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Old 11-19-2008, 07:43 PM   #91
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thanks danny,

i am running in 13.5 sedan...so i guess i need the power...
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Old 11-19-2008, 07:44 PM   #92
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trailranger: I'm not great with ohms law but if I were to test different packs at 135 amps for 60 seconds what info would I get and how would that be different than discharging a pack at 135 amps down to 6 volts and giving the info ?
How would I quickly compare a 25C 5200mAH pack to a 28C 5000mAH pack?

Read on...


60 seconds was just a figured I used to allow for a better average of the instantanous wattage. If the test was shorter, then a higher load could be used before the battery reached 3.00 or 2.75V under load. So once again the number could be manipulated if just a cut-off voltage was use instead of a required minimum test time. A longer test such as 300 seconds would more than likely be a better way to test for Average Maximum Wattage as the test time would be similar to the race time.

I see the Max Wattage as a easier figure to compare batteries with than C ratings as C ratings are very very subjective. Even if the C ratings were standardized then I still have to compare the trival capacity differences by looking at the battery label should one be present to compare batteries. By all means I am not saying a Max Wattage number should replace the battery label that we are all see on NiMH batteries. Those lables are great for comparing the details of the cells but in reality those details only lead to one thing available power. Work done is measured by watts, so might as well tell the racers how much work that battery can do.
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Old 11-19-2008, 07:44 PM   #93
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C rate might not be the only to tell if a pack is good but IR and voltage isn't always giving you the proper way. To point this out in 1998 or 1999 or so Sanyo released a 2200 NiMh cell that had lower IR and higher average voltage than the the Sanyo 2000 Nicad but when we tried the 2200s on the track we would be slower than when we used the 2000s even though the Turbomatcher and Turbo 35 should the opposite.

I can't talk for every Lipo manufacturer but all I can say is that when our supplier sends us test packs with better C rate the IR is typically better. Our 24C/5200 has a bit higher IR than our 28C packs. We did get a 35C sample packs from our supplier and it does have a bit better IR than our 28C pack.
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Old 11-19-2008, 07:48 PM   #94
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Originally Posted by trailranger View Post
How would I quickly compare a 25C 5200mAH pack to a 28C 5000mAH pack?

Read on...


60 seconds was just a figured I used to allow for a better average of the instantanous wattage. If the test was shorter, then a higher load could be used before the battery reached 3.00 or 2.75V under load. So once again the number could be manipulated if just a cut-off voltage was use instead of a required minimum test time. A longer test such as 300 seconds would more than likely be a better way to test for Average Maximum Wattage as the test time would be similar to the race time.

I see the Max Wattage as a easier figure to compare batteries with than C ratings as C ratings are very very subjective. Even if the C ratings were standardized then I still have to compare the trival capacity differences by looking at the battery label should one be present to compare batteries. By all means I am not saying a Max Wattage number should replace the battery label that we are all see on NiMH batteries. Those lables are great for comparing the details of the cells but in reality those details only lead to one thing available power. Work done is measured by watts, so might as well tell the racers how much work that battery can do.

So if I were to discharge 10C pack at 135amps and a 35C pack at 35 amps for 60 seconds like you mentioned I should get different wattage ?

What kind of equipment can do this as I have allot of confidence based on what the 3D Helicopter guys are telling us that our packs provide allot of power/watts.
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Old 11-19-2008, 08:08 PM   #95
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Originally Posted by Danny/SMC View Post
So if I were to discharge 10C pack at 135amps and a 35C pack at 35 amps for 60 seconds like you mentioned I should get different wattage ?

What kind of equipment can do this as I have allot of confidence based on what the 3D Helicopter guys are telling us that our packs provide allot of power/watts.

Yes you should see a difference

A 10C 3.7V pack would only produce on average about 500watts during the total discharge from start to finish. This is assuming the pack capacity was large enough to handle the discharge rate. A lower capacity pack would fail soon after test start.

A 35C 3.7V discharged at 35A would only produce about 145watts average during that discharge. Based on the 35A discharged rating, a 1000mAH battery is being tested.
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Last edited by trailranger; 12-04-2008 at 09:53 PM.
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Old 11-19-2008, 08:10 PM   #96
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Quote:
Originally Posted by trailranger View Post
How would I quickly compare a 25C 5200mAH pack to a 28C 5000mAH pack?

Read on...


60 seconds was just a figured I used to allow for a better average of the instantanous wattage. If the test was shorter, then a higher load could be used before the battery reached 3.00 or 2.75V under load. So once again the number could be manipulated if just a cut-off voltage was use instead of a required minimum test time. A longer test such as 300 seconds would more than likely be a better way to test for Average Maximum Wattage as the test time would be similar to the race time.

