anyone tried 25-50C nanotech ?

Has anyone tried the lower rated turnigy nanotechs (the 25-50C variety) ? Do they have any measurable benefits over the regular 20C variety ? Longevity alone can justify the price differential but I doubt anyone has done cycle tests on these. Any data will be appreciated.

I need to build a large pack (~2kwh) for a e-bent intended for long range touring and kind of torn between these 25-50C nanotechs and the regular 20C lipos. (Initially I wanted to use the 20ah lifepo4 pouches from a known brand but afaik they are not available any more).

I've never bought anything but the 45-90c versions, but if they indeed do use the same nano carbon conductivity enhancement as the 45-90c versions, they should benefit from excellent cycle life and low internal resistance. I've never seen/tested one though, so I've got no idea.

This touring e-bent is intended for full day long ride with pedaling and mild assist. Hence the 2kW pack will be used on average well below 1C discharge rate so IR is not so critical. I am more interested in capacity cycle life under these conditions: large DoD (>80%) but low charge/discharge rates.

I haven't tested them, but I believe they failed the quality test to become 45C cells, so HK labelled them 25C. A little suspicious to me.
-Olaf

olaf-lampe said:

I haven't tested them, but I believe they failed the quality test to become 45C cells, so HK labelled them 25C. A little suspicious to me.
-Olaf

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Where did you hear that, Olaf? They have a higher specific energy than the 45C cells (the packs are about 10% lighter).

Seems to me like if you want more cycles going with lifepo4 would be the solution. Since you don't need high c rates, why not just go with the cheaper 20c lipo and not worry so much about lifespan if you get it so cheap.

dogman said:

Seems to me like if you want more cycles going with lifepo4 would be the solution.

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For a large 2kw pack on a touring bike the energy density is key, most lifepo4 cells are noticeably worse than lipo (probably with the exception of a well known 20ah lifepo pouch that is not available now).

dogman said:

Since you don't need high c rates, why not just go with the cheaper 20c lipo and not worry so much about lifespan if you get it so cheap.

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At 2kW size you start thinking of lifespan of your $$$ . If weight was not an issue (but it is) getting 30% more capacity in 20C cells for the same $$$ allow shallower DoD and probably better cycle life overall.

olaf-lampe said:

I haven't tested them, but I believe they failed the quality test to become 45C cells, so HK labelled them 25C. A little suspicious to me.
-Olaf

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I do not beleive this is the case. 25C nanotechs are noticeably lighter that their 45C counterparts - check the HK site for pack weights of similar configuration.

Right now I am scanning huge thread on rcgroups forums regarding nanotechs. RC requirements are different but still interesting...
http://www.rcgroups.com/forums/showthread.php?t=1264578

curious said:

dogman said:

Since you don't need high c rates, why not just go with the cheaper 20c lipo and not worry so much about lifespan if you get it so cheap.

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At 2kW size you start thinking of lifespan of your $$$ . If weight was not an issue (but it is) getting 30% more capacity in 20C cells for the same $$$ allow shallower DoD and probably better cycle life overall.

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/\This. Plus, at least for the 5Ah packs I've been looking at, the 25/50C nano-techs are about $20 more than the 20C Turnigy's (using the Hong Kong price for the 20C's), so about 50% more. But, HK claims "almost twice" the cycle life, so a longer life for your money, and still a good bit cheaper than similar discharge level LiFePO4's.

Do you really need 2kw? That would take my touring rig about 150 miles. Even out here in the west, 70 miles between plugs is the max. But my bike is the torture saddle, so 1kw or so is plenty for me. On a road trip, I kinda want to go slower and really see everything, so two 600 wh pings does me fine for a slowish 70 mile day. 2 kw and my bike would handle like crap, and be unridable so I do see why you need the absolute best energy density to carry that much.

But it's a tradeoff, life cycle vs weight and size vs cost. Best deal for you may still be a good sale on ordinary 20c zippy's. But if you have to sacrifice 20% of the capacity to achieve good lifespan, carrying less lifepo4 may work just as good and last ok even discharging 95% as lipo discharged 80%. So maybe just carry 1.7 kw of lifepo4 instead?

Pouch cells of course, such as ones HK sells, or even pings cells if the need for amps is mild. Too much weight and volume in anything canned. Even plastic canned prismatics would get too heavy.

This is a bit OT but to clarify where 2kWh is coming from. I recently got a nice full suspension recumbent (SWB-style) and want to do multi-day touring (staying/charging in motels). Recumbent seat is sufficiently comfortable to ride many hours per day without much pain. I want to be able to ride full day between charges at 16-18mph with light continuous pedaling. So the ballpark is around 250Wx8hr=2kW and I am not 100% convinced it is enough . The drivetrain is reasonably efficient - a slow 6x10 9C and Kelly KBS 72V controller with proportional (as on my x5 bike) regen. Recumbent aerodynamics is actually quite good. OTOH I am quite heavy, plus need to carry another 10-20lb of junk even for "lightweight" touring. And I am a really big fan of mountain scenery ...

I carry 1.44kwh on my chopper.. (2 - 36v 20ah LiFePo4 batts)
With a top speed of 20mph I get about 84 miles out of them and if I drop it down to 16mph, I get 110+ miles. (dual motor setup).
I weigh 180, the bike itself weighs 80, and the batteries and motors weigh another 80.
Hope that helps with your calculations.
(and yes, I've recently tested the 110+ mile range on a nice 85 degree day here in Florida about a month ago)

Well, in any case, 30-40 pounds of any kind of pouch cells ought to fit the criteria for ya. That won't be that big a package, volume wise. My long distance rig is two 15 pound pingbatteries. With dual chargers, I could take an hour or two of break for lunch and have the equvilant of 2kw carried. The lifepo4 charging makes that kind of charging a tiny bit easier than with lipo. Just plug in when you stop for food. I figured my needs not on what I needed daily, but on how far to the next plug out here in the west. 50-70 miles between towns is typical.

