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Discussion Starter · #1 · (Edited)
This thread is to show my testing on various packs available on the market to show how similar most packs are as far as Internal Resistance which is directly related to the C rate of the cells/pack.

In my testing I noticed that performance data is only one part of the story when it comes to testing packs. It seems that packs from different factories have there own way of evolving over the cycle life of the pack. I attribute this differences to the raw materials used and how the cells are built.

I hope this thread will be used as an educational thread to help consumers better understand that a pack from factory A is different than a pack from factory B.

My testing consists of testing the cells IR using the ESR meter to see what kind of performance and C rate the pack has to offer.

I then do cycle life testing which consists of doing back to back cycling on a GFX using a 12 amp charge and 35 amp discharge with a 10 minute break in between cycles. I graph the results of cycle 1 , 25 and 50. If a pack does o.k. after cycle 25 I will go up to 50. In some cases I have to stop after the 25th cycle as the pack drops to much mAh.

My cycle life testing method is most likely harsher than what can happen in real world use but since I treat every pack the same this test is showing the difference between various packs.

I've decided not to reveal the names of the companies who sell the packs I'm testing as my goal is not to attack my competitors but to educate the consumer.

Hope this thread will help everyone better understand more about LiPo packs.
 

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Discussion Starter · #2 ·
SMC Premium Cetified 6500/25C/2S

This is the testing results of the sample pack of our new 6500/2S/25C Premium Certified packs. This sample pack is a wired version pack so the IR readings on the ESR meter are approximately 0.40mOhms lower than a inboard version pack and 0.02 higher average voltage at 35 amp discharge. I will do a test on the inboard pack once we get our first shipment.

Cycle 1

ESR IR - Cell 1: 1.80mOhms Cell 2: 1.68mOhms

GFX 35amp discharge data: 6600mAh - 7.49avg V - 3.5 IR

Cycle 50

ESR IR - Cell 1: 1.72mOhms Cell 2: 1.64mOhms

GFX 35amp discharge data: 6551mAh - 7.49avg V - 3.5 IR


The percentage of mAh drop from cycle 1 to cycle 50 is 0.8%
 

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Discussion Starter · #3 ·
6500/90C/2S Inboard

Here are the test results of a 6500/90C/2S pack that I purchased online for 124.95.


Cycle 1

ESR IR - Cell 1: 2.32mOhms Cell 2: 2.48mOhms

GFX 35amp discharge data: 6064mAh - 7.42avg V - 5.2 IR

Cycle 25

ESR IR - Cell 1: 2.92mOhms Cell 2: 2.60mOhms

GFX 35amp discharge data: 5046mAh - 7.43avg V - 5.9 IR


The percentage of mAh drop from cycle 1 to cycle 25 is 16.8%

Comments:

This pack clearly shows why I want to reveal my testing data. Not only is this pack 600mAh off of it's rating but is the worse pack I have seen so far under the cycle life test. You can see how this affects the voltage curve after only 25 cycles.

Since I know that our Premium Certified 6500/25C uses true 25C cells this so called 90C pack which has a bit higher IR means it's a 25C at best using my C rate testing standard.

The fact that the C rate is nowhere near 90C isn't really the major issue with this pack. The bad very bad results under cycle life testing is what I believe is the major issue. I know the factory that does these packs and when I tested there packs a year ago I noticed this fast drop in mAh. They seem to be using some different materials to try and get the IR to be good but at the expense of cycle life. This factories pricing is also on the low side.
 

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Discussion Starter · #4 ·
6500-65c-2s

Here are the results of a 6500-65C-2S Inboard pack I paid 99.95

Cycle 1

ESR IR - Cell 1: 2.0mOhms Cell 2: 2.04mOhms

GFX 35amp discharge data: 6376mAh - 7.46avg V - 4.3 IR

Cycle 50

ESR IR - Cell 1: 1.96mOhms Cell 2: 2.04mOhms

GFX 35amp discharge data: 6328mAh - 7.46avg V - 4.2 IR


The percentage of mAh drop from cycle 1 to cycle 50 is 0.8%

Comments:

This pack is reacting like our packs so I suspect that the cells come from the same factory we use. This pack is rated as a 6500 and only cycles out at 6300+ which I think is normal fluctuation within a batch of cells. I think anything +/- 5% is normal. The LiPo factpries use 0.5C down to 2.75V per cell to come up with there mAh rating. I personally use 35 amps down to 3v per cell.
 

