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Old Jun 09, 2014, 01:57 PM
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San Diego
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A123 alternatives?

I've been looking for alternatives to the Hyperion 1450 pack primarily to get some more flexibility for the installation in tight F3B fuselages. The A123 18650 cells seem okay, but I would like to get a bit more capacity.

I came across these cells by K2 Energy and was wondering if anyone had experience with them?

http://www.batteriesinaflash.com/spe...wer%20Cell.pdf

http://www.batteriesinaflash.com/ass...geable-battery

Are there any other LiFePO4 cells I should be considering?

I want to stay away from standard Li-Ion cells due to the fire risk.

Thanks in advance for any input.

Tom
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Old Jun 09, 2014, 02:27 PM
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Hey Tom,

I talked to Steve Belknap the last time I got some batteries from him about that. I think he seems to think that there are a couple of those formats with the 18mm diameters that work, but may not get to what they are rated. I don't know which ones he had seen though.

I don't know if you've ever used him for creating battery packs, but he's a really nice guy, and can make a clean pack from anything you want. I can give you his contact info if you want to ask him...

t
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Old Jun 09, 2014, 02:27 PM
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1850 li-mn
You can get 3.7v per cell. 35a discharge. 2500mah capacity.

But you need to run hv servos or regulators.
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Old Jun 09, 2014, 03:20 PM
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Tim, yes please send me his contact info.

Tom, thanks, I'll need to do some research on LMO and NMC cells.

Tom
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Old Jun 10, 2014, 01:53 AM
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There is a lot of choice because of ecigarettes
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Old Jun 10, 2014, 03:55 PM
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France
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Make you choice !

As Satinet said, because of the e-cigarettes, the choice of 18650 format battery because difficult Too much choice kill the choice !

You can start from 2500 mAh with 35A discharge current to 3400 mAh (and even more) with a much smaller discharge current.

You will find lots of information here:

http://lygte-info.dk/review/batterie...Test%20UK.html

Below is my new Li Ion battery for my next plane. I used a servo connector as balancer plug, to be used time to time.

I found this format very practical, easy to host in a F3X glider nose, providing great capacity, and enough discharge current, event for 6 demanding digital servos

Hope this help.

Pierre

www.planet-soaring.com
https://www.facebook.com/PlanetSoaring
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Old Jun 10, 2014, 07:58 PM
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Thanks Pierre,

That does help.
I wonder how many actual manufacturers there are and how many of these cells are just relabeled?

The site you gave a link to is very helpful. In addition to the information provided, it would be interesting to see a plot of capacity vs the number of cycles for a given charge and discharge rate.

Is it safe to assume that most of the cells used for e-cigarettes are either Lithium Manganese Oxide (LMO) or Lithium Nickel Manganese Cobalt Oxide (NMC)? From what I've read these chemistries are less likely to explode/catch fire than Lithium Cobalt Oxide (LCO) (the type that is used in cell phones and laptops), but it isn't clear to me if they are as safe as Lithium Iron Phosphate (LFP). (edit: after doing a little research some of these batteries are LCO. If the cell is protected it typically is an LCO cell).

From what I can tell the only downside to LMO or NMC cells compared to LFP cells is they don't last as many charge cycles or as many years. Most of the data I've seen indicates capacity for the LMO and NMC are good for around 300 cycles and 2 to 3 years while LFP cells are good for around 1000 cycles and 10 years. Of course the LFP cells have a much flatter discharge curve than the LMO or NMC cells (although at a lower voltage).

Certainly a lot to think about!

Tom
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Old Jun 11, 2014, 08:09 AM
Jeff Carr
Ft. Mill SC / Charlotte NC
Joined Mar 2001
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Tom

I know you are looking for capacity. Are the original A123 cells to large for your fuses? I use them in my Tragi fuses and they actually fit quite good. About 1/2 an inch from the front is all that is not used. I have them in a stick configuration and they are 2300 mils. After flying for 2-3 hours I usally put about 20% back in. I am however charging at 8 amps and in 5 mins fully charged. I charge with a cell pro 10 thru a balance tap. These cells rarely go out of balance but it's the easiest way to charge.

There is a guy on the groups who has done thousands of cycles on these cells with little discharge capacity loss. It's in the battery section on RCGroups. Interesting reading. I'm sure you know there are 2 sizes of the real A123 cell 1100 and 2300 capacity. I usally find them in the tool section in black and decker cordless tool section. Even the 1100 mil packs can go 3 hours before recharging. And if your worried about charging as I said at 8 amps your done in no time. These will fit your B fuses with no problem.

