My Turnigy Nano-tech 1 year experience

[BatteryKing]

I picked up four 6S 4000mAH 35C Nano-Techs for my Trex-500 a little over a year ago. (Yes they fit under the hood with dropped frames and with my metal heavy ESP kit the heli is perfectly balanced.)

Fresh I was getting a 0.3V drop on lift off (2250 RPM governed head speed for normal mode and up to 2650 RPM for Idle Up 2 on a Scorpion 3026 1400KV motor and 16 tooth pinion) and a 0.6V drop total when pushing up to 139.4A (3,200W) according to my CC ICE 100 logs. I respected the 80% rule and would generally charge right before flight, but never let the packs sit for more than 12 hours with a full charge. For the first few months the packs felt plenty strong, no noticeable sign of a drop off in output. After 5 months I took a measurement and the logs looked about the same.

I became very busy for about 6 months and left the batteries in storage mode (50% charge). While the batteries held this 50% charge level, when I finally took my Trex-500 up again I noticed the batteries felt softer. I cleared out the CC ICE logs and took fresh readings. What I came up with is a 0.5V drop on lift off and 2.6V drop at 99.6A (2,200W). I couldn't get above 100A even on fast, hard maneuvers.

Historically on fast, hard maneuvers I would hear a loud bang and the heli would instantly be going in a different direction as far as I could perceive, but now the blades bark loudly and I can see the transition. Nearly 100A is still lots of power for a Trex-500, but I get the sense there is not much time left on these packs.

[andersn]

got any idea on number of cycles?

I read a research paper, which indicated storage at room temp even at storage charge, would severly reduce capacity, storing at 2-3c was ideal ( fridge)

[BatteryKing]

I have around 50 flights per pack.

[The WoodCrafter]

Have you even done any Internal Resistance measurements on the packs?
It would be interesting to compair now to when they were new.

[BatteryKing]

Well while I haven't done a direct and exacting internal resistance (IR) check, you can get a general ball park idea of what it is. If you use the formula V = Ir and solve for r you have r = V/I so for r0 you have 0.6V/140A = 0.004 Ohm. For r1 you have r1 = 2.6V/100A = 0.026 Ohm. In other words the measured increase in internal resistance is 6.5x. If this trend continues, these packs will quickly become unusable.

[satgod]

Originally Posted by BatteryKing

Well while I haven't done a direct and exacting internal resistance (IR) check, you can get a general ball park idea of what it is. If you use the formula V = Ir and solve for r you have r = V/I so for r0 you have 0.6V/140A = 0.004 Ohm. For r1 you have r1 = 2.6V/100A = 0.026 Ohm. In other words the measured increase in internal resistance is 6.5x. If this trend continues, these packs will quickly become unusable.

I believe cycling at least once a month is best
you can try 4 or 5 good cyclings on them and do a 1.5-2c charge only

see what happens

thats how lipos are and i have friends that say after about a year of hard flight their nano-techs are about done
havent used them so I dont know for sure

[BatteryKing]

Well I figure opinions are are *** holes, but what really would make for a good next set of packs as I don't see the current nano-techs I have as suddenly being resurrected by any of the procedures being listed?

I know there are the super expensive Thunder Power packs and these are supposedly made in the US, which is a bonus, but for good Trex-500 packs it is still like $170 per pack. So far people I have talked to at the field have claimed anywhere from 150 flights on their TP packs before polishing them off to 1,000+ cycles and still going strong and they all have a story about screwing up a pack and it being totally their fault and TP replacing it hassle free. Plus these packs seem to have really low internal resistance and I see people at the field banging away their Trex-700s with TP packs and Neu-motors and no matter what they do (and they do some pretty crazy stuff) there is no audible change in head speed whatsoever. So I know I would be getting something pretty good, but plucking down ~$700 for a basic 4 pack setup I could field charge for more flights while also having some space for previous packs to cool is a bit steep.

One of my friends who does pop and lock on his Trex-700 basically every day is saying his SKY lipos are really good. If I remember correctly he bought his SKY lipos around the same time I bought my nano-techs, so he has had them for about a year or so. Except where I have like 50 flights per pack, he must have hundreds per pack by now. He sent me his current CC ICE logs and it looks like the packs are still kicking strong with at least one pack looking like it is still putting out the 40C rate claimed and the other packs reasonably close. It looks like he is averaging around 80A with spikes up to 180A on every flight, so these packs are definitely getting some abuse. For my Trex-500 setup this would be like $50 per pack, which is a lot less than the TP. Maybe not a top notch pack like the TP, but hey $50 vs. $170 and it will still be delivering what I need for a while to come granted I have the same experience with them as my friend has sounds very tempting.

I have heard some people talking about Blue Lipos, but the only guy at the field I know with them just likes to take it easy when he flies and for example I sold him a couple of Zippy packs that where disappointing to me because I wasn't getting anywhere near the advertised C rate out of them, but he says they feel fine to him, so I don't get the sense I will get any real stress test data out of him.

As this is not very many data points to make an informed decision and the new data points I have on the nano-techs leaving me with the desire for something better, what can you as a reader of this say on good battery bets? And please if you can talk about longevity experiences with packs as I thought I would be trashing packs a lot more in crashes while getting into this hobby, however am finding the combination of pucker factor, simulator, and putting the mCPX in time and time again until I figure out how to do the riskier stuff first is keeping me from doing all that many crashes on my bigger ships and at that the batteries tend to survive harsher crashes than I thought they would, so longevity is important to me now. (By the way my nano-techs that haven't been involved in any crashes are still going soft, so they are not going soft from the crash factor.)

[andersn]

I had some nano-techs that had been stored quite long, kinda felt same as you, but after maybe 5 cycles or so, IR started going down, and now they are quite happy again, maybe someone can explain the phenomenon. IR is down from high cell 7, to 4.9 and avg 4 on a 6s 2650 35-70c.