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Old Feb 24, 2011, 10:00 PM
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Cody f86saber's Avatar
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Turnigy Nano-Tech 3S 850mAh

I have a couple new samples of Turnigy Nano-Tech batteries as I've been curious of how good some are. These are 11.1V 3S 850mAh, rated for 25C continuous, 45C burst and a 5C charge rate.

They are quite small and light-weight for the marked capacity compared to others. I soft-cycle packs 14 times when I first get them to help detect any defects and neither appear to be defective from what I can tell, all cells balance evenly. Over the course of the cycles the voltage drop and IR decreased a little, allowing a slightly higher available capacity to be discharged. However, the voltage drop was still very fast for the low cycle rate. At low discharge rates of 1-2A the voltage drop differences should be very small and the greatest percentage of the packs' capacity should be obtainable while offering a strong voltage, that perhaps appeared to be a problem.

Code:
 At 1.0A discharge with an end cutoff of 3.7V/cell the pack could supply 522 - 534mAh.
At 2.0A discharge with an end cutoff of 3.7V/cell the pack could supply 431 - 435mAh.
That's a big difference for such a small discharge rate difference.
Code:
 At 1.0A discharge with an end cutoff of 3.65V/cell the pack could supply 650 mAh. 
At 2.0A discharge with an end cutoff of 3.65V/cell the pack could supply 522 - 567mAh.
Again, a large difference.
The 2.0A 3.65V/cell discharge is shown below for this Turnigy Nano-Tech 11.1V 850mAh 25-45C pack:
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Old Feb 24, 2011, 10:19 PM
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boingk's Avatar
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Wait, you're only discharging to 3.7 volts? That might explain your results. The graphs don't even show a pronounced drop in voltage at the point where you cut the test, indicating that you haven't even come close to the cells capacity. Check this thread and associated graphs for a proper discharge curve:

http://www.rcgroups.com/forums/showthread.php?t=1244249

I'd try discharging to 3.2~3.3 volts and see what you get. I'd bet that you'll either hit very close to the 850 rated capacity, or possibly exceed it by perhaps 1%. Remember, you won't do anything to your lipo cells unless you take them below 3v per cell under load, so 3.2~3.3v should be quite safe.

Cheers - boingk
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Old Feb 24, 2011, 10:24 PM
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Discharging to 3.65V, but the voltage drop is quite fast for such a low discharge rate of 2.0A. we don't expect an unrealistic 100%, though I would expect 80% that I can get from others. I have a few other 850mAh packs, one 20C pack has 70 cycles on it and it just outperformed this pack by a far margin.
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Old Feb 24, 2011, 10:39 PM
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Actually, my experience is damage is done if one discharges a pack too far below 80% of the total capacity.

The tests in your link are at 50C rates, mine was at 2.3C. That's a considerable difference and cross comparison without normalization taking into context this loading difference could be misleading. At first we look at the voltage curve and it looks good for a pack under load. We look at the capacity discharged and it also looks good from what we've seen. Then we see the actual low discharge rates and realize it's performing like an old gen pack. The nano-tech tests I've just shared are being outperformed by a lower rated equivalent capacity pack, which is of interest as the nanos are marketed as high performers. So far the IR is 18-20 mOhms per cell which is also high for a high performance pack.

I'm loading my 3.3V/cell test now.
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Old Feb 24, 2011, 11:22 PM
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Quote:
So far the IR is 18-20 mOhms per cell which is also high for a high performance pack.
Hmmm... that is interesting.

Quote:
I'm loading my 3.3V/cell test now.
No worries, be good to see the results.

Anyway, I only use budget gear as I'm not really a serious enthusiast (yet). For the guys that want the absolute best then yeah, sure $20, $30, $50 a pack is nothing. For me my budget is about $15 a pack for 3S and $7 a pack for 2S... including postage. So far so good, but obviously these packs aren't superstar performers.

Cheers - boingk
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Old Feb 25, 2011, 12:04 AM
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The bright side is they are only $10.
Discharged at 2.3C (2.0A) to 3.3V/cell cutoff, 751mAh, Vt reached the corner point.
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Old Feb 25, 2011, 12:44 AM
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Ah, thats more like it! I'm betting that if you pushed to the standard ESC-programmed 3 volt cutoff point it'd give 850mAh, too. Not that I'd recommend doing that every time.

