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Old Oct 14, 2003, 10:52 PM
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San Diego Lindberg, California, United States
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Sony US18650GR ???

Hi:
I came across some Sony VAIO battery packs rated at 14.4V @ 4000mA, configued as 4s2p. I tried a 2s2p in my S400 powered wing and the packs worked as well as my 1100 AAU 8 cell pack.
(almost as much peak power, but longer running)I tried some older sony LiIon cells, also 18650xx but they did not work nearly as well. Does anyone have the spec for the Sony US18650GR cell ? Is it really a 2000 mA cell ? What is the max discharge rate it can tolerate ? Or how can I measure, ie how low can I let the cell voltage drop under load ? 3 V ?

Just for the heck of it I dumped the 2s2p pack across my ammeter, and it shot past 40A and the test leads got hot ! Ooops

EP
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Old Oct 15, 2003, 03:33 AM
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Re: Sony US18650GR ???

Quote:
Originally posted by epkoncept
Hi:
I came across some Sony VAIO battery packs rated at 14.4V @ 4000mA, configued as 4s2p. I tried a 2s2p in my S400 powered wing and the packs worked as well as my 1100 AAU 8 cell pack.
(almost as much peak power, but longer running)I tried some older sony LiIon cells, also 18650xx but they did not work nearly as well. Does anyone have the spec for the Sony US18650GR cell ? Is it really a 2000 mA cell ? What is the max discharge rate it can tolerate ? Or how can I measure, ie how low can I let the cell voltage drop under load ? 3 V ?


There are several versions of these 18650 cells with ratings between 1200 mAh to ???. You might want to look on the internet under "energytec" and/or "sony" + "18650". At one time I found a site with lots of info on these, but lost the address now. These cells are usually safe up to 3C.

Just for the heck of it I dumped the 2s2p pack across my ammeter, and it shot past 40A and the test leads got hot ! Ooops

Keep abusing these batteries and you'll become a candidate for a Darwin Award and help cleanse the gene pool. You're very lucky that you didn't become a statistic. If you haven't already, you should read the sticky on Lithium batteries. They are good batteries if you know their limitations and restrictions. Be safe!

EP [/B]
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Old Oct 15, 2003, 07:49 AM
now that's a wattmeter...
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Look for a 2-letter code on the battery. Something like "G3" or "G4". These will indicate the capacity. Can't remember what exactly they represent, will have to try to dig out the Sony catalogue. Basically the higher the number, the higher the capacity. The G4 ones are 2000mAh, I have some of these myself.
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Old Oct 15, 2003, 08:04 AM
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>> Just for the heck of it

As Babblefish points out, it is not wise to do things with any type of lithium cell "just for the heck of it." Please do make an effort to understand the safety concerns specific to lithium cells before you have a big problem.
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Old Oct 15, 2003, 10:10 AM
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Have you guys ever used a oscilloscope + current clamp ?

Guys:
Thanks for the reminder of the dangers associated with LiIon cells. The short 0.1 sec or so short in to my ammeter is dangerous, but considering the thermal mass of the battery, a split second short should not cause a local temperature rise in a cell that would be catastrophic ? If that were the case, I don't think too many people would be using LiIon cells in models, as the peak current required to start a stalled motor is very large, ie several times the typically operating current. Incidentally, have any of you guys used a widebandwidth current clamp and a scope to capture the peak current when you turn on your motors ?
I looked at the threads, but does anyone really know what is the cause of the failure ? ie does a failure start at a macro or micro scopic level ?
The descriptions are still seem vague.

EP
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Old Oct 15, 2003, 02:31 PM
Random Flier
Oxford (UK) and Mtn View CA (USA)
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Regarding dumping current... don't forget that 18650s have a PTC discharge overload-protection built-in. The biggest hazard on discharge is getting a cell shutdown when you least want it but I have not come across any "Li-Poly type catastrophes" on discharge...

There was a thread a few months back with someone running a 1P pack of more recent 18650s in a ~10A app (4+C). These cells would seem to be very attractive if they become more "available"...