If you have any problems getting them I could take a ride over to the BD corp headquarters and see if they have spares. Cablelas just took over the old BD outlet so I don't have the regular store I use to get them .

Jeff
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Old Jun 11, 2014, 09:11 AM
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Pierre-
Are you running the cells that have a protection circuit?

Thanks,
Target
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Old Jun 11, 2014, 09:42 AM
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I'm not Target if that helps. I don't think you want the pcb for our purposes.
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Old Jun 11, 2014, 11:21 AM
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Quote:
Originally Posted by target View Post
Pierre-
Are you running the cells that have a protection circuit?

Thanks,
Target
No PCB on the cells I use.

Cheers,

Pierre
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Old Jun 11, 2014, 12:45 PM
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I'm not sure you could solder the cells well with a pcb.
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Old Jun 11, 2014, 01:39 PM
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San Diego
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Quote:
Originally Posted by Goinav8n View Post
Tom

I know you are looking for capacity. Are the original A123 cells to large for your fuses? I use them in my Tragi fuses and they actually fit quite good. About 1/2 an inch from the front is all that is not used. I have them in a stick configuration and they are 2300 mils. After flying for 2-3 hours I usally put about 20% back in. I am however charging at 8 amps and in 5 mins fully charged. I charge with a cell pro 10 thru a balance tap. These cells rarely go out of balance but it's the easiest way to charge.

There is a guy on the groups who has done thousands of cycles on these cells with little discharge capacity loss. It's in the battery section on RCGroups. Interesting reading. I'm sure you know there are 2 sizes of the real A123 cell 1100 and 2300 capacity. I usally find them in the tool section in black and decker cordless tool section. Even the 1100 mil packs can go 3 hours before recharging. And if your worried about charging as I said at 8 amps your done in no time. These will fit your B fuses with no problem.

If you have any problems getting them I could take a ride over to the BD corp headquarters and see if they have spares. Cablelas just took over the old BD outlet so I don't have the regular store I use to get them .

Jeff
Thanks Jeff,

The A123 26650 cells are way to big for the current F3B planes. Even the 18650 cells are a tight fit. The A123 18650 cells seem okay, but I've read some reports that the actual capacity is considerably less than 1100 mAh. Not sure if this has anything to do with the bankruptcy of A123 and new ownership or if they have always been that way. With the real capacity being 800 to 900 mAh, I wanted to see what other options were available. I want to be able to fly for around 2+ hours and still have a considerable reserve. Also if there is a high drain event (landing out in Distance and the surfaces are loaded until you can get the model) it is nice to have extra capacity. 1450 to 1500 mAh is about the minimum rating I feel comfortable with. As an aside, the recommended fast charge current for the A123 18650 cells is 4A.

With that said, the K2 18650E cells with 1500 mAh meet my requirements. The can take a 5.6 A continuous discharge and a 9.8 A peak. Since typically we don't draw much more than 4A in our F3B or J planes, these ratings seem okay. Peak charge current is only 1.5 amps, but that is okay since I typically would only have to charge overnight anyway.

But while searching for A123 alternatives, I came across the Lithium Manganese Oxide and Lithium Nickel Manganese Cobalt Oxide cells. The main reason I was interested in the LFP cells is their thermal stability. Apparently the LMO and NMC cells also have good thermal stability relative to LCO cells. It still isn't clear to me if they are as safe as LFP cells. Fire safety is a huge deal in SoCal. Their capacity is far superior to LFP cells and their current capability is good as well. The only downsides are they don't hold a steady voltage over the discharge cycle like LFP cells do and they don't have as many charge cycles or as long a shelf life as LFP cells. So you will likely have to change packs every couple of years.

So I think I'm going to by some of the K2 18650E cells and either the Sony 18650VTC5 cells or the Samsung INR18650-20R and do some testing.

Tom
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Old Jun 11, 2014, 01:42 PM
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Tom - I understand the bankruptcy of A123 was only the US distributor, not the Chinese factory where the cells are made (my business uses large quantities of A123s).

Simon
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Old Jun 11, 2014, 04:46 PM
Detail Freak
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Harbor City, CA
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The shorter versions of the 18650 are of interest to me if the capacity is enough. (18500 and 18490)
I saw one in the link listed that had no protection circuit.

Most of the cells listed stated they had the protection circuit; are most of the cells offered in both protected and unprotected circuitry? It didn't appear that way at first glance. I may have missed something.

R,
Target
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