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Old 10-04-2009, 03:40 PM   #31
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Danny was quick to replace every cell that had a problem that I have heard of. And if you go to the SMC thread, he mentions the swelling lipo's more then once.
NOOOOOOOO

SMC WAS OFF THE RADAR DURING 4200 OR 4800 CELLS failures funny you didn't defend their bashin' of other company
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Old 10-04-2009, 03:52 PM   #32
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I have a c-rating related question, I was running a 20c 2s 3200 orion with a high kv system and it swelled, was I asking too much of this battery? It was geared properly for the track and the temps for the motor and esc were reasonable...
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Old 10-04-2009, 04:03 PM   #33
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Yes. We keep records as to C rating adverstised on the label and what is actually found in the evaluations... although, since we have no rules for and no method to monitor and no right to enforce what people put on labels, we keep that information to ourselves.

I am very aware of which packs are true or truest to their labels.

I very unprofessional post. What does your post accomplish?

Your post would have been fine without the last sentence.
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Old 10-04-2009, 04:06 PM   #34
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Yes. We keep records as to C rating adverstised on the label and what is actually found in the evaluations... although, since we have no rules for and no method to monitor and no right to enforce what people put on labels, we keep that information to ourselves.

I am very aware of which packs are true or truest to their labels.
They why test them at all?

Why not publish what you found and exactly how you tested them, then let the manufactures defend their position and they can explain how they came to their own results.

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Old 10-04-2009, 04:12 PM   #35
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NOOOOOOOO

SMC WAS OFF THE RADAR DURING 4200 OR 4800 CELLS failures funny you didn't defend their bashin' of other company
As I stated, every cell issue on an SMC pack that I've seen was dealt with well.

As for them "bashin" the other battery manufacturers, some statements saying why and how your product is better is just aggressive marketing.

Now let's get back on topic.

Unless you're racing in the top 10% of the event you're competing in, C ratings mean so little as long as they're above 35C. It would also make more difference if you were running Mod, and even then only maybe 7-8 guys in Canada/USA would notice a difference from a 40C pack to a 50C pack. (All IMO)

The bulk of the racing that's done in the USA and Canada is 13.5, and those motors can't pull the amount of amps needed to see a power difference between a 40C and 50C pack.
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Old 10-04-2009, 06:00 PM   #36
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I can't remember where it was, maybe bigsquid, but they did a test and the results actually suprised me. A great deal of the 20c packs were better then some of the "reputable" 40 c packs. I'll see if I can find that link and post.
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Old 10-04-2009, 07:06 PM   #37
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What's with all the ROAR bashing?

The purpose of the ROAR tests was never to rate Lipos.

We check for proper hard case and then check to see if they fit within the allowed dimensions. We then perform safety tests consisting of an overcharge test, a short circuit test, and a drop test. We also test for capacity as a reference. It was never meant to be more than that.

The short circuit test gives us some insight to the packs discharge capabilities. It consists of a bank of resistor totaling 0.1 Ohm. With a 2S pack, this is approximately a 68-70 amp discharge. With a 4S pack, this is nearly 140 amps. It's not a true constant current test since the current decreases as the battery goes down the discharge curve. It is troubling when some packs turn into steaming melting piles after this short circuit test contrary to what the label claims they can handle (for reference a 3200 20C discharge limit is right about the ROAR Short circuit test, anything over 3200 should be well above the ROAR SS test). ROAR only requires that the pack doesn't go into thermal runaway during this simulated short circuit - the pack is not required to survive unscathed. However, ROAR is required to say the pack "passed", We can't say the pack "passed" but it sucked in the process.

We've discussed doing C rating tests at ROAR, but quite honestly, that would turn into a full time job and I refuse to do it. Doing a proper C rate test would be an iterative process to charge/discharge the pack and increase the discharge rate after every cycle. Doing it properly could take 20 or so cycles. I don't have the time to do that with the number of submissions that I get.
In addition, I do not have the equipement to discharge a 2S pack at 250 amps, let alone a 4S pack at 250 amps.

Keep in mind that even at a measly 70 amps, 12 guage wire runs almost too hot to touch and I get a lot of connectors (usually the fake deans type or badly designed bullet connectors) melting off. I don't think any connector can do 200+ amps.

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Old 10-04-2009, 07:48 PM   #38
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Come on you guys its a marketing issue. Think about do you think a company is going to print a different lable for each pack they produce? Yes its sensable but not plausable. If they were to print a lable for each pack it would raise their cost of production and for them to discount every pack that didn't test to lets say test 40c they would have to raise the price of the pack that actually tested at a 40c. So would you rather pay 180.00 bucks for a pack that that tested 40c or 130.00 for a pack that you hope is a 40c? This is where customer service of the manufacture comes in. Hope that there is good customer service for the consumers sake. If you have a issue with a product contact them and I am sure something can be worked out. This is not a ROAR issue. All they do is approve the batteries we use to race to make sure that they are safe and no real advantage over the other competition. my 2 cents.
You mean like they did for 20 years with NIMH and Nicad cells? Ya, I guess your right it would be way to expensive and difficult to do!
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Old 10-07-2009, 01:28 PM   #39
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MaxAmps.... Seriously Now.... They may make a quality pack but they would not be where I turn first. SMC or Thunder Power will be my first picks at buying what is actually printed on the pack.
smc lmao they are one of the biggest numbers gamers out there. like there new 50c single cell


