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Thunder Power RC ProModeler
Four Stroker

Elite Veteran

Atlanta

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If you discharge a cell at 30C down to some terminal voltage repeatedly, how many cycles does it take to destroy it ? If less than 100 I would not call it a 30C cell.

08-16-2016 04:55 PM
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Richardmid1

rrProfessor

Leeds, England

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I need a pack that I can beat on, get performance out of and still use it again tomorrow and the next day. Turnigy is not that pack, nor will it ever be.
Well they are for me and a lot of other people too!

Busher, I've always used the Turnigy 20-30C packs. Stick a cell checker on the balance lead when you get them and if they are out by more than 0.1v put them on a 0.5C charge (accurate charge if you use a cellpro charger) and observe how long they take to fully balance, it should only take about 5 minutes. If it's taking longer check the IR of the cells, they should be fairly close. If the cell IR's are far out and the pack still isn't balancing stop the charge and email them. Do all this before messing with the connectors, just use small crocodile clips to do the charging. Out of the maybe 40 Turnigy lipos I've had over the last 8-9 years I've had to do this twice!

60% of the time, it works every time!

08-16-2016 05:23 PM
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LaDon

Veteran

Fort Dodge .Ia

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I have read the different testing for c ratings. Personally some seem pretty bogus. But there really is not a complete standard. I am not an EE. Never will be either. From what I understand it isn't like there is a horsepower dyno where it should be the same. Even there you can drum up some free horsepower with weather parameters.

Thing is by one of the tests that are done the TP packs prolly will show 70c. Others 50c. Now if you ask me that particular test which had something about drawing it down real slow x time before dead / q r squared or whatever come up with a c rating was a little fishy. This also did not come from a lipo manufactuer.

Myself I think it should be measured with equipment to determine the actual discharge rate with equipment. Formulas might be close but not perfect. Not all formulas work in all areas

Bottom line is use what works for you and your application. As stated above we have never had a turnigy last much more that 20 to 30 cycles in our helis or edf jets. Those are really hard on batteries too. But with the same setup but different packs we can get 250 to 300 cycles out of them. That adds up to be cheaper in the end.

Also I have seen 2 of our helis light up one of a friends and another friends light his up and every one of them were from the turnigy packs. One friend won't even let his sit for an hour charged without putting it back in storage. He is anal about his batteries. Just remember the real proof isn't what any of us say it is up to you to keep track and see what works best for you. Not what works for me or Richard or anyone else for that matter because we don't know what you want to get out of your flying.

Team Jr

08-16-2016 06:50 PM
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AirWolfRC

rrProfessor

42½ N, 83½ W

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Manufacturers can claim some fanciful numbers if they don/t have to be complete. If you include the internal resistance of the pack, then you can quantify a pack.

Let's say you pull 20C. The question is what is the voltage droop while pulling that 20C ? Clearly you can get a very high C rating if you just short out the battery.

I don't know of any manufacturer that tells you what the output voltage is under the advertised C rating.

08-16-2016 08:01 PM
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Richardmid1

rrProfessor

Leeds, England

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I believe it is until the cell voltage drops to 3v.

60% of the time, it works every time!

08-16-2016 08:07 PM
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ICUR1-2

Key Veteran

Ottawa, Ontario

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Reading through these posts it looks like those who fly hard all the time need quality packs, understandable
I would not call Turnigy lipo's junk they do well for the type of flying I do. I just bought another set of 3 for less than 200$ cdn.

I have a set of 3 nano techs 6s3000 25C-50C I am about to retire they are 3 years old and only have slight puffiness to them.

Maybe some need $$$ quality batteries but I know many don't

spending time, paying attention

08-16-2016 09:36 PM
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Richardmid1

rrProfessor

Leeds, England

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http://rc.runryder.com/helicopter/t801457p1/

This guy needs quality packs for sure! It's those people who try Turnigy packs and wonder why they don't last! Actually he still gets 4 minutes which is fine for the 20C Turnigys but if he went from mild 3d to hard 3d with the same setup NO lipo would last long!

60% of the time, it works every time!

08-16-2016 10:05 PM
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ICUR1-2

Key Veteran

Ottawa, Ontario

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I know the same heli with 2 different pilots will get different flight results.
It's depends how hard you fly

spending time, paying attention

08-16-2016 10:28 PM
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Richardmid1

rrProfessor

Leeds, England

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Still waiting for evidence of any lipo capable of more than 30C continuous!

$100 Paypal for proof!

Must deliver at least 80% capacity and stay above 3v/cell and below 60 degrees C.

FWIW C ratings do matter when it comes to battery life and performance, all im saying is you don't know what your getting despite what it says on the label.

60% of the time, it works every time!

09-01-2016 12:24 PM
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LaDon

Veteran

Fort Dodge .Ia

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Good god Richard get off of it. None of us have the actual test equipment to prove it the right way prolly including you. Your charger is not a correct basis either. You would need the setup like that guy has in the video and unless someone just wants to go out and blow money just to prove a point it is meaningless.

I don't think anyone has actually argued that the c ratings really make it

Team Jr

09-01-2016 01:01 PM
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Richardmid1

rrProfessor

Leeds, England

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. I don't think anyone has actually argued that the c ratings really make it
Erm apart from you!

60% of the time, it works every time!

