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Old Aug 06, 2012, 12:33 PM
wood is good
loNslo's Avatar
United States, CA, Marina Del Rey
Joined Jun 2012
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Mark--Hiya, neighbor!

This is my first entry into R/C flying, and my first modeling in ~50 years! I have just barely begun a 1/5-scale Monocoupe, from plans:
http://www.rcgroups.com/forums/showthread.php?t=1679601
and have just purchased a 4-channel 55" Cub ARF to use as a trainer:
http://www.bananahobby.com/2088.html

For the trainer I've just received from ProgressiveRC (thanks to everyone here who has been so generous with their inputs) the iCharger 206B with Junsi P350 power supply and a parallel board for charging the recommended 14.8V 4S 2200mAh 25C Li-Po batteries which I am about to order (4).
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Old Aug 06, 2012, 05:23 PM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,132 Posts
That is consistent with results I found for an old and tired battery.

I don't know exactly what protocol the PL8 uses for IR measurement but it is a much shorter measuring period than either the iChargers or the ESR meter. The 300uS was what Tim Marks quoted at some stage I think. It is also not a simple DC loading but takes place as an interruption to the charge current as far as I can tell. With an old battery the voltage takes longer to settle. My conjecture is that this is what causes discrepancies between the PL8 and the other methods with some batteries.

My measurements of the iCharger showed that

The iCharger adjusts level of the IR current pulse as a function of cell count.
The iCharger adjusts length of the IR current pulse as a function of balance lead connected or not.

However in all cases the current loading pulse was between 50 and 170mS after a ramp up over about a 50mS period. These times are of the same order as the ESR meter which Wayne has established allows the voltage level to stabilise to an acceptable accuracy.

I have not attempted to analyse the exact way in which the PL8 does its measurement but Tim Marks has stated in the PL8 thread that it measures IR with very short rests at frequent intervals.

My speculation (and this is pure guesswork) is that the IR functionality wasn't put there to measure IR accurately in absolute terms but to compare IR between cells and over time for safety reasons.

I am sure that is how they do their automatic 2C or 3C charge rates also.

I'm guessing the IR display is one of those, "We have the data, why not display it" things. It may be that there was no serious attempt to check it was a reasonable measure of practical real model use IR. It just turned out to work.

Just to be clear; the discrepancies I have found with the PL8 have been only with batteries that are no longer of any interest for practical use and which have effective C ratings of 4-5C or less - ie junk.

John

Quote:
Originally Posted by kimmik View Post
hi mark thanks for the comment. i'm on 1.07, while 1.10 is the newest version though the blurb says it just improved 1S charging, not any other features.

also, a fellow member on the australian website told me of the same issue on his PL8, so it seems to either be a universal issue that has gone unaddressed, or we're both lucky enough to get the ugly stick.

He had a lipo that couldn't even do 2C, but measured 1.5mohm/cell on the pl8. Icharger measured 25mohm/cell, much more realistic.

my best guess is, the PL chargers are using too short of a pulse load to measure the ESR, say 1ms, so teh lipo capacitance is contributing to the measurement. i'll try to scope the charger output at some point to get clues.

edit: read on the pl8 thread that icharger uses a 100ms measurement, whereas powerlab uses 300us. which explains my observation that new (as opposed to old and tired) lipos get greater consistency of measurement between the two chargers.
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Old Aug 06, 2012, 10:59 PM
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PL8
"IR is measured with the voltage rise difference between full charge current and zero amps. The current is turned off for 300uS and the at rest battery voltage is compared to the charging battery voltage on a cell by cell level.

Tim Marks"
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Old Aug 08, 2012, 08:27 PM
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Yeah, so disappointed...

There is great potential for the high res hardware to measure DC esr but they did not program such.
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Old Aug 08, 2012, 08:33 PM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,132 Posts
But the nice thing about a microprocessor driven charger with automatic firmware updating is that it would be straightforward to upgrade to such functionality......
Quote:
Originally Posted by kimmik View Post
Yeah, so disappointed...