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Discussion Starter · #5 ·
I will post more results as they become available. Currently doing cycle life testing on a 6600-65C-2S inboard pack then it will be a 5300-65C-2S inboard pack.

So far the 3 packs above are showing what I want everyone to know about. The most expensive pack is the worst pack but has the best specs on the labels.
 

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Discussion Starter · #8 ·
SMC 3800-30C-2S inboard

When I tested the 6500-25C-2S sample pack I was pretty amazed at the low percentage of mAh drop over 50 cycles. I asked the factory to send me a lower mAh pack so I can test it and see if the reason why the 6500 did so go was due to it being a 6500.

Here are the results of a 3800-30C-2S pack from the factory that makes all our packs.

Cycle 1

ESR IR - Cell 1: 2.68mOhms Cell 2: 3.00mOhms

GFX 35amp discharge data: 3995mAh - 7.40avg V - 6.0 IR

Cycle 50

ESR IR - Cell 1: 2.60mOhms Cell 2: 2.92mOhms

GFX 35amp discharge data: 3956mAh - 7.40avg V - 5.7 IR


The percentage of mAh drop from cycle 1 to cycle 50 is 1.0%

Comments:


Based on this test it seems that when packs come from the same factory they seem to react the same regardless of the mAh.
 

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Information is invaluable

Danny, I cannot thank you enough for what you're doing here. This is an area that is far overdue. The continued climbing claims of some battery resellers is ridiculous and your information helps to educate the buying public of how numbers are deceptive.

I'm looking forward to more results from your laborious testing.

Thanks for what you do for us.

--Shags
 

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Discussion Starter · #10 ·
Thanks for the support and I hope allot of people can see my threads on this site and learn from them. I had a good concept of Lipos but I must admit my recent intensive testing has really thought me allot and building my own C rate tester has been a real eye opener.

Will have results on another pack tomorrow.
 

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What is the point of only testing batteries "harsher" than how they would be used in real world applications? How many un-named battery tests before we see a post that SMC batteries perform better under "harsher" testing?

If you are truly interested in educating consumers, please test using different charge/discharge rates that closely match how batteries are being used in the real world. At least see if lower charge/discharge rates have similiar results to the "harsher" rates.

Is it possible that cheap no-name lipo batteries from "bad" factories perform virtually the same as name-brand exclusive race lipo batteries from the "good" factory (that I'm sure SMC uses) under real world conditions? I'm not suggesting that this is the case, but since that is not what is being tested how do we know?


If I'm racing in a class where the motor pulls a lot less than 35 amps and uses 1500mah or less in a heat/main race, why do I care how a battery performs under "harsh" conditions discharged to a rate it would never go down to during a race. I only care how my battery performs in the range I'm using while on the track.

-----------

I think I'm going to rent various full-sized vehicles and test the full mileage when going 100mph. I'll make sure to post my results. I'm sure the data will prove useful to all the soccer moms and daily commuters.
 

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If I'm racing in a class where the motor pulls a lot less than 35 amps and uses 1500mah or less in a heat/main race, why do I care how a battery performs under "harsh" conditions discharged to a rate it would never go down to during a race. I only care how my battery performs in the range I'm using while on the track.
If you are in a traction limited condition (like loose dirt), maybe you don't care. But for carpet and clay it is easy to be running a continuous discharge of 35 amps. I know for a fact my 1/8 scale late model draws an average of 35 amps over a 5 minute run and that is on loose dirt. I had a friend who dumped a 6600 mAHr lipo in a 10 minute run in a 4WD SCT - that was over 35 amps average.

