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Apr 02, 2018, 11:22 AM
Thanks Wilber and Orville !.
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Apr 02, 2018, 01:19 PM
aka JetMan Joe
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Thread OP
Ha! That got my day started with a grin

Joe
Apr 02, 2018, 02:10 PM
tic
tic
thunderscreech
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I'd like to see a test on the little 1s cells some time... I'm always buying those things and have spent a small fortune on them. They don't seem to provide near the longevity as large multi cell packs even when properly cared for and not strained in use.
Apr 02, 2018, 03:54 PM
Thanks Wilber and Orville !.
sonic liner's Avatar
I have a small hand full myself.
The key must be to store them at the proper voltage. With that tiny connector its tough to probe since their so close and unless your careful it will get damaged. Perhaps buying a female side and mounting it on some kind of plate or bracket with leads coming off of that would work. Keeping them in a Tupperware in the fridge clearly marked helps also.
With the USB port charger it's either full or mostly empty...thus the short life span.

Pete
Apr 02, 2018, 04:08 PM
Registered User
Joe,
Thank you for another round of informative results.
I think what will be interesting to see is your summary table with all results divided by battery weight. From it it will be clear what manufacturers have the technology for beating HK by making a heavier battery.

I think the most important parameter for longevity in EDF is temperature rise. On your tests there are clearly 2 types of batteries: where V increases after a while due to heat and where it does not. The 1st one is also seen on "classical" batteries like Turnigy Heavy Duty where it delivers close to TG by simply running hotter.
Apr 02, 2018, 04:20 PM
tic
tic
thunderscreech
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I use a good multi function charger and store them @ 58 degrees F around 3.8vdc. Agree the tiny connectors are a pain and sometimes wonder if the connector is bad but the cell is still o.k.
Apr 02, 2018, 06:15 PM
The best in EDF since 2005
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I have been reading some technical papers from my Chinese engineer on battery conductive agents and its quite interesting to see the tech of the various well known and fairly new agents in use.

VGCF, CNT's and Graphene are the advanced agents being worked with today, and there are similarities in their properties, conductivity is the same across all three, yet surface area is quite different with Carbon Nano Tubes appearing to have the highest surface area per gram, would explain why graphene packs are heavier per se.

Both CNT's and Graphene are in the spotlight in China, they consider CNT's to be more usable though as their negatives, the dispersal inside the cell is easier to overcome compared to the cost and production difficulties of graphene.

Most benefit with least amount of material was another topic, with Graphene offering the most conductivity, but the liquid absorption ability of carbon nanotubes in the electrolyte is stronger.

There was also some concerns from other industry insiders about the electron of a conducting agent that adds pure graphite detaching itself after dozens of cycles, affecting battery cycle stability, they then go on to say;
"However, both the electronic conductivity and ionic conductivity of carbon nanotubes are good, it’s more helpful to improve the battery cycle life."

So there are interesting times ahead for sure, my current battery range are made with CNT additives, explains the long cycle life we see with these packs and the strong power output.

End of the day I feel it boils down to quality of manufacture and purity of materials, combined with long term grading of cells and storage times before being retested and built into packs.
Latest blog entry: Extreme RC AUSTRALIA
Apr 02, 2018, 06:52 PM
aka JetMan Joe
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Thread OP
There have been some recent questions about IR. I've been exchanging emails with Wayne Giles and he provided some history on the topic along with a timely evaluation about why the Hobby King Graphenes have been an IR game changer. I've posted portions of our talk here with his permission:

'---------------------
"Re the sag/ recovery saga, If I can bore you with a little history which also relates to IR v Performance, it should help to explain the ‘Lipotool’

I had always thought IR must be important and therefore I built a little rig to measure IR and when I did any discharge testing, I always included IR with the results. My testing always consisted of discharging a pack at constant current from 4.2V/cell down to 3.0V/cell starting at 25⁰C. I ran a couple of low C charge /discharge cycles first and then did plots @ 5C,10C,15C,20C,25C,....etc until the pack showed that it was overstressed. My three criteria were:

1) Temperature rise < 55⁰ C
2) Cell Voltage @ 50% discharge >3.50V
3) No positive slope on the plot ie no sag + recovery.

I cannot mathematically justify these but they invariably seemed to coincide with each other, so I used them to determine the pack’s maximum discharge rating.

I noticed that low IR packs performed much better and looking for a correlation, knowing that heat was the problem and IČR was the initial heat dissipated, I discussed it with JJ and Mark F and between us we decided that a reasonable initial maximum heat dissipation was 6Watts/Ah/cell. So this produced the Lipotool as the max safe continuous current = Square root of (6 x Ah/IR)

I ran back over most of my previous testing and was frankly amazed to see how accurately and consistently this would forecast the max discharge capability of all the lipos I had tested, based on the above three criteria.