There is great potential for the high res hardware to measure DC esr but they did not program such.
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Old Aug 12, 2012, 04:57 PM
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Chicago, USA and Manila, Philippines
Joined May 2007
153 Posts
Glacier batteries

Posted IR data on Glacier battery 3s 30c/1000mah and 3s/30c/2200mah on data thread.

http://www.rcgroups.com/forums/showp...2&postcount=40

on 3s 11.1v 30c/2200mah I had an IR of IR 4, 4, 11 million ohm per cell as received at 74F. Dale of epbuddDotcom gave me an #RMA to return the 3s/2200mah battery for exchange but I am still holding it for now.. will update about that battery.

comparing my genAce 3s 25c/1000 to glacier 3s 30c/1000mah, they are exactly the same design physically and same weigh too except on the balanced tap on glacier battery is a few inches longer.


elmer...
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Old Aug 12, 2012, 09:49 PM
Battery Puffer
Orange, California, United States
Joined Nov 2001
996 Posts
I may have missed it but I have a question about how reliable the info really is since its only testing the cells at 15 amps for a very short period. Now I have models that pull 25 amps and then I have some that pull over 300 amps. Only the best battery will handle the 300 amp load but the crappy battery will handle the 25 amp load no problem. I see guys seing great numbers on there old packs but are they truelly great numbers? Unless the pack is total crap this devise is only telling you if you have a bad cell or all cells are bad. Seems to me at only a 15 amp draw the pack the pack would have to be pretty far gone to show any real performance issues. Now don't get me wrong. I like the idea of this device and I want to buy one. Just not sure that my cell voltages I get when charging doesn't give me the same info when you can read alot into what the end voltage ends up at when the charge is over. Very curious on your thoughts.

Mark
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Old Aug 12, 2012, 10:41 PM
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Prof100's Avatar
Canton, Michigan USA
Joined Jul 2007
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Quote:
Originally Posted by MarkF View Post
I may have missed it but I have a question about how reliable the info really is since its only testing the cells at 15 amps for a very short period. Now I have models that pull 25 amps and then I have some that pull over 300 amps. Only the best battery will handle the 300 amp load but the crappy battery will handle the 25 amp load no problem. I see guys seing great numbers on there old packs but are they truelly great numbers? Unless the pack is total crap this devise is only telling you if you have a bad cell or all cells are bad. Seems to me at only a 15 amp draw the pack the pack would have to be pretty far gone to show any real performance issues. Now don't get me wrong. I like the idea of this device and I want to buy one. Just not sure that my cell voltages I get when charging doesn't give me the same info when you can read alot into what the end voltage ends up at when the charge is over. Very curious on your thoughts.

Mark
Mark,

The pack resistance and cell resistance is an indicator of the health of the battery. Lower is better. Although you want to measure lipos cell and pack resistance at a consistent temperature, you can still get a relative indicator of pack's health at higher or lower temps.

The amp load is just a means to determine the mOhms resistance of a cell or pack. Testing was done at higher amps when developing the ESR meter as I recall from reading posts on this thread. It didn't make any difference.

Bill
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Old Aug 13, 2012, 01:26 AM
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Rugby, UK
Joined Feb 2007
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Mark,

Bill is correct. The ESR is independant of current but is a measure of how good a lipo is at any current. Obviously it varies with the size of a lipo cell; larger cells are lower, which is why the calculator must be used to compare lipos of different capacities.
Here is the post Bill refers to ( I think)
http://www.rcgroups.com/forums/showp...&postcount=378

Wayne
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Old Aug 13, 2012, 03:56 PM
Battery Puffer
Orange, California, United States
Joined Nov 2001
996 Posts
Thanks Wayne, that makes sense. I also sell lipos and I thought this would make a great tool to check the packs are alright before I ship them. Thanks for making this tool available for the general public.

