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Old Sep 11, 2014, 08:29 AM
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Originally Posted by Wayne Giles View Post
It is always better to read the IR at the fully charged condition.
The value does not vary very much with charge state; just a slightly lower figure at full charge, but better to be consistent as readings are used comparatively, so minimise any variables. ( Temperature is also important here.)
It is particularly important when measuring a 2S pack as the electronics within the unit are powered by the lipo under test and require a minimum voltage of 7V to be maintained during the measurement pulse for accurate results.

I derived the 20milliohms from the Lipotool on the basis that if a 2200 cell cannot deliver 12C (26A) without producing excessive heating, then it is time to retire it.
Obviously the IR figure will be different for a different cell capacity and you can always argue that my 12C figure is too high or too low, but the principle would be the same.

Wayne
Does pack C rating play any kind of role in determining pack usefulness with regard to cell/pack IR?
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Old Sep 11, 2014, 09:27 AM
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Originally Posted by itsme2 View Post
Does pack C rating play any kind of role in determining pack usefulness with regard to cell/pack IR?
Read this post and this post and your query will be answered.

Also, I personally prefer to make my IR measurements at storage value as this is the voltage potential that my packs are stored nearly all of the time. As such, it's far more convenient for me than fully charging my packs and then allowing them to stabilize at room temperature for at least an hour before testing.

Mark
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Old Sep 11, 2014, 10:05 AM
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Originally Posted by mrforsyth View Post

Also, I personally prefer to make my IR measurements at storage value as this is the voltage potential that my packs are stored nearly all of the time. As such, it's far more convenient for me than fully charging my packs and then allowing them to stabilize at room temperature for at least an hour before testing.

Mark
I like the convenience factor. For folks like myself who do not get to fly outdoors during the Winter months checking IR at storage voltage is a lot more convenient.
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Old Sep 11, 2014, 10:31 AM
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Originally Posted by Ohmic View Post
I like the convenience factor. For folks like myself who do not get to fly outdoors during the Winter months checking IR at storage voltage is a lot more convenient.
That's fine as long as you are consistent in your conditions.

Certainly storage conditions are more convenient, but remember the 2S limitation.

Wayne
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Old Sep 11, 2014, 10:59 AM
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One other advantage of using storage voltage is that's how most new packs arrive, so you can do an initial check then.
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Old Yesterday, 11:09 AM
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Regarding HV lipo's such as the Revo silver HV series, is the IR measured at a given temperature comparable to usual 4.2v lipo's?
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Old Yesterday, 01:33 PM
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Originally Posted by like2fly! View Post
Regarding HV lipo's such as the Revo silver HV series, is the IR measured at a given temperature comparable to usual 4.2v lipo's?
Alex,

Sorry, I don't have any experience of HV lipos, as I haven't tested any yet, so I haven't got a clue! I know that is of no help, but I didn't want to ignore a question on this thread.

Anyone else be more helpful? - they coudn't be less!

Wayne
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Old Yesterday, 01:52 PM
Hamburger
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I have a few 3S 2450 of the 4.27 HV type.
IR is about 4 milliOhms / cell. So far I have only begun using them in a small heli with a max of 40A draw and 15A average. Not much of a load for a heavy duty "70C"rated battery (sorry for the irony). What I can say is that the lowest voltage under load is 10.8V for the HV lipos compared to the 10.4V for some other 3S 2600 non-HV lipos (but those have an IR of about 7 milliOhms/cell ; not easy to compare)
Maybe some of the more experienced will know how to interpret that.

Both types are only ever so s slightly warm to the touch after a flight in a 25Celsius environment and I cannot measure temp.
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Old Yesterday, 06:46 PM
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Quote:
Originally Posted by Wayne Giles View Post
Alex,

Sorry, I don't have any experience of HV lipos, as I haven't tested any yet, so I haven't got a clue! I know that is of no help, but I didn't want to ignore a question on this thread.

Anyone else be more helpful? - they coudn't be less!

Wayne
Hi Wayne,

I have some 6S that I will be measuring the High Res ESR regularly on while performing life cycle testing. Hopefully I will be able to develop some kind of comparitive trending as the packs degrade. I'm still working out software issues on the test system but hope to be on it before too much longer.

Joe
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