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Old 06-14-2009, 07:40 PM   #16
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Originally Posted by chensleyrc1 View Post
I don't see how the C rating effects top speed. C rating is a discharge current. For higher top speed the voltage has to be increased. The only thing I can see the C rating effecting is acceleration. But I might be wrong.
Once you go beyond 25C in a 17.5, it won't matter how high the C rating is. You won't see a performance difference.
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Old 06-14-2009, 07:55 PM   #17
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How do you know how many amps your motor draws?
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Old 06-14-2009, 08:00 PM   #18
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A new pack will always help out. I've gone between a 30C 5000 and a 40C 5000 and noticed a significant difference in acceleration (with a 17.5). The 40C pack was almost .3 of a second faster per lap (the 30C was 5 months older and had been through quite a few cycles). Even with a relatively high wind motor, the momentary amp draw can be quite high from take off of when there's high tyre grip creating resistance through the drive train. From my personal experience i've found the higher 40C performed better when the the temps were rising over the 30C. As for brands, i've tried both Thunderpower and SMC and have found them both to be excellent. Like anything, buy the biggest and highest C rated pack that you can afford from a reputable company. If i was to buy again i'd say the Thunderpower 40C 5000mAh or the SMC 5200mAh 40C C-Max.
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Old 06-14-2009, 11:42 PM   #19
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Bigger packs do make a difference. I ran the IP 3800's 25C in 17.5. My best time was 18 laps, 6m11.32s with a fastest lap of 0m19.58s. Then once i changd to my SMC 5200 40C Packs at the first club meet with them my best time was 19 laps, 6m19.50s with a best lap of 0m19.23s, thats a .35sec improvement on fastest lap and an approx 11 sec improvement on overall time.
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Old 06-15-2009, 03:18 AM   #20
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are you guys using the lipos with corally plugs or deans plugs
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Old 06-15-2009, 08:12 AM   #21
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I run deans
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Old 06-15-2009, 11:43 PM   #22
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are you guys using the lipos with corally plugs or deans plugs
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Old 06-16-2009, 10:49 AM   #23
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Ok so has anyone actually been using say a 20c then upgraded to a 40c and noticed any difference too speed or lap times etc? (same mah) in 17.5 class

does it increase heat levels in the motor etc?
Just converted from Trakpower 4900 25C to Thunderpower 5000 40C in 17.5. The new pack factor is a possible consideration, but I believe I've picked up at least .5 sec per lap. No noticeable change in motor temp.
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Old 06-18-2009, 10:02 AM   #24
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Originally Posted by Smitty1092 View Post
C rating effects everything. Electric motor's take all the power they need. So if a 5000 mah 20C only provides 100 amps and a 5000 mah 40C provides 200 amps. And if your motor can take 150 amps then the 20C is simply not enough to get the most out of your motor. Plus the more amps you battery can put out the less voltage drop it will have. Correct me if im wrong anyone
I understand that higher C rating may lower lap times with some motors (don't know if a 17.5 draws 100amps even at startup), I just have a hard time believing it effects top speed of any motor, a motor draws the high amps on start up then lowers to an average well below 100amps, more like 10-20 at top speed.
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Old 06-18-2009, 10:25 AM   #25
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Quote:
Originally Posted by chensleyrc1 View Post
I understand that higher C rating may lower lap times with some motors (don't know if a 17.5 draws 100amps even at startup), I just have a hard time believing it effects top speed of any motor, a motor draws the high amps on start up then lowers to an average well below 100amps, more like 10-20 at top speed.
I thinnk there is Relativity to Internal resistance, naturally pack with higher C rating have more Voltage on 100AMps load down to 10Amps load,

Watt=Horse power.

Watt=Amps X volt

higher Voltage during 10 amps discharge down straightway can be equal to higher top end speed. IMO
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Old 06-18-2009, 10:31 AM   #26
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Quote:
Originally Posted by chensleyrc1 View Post
I understand that higher C rating may lower lap times with some motors (don't know if a 17.5 draws 100amps even at startup), I just have a hard time believing it effects top speed of any motor, a motor draws the high amps on start up then lowers to an average well below 100amps, more like 10-20 at top speed.
All motors want to run at an rpm proportional to the voltage supplied. This is its kv.

High C rated packs generally( I paid big bux so it better) maintain a higher voltage through their discharge curve.

Therefore higher top speed.
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Old 06-18-2009, 12:54 PM   #27
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Plus the slightly higher voltage under load will in turn cause the motor to draw slightly higher amperage as well. This is where the extra speed and torque come from...
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Old 06-18-2009, 05:25 PM   #28
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no joke 17.5 with a thunder power 40c 5000 = 13.5 with orion 3600.

both hacker motors, but different speed controls.

my 13.5 with the Thunder Power was motoring 10.5s down the straight. I was demolishing everyone on the straight in 17.5 until they went out and bought the TP 5000s

You will see more of a difference with batteries in stock racing and in spec racing then in any other class IMO.

Someone told me the got their car teched in a Slash spec class because they were destroying people using the TP batteries.

Im curious to see if the SMC batteries are as fast
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Old 06-18-2009, 10:34 PM   #29
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I run SMC's and had a TP 5000 40C, the SMC's were a little better IMO. But the TP wasn't a slouch neither, I ran both back to back at the last Novak race and did better with the SMC so thats all I run now. But that was in 13.5 foam.

And about the C rating for top speed, I do understand the relation to current to power, it was just that I couldn't see why amperage had anything to do with top speed, which was answered earlier by the batteries with the higher C rating also have higher voltage. Now my question is, if they start at the ROAR voltage limit, wouldn't they have same top speed? I have a electronics degree and have been a technician for 18 years now, and the only way I have seen a motor increase top speed was by increased voltage. Sorry to beat a dead horse, just trying to relate
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Old 06-18-2009, 11:32 PM   #30
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Now my question is, if they start at the ROAR voltage limit, wouldn't they have same top speed?
8.4V is the limit? I assume so.

That voltage is with no load. As soon as you apply load the voltage will drop. Good batteries with higher C have a greater capacity to deliver higher current, so are able to maintain higher voltage under load.

My first lipos, fully charged and warm, would drop to 3v at 8C load. Now the better ones will stay above 3.5v when subjected to 40 even 50C.
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