Project to expose C rating deceit w/ Wayne Giles meter - RC Groups
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Sep 15, 2017, 10:48 AM
working on https://lipo.lol
d0uglas's Avatar
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Project to expose C rating deceit w/ Wayne Giles meter


Gents, I hate how battery vendors have been getting away, with really no risk, with pulling C rating figures out of their butts and stamping nonsense on the battery labels. So in a bid to inform consumers who care either about true discharge rates or who's telling the truth, I bought the redoubtable Wayne Giles ESR/IR meter to test new batteries myself and have been turning it into a website. I really don't want to screw this up out of the gate, so I'd like your help, please. This is it:

https://lipo.lol

Especially in the beginning of something like this, something that includes revealing negative things about people trying to make money, it's important that I diligently follow the right procedure for testing each battery from the start. I am not going to monetize the site in any way, only want to offer up some accurate data.

I concede that I know less about battery physics than many/most/all of you, so could you kindly eyeball the site and advise either if I'm off to a good start or if I should change anything before I try to get some eyes on the site? I'd sure appreciate it.

By the way, anybody want to buy a pricey "75C" Glacier 1800mAh 3S from me that's actually, on its best run, only 26C? Yeah, didn't think so....

I don't think the Better Business Bureau will be too helpful here. So thank God for Wayne Giles!! And for you for whatever help you fellas and the wattflyer crowd can give me.

Cheers, Doug

Last edited by d0uglas; Sep 15, 2017 at 12:16 PM.
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Sep 15, 2017, 12:32 PM
Frankenstein recycled packs
rampman's Avatar
You are opening up a can of worms but have at it.
I build that meter now for Wayne as he is finally retired (again) and enjoying life.

I test a LOT of batteries before and after they hit the market and the highest true C packs I have seen is the Turnigy Graphene which were introduced to the market around February 2016. These, like your meter shows, will read around 32C. There have been new entries into the market, mostly targeting the 250 quad racer market, and a few of these test near or the same as these Turnigy Graphene's.

What I am seeing is most other new brand of packs will be in the 19C to 25C range. My opinion is a 25C pack is still a remarkable pack and not bad by any means.

Now the tough part... Some of these lower C rated packs still hold up really well to load tests.
C ratings is only 1 piece of the puzzle though one of the more important pieces though some will disagree with that statement.

Another problem we see is standardization across all sizes of packs and from one order to the next. Where a newly released line tests at xxC, 6 months later the C may be down 3 or more points.

One thing I have noted is the ESR meter C rating can usually be doubled on short bursts of, say 10 seconds, a few times per discharge.

While I appreciate your efforts I hope you don't get too frustrated in the process.

Rick
Sep 15, 2017, 01:44 PM
working on https://lipo.lol
d0uglas's Avatar
> You are opening up a can of worms

Story of my life! Yes, I do feel risk in doing this.

I figure tunnel vision of the C rating of the first few cycles of a pack is necessary to keep the number of worms escaping manageable. While data of degradation over time, for example, would be valuable, unless I devote my life to this, I can't get that data and call the procedures uniformed and controlled.

I'm not expecting much traffic or to change the world with this site, so if I manage not to lose all my money on lawyers' fees, there's already been enough value in this project from what I've learned along the way to make it worthwhile to me. It would be satisfying if a few of those who visit as I add more data are intrigued enough to buy a meter.

Thanks for contributing to the operation and for all you wrote here. I'll have at it a bit more.

Doug
Latest blog entry: telemetry: worth the weight?
Sep 15, 2017, 05:22 PM
Registered User
Doug,

Congratulations on your enterprise.
I hope people find it useful: the fictional C ratings written on most Lipos are still as wildly out percentage wise, in most cases, as they were when this subject was first broached.

