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Old 11-19-2008, 02:19 PM   #1
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Default False Lipo advertising

I would like to let everyone know that they need to be careful when buying Lipos as it seems like the trend with Lipos is to inflate the capacity or the C rate and in some cases both.

I've been testing Lipos for awhile now and in some of my initial tests we got packs that claimed they were 25C and when we sent them out for C rate testing they were only 15C at best. That was over 2 years ago. Now that Lipos have become the power of choice and most of the Lipo manufacturers come out of China it's very easy for companies to purchase and sell Lipos.

As testing C rate requires expensive equipment the Lipo manufacturers and resellers know this so they can claim any C rate as they know it's very hard to test. So some rely on this to claim higher C rates which keeps the cost down so they make higher profit margins and it makes there pack more marketable.

SMC was the first to release a true 28C pack and the reason why we called it 28C is because that is what it truly is. Our supplier which we feel makes the best performing Lipos with true C rate has told us that true 35C packs are fairly hard to do and the technology wasn't possible until recently. I also asked him how some can claim 5200 with 35C in the ROAR case size which limits the cell size and he told me it was impossible to make a pack with true 35C with 5200 in that case size. This lead me to buy one of these 5200/35C packs so I could test it.

Here are the results with the following set up on my GFX: 2C charge with a 35 amp discharge down to 6 volts. Voltage sensing leads attached straight to the power leads.

5200/35C: 517seconds (5025mAH) , 7.33 average voltage and 7.5 IR.

This pack was sent to a lab to get tested for C rate and at 25C discharge it only held 80% of it's capacity. Our packs are rated at 90% at full C rate discharge. So this pack which is suppose to be 35C would most likely be closer to 20C based on our testing method of 90% capacity retention.

Here are results from one of our 5200/24C packs to show what I'm talking about.

SMC5200/24C: 540(5250) - 7.38 - 6.3

This is a true 24C pack which will retain 90% of its capacity under full C rate discharge.

The reason why I started this thread is to let the consumers know that they need to be careful when buying Lipos as it's very easy to be mislead and be taken advantage of. The 5200/35C pack is being sold for 119.95 from an online shop and our 5200/24C pack is being sold for 74.95 from that same online shop.

I know as a consumer I expect to get what I paid for so I hope this thread will help racers better understand how some companies are trying to take advantage of them.
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Old 11-19-2008, 02:24 PM   #2
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Old 11-19-2008, 02:26 PM   #3
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Damn Danny, You just messed up my plans to buy batts by the bulk and resell them... I had the 5200mah/45c stickers all printed up....lol

Thanks for the heads up.....
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Old 11-19-2008, 02:28 PM   #4
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Old 11-19-2008, 02:28 PM   #5
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How interseting this thread pops up..... and I'm so glad to read it!!!

ROAR is currently working on and will be implementing a system that would clearly evaluate C rating in submitted batteries to force truth in labeling of ROAR approved products....

also, ROAR will be working on truth in the future of labeled products.. meaning, verifying things don't change after the approval is posted.

Thank you Danny for writing this thread! I'm glad your the first to be on board with ROAR's upcoming policy.

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Old 11-19-2008, 02:30 PM   #6
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Danny - just so we are all on the same page, may I ask what you specifically define as C Rating and the parameters being used to test your packs?
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Old 11-19-2008, 02:33 PM   #7
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Danny....can you let us know what formula you were using by calculating the "C" rating..? I know very little about this thing but keep reading brands keep getting the C rating higher and higher (from 20 to now 35C)...how does that work? Thanks.........
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Old 11-19-2008, 02:41 PM   #8
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Quote:
Originally Posted by Dawn Sanchez View Post
Danny - just so we are all on the same page, may I ask what you specifically define as C Rating and the parameters being used to test your packs?
I will get the exact teting procedure hopefully later tonight as I need to get our supplier to give me all the details. I pretty sure I know how they do it but I want to make sure I say it correctly.
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Old 11-19-2008, 02:44 PM   #9
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Danny....can you let us know what formula you were using by calculating the "C" rating..? I know very little about this thing but keep reading brands keep getting the C rating higher and higher (from 20 to now 35C)...how does that work? Thanks.........
There is no formula for getting C rate. Typically it's the ability of the pack to retain it's capacity under the maximum C rate. Some manufacturers use 80% but typically the manufacturers who do high end cells will use 90%. This means if the capacity is 1000 at 1C discharge it needs to 900 at 35C.
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Old 11-19-2008, 03:06 PM   #10
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Originally Posted by Danny/SMC View Post
There is no formula for getting C rate. Typically it's the ability of the pack to retain it's capacity under the maximum C rate. Some manufacturers use 80% but typically the manufacturers who do high end cells will use 90%. This means if the capacity is 1000 at 1C discharge it needs to 900 at 35C.
The ratio of c rating to amperage discharge is what again?