This formula worked well for years until Turnigy Graphene appeared and with those it is far too conservative, showing a genuine 50C pack as 32-34C. Presumably this is because they have a very low IR and a low temperature coefficient which is what other makers have not yet attained. Makers using a high temperature coefficient to attain a low IR at higher temperatures are surely sacrificing life for performance.

Although your testing is Constant R instead of Constant Current and you are specifically looking at EDF related performance, I am still surprised that you found so little correlation with IR, not doubting your results however. I assume you are always starting from a standard temperature, as any pack will sag at a low enough temperature and high enough load. "

'------------------
Thanks Wayne!

For a very detailed explanation about IR please refer the JJ604's highly informative posting on page 34. It can also be found using the index on page 1 under "JJ604- Why IR is useful"

Joe
Last edited by MCSGUY; Apr 02, 2018 at 07:07 PM.
Apr 03, 2018, 12:18 AM
Registered User
@MCSGUY

i don't understand how the hyperions performed so poorly in the 4.20 test....

first thing that gets me is the weight, now given my packs are the 60c packs, but they weigh in at 654g on my scales, which are ones we use for F3A world champs to measure components and all up model weight before going overseas, so i'd consider them accurate (last year there was a 6g difference in all up weight between our scales and the ones used at the world champs)
i own the G7 5200 60c packs, have pulled them down to 20% and not had them get above 38 degrees C on my infa red sensor...
i also know for a fact mine on average charge up to around 5115mah @4.21v over 10 charges
on my stumax 90mm EDF setup, i use a HET 700-68-2250kv, hobbywing 200a ESC, and see a peak avg of 172A, i had cycled this setup 5 times before doing a full peak run and discharging down to 20%, without ballooning.

knowing what these packs hold on a 4.2v charge and seeing the drop off to 4% tells me they discharged the fastest ie had the highest avg amp draw until they were drawn right down, and, were also well beyond what anyone would recommend drawing the packs down to. anything under 15% on a lipo is a good way to destroy it and i wouldn't go under 20% on a full load test.
which also explains the heat and low avg amp draw.

i find your figures completely different to my own.
would you be willing to re-do the test with the cutoff being 20% capacity? im curious to see the results across the board.
Apr 03, 2018, 01:19 AM
aka JetMan Joe
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Thread OP
Quote:
Originally Posted by XCSEDAN
i find your figures completely different to my own.
would you be willing to re-do the test with the cutoff being 20% capacity? im curious to see the results across the board.
What you're subjecting your packs to is not necessarily what I'm subjecting mine to so we may have a little apples and oranges comparison going on. However I am open to learning as much as I can about the things I'm interested in.

Please lay out exactly what you want me to do and what you think I may discover by doing so. I think I understand what your getting at but provide like specific bullet points of the steps you want to see without the back ground info.

Thanks,

Joe
Apr 03, 2018, 03:07 AM
Registered User
Quote:
Originally Posted by MCSGUY
What you're subjecting your packs to is not necessarily what I'm subjecting mine to so we may have a little apples and oranges comparison going on. However I am open to learning as much as I can about the things I'm interested in.

Please lay out exactly what you want me to do and what you think I may discover by doing so. I think I understand what your getting at but provide like specific bullet points of the steps you want to see without the back ground info.

Thanks,

Joe
sure thing Joe,
for myself, with keeping longevity of packs in mind as well as safety, i do not draw my packs below 20% of their indicated capacity.
and i also measure when fully charged to see pack capacity. for me this is real world conditions, and what I'd ask if you can replicate?

assuming its not too much of an issue for you, also don't go buying any extra packs to do this, I don't want to put you out of pocket.

what i would like to see for example:
a 5000mah pack, drawn down to 1000mah, using the rated C rate of the pack,
the hyperion 90cmax packs i believe are 40-45c constant, so drawing down at 45c.
turnigy graphenes come in an array of C ratings, the 45c packs i saw on HK were rated at 45c constant 90 burst, so in this event, discharge at 45c down to 1000mah

if you would prefer to discharge them at one flat rate like previous (35c) down to 20% of rated capacity that would be interesting to see as well.

im curious to see how the packs discharge, and what sort of heat is generated given the real world flight margin of 20% capacity being left in the pack.
questions im looking to answer are; are the packs over rated for real world flight conditions? if so by how much? does the manufacture variance allow for enough headroom or not?
i don't have the consistency on size of packs, brands and C ratings to do the test myself.
also if you could list what equipment you used, just so we can use that as a reference (or tell me which which post its in and ill have a looksee)

the tables that you used before will be sweet, btw i don't know how familiar you are with excel but you can get it to conditional format data, make your spreadsheets automatically rated highest to lowest with colour coding, or using specific values.
Apr 03, 2018, 09:25 AM
Quadaholic
--Oz--'s Avatar
Quote:
Originally Posted by MCSGUY
I have also witnessed that a pack having lower IR will tend to propel a jet a few MPH faster but run hotter then one with a higher IR.
Did you mean run cooler?

