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Old Aug 18, 2012, 11:15 PM
mondo1948
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Rocky Hill, Connecticut
Joined Dec 2007
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Quote:
Originally Posted by REVOJohn View Post
Hi there3 bigroger.
I thought I sent you a reply but we don;;t have a 4000mhr cell. Only 3700 and 4000. Take a look at the specs of the 4S pack on our site and see is she's light enough for you.
He's asking for a 4000mah battery and you tell him you only have 3700 and 4000. If you don't have 4000mah, then how can you have 3700 and 4000?

I think you should take a look at what you write before you publish it. I think you meant to say you have 3700 and 4400.

Mondo
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Old Aug 19, 2012, 12:38 AM
can't buy vaporware
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United States, MN, Minneapolis
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John,

Are the balancing wires solid or stranded?

Thanks.
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Old Aug 19, 2012, 12:39 AM
can't buy vaporware
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United States, MN, Minneapolis
Joined Nov 2011
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Quote:
Originally Posted by mondo1948 View Post
I think you should take a look at what you write before you publish it. I think you meant to say you have 3700 and 4400.

Mondo
My posts turn out like that too when I use the iPad. That thing is always messing up what I write.
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Old Aug 19, 2012, 01:20 AM
ancora imparo
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Melbourne, Australia
Joined Jul 2005
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Thanks John. Appreciate the nice example. The interdependency of current, cell voltage, discharge time and cell life seems to be an equation that can be bent by some of the the marketing guys at will. All credit for not doing it.

You could probably call it 200C if you snuck in an extra cell to keep the pack voltage above minimum for the short time required.


JJ

QUOTE=REVOJohn;22486062]Hi there JJ. Glad you are enjoying the LiPOs
As for IR and C rate this is a very interesting question. I'd say there is a direct correlation BUT you probbly could not put a formule too it as there are other parameters at play here.
eg expected cycle life, cell weight, max permissible temperature.
Give you an example. We've built missile battery systems for a country that'll remain disclosed. They requirement was a 7S 15Ahr battery pack with 1500A take off current (and a hugh G force too). Now thats over 100C and we managed to pull it off. But can I claim the bats are 100C. No. I'd say the 1500A could have been repeated mayb 5 - 20 times before that pack died but for this application it was fine. Charge Once......launch once and no return.

So in applying C rate, Capacity, Weight $ in comparisons IR is important but cycle life expectancy is also a factor. Lower the IR and C rate increased as with cycle life too[/QUOTE]
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Old Aug 19, 2012, 08:07 AM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
34,834 Posts
Quote:
Originally Posted by REVOJohn View Post
Yah i dont think he meant solid Cu wires. That'd be cupper rods heheheee. I think he was referring to stiffer PVC wires.
I do not know about in your country but here in the USA there are many gauges of copper wire that are single strand (solid) that are indeed wires not rods. The term copper rod would be used for large diameters such as 1/2" or larger such as used for grounding rods.


It seems that my post stating that no ones uses solid wire for balancing leads is either being over looked , ignored or dismissed by some.

To clear the issue up as to your LiPoly's balancing leads why not just post the wire gage,starnd count and type of insulation used ?

Charles
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Old Aug 19, 2012, 09:20 AM
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Singapore, Singapore
Joined Apr 2012
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Quote:
Originally Posted by N6145k View Post
John,

Are the balancing wires solid or stranded?

Thanks.
definitely standard but no silicone coverer.....high temp PVC
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Old Aug 19, 2012, 09:23 AM
REVOJohn's Avatar
Singapore, Singapore
Joined Apr 2012
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Quote:
Originally Posted by jj604 View Post
Thanks John. Appreciate the nice example. The interdependency of current, cell voltage, discharge time and cell life seems to be an equation that can be bent by some of the the marketing guys at will. All credit for not doing it.

You could probably call it 200C if you snuck in an extra cell to keep the pack voltage above minimum for the short time required.


JJ

QUOTE=REVOJohn;22486062]Hi there JJ. Glad you are enjoying the LiPOs
As for IR and C rate this is a very interesting question. I'd say there is a direct correlation BUT you probbly could not put a formule too it as there are other parameters at play here.
eg expected cycle life, cell weight, max permissible temperature.
Give you an example. We've built missile battery systems for a country that'll remain disclosed. They requirement was a 7S 15Ahr battery pack with 1500A take off current (and a hugh G force too). Now thats over 100C and we managed to pull it off. But can I claim the bats are 100C. No. I'd say the 1500A could have been repeated mayb 5 - 20 times before that pack died but for this application it was fine. Charge Once......launch once and no return.

So in applying C rate, Capacity, Weight $ in comparisons IR is important but cycle life expectancy is also a factor. Lower the IR and C rate increased as with cycle life too
[/QUOTE]


>>>>Fully agree. I know and have been in most of the factories in China. Actually they are very honest and they sell what they can make. But...its the next entry level to market that either overstates a battery or sells factory seconds.So typically you get what you pay for to most extents.
I can read most brands specification and know who is supplying them and if they are true to specification.
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Old Aug 20, 2012, 03:14 PM
Registered User
Chicago, USA and Manila, Philippines
Joined May 2007
153 Posts
so to conclude everything at 68deg F tested IR for typical RC hobby users which we are hoping of 100 cycles or more to last assuming we do not abused them are the ff:

Revo 4s/2200mah/60c IR avg. 4.3 = 25C rating
GenAce 4s/2200mah/25c IR avg. 8.5 = 18C ( 20 to 40 cycles)

http://www.jj604.com/LiPoTool/

Quote:
Originally Posted by N6145k View Post
Just did some testing with the 3010b charger and the balance board that came with it. For the Revolectrix 60C batteries, the average resistance is 4.3 mOhm per cell. For comparison, I have 7 gens ace 25 c batteries with 20-40 flights on each. The average resistance is 8.5 mOhms per cell.