I have 12 (2-3s) packs of 25-50 nanotech, but more for testing purposes because of their relatively high discharge charge rates, so I can use them for quick controller motor tests with high Amps. I would consider to use something else if I need to carry it under my but for 8h a day. All Lifepo4 pouch cells are in stock now by hobbyking and they have the same weight as my Turnigy Nano-tech (if info is right). As reference my LiPo Nano-tech 4000mAh 2S weights 0.56 lbs or 254g and was sold as 323g (info from Hobbyking) and ZIPPY Flightmax 4200mAh 2S1P 30C LiFePo4 Pack is listed with 320g (is even 3g lighter and 200mAh bigger, compensating V difference).

On turnigy lifepo4 vs other options - it is more accurate to compare larger pack weights.
turnigy lifepo4 30C 6s 4500mah pack is 899g,
turnigy nano 25C lico2 5s 5000mah is 643g
turnigy lico2 20C 5s 5000mah is 666g,
zippy lico2 15C 5s 5000mah is 578g.
All have about the same total energy storage. 25C nano is quite good in terms of energy density but roughly 40% more expensive. If I can get 40% more cycles under low-C/high-DoD conditions from the nano packs they make perfect sense, but I am not sure this is the case.

How much weight are you planning to reserve for battery + BMS + Charger?

Somebody will just have to grind out some cycles to prove the claim for longer cycle life on the nano packs in real world use.

May as well be you eh? Somebodys got to do it. Still got years to go on my part, proving a ping can go 1000 cycles.

Hi,

curious said:

On turnigy lifepo4 vs other options - it is more accurate to compare larger pack weights.
turnigy lifepo4 30C 6s 4500mah pack is 899g

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I'm pretty sure someone tested these (search the forum) and the quality wasn't very good (putting it politely).

curious said:

All have about the same total energy storage. 25C nano is quite good in terms of energy density but roughly 40% more expensive. If I can get 40% more cycles under low-C/high-DoD conditions from the nano packs they make perfect sense, but I am not sure this is the case.

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Since you would need more than 40% more cycles to come out ahead maybe buying the 20c makes sense. If you treat them well by the time they need to be replaced prices will probably have decreased (maybe Dr. Bass will be selling used cells from Volts or Leafs ).

EDIT ADDITION:
Should which cells are available in the U.S. warehouse be a factor (cheaper shipping)?

BTW you know if you sit on a HC product page for a while (the first time so you might need to delete cookies or change browsers) you usually (always?) get an offer for a substantial discount?

MitchJi said:

BTW you know if you sit on a HC product page for a while (the first time so you might need to delete cookies or change browsers) you usually (always?) get an offer for a substantial discount?

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Usually. I tried that with a charger I was looking at and it kept giving me a link to help pages instead.

I've been considering the nanotechs for a build in the new year. The high current handling is my primary interest, secondary how safe they are. I plan to box and direct any explosive forces for jet propulsion. liveforphysics did a great job demonstrating the 45-90C current handling but I haven't seen him blow any nanotechs up yet. :wink:

I've found two incidents with them thus far. One 4000 mAh 25-50C deliberate puncture test. With the outer peeled back, the cell membrane is then punctured with a metal knife. Pack smolders with hot embers at the puncture, smokes and burns itself out. It didn't smoke for as long as my brother's rally car rear brakes after his brake test this afternoon. :lol:

[youtube]EUmfpTxUjNg[/youtube]

Another 5000 mAh 45-90C where the pack was used in an RC car that hit a fence (no hard case was used!) where the battery popped out of the car and smoldered itself to pieces.




I'm sold on their current handling and ability to smoke, which are really the same feature.

I haven't seen any cycle tests to speak of their longevity. Ampeater in another thread said he was buying some for cycle testing. You could ask him if he did the tests.

HK customer support honestly answered that they do not have information to predict if nanos have longer cycle life under low-C regime. Did not find anything conclusive elsewhere. I guess I have to look inside my wallet and flip a coin

I'm really interested in this particular topic,and appreciate the experience and info from people on this site.
My battery pack will need replacement in a few months,so I've been searching for data and info various battery options,I was leaning towards Ni-Cd packs because of simplicity,price,etc.,but 8ah packs are just too small(So yes,I've abandoned this option for now),so that leaves me trying to decide on either LiFePO4 or the high rate Li-Poly packs... So now I'm trying to find out lots of info and data on both so I can decide on one.
There is lots of knowledge and valuable experience on the LiFePO4 cells here,but not so much on the Li-Poly cells. From what I've learned so far is that the high-rate(25C-50C)Li-Po's have a very high C rate,and are lighter but more expensive,but their life cycles is still relatively unknown yet. On the other hand the LiFePO4's have a longer track record,are less expensive,less fire risk,and still a good C output rating.
Am I correct so far?
So this leaves for me the questions about the reliability and how many life cycles of the Li-Po's? :?
I've seen a few prices for a 72v-12 ah LiFePO4 10-20C battery packs,but I don't know the price of the same Li-Poly packs yet.
And so the age-old question... Which one is the better choice??
These are both quite expensive packs for a guy like me living on a small injury pension so I've got to make the best choice.
Thanks folks for your help and opinions!