battery Pack that is being sold by <A HREF="http://sales.goldmine-elec.com/prodinfo.asp?prodid=3948">the Electronic Goldmine</A>. I suspect that this was lost in the Great 2001 Crash . I would like to rekindle that discussion.

I just received 5 cells. Although I requested "Made in America" as was suggested in another discussion, all packs were "Made in Japan". 4 packs had a charge between 7 and 8 volts, while 1 had a charge of .1 V. Yikes!

I also ordered the power converter as recommended (can't find a link for that), so I decided to try charging the "bad" battery. After about 15 minutes of charging, I checked the voltage from the "bad" battery and it showed 7V. Great! I then put a motor on that battery and it spun a prop with great umph for more than a minute. Hopefully, I received no bad packs.

Looking carefully at the cells and the included protection circuit board, I began thinking that this new battery looked familiar. I got out my $40 Lithium that I purchased from <A HREF="http://www.batteriesamerica.com/newpage8.htm">Batteries America</A>. Without cutting the shrinkwrap of my $40 Lithium, I would guess that the inards of this Qualcomm Lithium battery are the same as the Batteries America battery.

BTW, Does anyone have any information on the protection circuit in this battery. I am guessing that it prevents the battery from falling below a certain voltage, which would explain the low voltage that was measured upon arrival. But I wonder if it also protects the battery from being overcharged. Any thoughts?
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Old Sep 11, 2001, 08:51 AM
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Go and take a look at the Panasonic Li-Ion catalog. It gives some recommendations as to what the protection circuitry should do. Based on that, I suspect these boards monitor the individual cell voltages and protect agains overcharging and overdischarging. They probably also limit the charge/discharge current.

However, I'm not sure if they have some active current limiting or if they simply have short-circuit protection (ie. a fuse) that can't be reset. Since I wasn't sure how the current limiting would behave, I removed the boards from my cells. I just monitor the cell voltages myself when I'm charging. Right now I'm just using a BASIC circuit for charging (just a constant current supply), so it requires some supervision. I've designed a more "intelligent" charger for these cells, but I haven't gotten around to building it.

The Panasonic Li-Ion catalog can be found here. If you have Sony cells, THAT catalog can be found here.

The Panasonic cells are CGR18650's and the Sony cells are US18650's. The Sony cells are a little bigger and a few grams heavier, but they're rated at 1500mAh rather than 1400mAh. Sony also specifies a max discharge rate of 2C for their cells, wehreas Panasonic only says 1C.

Hope this helps!

KC

PS - for anyone who's looking for these Qualcomm packs, they still have them at Electronics Goldmine as part number NV7005.
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Old Sep 11, 2001, 02:13 PM
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LION Batteries

Which batteries is the Goldmine selling? Both?
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Old Sep 11, 2001, 05:10 PM
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Depending on the particular pack you get, you'll get either Panasonic or Sony cells. In my order of three packs, I got two with Panasonic cells and one with Sony cells. For all I know, there may be cells from other manufacturers as well. I've only seen Panasonic and Sony myself. Based on the level of refinement of the circuit board in the pack, it looks to me like the ones with Sony cells are "newer."

KC
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Old Sep 11, 2001, 05:41 PM
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Thanks K.C.

I've been pulling my hair out trying to find the old Post on the GoldMine Lithium batteries. I got a dozen of them and I needed the min and max voltages.... Thansks again

Wayne
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Old Sep 11, 2001, 08:26 PM
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K.C. What color?

K.C. Do you know what color cells are from what company? I had assumed that the pink ones were from Panasonic.

Thanks.
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Old Sep 12, 2001, 07:39 AM
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Pink ones? Hmmmmm... I don't have any pink ones, so I don't know WHO they came from. The Panasonic ones are light blue and clearly marked as Panasonic CGR18650 Li-Ion batteries. The Sony cells are a darker blue and a little bit longer, and are marked with "Sony" and "US18650."

I haven't seen the pink ones, tho. Are there ANY markings on them? They could be Sanyo cells. Unfortunately, the Sanyo 18650 datasheet (found here) doesn't have an actual picture of the cell, so you can't tell what color it is. Of course, the pictures of Sony and Panasonic cells look a lot different than the cells I have. I suspect they change the appearance of their products fairly often to keep them looking new & modern. If you do have Sanyo cells, I'm not sure what to do about charging them, since Sanyo doesn't provide the same handy guides that Panasonic and Sony do. I suspect the same max and min voltages apply to all hard carbon lithium ion cells, but the different manufacturers have different specs about max charge & discharge currents. That's probably a matter of how low they can get the internal impedance of the battery and what sort of thermal enviornment they assume you'll be using the cells in.

If you figure out who made the pink ones, let me know. I just ordered a couple more packs and may end up with some myself.

KC
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Old Sep 12, 2001, 09:42 AM
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Pink ones..

The pink cells are from packs all marked "Made in USA" they conform to Panasonic's data sheet with regard to charge/discharge voltages and capacity. The markings on them look more like some internal code and have nothing to do with the model type. I note that charging them at 1C and discharging them in a 3-pack with a 280 on an IFO produces very little warming, implying that I could push harder. Of course, I won't do this.
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Old Sep 12, 2001, 10:57 AM
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charger for lithium from Goldmine?