Either way, not bad for the money... and if you realise that 750mAh is 87.5% of the total claimed 850mAh capacity, that ain't bad for 3.3 volts finishing voltage! Especially for 10 bucks.

Cheers - boingk
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Old Feb 25, 2011, 12:59 AM
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Meh, it's not nothing when we consider it's doing this at only 2.3C, ie 2A.
A Thunder Power TP850 45-90C can do this at 30A. But it costs more.

The standard 3V/cell cutoff will give the full capacity, but that's useless since we can't safely deplete it all and the purpose of a 25C-45C pack isn't to be used at 1C, or 2C or 3C. A 25C-45C pack should be capable of operating at 25C (in this case it would have been 21.25A) whilst providing 80% of it's capacity before each cell drops to 3V at this rated C loading. It's a high standard but some can do it. The Nano battery is going to have problems with voltage drop at 15A to 21.25A usage (test results later), while other 25C performance batteries don't. Some are very good today at upholding their voltage, to an extent that necessitates timing our useage; the LVC on an ESC is rendered useless since the voltage doesn't drop even under a heavy load until the high quality packs are almost completely discharged, and because of it they offer great power. This all doesn't mean that the Nano-Tech is a bad battery, it's just not a breakthrough in energy storage design that I can tell. It's unfortunate that it's IR and Vd are as high as they are.

We only have roughly 80% of the cell's total energy capacity to work with. We want access to this energy to attain reasonable run times and Power to do work. If a pack can provide a constant quality voltage magnitude for a majority duration while under it's rated C loading, that is excellent. If it can only provide this voltage for a majority duration at a low current it may be a poor choice for the chosen application.
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Old Feb 25, 2011, 08:16 AM
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[QUOTE=Cody f86saber;17512484]Meh, it's not nothing when we consider it's doing this at only 2.3C, ie 2A.
A Thunder Power TP850 45-90C can do this at 30A. But it costs more.

QUOTE]

yes, but you're one is 45-90c the other is 25-45c???
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Old Feb 25, 2011, 09:50 AM
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The other pack I noted for comparison is a 20C rated 850mAH J-Power/Banana Hobby pack and outperformed the higher rated Nano. The TP850 is 45C-90C, for comparative illustration only. I just did two flight tests at the field and the 25C-45C Nano is struggling at 12.9C-15.3C (11-13A) with enough voltage sag that it just isn't performing quite as well as what would be expected from a 25C battery. The test is by no means conclusive, nor is it intended to be. It simply illustrates my experience. I'll have some more tests up later at high rates.
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Old Feb 25, 2011, 10:57 AM
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Cody,

Curious but have you tried a 25C (or 20C to be nice) discharge to see what that looks like?

Berardino
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Old Feb 25, 2011, 11:03 AM
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Joined Feb 2007
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Turnigy Nano-Tech 3S 850mAh

In the old NIcad days the industry standard measure of capacity was to discharge it down to 0.9V/cell at exactly 1C and I assume lipos are the same. I measured some Loong Max packs, looking for mismatch between cells last year, and was rather surprised at the accuracy of the capacities.
I discharged at exactly 1C down to 3.0V/cell and all the packs I measured (all 3S 2250 packs) showed results within 1% of their claimed capacity and the maximum capacity mismatch between cells in a single pack was 0.7%.
Presumably the close tolerance within a pack is because a discharge below an average of 3V/cell would be disastrous for the lowest capacity cell.

Wayne
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Old Feb 25, 2011, 11:11 AM
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Yup. I'm doing a few, I've got to buy a 0.5 Ohm dummy load so I can also present 25C.
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Old Feb 25, 2011, 12:41 PM
Patrick Jenkins
USA, LA, 5
Joined Dec 2006
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remember, the factory specs for the vendor start at 2.75V per cell. So 3V is the saftey margin set up by the industry. I too have these 850mAh nano packs and have wondered if their capacity was accurate. I seem to get the same punch outs compared to using 1000mah packs but that may be because they are lighter.
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Old Feb 25, 2011, 01:37 PM
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Hughes500Bob's Avatar
Southeast PA
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Depeleting a lipo below 80% capacity will greatly shorten it's life and servicability.

http://www.rcgroups.com/forums/showp...1&postcount=11

http://www.tjinguytech.com/charging-how-tos > 80% rule

IMO if you keep trying to pull 100% of the rated capacity out of your packs they will be ruined in short order.

Bob
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