Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
devin, post:21, topic:17037 Wrote:battery amps = motor amps x (% duty cycle / 100)
@Ackmaniac
if we use this ^
40 battery amps = 1440 W / Pack V: 36 V
battery amps = motor amps x (% duty cycle / 100)
can be rearranged to:
motor amps = battery amps / (%duty cycle / 100)
so:
1440W = 42.1052 motor amps = 40 battery amps / (%95 duty / 100)
",0,0,http://www.electricskateboard.builders/t/theismymathrightthread/17037/22,20170202 13:27:43 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
@Ackmaniac
@ 0 rpm
1440W = PWM Effective Voltage: 4.8V = Motor Amps: 300 A
",0,0,http://www.electricskateboard.builders/t/theismymathrightthread/17037/23,20170202 13:33:57 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
@Ackmaniac
0.1403 = Motor Amps @ %95 duty @ 1440W: 42.1052 A / Motor Amps @ 0 RPM @ 1440W: 300 A
%14.03 = 0.1403 x 100
In simple terms motor amps at 95% duty 1440w is %14.03 of motor amps at 0 rpm 1440W.
",0,0,http://www.electricskateboard.builders/t/theismymathrightthread/17037/24,20170202 13:37:04 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
devin, post:13, topic:17037 Wrote:If you are asking:
Which RPM does 1440W electrical = 95% duty cycle?
@Ackmaniac
we know that whenever duty cycle = 100%
it means:
battery amps = motor amps
",0,0,http://www.electricskateboard.builders/t/theismymathrightthread/17037/25,20170202 13:46:52 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
@Ackmaniac
from ohm's law we know that short circuiting the motor leads would lead to:
Battery Amps: 2250 A
Watts: 81000 W
",0,1,http://www.electricskateboard.builders/t/theismymathrightthread/17037/27,20170202 13:55:11 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
@Ackmaniac
We know that % No Load Rpm is linearly proportional to % Battery Amps @ 100% Duty
",0,0,http://www.electricskateboard.builders/t/theismymathrightthread/17037/29,20170202 13:57:06 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
Ackmaniac, post:28, topic:17037, full:true Wrote:OK forget about it. I thought we can have a interesting talk. My fault.
@Ackmaniac
Since the question you asked is:
Which RPM does 1440W electrical = 95% duty cycle?
this is effectively the same as asking:
Which RPM does 1440W electrical = 100% duty cycle?
this is effectively the same as asking:
Which RPM does 40 battery amps = 100% duty cycle?
",0,5,http://www.electricskateboard.builders/t/theismymathrightthread/17037/30,20170202 14:03:18 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
@Ackmaniac
We know that:
0% RPM @ 100% duty cycle:
2250 Battery Amps
100% RPM @ 100% duty cycle:
0 Battery Amps
So the question becomes:
Which XX.XX% RPM @ 100% duty cycle:
40 Battery Amps
It is the same as asking:
Which XX.XX% RPM @ 95% duty cycle:
40 Battery Amps
^*I think :thinking:
",0,1,http://www.electricskateboard.builders/t/theismymathrightthread/17037/32,20170202 14:08:57 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
Ackmaniac, post:33, topic:17037, full:true Wrote:OK now that we asked multiple times it would be nice to see some posts that help us with the answer.
@Ackmaniac
Well if use
0.01777 = 40 A / 2250 A
%1.777 = 0.01777 x 100
In simple terms (1440 W @ 95% duty) 40 battery amps is %1.777 of 2250 A (%100 max) battery amps
",0,0,http://www.electricskateboard.builders/t/theismymathrightthread/17037/34,20170202 14:17:35 UTC
Posts: 239
Threads: 27
Joined: Jun 2016
Reputation:
0
@Ackmaniac
you said:
Motor KV: 190 KV
Pack V: 36V
so:
6840 rpm (%100) no load max = 190kv x 36v
%100  1.777% Max A = %98.23
So if I had to hazard a guess I'd say:
1440w @ 95% duty = %98.23 of no load rpm
6840 no load rpm x 0.9823 = 6718.93 rpm
Ackmaniac, post:14, topic:17037 Wrote:Pack V = 36V, Ohm Resistance = 0.016, Batt = 1000 /Motor = 1000 /Absolute Max = 2000 Amp Limit Settings, and Motor KV = 190
devin, post:13, topic:17037 Wrote:If you are asking:
Which RPM does 1440W electrical = 95% duty cycle?
@Ackmaniac
In simple terms my back of the napkin guess is:
1440w electrical @ 95% duty = 6718.93 rpm
^^ take this with a huge grain of salt (probably wrong)
:thinking:
",0,1,http://www.electricskateboard.builders/t/theismymathrightthread/17037/35,20170202 14:28:14 UTC