Is the C rating supposed to be an exact value of amperage a pack can discharge at? I thought you calculated the max amp draw the pack was capable of by multiplying the C rating times the amperage capacity the pack was capable of holding.
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Old 11-19-2008, 03:15 PM   #11
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There is no formula for getting C rate. Typically it's the ability of the pack to retain it's capacity under the maximum C rate. Some manufacturers use 80% but typically the manufacturers who do high end cells will use 90%. This means if the capacity is 1000 at 1C discharge it needs to 900 at 35C.
So Danny, if you’re saying there’s no formula for getting C rating, then everyone’s packs (including yours) are just making up the numbers, or taking what the factories tell them and using it? Please don't get me wrong, I am just trying to understand HOW to explain to others if someone asked the same question like I did....thanks
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Old 11-19-2008, 03:16 PM   #12
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Danny,

How about instead of worrying about a standardized C rating, why don't you take the lead here and rate your LiPOs on average voltage and internal resistance, numbers that are actually meaningful to us?

I never cared how much amperage I could dump my Nicad or NIMH cells at, and I don't much care how much amoerage I can dump my LiPOs at, but if the manufacturers would lable them with runtime, average voltage and internal resistance, I could comparison shop with some useful data...

Thanks
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Old 11-19-2008, 03:22 PM   #13
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So Danny, if you’re saying there’s no formula for getting C rating, then everyone’s packs (including yours) are just making up the numbers, or taking what the factories tell them and using it? Please don't get me wrong, I am just trying to understand HOW to explain to others if someone asked the same question like I did....thanks
I think by formula what you guys want to know is the constant amp rate is it's C rate times capacity to figure out the amp constant amp draw. So 1000/35C pack would be able to pull a constant 35 amps while remaining at 90% of it's rated capacity.

Lipo manufacturers test there cells to determine the C rate. The way this is down is to discharge a cell at different C rates while increasing the rate. Once the cell reaches 90% of its capacity that is considered the C rate. Some manufacturers will use 80% but the high end manufacturers use 90%.

For mAH it should be rated at 1C but we see some manufacturers use .5C but as long as they mention it there is nothing wrong with this.
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Old 11-19-2008, 03:23 PM   #14
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Danny,

How about instead of worrying about a standardized C rating, why don't you take the lead here and rate your LiPOs on average voltage and internal resistance, numbers that are actually meaningful to us?

I never cared how much amperage I could dump my Nicad or NIMH cells at, and I don't much care how much amoerage I can dump my LiPOs at, but if the manufacturers would lable them with runtime, average voltage and internal resistance, I could comparison shop with some useful data...

Thanks
I totally agree, average voltage, runtime and IR seem to be what matters to most racers.
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Old 11-19-2008, 03:26 PM   #15
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Average Peak wattage would be a more simple number to look at

like 1000W @ 135A

The test should be the average continous wattage for at least 60 seconds

you can't fake work not being done, At some point less power is outputted becuase the increased load will severly drop the voltage.

Watts = Work Done = V x A

So if you were comparing several 5000 MaH packs, DUH most wattage wins. But if you were different capacities, C ratings just confuses things. The Average Peak wattage would help keep the all the labels in perspective at first glance. The IR, Runtime, and AV should also be on the label for side-by-side comparison should the wattage be equal.
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