Using a constant Resistance load, did you change the resistance for the HV packs or did you keep it the same for all packs?
If same, what resistance did you use?
Apr 03, 2018, 11:08 AM
aka JetMan Joe
MCSGUY's Avatar
Thread OP
Quote:
Originally Posted by --Oz--
Did you mean run cooler?

Using a constant Resistance load, did you change the resistance for the HV packs or did you keep it the same for all packs?
If same, what resistance did you use?
Usually I see a somewhat higher current so I've always attributed that to the lower IR causing higher temp. However I've recently come to understand that pack chemistry can be manipulated regarding the temperature coefficient as I posted below:

"This formula worked well for years until Turnigy Graphene appeared and with those it is far too conservative, showing a genuine 50C pack as 32-34C. Presumably this is because they have a very low IR and a low temperature coefficient which is what other makers have not yet attained. Makers using a high temperature coefficient to attain a low IR at higher temperatures are surely sacrificing life for performance"

So actually I'm learning new stuff about Lipo tech all the time. This may explain why I saw a higher temp in some of my lower IR packs.

I applied the same resistance on all packs using the hardware shown on page one set at the approx. ohm values necessary to get the initial power levels (I refined the adjustments by testing packs early on). The comparison approach I wanted to use did not require the settings be exact but just close enough for my purposes. Some packs put out slightly higher amps then others at the same load.

Joe
Last edited by MCSGUY; Apr 03, 2018 at 11:34 AM.
Apr 03, 2018, 01:37 PM
aka JetMan Joe
MCSGUY's Avatar
Thread OP
Quote:
Originally Posted by XCSEDAN
....keeping longevity of packs in mind as well as safety, i do not draw my packs below 20% of their indicated capacity.
and i also measure when fully charged to see pack capacity. for me this is real world conditions, and what I'd ask if you can replicate?

what i would like to see for example:
a 5000mah pack, drawn down to 1000mah, using the rated C rate of the pack,
the hyperion 90cmax packs i believe are 40-45c constant, so drawing down at 45c.
turnigy graphenes come in an array of C ratings, the 45c packs i saw on HK were rated at 45c constant 90 burst, so in this event, discharge at 45c down to 1000mah

im curious to see how the packs discharge, and what sort of heat is generated given the real world flight margin of 20% capacity being left in the pack.
questions im looking to answer are; are the packs over rated for real world flight conditions? if so by how much? does the manufacture variance allow for enough headroom or not?
i don't have the consistency on size of packs, brands and C ratings to do the test myself.
also if you could list what equipment you used, just so we can use that as a reference (or tell me which which post its in and ill have a looksee)

the tables that you used before will be sweet, btw i don't know how familiar you are with excel but you can get it to conditional format data, make your spreadsheets automatically rated highest to lowest with colour coding, or using specific values.
The test hardware is shown on pages 1 and 6. Page 1 also has a hyperlinked index that enables you to jump directly to previous tests and significant posts.

Excel is definitely powerful, I've only mastered a fraction of it. I've always manipulated the .CSV files directly into custom interfaces the way I've done with the charting software. However it looks like tables are the most popular viewing format so I probably should up my Excel game.

Precise capacity evaluation is typically handled using a constant current approach. I use constant resistance because I want to replicate an EDF running at WOT where we see current diminish while temperature increases. My intentions are to compare one pack to another in as close to identical conditions as possible. Conditions that are often abusive.

That being said in the last test series the 35C/90sec./4.35v pretty much nailed the 80% target, at least as closely as my method can get. The top 5 in that category averaged 81% usage where as the bottom 2 averaged 88%. The results tell me what I wanted to know: which pack will do the best job in my application and is it's listed capacity accurate to that application.

"Best" is determined by an individuals needs where weight and price usually have a bearing.

However the question I think you wanted answered is if the test period was limited to match the Hyperions 80% capacity would it's performance have improved? It may have but the answer I can provide based on the threads intended purpose is: Relative to the competition of 5000mah labeled packs the 5200mah labeled Hyperion ranked 6th out of 7 in regards to estimated capacity.

Joe
Last edited by MCSGUY; Apr 03, 2018 at 01:54 PM.
Apr 03, 2018, 08:42 PM
big ignore list/drama is dumb
brushless55's Avatar
Quote:
Originally Posted by MCSGUY
"Best" is determined by an individuals needs where weight and price usually have a bearing.

Joe
Said very well Joe


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