09-01-2016 01:11 PM
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LaDon

Veteran

Fort Dodge .Ia

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That's the problem Richard and you just don't get it. Ppl don't have the right equipment. Get off of it please. It amazes me you wonder why nobody posts after you. It is because you just won't drop it. And yet you have zero proof in your claim either. I could have just made up some IR numbers that will make 50c and said here you go and you couldn't prove me wrong. That is why this topic is so stupid. If you want the proof one way or another have that guy in the video you posted make one. It either will make it or not. That would be the best way but to sit on here and stir the pot and ask opinions means nothing. Because they are just opinions until someone proves it on actuall test equipment. Period.

And show me where I said they make it. If you would read my post above I read a test that shows a way they do. But under that I said it seemed a little fishy on the test

Pay attention

Team Jr

09-01-2016 01:18 PM
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LaDon

Veteran

Fort Dodge .Ia

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All I have ever said is that the higher rated batteries do come down cooler. That is an easy fact to prove

Team Jr

09-01-2016 01:23 PM
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Richardmid1

rrProfessor

Leeds, England

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Get off of it please. It amazes me you wonder why nobody posts after you. It is because you just won't drop it.
No! This is my topic! I won't drop it till people like you stop posting false or incomplete info! I'm trying to help people out here, save them some money and try stop the battery manufacturers taking us for a ride. If everyone knew the truth battery prices would start to come down!
I could have just made up some IR numbers that will make 50c and said here you go and you couldn't prove me wrong.
A simple photo of the charger display and battery being charged is all it would take.
And show me where I said they make it.
Well from watching that video and stuff if I understood it correct he said that the opti power battery made the c rating. He also had 50c batteries there which we didn't see tested I don't think but if opti power don't put on a c rating that ain't correct them by his method it must have made it.

60% of the time, it works every time!

09-01-2016 01:55 PM
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AirWolfRC

rrProfessor

42½ N, 83½ W

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What's the big problem ? ?
You spend about $100 on a data logger and put on a dummy load (big resistor) on the battery and run it.

Then you only have to buy a few batteries.

09-01-2016 03:25 PM
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Richardmid1

rrProfessor

Leeds, England

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What's the big problem ? ?
None now he's on ignore!
You spend about $100 on a data logger and put on a dummy load (big resistor) on the battery and run it.
Then you only have to buy a few batteries.
Exactly yet there is no evidence of it on the internet, I can't find any anyway!

60% of the time, it works every time!

09-01-2016 03:30 PM
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AirWolfRC

rrProfessor

42½ N, 83½ W

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I wasn't suggesting you "find" it,
I was suggesting you "make" it.

09-01-2016 07:09 PM
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Richardmid1

rrProfessor

Leeds, England

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I've actually had a go using my ebike I cobbled together which has watt meter on it and a cycling turbo trainer but it has no resistance adjustment and tops out around 50A on 6s. I did actually test a 1600mah 30C pack I have and it did make the 30C although it got so hot I couldn't hold it in my hand! I don't have any higher C rated packs to test at the moment but I might get a small one to test.

60% of the time, it works every time!

09-01-2016 07:16 PM
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Richardmid1

rrProfessor

Leeds, England

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OK this is hard to do but some might appreciate my honesty and ultimately it gives us more info which is great. Here goes and flame suit on...

I bought a Turnigy multistar 6s 800mah 60C pack to test. I inputted the highest single cell resistance into the C rating calculator which was around 7 mohms which put the pack around the 30C mark according to the calculator. I tested the pack on my ebike contraption which has a watt meter. I thought I would go easy on the pack and initially try a 40C discharge (32A). It held up very well and held around 21v! I stopped the test after the pack had given around 440mah as it was doing so well and I didn't want to hurt the pack before trying a higher C discharge. The pack was only warm, I didn't have a temp gauge but if I had to guess ide say around 30 degrees C. I will be testing the pack again tomorrow at the full 60C (48A).

Looks like I owe myself $100! (embarrassed face!)

More to the point, it proves the C rating calculator is rather inaccurate! Oops!

60% of the time, it works every time!

09-05-2016 05:56 PM
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AirWolfRC

rrProfessor

42½ N, 83½ W

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What "C rating calculator" are you talking about ?

The only limitation on "C" rating for a cell would be the max operating temperature of the pack. If you can come up with a thermal resistance of the pack (ºC/W) and the max internal operating temperature, (just like power dissipation of electronic components) you can calculate that.

Another way is if you know the internal resistance of the pack. Then figure the heat generated within the pack. Once you know that and the thermal mass of the pack, you can calculate the short term power you can pull from the pack and for how long before it gets too hot.

Knowing the thermal resistance of the pack in the installed environment and the power generated within due to the internal resistance, you can calculate an effective "C" rating.

To get the internal resistance, you can believe the manufacturer, if they publish that info, or test for it yourself. Setup a test where you load up the pack at, let's say "1C", and measure the voltage. Change the load to , let's say "1.5C", and measure the voltage drop. Flip back and forth to verify the readings. Do a little algebra and solve for the internal resistance.

Just as an empirical observation, generating 10 watts inside a cell in an enclosed environment (as part of a pack), will make the pack quite toasty after only a few minutes. For a 3A, 3.8V cell pushing 20C, an internal resistance of 2.8mohm will produce 10 watts inside the cell.

10W / 60A = 0.1666V drop within the cell
0.1666V / 60A = 0.002777 ohms

09-05-2016 09:27 PM
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