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Old Jan 23, 2013, 07:50 AM
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Originally Posted by REVOJohn View Post
total capacity of course
the standard is the whatever c rate the battery is claimed to be it should be able to deliver those amps from full charge to 3.0v without serious overheats......no one actually specifies what overheating actually means or how many cycles you should be able to perform. even the worst of cells could probably do 60c oncce.

my take.........the cell/pck should not excess 70 - 75degC under this type of constant current loading.......about 100 times at least
That would make a great standardized test. Would be interesting how many could even come close to 100 cycles.
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Old Jan 23, 2013, 11:00 AM
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Quote:
Originally Posted by REVOJohn View Post
total capacity of course
the standard is the whatever c rate the battery is claimed to be it should be able to deliver those amps from full charge to 3.0v without serious overheats......no one actually specifies what overheating actually means or how many cycles you should be able to perform. even the worst of cells could probably do 60c oncce.

my take.........the cell/pck should not excess 70 - 75degC under this type of constant current loading.......about 100 times at least
John,

Are you saying that your "60C" packs will deliver 60 x their AH rating in amps over a full capacity discharge without exceeding 75degC starting from, say 25degC ? And survive this treatment for 100 cycles ?

Wayne
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Old Jan 23, 2013, 03:36 PM
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I couldn't venture an opinion on all that nor could I venture a guess on 100 cycles, and I'm certainly not trying to speak for John, but I can say that 2 test cycles looked good enough to make me a customer.

Joe
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Old Jan 23, 2013, 03:40 PM
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I only have qualitative data, MCSGUY. I'm not sure what the other guy from austrailia didn't like about these batterys, and from what I understand, even if you don't like them, revolectrix will take them back. I wouldn't know because I liked mine. STDGZ has some now so hopefully we can get his qualitative or quantitative view of the revolectrix batteries soon.
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Old Jan 23, 2013, 03:58 PM
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Nice test but 180A (36C) dump for 60 seconds is a far cry from the rated 300A 60C full DOD dump for 100 cycles...
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Old Jan 23, 2013, 05:00 PM
aka JetMan Joe
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Nice test but 180A (36C) dump for 60 seconds is a far cry from the rated 300A 60C full DOD dump for 100 cycles...
Thats a fact. However my interest is testing batteries at the level I will actually use them at and find the best for my money. The problem the manufacturers have to deal with is users (you and I) who don't want to deal with 6-8awg wires and 8mm bullett connectors. Revo did use 8AWG for awhile but got bad feed back because guys could not solder their connectors on so they went back to what is essentially the industry standard of 10awg. Therefore the wires will melt the solder off the terminations at around 250A, maybe even less. But what the High C is supposed to do if it's the real deal is run cooler then the lower C units at the power I use. The good ones will also reach "down to their ankles" and grunt out more then the other can when it's half empty and you need to get over the top of some complicated show off maneuver. And be able to repeat that process for over 100 cycles, maybe even 200

My $0.02 for what it's worth
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Old Jan 23, 2013, 06:20 PM
ancora imparo
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John, not wanting to buy into the argument about whether these packs perform for various folks or not - that is important but very much dependent on what they use them for and highly subjective.

I am however really interested in your 70 -75 degrees C figure as info on the maximum allowable temp for LiPo cell use is surprisingly rare. There is plenty of good stuff on discharge rates and the effect of temperature on capacity and voltage but not much on temperature degradation and lifespan. We are all fairly convinced that heat is the enemy of the LiPo but it is hard to get reliable (not vendor/hobby magazine) data on this.

Since you know a lot more about this than most of us would be interested in where you get this number from.

I collected some bits and pieces but some of it is quite old. I suspect this particular parameter has not moved much though as other LiPo features have improved.


NOTE: "C" in all this refers to temperature in degrees C not the C rate unless explicitly stated.


1) "Charging/discharging operations cause the cell temperature to rise. It is essential to suppress this heat generation because high temperatures above
 50 C generally induce cell degradation."

Research and Development Work on Advanced Lithium-Ion Batteries for High-Performance Environmental Vehicles, Hideaki Horie
in: Lithium Ion Rechargeable Batteries. Edited by Kazunori Ozawa Copyright ! 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 978-3-527-31983-1

2) "Operating temperature discharge only as 0-60C"

Batteries in a portable world by Isador Buchman Second Edition 2004

3) "Operating temperature discharge only as -20-60C"

Batteries for Portable Devices by Gianfranco Pistoia (2005) and the Sony Lithium Ion Rechargeable Batteries Technical Handbook give the same max temperature.

4) "The general rule is if you can't comfortably hold a LiPo pack tightly in your hand after using it, it's too hot. This equates to anything higher than about 50C (122F)."
Typical "Hobby" advice from RCHELICOPTERFUN.COM

5) "Most Li-ion batteries on the market today indicate 60C as their upper usage temperature. The majority of batteries currently on the market have graphite anodes. Graphite is not stable and can react chemically with the electrolyte in the cell. During manufacture and formation of the cell, a passive layer is formed on the anode surface, the SEI (Solid Electrolyte Interface) layer, which prevents continued reaction between the electrode and the electrolyte. Already at temperatures below 90C, the layer can begin to break down, allowing exothermal gas evolving reactions to begin. If a sufficiently large area of the SEI layer breaks down, the cell may enter thermal runaway."

Battery Technologies
A General Overview & Focus on Lithium-Ion: Tom O’Hara and Dr. Maria Wesselmark, Intertek, 2012.

6) "...self-heating of lithium-ion graphitic anodes in the presence of electrolyte initiates at temperatures in the 70 to 90C (158 to 194F) range."