You care because when a pack loses capacity over its cycle life, you end up with lower voltage at any given point on the discharge capacity curve. Even if you are only using 1500 mAHr you will have lower voltage at every instant of your run with a pack that has lost total capacity. So unless you are traction limited, it is good to know which packs maintain capacity, and thus, voltage. Another "unless": Unless you buy new packs every 2-3 races.
 

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The issue that Danny has raised is the issue of standards (lack of in this case). The NIMH world we used to live in wasn't perfect but most of the industry suppliers had a standard that in most cases could be replicated by the consumer. Get a CE matched pack, run a cycle on your our CE Turbo or GFX and get comparable numbers.

The issue we have today is that there is no comparable rating system for lipo. Sure some won't care and in the strength of advertising will sell units despite what a standard rates their packs.

Why is it important?

1- Consumers should be educated or have tools to become educated - so they can make the best purchase decision whether they are hobbyist and need something 'just enough' or for 'maximum performance'. Today - their are claims that can't be justified. That equals in little protection for the consumer.

2- Unlike our sub-c days - there is too much unregulated product in the market. Sure it is great that there is choice but anyone can order in quantity LIPO packs, slap a label on the case and fool a consumer to believe that what they have is a quality product. True rating won't solve the influx of bad product but it will provide a measurable and repeatable filter on what is available. The established companies that have been matching/selling batteries have a brand and revenue to protect and can't afford to push bad product.

Competitive R/C has always paid premium for better performance. Somewhere between making the jump from NIMH to LIPO we lost a standard that helped not on differentiate product and also made selection easier. Today we purchase product blind - this is a good first step in ensuring what you pay for is what you get.
 

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Discussion Starter · #14 ·
IndyRC Racer: There are three reasons why I don't test at so called real world amp draw. The first one is I need a test that will not take 6 months to do per pack. I designed this test to better understand what packs/cells do from different factories as I want to release some lower priced packs but don't want to release packs that will drop off quickly. Two there are many types of racing so how would I determine what type of racing I want to test for and the the third to do what you think is best I would need to use variable discharge as this is what happens in real pack use.

Bottom line is I'm using my testing method that will show me how different packs react under the same controlled testing conditions. In the end I decided to share my info to help people better understand. Yes SMC packs hold up the best using this method but I have always known our packs were built using the best materials as we pay 9 dollars more per pack on a model with the same specs. There has to be a reason for the difference in price and this is what I set out to find.

If anyone ever wants to test packs the way I do feel free to contact me and I will explain my testing methods in detail and if someone want to do real world testing and post results that would be very good as well. I'm spending allot of money and time to do these tests and as far as I know it no one else has ever done this or if they have no one is posting the info. The so called independent sites who have been testing packs and posting results don't even consider cycle life testing.
 

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I personally believe the testing Danny is doing is accurate and as unbiased as humanly possible. Anyone saying differently should spend the money for test equipment and give it a try themselves. As Danny noted he is more than willing to share the testing requirements and procedures so that anyone can duplicate the testing and self-verify as to the accuracy of his work. He put this out for everyone to see and read. How much more open and honest can the man be?

Over the past 5 years I have tested thousands of RC battery packs using data logging and digitally controlled discharge rates in a controlled environment and this includes thousands of dollars worth of LiPo packs and cells. The results were a true eye opener to say the least. Approximately 2-1/2 years ago some of my work was posted as graphs, which showed a small but accurate part of the testing and while many people welcomed my testing, many were skeptical to the point of making irrational, mean personal attacks. I even received e-mails from the CEO of one of the larger RC battery companies in which he threatened legal action because he did not like seeing the truth about his packs going public.

I have also tested many, MANY packs for cycle life and long term performance such as Danny is doing now and I saw results very similar to his. I have spoken with Danny more than once about the lack of Lipo industry standards and I suggested that he, SMC as an RC industry leader, set standards for the industry to use going forward. He is spending incredible amounts of money and time which will benefit all of us. Rather than anyone criticizing his work, we should all be applauding it. Thank you Danny!!!!