The Revolectrix batteries have not been flown yet. They were parallel charged/discharged 3 times on the 3010b.

For these measurements, the temperature was 68 degrees, and the packs were either individuall (trial 2) or parallel (trial 1) storage charge.

Last time I was using a paraboard, to take IR, which I think made the measurements less reliable due to an LED on it.

See attached for raw and quickly formated data and simple analysis.

It looks like I have a couple of very good gens ace batteries (1.b and 1.c).

I haven't done this before so I am unsure how these revolectrix cells will measure up after they get a few flights on them.
Quote:
Originally Posted by REVOJohn View Post
Hi there JJ. Glad you are enjoying the LiPOs
As for IR and C rate this is a very interesting question. I'd say there is a direct correlation BUT you probbly could not put a formule too it as there are other parameters at play here.
eg expected cycle life, cell weight, max permissible temperature.
Give you an example. We've built missile battery systems for a country that'll remain disclosed. They requirement was a 7S 15Ahr battery pack with 1500A take off current (and a hugh G force too). Now thats over 100C and we managed to pull it off. But can I claim the bats are 100C. No. I'd say the 1500A could have been repeated mayb 5 - 20 times before that pack died but for this application it was fine. Charge Once......launch once and no return.

So in applying C rate, Capacity, Weight $ in comparisons IR is important but cycle life expectancy is also a factor. Lower the IR and C rate increased as with cycle life too
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Old Aug 20, 2012, 05:26 PM
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That was my point previously.

Based on my iCharger tests and the C rating spreadsheet I would expect the revo's to measure in below 1mOhm per cell and the gens, sinced they have been cycled maybe 2-3mOhm per cell.

I've got gens, 25C 1550mA packs that have over 100 cycles each and way over their discharge specs (>40A) that still measure 5-7mOhm per cell and gens 30C 2200 packs that measure 2-3 mOhm per cell.
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Old Aug 20, 2012, 05:36 PM
can't buy vaporware
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United States, MN, Minneapolis
Joined Nov 2011
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Quote:
Originally Posted by bigroger View Post
I've got gens, 25C 1550mA packs that have over 100 cycles each and way over their discharge specs (>40A) that still measure 5-7mOhm per cell.
The 3010b has one significant digit. My gens ace 25c 2200mah 4s, of which two are still showing good specs., show 4-5 mOhm. And I have only drained one of my batteries to LVC once, and charge at 1 to 2C.

I'm inclined to think that 1. the 3010b is not lab equipment. and 2. gens ace 25c batteries vary from lot to lot. (I bought my gens ace 25c over 2 or 3 different purchases).
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Old Aug 20, 2012, 05:43 PM
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Chicago, USA and Manila, Philippines
Joined May 2007
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yes you are correct but no one has the guts to say point blank that 60 to 65c is just a marketing hype and it doesn't exist today for Rc Hobby.

Just to give Revo a benefit of the doubts, can we re test the IR at ambient temp of 72F and repost the results please..


Quote:
Originally Posted by bigroger View Post
That was my point previously.

Based on my iCharger tests and the C rating spreadsheet I would expect the revo's to measure in below 1mOhm per cell and the gens, sinced they have been cycled maybe 2-3mOhm per cell.

I've got gens, 25C 1550mA packs that have over 100 cycles each and way over their discharge specs (>40A) that still measure 5-7mOhm per cell and gens 30C 2200 packs that measure 2-3 mOhm per cell.
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Old Aug 20, 2012, 05:54 PM
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the 3010B might not be a lab equipment but its very good enough to measure an IR of a lipos...

http://www.rcgroups.com/forums/showthread.php?t=1578001

http://www.rcgroups.com/forums/showthread.php?t=1577989

http://www.rcgroups.com/forums/showthread.php?t=1323465

Quote:
Originally Posted by N6145k View Post
The 3010b has one significant digit. My gens ace 25c 2200mah 4s, of which two are still showing good specs., show 4-5 mOhm. And I have only drained one of my batteries to LVC once, and charge at 1 to 2C.

I'm inclined to think that 1. the 3010b is not lab equipment. and 2. gens ace 25c batteries vary from lot to lot. (I bought my gens ace 25c over 2 or 3 different purchases).
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Old Aug 20, 2012, 05:58 PM
can't buy vaporware
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Originally Posted by yurstruly View Post
With one significant digit?

Or am I doing something wrong?
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Old Aug 20, 2012, 06:09 PM
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Singapore, Singapore
Joined Apr 2012
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Quote:
Originally Posted by yurstruly View Post
yes you are correct but no one has the guts to say point blank that 60 to 65c is just a marketing hype and it doesn't exist today for Rc Hobby.

Just to give Revo a benefit of the doubts, can we re test the IR at ambient temp of 72F and repost the results please..
totally disagree with this statement that its all marketing hype. I fyou think thats the case get a cell and put them on a westmountain and see for yourself. Now when you get to claiming 80C - 100C.....then i do agree abuot marketing hype
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Old Aug 20, 2012, 06:36 PM
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Rugby, UK
Joined Feb 2007
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Quote:
Originally Posted by N6145k View Post
With one significant digit?

Or am I doing something wrong?
I agree. You cannot expect to take meaningful comparative measurements of cells with an IR of 2 - 3milliohms with a resolution of 1 milliohm. The potential error with a perfectly accurate sytem is up to 50%.
This is not a criticism of the i charger; it is fine for smaller and older cells where the figures are 10 milliohms and up.

Wayne
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