The July 2011 "Lithium-Ion batteries Hazard and Use Assessment Final Report" by the Fire Protection Research Foundation

7) The Solid-Electroyte Interface is stable at normal operating temperatures but when heated to around 110 C it will break down and allow an uncontrolled reaction between the stored lithium ions and the electrolyte (thermal runaway). This process occurs regardless of the positive material used but, depending on the positive material and thermal characteristics of the cell and battery, the heat released may also destabilize the positive and result in a fire."

UNDERSTANDING LITHIUM-ION TECHNOLOGY Jim McDowall Business Development Manager Saft America Inc. (2008)

8) A presentation by GMBH (a manufacturer of LiPo cells) showing results of safety and performance testing states that a fully charged cell stored at 65C is "normal" after 10 days of storage and at 80C after 4 days.

From all of the above I am thinking that 60C is a sensible maximum UNIFORM temperature limit for a LiPo pack.

However the heat is generated throughout the pack but has to be transferred through to the surface to the ambient air. The centre of a pack, particularly a big one with higher volume to surface area, is going to be a LOT hotter than the measured surface temperature. If you measure surface temperature while testing LiPos the temperature continues to rise substantially for some time after the load is removed because the heat is still transferring from the interior to the surface.

So I was wondering if you know of any reliable data on:
1) What the internal temperature is at the centre of a Revo pack discharging at the "60C" rate.
2) What the degradation in capacity and increase in IR is for a pack cycled at a 70C temperature.

Thanks, John
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Old Jan 24, 2013, 07:53 AM
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John sent you an email yesterday about the customs declaration
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Old Jan 24, 2013, 04:27 PM
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hey guys all great replies. sorry for the delay but we're on the other size f the world.

yup its heat heat heat. generally most manufacurers will give you a 0 -maybe 60degC top end operation range for lipo in consumer electronics market.
ok here is the crunch.....what makes this number.
basically its electroltye solvent ignition temperature and it'll depend on what the factory uses. low power application cells can have a lower temperature liquid whist high temp batteries - yes you can buy high temp batteries for use in down hold mining drill bit batteries....cn withstand higher temperatures before burning up.

most rc batteries should be able to get to 90degC before thermal runaway starts. we like to give a bit of safety margin and say 70.

anyway at revo and national university of singapore we're opening a rc lipo educational website and it'll be open in a few weeks. keep a look out for LITHIPEDIA
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Old Jan 24, 2013, 04:28 PM
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Originally Posted by Wayne Giles View Post
John,

Are you saying that your "60C" packs will deliver 60 x their AH rating in amps over a full capacity discharge without exceeding 75degC starting from, say 25degC ? And survive this treatment for 100 cycles ?

Wayne

yes correct wayne. when we see other lipos bloating at a mere 10 cycles it surprises me that customer go back and buy them again. anyway the singapore and aussie rc community have moved to revo and can see the difference
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Old Jan 24, 2013, 04:52 PM
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Originally Posted by REVOJohn View Post
yes correct wayne. when we see other lipos bloating at a mere 10 cycles it surprises me that customer go back and buy them again. anyway the singapore and aussie rc community have moved to revo and can see the difference
That sounds outstanding John. I am in UK. Where can I get one to try?

Wayne
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Old Jan 24, 2013, 05:10 PM
ancora imparo
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Thanks for the info, John. I would think the argument will be about the difference between the safe ignition temp and the reasonable highest temp for decent pack life but I am sure that will keep people occupied for some time!

Wayne's point about the practical test over a full discharge without exceeding a critical temp AND keeping performance for 100 cycles is more important to all of us. Look forward to the results of the tests that confirm that.

The LiPo education web site is an excellent idea - congratulations on that initiative. Hopefully it will become a place for reliable confirmed data and help clarify some of the rubbish that is promulgated.

Quote:
Originally Posted by REVOJohn View Post
hey guys all great replies. sorry for the delay but we're on the other size f the world.

yup its heat heat heat. generally most manufacurers will give you a 0 -maybe 60degC top end operation range for lipo in consumer electronics market.
ok here is the crunch.....what makes this number.
basically its electroltye solvent ignition temperature and it'll depend on what the factory uses. low power application cells can have a lower temperature liquid whist high temp batteries - yes you can buy high temp batteries for use in down hold mining drill bit batteries....cn withstand higher temperatures before burning up.

most rc batteries should be able to get to 90degC before thermal runaway starts. we like to give a bit of safety margin and say 70.

anyway at revo and national university of singapore we're opening a rc lipo educational website and it'll be open in a few weeks. keep a look out for LITHIPEDIA
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Old Jan 25, 2013, 04:18 PM
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Ordered a set of the Diamond 3200mah 6s packs, they will be put to the test in my 600EFL Pro with a 7500 watt KDE motor.

Looking forward to seeing what they can do!
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Old Jan 25, 2013, 06:11 PM
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Just FYI, I bought three Revolectrix Diamond packs for use with my test stand: 2s/3s/4s 2200mAh. They arrived superbly packaged.

All passed the balance test on my TP205-V, so I set about charging them with my simplistic, little Apache 1500.

2s 2200, starting voltage 7.60v, end voltage 8.40v, 1682mAh passed through the Medusa Analyzer Pro.

3s 2200, starting voltage 11.70v, end voltage 12.56v, 1029mAh passed through the Medusa Analyzer Pro.

4s 2200, starting voltage 15.19v, end voltage 16.72v, 1269mAh passed through the Medusa Analyzer Pro.

Revolectrix states that they ship at 3.84v/cell.. so that seems pretty accurate. How much actually went into each pack is moot, but all packs got close enough to 4.2v/cell by the time the green light came on!

Cheers, Phil
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Old Jan 25, 2013, 09:52 PM
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uk. try our online webstore or www.revolectrix.co.uk also

dr kiwi. tks for the test ad all shows well but personally i would expect any pack to be able to do that
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