Can someone point me to the charger to charge the lithium batts from Qualcomm at Goldmine? Thanks

Ric
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Old Sep 12, 2001, 11:53 AM
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Li-Ion discharge current

Quote:
I note that charging them at 1C and discharging them in a 3-pack with a 280 on an IFO produces very little warming, implying that I could push harder. Of course, I won't do this.
Quacker...

How much current are you drawing with a 280 at 10.8V (I'm assuming you've got the 3 cells in series)? I'm just using my lithiums on my little Pico Stick, so I'm pretty sure I'm not drawing more than 1.5A or so. I'll go measure it tonight to see.

I'm not sure if the max discharge current is limited by battery core temperature (ie heating due to internal resistance) or by the basic chemistry of Li-Ion batteries. I suspect it's heat related. But, like you, I certainly wouldn't assume that just because the battery isn't very "hot" to the touch, that it's okay. For all I know, it may take very little internal heating to damage a Li-Ion battery.

It would make sense if this were simply a heat issue, since Sony rates their Li-Ion cells at twice the current as Panasonic. Either Sony cells have a lower internal resistance or can handle more heat, or Sony isn't as conservative with their ratings. If the discharge current rating were simply a limitation of Li-Ion technology, then Sony and Panasonic would have the same ratings.

I'll bet you can push any Li-Ion cell beyond 2C, or even to the 3C that Sony states as the shutoff current for the protection circuitry. It's just a matter of how long the battery lives before it wears out. I wouldn't go past 3C, however, since Li-Ion batteries WILL explode if abused too much. I suspect 3C is okay, since Sony states it in their literature, and they would've allowed a decent margin beyond their recommendation, just to be safe.

Both manufacturers suggest that you contact them if you plan on going beyond their ratings. Maybe I'll give them a call and see what they say.

KC
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Old Sep 12, 2001, 12:35 PM
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More about Li-Ion discharge current

Okay, here's my theory about why Li-Ion batteries are limited to lower discharge currents:

It occurred to me that Li-Ion batteries have solid-state electrolytes, as opposed to NiCd and NiMH which both have liquid electrolytes. Currents is going to flow more smoothly across a liquid-to-solid (electrolyte/anode or electrolyte/cathode) interface than a solid-solid interface. A solid-solid interface will have spottier contact, resulting in localized points of higher resistance within the battery, and therefore localized "hot spots." So while the battery case may not get particularly hot, there could very well be tiny spots inside the battery that are extremely hot. When a hot-spot gets too hot, it destroys that little part of the cell, thereby reducing the overall cell capacity and increasing the likelyhood of more hot-spots in other places. So the discharge current needs to be low enough to guarantee that any hot-spots that form won't be hot enough to do damage.

Note that Tadiran cells are Li-Metal, and are rated for much higher discharge rates (on the order of 10A, I think). That's the reason Tadiran LiM cells cost so much. I'm not sure why Li-Metal allows for higher currents, since I think it, too, uses a solid electrolyte. Perhaps my theory isn't quite right...

Just my guess. If anybody knows for sure, please join in!

KC
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Old Sep 12, 2001, 05:22 PM
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KC: I will not publish the current for fear that it will be taken as an endorsement or benchmark for what must be "OK" to do. I also hesitate to say or do anything that will make people comfortable with pushing these batteries. There were many cautions and warnings that I put out on the postings that were lost in the crash. I have not changed my point of view. I now regret even my recent post in this tread. The problem in the earlier threads was that the opinions were composed of mostly anicdotal information and blind guessing. There was very little if any actual data. People should be aware that just because some guy says it worked for him, that is no sign that it will work for you. That guy might have been on the edge of a real problem and never known it. Why repeat that kind of experiment at your own peril?
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Old Sep 12, 2001, 06:25 PM
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Quote:
KC: I will not publish the current for fear that it will be taken as an endorsement or benchmark for what must be "OK" to do. I also hesitate to say or do anything that will make people comfortable with pushing these batteries.
Fair enough - I agree that these batteries are a potential hazard. I personally don't plan to push them beyond their recommended ratings. Li-Ion batteries fail in a rather unpleasant fashion and I don't want to damage my plane, much less MYSELF, pushing the envelope of batttery performance.

To anybody else who's picked up some Li-Ion cells, I agree with Quacker - be careful with them. It's important that you treat them as their manufactures suggest. In particular, make sure you charge them PROPERLY. There seem to be several different chargers out there that people are using to charge Li-Ion cells. Whatever charger you're using should supply the right charge current and voltage (4.2V per cell & <0.7C current, as per Panasonic & Sony). Li-Ion batteries aren't as robust as NiCd or NiMH and react badly if mistreated.

It is NOT my intent to encourage the misuse of Lithium Ion batteries. Rather, I'm simply curious about how the technology works, and what it's strengths and limitations are. And I don't intend to discover them the hard way.

KC
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Old Sep 12, 2001, 07:37 PM
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Thanks, KC.
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Old Sep 13, 2001, 07:01 AM
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*nod*
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