It started with this thread: https://www.rcgroups.com/forums/show...cement-Overdue

This led to the "Lipotool" as discussed in John Julian's thread here: https://www.rcgroups.com/forums/show...a-LiPo-battery

There is all the background info in those two threads, which I assume you are aware of. The "Lipotool" calculator is incorporated in the meter but it is based on assuming that the max safe INITIAL heat dissipation within a lipocell is 6W/Ah/Cell at a starting temperature of 22*C
As the discharge proceeds the cell temperature rises which reduces the IR and the heat dissipation within the cell.
Inevitably the temperature coefficient of the IR varies in different lipos so that the forecast max safe continuous current, ie "C" value must be a"Rule of thumb"

I found in comparing forecast "C" ratings with real continuous constant current testing that the correlation was surprisingly close if a little conservative.
This was over much testing of many different makes and sizes of lipos, from 100mAh up to and above 5000mAh.

The largest error I have seen is on the Turnigy 65C Graphene Lipos where my meter read 32 - 33C as yours has, whereas real full discharge testing showed my sample was capable of 45C, even 50C at a stretch but that difference is exceptional, all other testing I have done suggests the forecast "C" to be accurate or a little conservative providing care is taken with temperature control.

Most readers of RCG Batt & Chargers must be aware of the fiction of C ratings but many users still find it difficult not to believe a specification printed on an item they are buying.

Wayne
Sep 15, 2017, 06:28 PM
Registered User
This is a tricky business to get into. IR and computing C rating from it is very temperature sensitive. Unless you can do your testing under very controlled conditions you are asking for trouble. To do good testing you need to be able to prove that your equipment and test methods are accurate. I would not touch this with a 10 foot pole.
Sep 15, 2017, 06:40 PM
Space Coast USA
hoppy's Avatar
[QUOTE]
A question Doug.......What is your interpretation of what 20C means?

Back in 2007 we were debating that.

A post from RC-Tester ( https://www.rcgroups.com/forums/show...ie&perpage=100 )

Quote:
Quote:
Originally Posted by Magrat
Lipo rating has no compliance standard I can find and no defined methodology for arriving at a rating. Seems you can stick whatever rating you like on it.
Absolutely true, lets see how many interpretations of '20C' we can come up with:
It will discharge at 20C without causing a fire
At 20C discharge it will not dip below 3.0V (or an arbitrarily chosen voltage)
It will survive XX cycles at 20C discharge
The mean discharge voltage will be >= 3.4V at 20C discharge
It will deliver >80% of capacity at 20C discharge
It can be discharged at 20C, but might be useless afterwards
It will remain below 140F at 20C discharge

We all agree the manufactures interpretation is an unknown. Has an interpretation of the method you are using been described? Sorry. I haven't kept up with that IR thread to know much about the details of how the rating is derived. I assume temperatures and other factors have been considered.
Sep 15, 2017, 06:50 PM
working on https://lipo.lol
d0uglas's Avatar
My inner lawyer is advising me to wait a bit to let someone else, ideally from that 2007 thread, take a good stab at that with a new debate ensuing, while I go back and read that thread.

Perhaps I should ask each vendor for their own interpretation of a 20C rating.
Latest blog entry: telemetry: worth the weight?
Sep 15, 2017, 06:54 PM
Registered User
I'm curious to see what you measure on old-school, low dollar, 20c batteries that we all used successfully for years.
Sep 15, 2017, 06:59 PM
working on https://lipo.lol
d0uglas's Avatar
Quote:
Originally Posted by Yoda466
I'm curious to see what you measure on old-school, low dollar, 20c batteries that we all used successfully for years.
I would love to offer a battery testing service for new and really old batteries. I think the public service and the data is worth my covering the return shipping.
Latest blog entry: telemetry: worth the weight?
Sep 15, 2017, 07:15 PM
working on https://lipo.lol
d0uglas's Avatar
Quote:
Originally Posted by Volt_Ampere
I would not touch this with a 10 foot pole.
Well I discovered with a python or bash script that the domain lipo.lol wasn't taken, grabbed it on an impulse buy, sat on it for a year wondering "Now what is most 'lol' about lipos?" and the answer, competing with a stack of youtube lipo fire videos, is C ratings.