And FYI Fantom is not a battery company. they are a sticker company always have been. they buy cells from suppliers (smc in the past, now thunder power) and sticker it
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Old 10-07-2009, 01:53 PM   #40
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I agree that roar should not post their results, it is not for a sanctioning organization to rate manufactures. But I have 1 issue with this. I would think that if the c rating does not match the marketing or labeling, does this not cause a potential safety issue? that would bother me that ROAR finds a battery that does not meet the specs they advertise. then a user trys to run the pack at that high level and then poof.
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Old 10-07-2009, 03:27 PM   #41
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linger,

I do not understand why a proper C-rating requires 20 charge/discharge cycles, and why does the discharge rate need to increase with more cycles?

A few years ago you could buy matched NiMH cells. The cells sold by reputable companies were charged up, then discharged at a constant 30-ampere using a current regulator. The cutoff was set at 0.9 volts and the time of discharge was used to calculate a C-rating. I doubt if this was done more than a few times, otherwise the testing would use up cycles prior to selling the matched cells.

Am I missing something in LiPO testing? Why would it take 20 cycles at increasing rates of discharge?
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Old 10-07-2009, 03:44 PM   #42
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the internal resistance of each cell gets better during the initial break in cycles. 10-20 cycles seems to be the number being reported.

When i get new packs I use a p-touch to tape the IR on each pack and measure them during the course of it's life.
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Old 10-07-2009, 03:47 PM   #43
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I would think that if the c rating does not match the marketing or labeling, does this not cause a potential safety issue?
good question,
It would pose an issue, assuming that racers have an application that actually utilizes the cells marketed specs. For example, look at the many 5000 40C packs out there. There is not a single racing class that can remotely pull 200 amps continuously. My opinion is that it would be a waste of time to verify if the pack can sustain 200 amps if there is no application to match. By definition, a pack discharged at 40C would dump it's entire contents in 1.5 minutes.

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linger,

I do not understand why a proper C-rating requires 20 charge/discharge cycles, and why does the discharge rate need to increase with more cycles?

A few years ago you could buy matched NiMH cells. The cells sold by reputable companies were charged up, then discharged at a constant 30-ampere using a current regulator. The cutoff was set at 0.9 volts and the time of discharge was used to calculate a C-rating. I doubt if this was done more than a few times, otherwise the testing would use up cycles prior to selling the matched cells.

Am I missing something in LiPO testing? Why would it take 20 cycles at increasing rates of discharge?
Sorry, I didn't elaborate. I was referring to the method of testing a cell with the intent of determining the discharge C-rate. You start with a low enough C rate discharge that you know the cell will pass, and then you keep ramping up from there until the cell fails (usually temp, voltage cutoff or capacity). For example, you would start somewhere around 10C and go up in 2C increments. You gotta start low. There are "20C" labeled cells that can't handle 15C.

"time of discharge was used to calculate a C-rating" - no I think you are confusing C-rating with capacity, which ROAR does record for every pack that it tests.
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Old 10-07-2009, 04:21 PM   #44
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good question,
It would pose an issue, assuming that racers have an application that actually utilizes the cells marketed specs. For example, look at the many 5000 40C packs out there. There is not a single racing class that can remotely pull 200 amps continuously. My opinion is that it would be a waste of time to verify if the pack can sustain 200 amps if there is no application to match. By definition, a pack discharged at 40C would dump it's entire contents in 1.5 minutes.

I would agree, but there are lower c rated pack and lower capacity rated cells. I have even heard of racers running the lower cap packs and lower C rated packs to get the heat up. At this point the racer would be runnning at the packs limits. so there is an instance where roar aproaval would be questionable in terms of safety. especially if the pack did not discharge at the spec'd C rating. I would think aproaval should be based on class the cells would be run in. I hate to add more complexity to rules for batts, but safety is safety and remember ROAR is a sanctioning body and safety is one of the issues that ROAR should be "watching out for us".

I think if it is not considered, you may see your insurance coverage under ROAR may increase in cost as these cells start being used to their MAX.
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Old 10-07-2009, 04:31 PM   #45
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My opinion is that it would be a waste of time to verify if the pack can sustain 200 amps if there is no application to match. By definition, a pack discharged at 40C would dump it's entire contents in 1.5 minutes.
This is more to the point. "C" rating doesn't matter, voltage under load and punch/rip on the track does. While in general Higher C ratings indicate lower IR it doesn't guarantee better performance when racing rc cars that draw a fraction of the 40C the battery may be capable of.

After all this time using Lipo's you think someone would have done some good unbaised testing of the top brands, but no!

SMC say that their 6000 28C is a better performing battery than their 5200 40C in stock racing. What does that say about C ratings versus performance?

I have done discharge curves on quite a few different Lipo's and so far the Thunder Power/Fantom Pro Race 40C are the best. They are also the most highly regarded batteries on the track.
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