Some stats from wattmeter
04-13-2010, 02:37 AM
#1
Tech Rookie
Thread Starter
Some stats from wattmeter
Gday from Orstryleeyer
Have been running some tests on my Durga tonight with a watt meter attached, before ending with a full speed hump of the neighbours car (broken front shock and CF tower).
Specs are :
EZrun 4300kV motor, Lipo1 is a housebrand 7.4v 5200mAh 35C, Lipo2 is Li-Power 11.1v 5400 20C, Losi 9515 ESC at 100A/540A, gearing 21/91 at 2.055 internal.
Lipo 1
7.4 v spec, shows 7.77 V running off ground with no load, and 6.85 at speed on road.
37.0 to 44.5 Amps peak no load (44.5 is under braking), and 91.8 A peak on road
Watts, 339 no load rising to 629 on road at speed.
Lipo 2
11.1 v spec, shows 11.46 V running off ground with no load, and 9.9V at speed on road.
32.8 Amps peak no load (no change for under braking), and 106.3 A peak on road
Watts, 377 no load rising to 1059 on road at speed.
So both batteries drop by 10% under full throttle with the older 20C 5400mAh dropping by a little bit more.
The car runs quicker of course with the 11.1V.
But the bit that tangles me up that 35C*5.2 (5200mAh) is 182 Amps peak from the Lipo 1 battery, vs 20C*5.4 = 108A from Lipo 2.
Have been running some tests on my Durga tonight with a watt meter attached, before ending with a full speed hump of the neighbours car (broken front shock and CF tower).
Specs are :
EZrun 4300kV motor, Lipo1 is a housebrand 7.4v 5200mAh 35C, Lipo2 is Li-Power 11.1v 5400 20C, Losi 9515 ESC at 100A/540A, gearing 21/91 at 2.055 internal.
Lipo 1
7.4 v spec, shows 7.77 V running off ground with no load, and 6.85 at speed on road.
37.0 to 44.5 Amps peak no load (44.5 is under braking), and 91.8 A peak on road
Watts, 339 no load rising to 629 on road at speed.
Lipo 2
11.1 v spec, shows 11.46 V running off ground with no load, and 9.9V at speed on road.
32.8 Amps peak no load (no change for under braking), and 106.3 A peak on road
Watts, 377 no load rising to 1059 on road at speed.
So both batteries drop by 10% under full throttle with the older 20C 5400mAh dropping by a little bit more.
The car runs quicker of course with the 11.1V.
But the bit that tangles me up that 35C*5.2 (5200mAh) is 182 Amps peak from the Lipo 1 battery, vs 20C*5.4 = 108A from Lipo 2.
- Q1. It looks like volts are more important than amps in terms of speed?
- Q2. And the higher C rating of lipo 1 is wasted, as the car only drew 106A in the road run.
- Q3. Therefore I could be better off buying higher voltage and lower 20 C batteries, and not outlaying for high C ratings for any reason. But wouldn't an 11.1V and say 35C offer any gains (I guess it might run cooler if the 5400/20C is actually running at it's peak draw?
04-13-2010, 06:12 AM
#2
Great data. I wish I had a data recording tool like this to do my own measurements.
It is not surprising that the 11.1v Lipo produces more speed. Voltage does translate to speed steady state. That is why most of the ESCs manage the voltage. Currrent is a measure of acceleration. Your data did not show any acceleration information.
Some people claim that the higher C rated batteries offer more punch. I have experienced this too. I have 16C, 25C and 40C batteries and the 40C is noticably more punch on acceleration out of a corner. I also have a 40C 3S Lipo that is out of control in my SC10. I rarely use it except at races were I can run 2S in Stock and 3S in Open. I have to dial down my EPA.
It is not surprising that the 11.1v Lipo produces more speed. Voltage does translate to speed steady state. That is why most of the ESCs manage the voltage. Currrent is a measure of acceleration. Your data did not show any acceleration information.
Some people claim that the higher C rated batteries offer more punch. I have experienced this too. I have 16C, 25C and 40C batteries and the 40C is noticably more punch on acceleration out of a corner. I also have a 40C 3S Lipo that is out of control in my SC10. I rarely use it except at races were I can run 2S in Stock and 3S in Open. I have to dial down my EPA.
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