But yes this is risky business which is why I am making an earnest effort to follow a procedure using equipment that all passes muster in general as best as I am able. And further to that end beyond what I already came up with is asking here and elsewhere for advice. Yours is that this is way too risky - noted. I'll act accordingly, short of ditching it tonight.
Latest blog entry: telemetry: worth the weight?
Sep 15, 2017, 09:40 PM
Space Coast USA
hoppy's Avatar
A long time ago Hyperion stated that their packs would less than 50 cycles when discharged at the rated continuous duty C-rate. Pretty safe recommendation......you might get 50 cycles or 5 cycles.

Haven't seen any other ratings with a qualifier for what the operation at the MCD rate means in terms of battery life.
Last edited by hoppy; Sep 15, 2017 at 11:02 PM.
Sep 16, 2017, 07:26 AM
Registered User
Hoppy,

I agree that some criteria must be defined if a sensible comparison is to be made between the claimed performance and the practical performance, but also between different makes so that even if they don't meet specification at least we can see by how much.
Can I comment on your list:-

Absolutely true, lets see how many interpretations of '20C' we can come up with:

1) It will discharge at 20C without causing a fire - This must be a given, not used as a measurement.
2) At 20C discharge it will not dip below 3.0V (or an arbitrarily chosen voltage) - I use 3.50V as a criteria at 50% discharged.
3) It will survive XX cycles at 20C discharge - This would be nice to know but not practical to measure without equipment + unlimited time.
4) The mean discharge voltage will be >= 3.4V at 20C discharge - Difficult to measure - use (2)
5) It will deliver >80% of capacity at 20C discharge- 80% is too low - see below, but not sure it relates directly to C value
6) It can be discharged at 20C, but might be useless afterwards - Again a given that it must survive without significant damage.
7) It will remain below 140F at 20C discharge - Temperature is very much one of my criteria.


The user reasonably expects that the claimed "C" rating means that he can take that specified current continuously over a full discharge, that is the maker's claim.

When I was discharge testing, I always ran several tests on a lipo pack starting at 5C and increasing the current in 5C steps up to the level where the packs showed obvious signs of overstress. At this point I stop testing and conclude that the previous test was the max "C" limit.
The criteria I use are:-

(1) Temperature rise on pack surface, starting from 25*C not to exceed 60*C ( You could argue that is too generous)
(2) Cell voltage at 50% discharge should be >3.50V/cell
(3) The discharge plot must show a steady negative slope ie no voltage sag and recovery which I believe damages the cell - see attachment. The upper red plot is a normal discharge. The lower one shows sag and recovery; obviously overstressed.

As I always measured the IR values when testing and was aware that heating was a function of current squared and IR, then I looked for a correlation and the "Lipotool" was developed from that, in conjunction with Mark Forsyth and John Julian, and showed such good forecasting of real "C" values that we decided it was worth posting.

Although I don't think that capacity delivered is directly involved in deciding on real "C" rating, I have found that good lipos deliver 95-100% of claimed capacity when discharged to 3.0V and even poor packs will deliver 90 - 95%.

Wayne
Last edited by Wayne Giles; Sep 16, 2017 at 07:56 AM. Reason: Error in last statement
Sep 16, 2017, 07:46 AM
Registered User
Quote:
Originally Posted by Yoda466
I'm curious to see what you measure on old-school, low dollar, 20c batteries that we all used successfully for years.
Most 20C lipos will deliver 20C, as the claims rise, the % truth decreases, so don't just halve the maker's claim as some people do.

Here is a plot of a Haiyin 20C rated pack and a plot of a GensAce 55C rated pack both being discharged at 25C. You can see that they are virtually identical.
For information the GensAce is the red plot and the Haiyin is the blue plot.

Wayne
Sep 16, 2017, 08:22 AM
Registered User
Excellent info. Thanks Wayne.


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