Mark
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Old Sep 06, 2012, 08:20 PM
Frankenstein recycled packs
rampman's Avatar
USA, AZ, Gilbert
Joined Jan 2006
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I use this tool as a good barometer for packs. I got bit last weekend though.
A buddy with four 5000mah 40C Sky Lipo packs that he purchased less than a year ago could no longer fly his EDF asked me to check his packs. I knew he was one of the worse lipo abusers out there as he stores at 100% charge and in his garage here in hot Arizona. I did a quick IR check on all 4 packs and thought they would work on my lower amp draw prop planes and I paid him $10 each for these 4 packs.

Individual cell IR values on the 3S packs with my PL8 and mah out at 20A and 2A as of today are:

4.2
4.2
4.2
1653 mah out at 20A
2435 mah out at 2A

5.0
6.3
6.8
157 mah out at 20A
2764 out at 2A

The 4S packs were
5.6
3.2
3.3
2.2
705 mah out at 20A
3066 out at 2A

1.9
3.4
1.8
2.9
241 mah out at 20A
1416 out at 2A

Now, those values sound good enough to me to pass on to some of my students for low amp draw trainers as they should be at least 10-15C packs... without logging in a getting real values off the tool.

What am I missing here? Is there something with the brand or am I reading the IR's wrong or ____ ?

Disclaimer: This is not to knock the lipo brand, he flies at over 100A and usually till he hits LVC on most flights, stores at full charge all the time and in his garage which exceeds 105F in the summer. No current pack can survive this abuse.

Rick
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Last edited by rampman; Sep 06, 2012 at 11:01 PM. Reason: Added mah size of packs
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Old Sep 06, 2012, 08:41 PM
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That's what I would call abuse. Can't expect much more when you treat them like that.
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Old Sep 06, 2012, 08:46 PM
That's a funny word
NE Ohio
Joined Apr 2003
3,686 Posts
Quote:
Originally Posted by rampman View Post
I use this tool as a good barometer for packs. I got bit last weekend though.
A buddy with four 40C Sky Lipo packs that he purchased less than a year ago could no longer fly his EDF asked me to check his packs. I knew he was one of the worse lipo abusers out there as he stores at 100% charge and in his garage here in hot Arizona. I did a quick IR check on all 4 packs and thought they would work on my lower amp draw prop planes and I paid him $10 each for these 4 packs.

Individual cell IR values on the 3S packs with my PL8 and mah out at 20A and 2A as of today are:

4.2
4.2
4.2
1653 mah out at 20A
2435 mah out at 2A

5.0
6.3
6.8
157 mah out at 20A
2764 out at 2A

The 4S packs were
5.6
3.2
3.3
2.2
705 mah out at 20A
3066 out at 2A

1.9
3.4
1.8
2.9
241 mah out at 20A
1416 out at 2A

Now, those values sound good enough to me to pass on to some of my students for low amp draw trainers as they should be at least 10-15C packs... without logging in a getting real values off the tool.

What am I missing here? Is there something with the brand or am I reading the IR's wrong or ____ ?

Disclaimer: This is not to knock the lipo brand, he flies at over 100A and usually till he hits LVC on most flights, stores at full charge all the time and in his garage which exceeds 105F in the summer. No current pack can survive this abuse.

Rick
I'm guessing that "mah out" means that you discharged at the spec current down to a predetermined volt cutoff. I'm also guessing at what you're asking and that is why the difference between the capacity during the two different discharges on the same pack? Nothing about your figures surprises me , and I'd say the packs are slightly puffed , right? (just a guess)
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Old Sep 06, 2012, 08:47 PM
That's a funny word
NE Ohio
Joined Apr 2003
3,686 Posts
Or you could be asking why the IR is so low?
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Old Sep 06, 2012, 09:20 PM
Frankenstein recycled packs
rampman's Avatar
USA, AZ, Gilbert
Joined Jan 2006
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Quote:
Originally Posted by gulio View Post
Or you could be asking why the IR is so low?
Yes, considering how poorly they perform. I was expecting better at 20A at the least.
I had charger discharging into a 4S5P A123 pack and set to 3.5 volt. Recovery jumled up to the 3.9's immediately after charger turned off.
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