[edit: oops. memory fade - thread mentioned ~7.5A from these Dell-pack-derived 2230mAh cells...]
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Old Oct 15, 2003, 04:19 PM
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PTC is a thermal device

The response of the PTC is slow as it is a thermal device that actually expands and reduces its conductivity when a high current flow causes it to heat up.
I am not sure, but I thought the PTCs were typically located at under the postive terminal, and if the batteries are end to end soldered the PTC temp may not rise quickly !
EP
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Old Oct 15, 2003, 09:32 PM
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EP, it's not always easy to tell how much someone knows about lithium cell safety. I would rather err on the side of assuming that someone knows very little and say something they already know than assume that someone knows a lot and not say something that might help them avoid a future problem.
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Old Oct 16, 2003, 02:06 AM
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San Diego Lindberg, California, United States
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dave, I'm in total agreement with you!

Dave:
I appreciate everyone's advice. I do remember one experience with trying to get some dead LiIon cells to take a charge, I got them so hot, that they vented out something smelly ! Long time ago I didn't know the correct procedure for bring up cells that were under voltage ! I know better now.

If anyone has any specs on the Sony US18650GR cells that are supposedly rated at 2000 or 2200 mAH, I would really appreciate it if someone could point me in the right direction as to where I can find that info ? I tried to search Sony, Energytec, LiIon,.. but all the info I could find were specs on a physically similar Panasonic cell. I am not 100% sure, but I beleive the anode material /construction is different between the Sony and Panasonic cells, the latter is graphite and the former is carbon. The graphite anode cells have a higher voltage curve.So I assume many of the other parameters are different.

EP
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Old Oct 16, 2003, 02:51 AM
now that's a wattmeter...
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Singapore
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Ah yes I managed to dig up the Sony catalog of Ion cells, hope this helps.

Download it from my webpage here.
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Old Oct 16, 2003, 08:42 AM
Straight up is all I ask
Fairfield Ct USA
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On average these cells give out 10 watts per cell. Good for a speed 280 on 3 cells . I've seen 120 watts from 3s2p but that pack did that only once then dribbled down to the usual low if that. It is exciting to experement but it is more exciting to fly with cells that really work . These type cells I give a resounding dont really work. Ben there done that . Good Luck

James
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Old Oct 17, 2003, 11:43 AM
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thanks for the info

Simingx:
thanks for the pdf. I knew I had seen this info before but I guess now, Sony's removed all that info from the internet.

jmolwitz
Thanks for the comments. I've noticed that too when I was used batteries from the recycling boxes. However, the last few packs I got out of the recycling box seem much better. I've now flow 1 pack of the US18650GR(2000mAH) in a 2s2p for 3 flights of 20 minutes each on my foamie wing with a DD gunther prop with an S400 6V motor.

EP
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Old Oct 17, 2003, 05:55 PM
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EP,
The GR cells do work a little better. A 2C discharge will yield almost full capacity. You can get 3~4C, but you need to keep it to bursts of 30 seconds to a minute. Then back off for a minute or so to let them "rest". Doing that you can still get over 80% or so of capacity and a fairly decent discharge rate, if only in bursts.

The protection circuits supplied with those cells limits discharge to ~2C. To get full capacity you have to stay under that value.

Jimmy
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Old Oct 17, 2003, 07:07 PM
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thanks again Ezone

Jimmy:
Coincidentally, that explanation is similar to my current usage. I am flying on a slope so I have to run WOT on the way back up and then float around. I am pretty sure that I am getting about 2Ahrs out per charge because I can fly atleast twice as long as my 1100 AAU packs. I don't have any protection other than what is inside the cells, ie the PTC ? I am pretty bappy with the 2s2P arrangement, ie its almost an ounce lighter than my 1100 AAU pack but I can fly twice as long !

Other than the GR suffix I noticed that on the green wrapper of the Sony cells I also see some other numbering, and amongst this additional lettering is a prominent "G6" which I believe probably refers to the generation of the cell.( that was marked on the cells from a 4400 mAH 3s2p VAIO battery pack.

EP
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