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Old Feb 03, 2016, 02:28 AM
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I have several models running with A123s, and they're mostly propped to draw between 35A and 45A -- i.e. up to 18C. The only thing to watch out for is that when they're empty, they're really empty; there's no chance of a short burst of power like you can get with LiPos by resetting the throttle if you let them run until lvc kicks in.
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Old Feb 03, 2016, 10:34 AM
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Originally Posted by i_r_beej View Post
I'll say. I read the first page, skipped to the last and now I'm ready to pee my pants in terror! just got my first LiPo battery and wondering if I should just take it back to the store and get a NiMh instead!

Just kidding. But still... Jeez.
If you do pee your pants, make darned sure you don't have a LiPo in your front pocket.
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Old Feb 03, 2016, 11:50 AM
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Originally Posted by vollrathd View Post
The 2500 Mah A123 spec sheet indicates they are rated for 70 Amp or 28 C discharge.
I guess it varies depending on the make then. The ones I looked up were 10C which would be 25 Amps. I have no idea who is the original maker of the A123 battery. Also their original application. Just about all round cells have one other than RC use. For example 18650s were originally designed for laptop computer battery packs, but now they are used in lots of different devices.
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Old Feb 03, 2016, 12:15 PM
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A123 'cells' were produced by A123 Systems, Inc.

The idiots at A123 Systems managed to 'kill' the company. They were to be used in automobiles and electric storage facilities and the like.

The cells are still available. I've used nothing but them in all of my planes weighing 3 lb. or more since 2006, and continue to do so.

The C rate on A123 cells is 15C. The best static amp draw, for good flight times, 6 to 7 minutes depending on flying style and airframe, is around 35 amps, which yields approximately 100 watts in per cell.
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Old Feb 03, 2016, 04:17 PM
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Originally Posted by Ken Myers View Post
A123 'cells' were produced by A123 Systems, Inc.

The cells are still available. I've used nothing but them in all of my planes weighing 3 lb. or more since 2006, and continue to do so.

The C rate on A123 cells is 15C. The best static amp draw, for good flight times, 6 to 7 minutes depending on flying style and airframe, is around 35 amps, which yields approximately 100 watts in per cell.
Here is where I've been buying my A123's. They are an authorized USA reseller of these cells. These are the new 2500 Mah type "B" A123 cells. Kind of expensive at $20.10 each. But their price drops to $9.30 if you buy 10 or more cells.
http://www.a123batteries.com/product-p/anr26650m1-b.htm

I just received an order for (39) 2500 Mah A123's for my electric conversion of a 50 cc 95 inch wingspan model. The supplier is in Michigan, USA. The A123's showed up two days after the order was placed.

FYI, for those trying to solder to these cells, it takes a 100 Watt temperature regulated Weller Soldering iron, along with some Home Depot Oatey H-20 water soluble paste flux to solder to these cells.

As for how long these cells last, a fellow club member has a two cell A123 2300 Mah pack that was purchased in 2009. It is used in his turbine powered jet. The shrink wrap on the pack was "Sunburned" to where it was an obvious different color that part of the pack that was hidden from sunlight.

I just ran a discharge test on that pack at 15 Amps. It's voltage was a percent or so less than a brand new pack, and it's ampere hour capacity was also within a few percent of a brand new pack. He put it back into his turbine model.
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Old Feb 03, 2016, 07:13 PM
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Quote:
Originally Posted by ignernt_dweeb View Post
If you do pee your pants, make darned sure you don't have a LiPo in your front pocket.
My pants are Nomex.
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Old Feb 04, 2016, 04:46 PM
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Originally Posted by diablo2112 View Post
Cost me about $200 to build myself, with a bulk purchase of 18650 cells off eBay. ......................
Which ones are they?
I see that ebay offers many different brands.
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Old Feb 05, 2016, 03:00 PM
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Originally Posted by Jim.Thompson View Post
Which ones are they?
I see that ebay offers many different brands.
I bought these about 18 months ago, a bulk purchase of 120 cells for $180. The seller is no longer on eBay. Here's the details on the cells. I haven't had to make any more packs, so haven't done the research to find another supplier.

These were 18650 Li-Mn cells rated at 2200 mAhr. These cells are labelled as "INR" which I believe is a newer Li-Ni-Co-Mn chemistry. They retain the safety characteristics of traditional Li-Mn cells, while being capable of higher discharge rates (up to 5C). Samsung manufactures these cells, and I suspect these were Samsung cells labelled for off-brand sale.

Here's many more details on how I made the 11S10P pack for those that are interested.

https://endless-sphere.com/forums/vi...hp?f=3&t=59735
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Old Feb 06, 2016, 10:35 AM
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They would be the Samsung INR18650-22R then. The latest is the INR18650-25R with 2500mAh. Though they are LiMN not LiFe so not the same thing at all. They're safer than LiPos, but they're not as safe as LiFe. They can catch fire if abused. I figured something was different when you said the capacity was 2200mAh. LiFe 18650s don't have capacity that high, example. Also those INR cells are high drain. I know the 25R is 20A continuous, you said they're 2C.
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Old Feb 06, 2016, 02:11 PM
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Samsung INR18650-22R

There are many listings for cells so described on ebay:

http://www.ebay.com.au/sch/i.html?_f...0-22R&_sacat=0

They all cannot be genuine, surely?
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Old Feb 07, 2016, 01:05 PM
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There's a lot of fakes on eBay. Personally I would recommend against using eBay to buy Li-Ion cells unless it's a known trusted seller. Counterfeits of the inexpensive Chinese brands are most common, but they've also been known to fake the big name brands as well. A dead giveaway is when they advertise much higher capacity than can be reasonably achieved with the cell size. For example a 4000mAh UltraFire 18650 is definitely a fake. To add insult to injury, they often use cells sold for recycling and slap fake labels on them. Those can include factory rejects that fail to pass safety standards.
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Old Feb 08, 2016, 11:53 PM
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How dangerous are lipo's when just sitting and not charging. I inspect my batteries before and after a charge but I wanted to know the danger of them when just sitting. Is there a chance of them just spontaneously lighting up even when sitting alone?
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Old Feb 09, 2016, 06:43 AM
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Very rare that a "sitting" lipo will ignite but there are reports of it happening so we can't say it never happens, well, some will say it never happens but that doesn't agree with some reports. I always store/charge/transport in a metal box just in case.
BTW, lipos under 40% charged are not likely to "vent with flames" even when severely abused.

Some of the reported cases:
http://www.rcgroups.com/forums/showp...52&postcount=5
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Old Feb 09, 2016, 09:12 AM
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Thank you for the info. I typically charge mine after I go out and fly so they are ready for the next day. I always charge them in direct supervision but I do leave them at full charge so I can fly the next morning.
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Old Feb 09, 2016, 11:05 AM
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I used to charge my LiPos after use, and sometimes they would go a month or two before reuse. Several of my LiPos swelled under these conditions. Lately, I've been placing all my LiPos into a storage state of 3.85V/cell after use if I'm not certain I'll be reusing the pack within a day or two. My chargers have a setting that does this automatically, either charging or discharging the pack to this condition.

I haven't had a battery swell since I've adopted this practice. It's a bit more work, as I have to charge the batteries before use, but the safey and longevity advantages are worth it, IMHO.
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