Tom Himes
Engineering Manager
Spec Point Concepts
 

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First off, thanks Danny for responding to my post.

I guess what I would ideally like to see is someone teach the consumers how to test their own batteries using equipment that they already possess. At the level I participate in R/C, I have no desire (or budget) to purchase a Turbo 35GFX. For that matter, I don't have much of a budget to purchase new batteries.

Since there is no industry standard to rate Lipo batteries, maybe a company (SMC?) could develop inexpensive equipment that could do just that. If that isn't practical, why not develop a smart device app (Android/iOS) that people could use to monitor or track their own battery's performance (depending on the type of discharge device at their disposal).

In closing, I will always be a skeptic. But that doesn't mean that I don't mind being proven wrong. As long a there are people out there that are willing to test products and share their results, consumers will be better off for it.
 

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Discussion Starter · #17 ·
6600-65C-2S Inboard

Here are the test results of a 6600-65C-2S inboard pack I paid 47.00 dollars.

Cycle 1


ESR IR - Cell 1: 2.52mOhms Cell 2: 2.68mOhms

GFX 35amp discharge data: 6833mAh - 7.35avg V - 5.8 IR

Cycle 50

ESR IR - Cell 1: 2.52mOhms Cell 2: 2.64mOhms

GFX 35amp discharge data: 6726mAh - 7.37avg V - 5.3 IR


The percentage of mAh drop from cycle 1 to cycle 50 is 1.6%

Comments:

Seems like this packs initial voltage picked up some over the cycle life so it offset the mAh drop. Based on the IR and voltage curve I would assume the C rate using my standard to be 15 to 20C.
 

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Discussion Starter · #18 ·
IndyRC Racer: It's very hard to have a way for the regular racer/consumer to test his packs since no one has the same equipment. I do understand buying a GFX for most makes no sense.

The ESR meter is a great tool at a reasonable price. I would recommend a few guys get together and share the costs of this meter and then you can rate your packs.

If you have a charger that has discharge capabilities set it to discharge your pack down to 3v per cell. Let the pack cool down and then do a full charge on the pack and register the mAh. Once in awhile repeat this step and see how much mAh the pack will accept from discharge to full charge. This will show you if your pack is losing mAh. This isn't as accurate as doing it under discharge but can still give you good results. Make sure to control the temperature of the test as if the temp is warmer the pack will take a charge easier as the IR will be lower.

In the end I have always enjoyed sharing my knowledge. My goal has always been to sell the best possible packs and in the sub-c days there was allot less BS and it was easy for customers to make a good decision as to what packs to buy.
 

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Discussion Starter · #19 · (Edited)
5300-25c-2s

Here are the test results of a 5300-25C-2S pack I paid 40.00 dollars.

Cycle 1


ESR IR - Cell 1: 1.48mOhms Cell 2: 1.40mOhms

GFX 35amp discharge data: 5608mAh - 7.48avg V - 3.7 IR

Cycle 50

ESR IR - Cell 1: 1.72mOhms Cell 2: 1.56mOhms

GFX 35amp discharge data: 5493mAh - 7.46avg V - 4.0 IR


The percentage of mAh drop from cycle 1 to cycle 50 is 2.1%

Comments:

This pack is a wired version pack and to get the data to be as accurate as possible I tap into the voltage sensing leads to get the voltage and IR measurements. This means the IR will be 0.40mOhms lower and the average voltage will be 0.02 higher than if the pack would be inboard style.
 

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Danny the work you are doing is fantastic thank you.

I understand what you are doing but I don’t feel like I am much more educated in buying LIPOs, all I get from your testing is that expensive batteries are possibly no better than cheap batteries.

Have you found any common occurrences between batteries that do perform well and batteries that dont? eg. the weight of the battery etc

I would love to know the brands that you have tested, I understand that you wont release them but I think it would be good if you did.
 
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