I see the Max Wattage as a easier figure to compare batteries with than C ratings as C ratings are very very subjective. Even if the C ratings were standardized then I still have to compare the trival capacity differences by looking at the battery label should one be present to compare batteries. By all means I am not saying a Max Wattage number should replace the battery label that we are all see on NiMH batteries. Those lables are great for comparing the details of the cells but in reality those details only lead to one thing available power. Work done is measured by watts, so might as well tell the racers how much work that battery can do.
I see what you are getting at, but wouldn't just an easy Milli watt/hour rating be enough to give you the same over-all measurement to compare between batteries? More over-all wattage is an absolute measurement to compare batteries of the same capacity range. Would this suffice? All you would need is the GFX, no expensive or proprietary equipment needed. So the average discharge voltage multiplied by the actual discharge capacity would give you the wattage. I am assuming you know the formula but for those that don't. IE: 7.40 volts X 5000 mah = 37,000 Milli watt/hrs. or 37 watts per hour. It's just like we did on Nimh as well.
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Old 11-19-2008, 08:11 PM   #97
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Have not miss the point , and still say when SMC introduces its 35C they will howl same as now when the other`s come out with 40C.....

If SMC says C-ratings are not truth full, why even
use C ratings on their products ?
The only "howling" I hear is the laughter at you missing the point. If you want to take shots at us, get a running start. Our packs are for real. Deal with it.
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Old 11-19-2008, 08:24 PM   #98
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Originally Posted by jeffb View Post
I see what you are getting at, but wouldn't just an easy Milli watt/hour rating be enough to give you the same over-all measurement to compare between batteries? More over-all wattage is an absolute measurement to compare batteries of the same capacity range. Would this suffice? All you would need is the GFX, no expensive or proprietary equipment needed. So the average discharge voltage multiplied by the actual discharge capacity would give you the wattage. I am assuming you know the formula but for those that don't. IE: 7.40 volts X 5000 mah = 37,000 Milli watt/hrs. or 37 watts per hour. It's just like we did on Nimh as well.
The real formula would be

AVERAGE VOLTAGE X Capacity MAH / 1000 X 60Mins/hour X 60Sec/Min / Elasped Time Seconds = Average Joules or Average Watt/Seconds

But the formula would not take in account for voltage drop because of the physical limitations of the cell. I can take a 20C 5000mah pack discharge at 0.1C and get 5500mah. I do the same at 20C and I get 4500mah. But If I were to discharge at 30C I would only get 3000mAh and the pack would be toast. Discharging beyond the rating should yield less average wattage because of the signicant voltage drop and a dead pack. Dischrage below the rating would yield less average wattage since the load (AMPS) was not high. This why when lookng at the graph I posted that totat wattage climbs at a linear rate then falls off. The lesser loads are below the max power point, and the higher loads are beyond the max power point.
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Old 11-19-2008, 08:25 PM   #99
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I'm actully thinking of doing such a test. If I do it I will be accused of bias so I may purchase the equipment and packs and let an independent person do the test.
Danny,

JorgD also did some lipo testing on another thread. You may want to take a look.
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Old 11-19-2008, 08:39 PM   #100
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Call it a chocolate souffle or a yak sphincter for that matter, I'm just saying it doesn't matter to me what the C rating is, I'd rather know the average voltage, runtime, and internal resistance.

When I raced Nicad and NIMH I never asked a manufacturer how much current I could continually draw and still maintain 90% capacity, I looked for average voltage and IR for stock racing, and runtime was the primary factor I looked at for mod racing. Nicad and NIMH cells have C ratings too, but no one ever advertised them or even cared about them.
Get used to it now brah.
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Old 11-19-2008, 08:59 PM   #101
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C rate might not be the only to tell if a pack is good but IR and voltage isn't always giving you the proper way. To point this out in 1998 or 1999 or so Sanyo released a 2200 NiMh cell that had lower IR and higher average voltage than the the Sanyo 2000 Nicad but when we tried the 2200s on the track we would be slower than when we used the 2000s even though the Turbomatcher and Turbo 35 should the opposite.
I was away from racing from late '95 to around '2000, so I missed that... Any idea why those 2200's didn't do the job?
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Old 11-19-2008, 09:00 PM   #102
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The only "howling" I hear is the laughter at you missing the point. If you want to take shots at us, get a running start. Our packs are for real. Deal with it.

Too funny , see u when the 35 comes out


if SMc can get one to sell .....
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Old 11-19-2008, 09:10 PM   #103
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if SMc can get one to sell .....
If you only knew half as much as you THINK you do!!

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Old 11-19-2008, 09:11 PM   #104
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Too funny , see u when the 35 comes out


if SMc can get one to sell .....
Anyone who met me at the IIC race got to see a sample pack of 35C from our supplier. That was almost 3 months ago.
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Old 11-19-2008, 09:12 PM   #105
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