Micro Motor Community

Overheating brushed motors


#1

Hi guys
I just built an 85mm whoop using the betafpv 85mm whoop frame
F3 Brushed Flight Controller , just the generic whoop controller , running Betaflight

The motors running extremely hot after 3 minutes
They are just Chaoli 8.5x20 , 39000 rpm . Not high power or high RPM
Im only running 1/2 throttle, these motors shouldnt have an issue with a quad this size .

Any ideas ?
The cant fly it with overheating motors, they wont last or the frame will melt.


#2

so far ive tried …
smaller & lighter 3 blade props, standard PIDS, PWM of 16000 & 32000 , Enable “Motor PWM speed Separated from PID speed”

Motors still running very hot .
Just the way its going to be ?
Should I try 53500RPM racestar motors ? higher RPM usually means more heat ?


#3

How hot you talking? It is normal for brushed motors to get warm. They start getting damaged when they are too hot to touch.

PWM rates won’t really affect temp. You may need to lower your PIDs since the motors have more thrust than 6mm.


#4

Hot enough that I can only touch motors for less than a sec. Not hot enough to burn, but too hot to hold .
Ive tried lowering the PIds drasticly, that ddint help either

Tiny 65mm whoop I run 5 batts through it back to back & those motors only get warm.

55grams , so 4x 8mm motors shouldnt be straining to lift that ?
I may try some other motors. It may just be a failed build , so I’ll fly it till it will fly no more
I can allways use the parts in something else I guess.

The 65mm whoop is more fun,
but this new 85mm whoop is more like a cruiser , relaxing to fly .


#5

I might try an older betaflight build. Could allways be something in the version I’m using .


#6

You could try cutting the props up into 2 blades, it will have less power but the motors should get less hot and it should increase flight time. I’m not sure about the performance though, only try if you have enough spare props.


#7

I am having a similar problem with a Beta 75 that I just built. All four motors get very hot, very quickly.

Here’s my setup:

BetaFPV Beta Cube F3 FC & Cam/VTX combo - DSMX with OSD
BetaFPV 7X20 17500kv motors
4-blade props
BetaFPV 550mAh HV LiPo
47.36 grams AUW

BetaFlight 3.2 with Project Mockingbird setup

Flight time: 3:30 (average over 4 batteries) - just hovering to break-in brand-new motors.

I mean these motors get really hot.

Any ideas?


#8

What pids are you running? Very high D can cause heat. Also, what is your motor PWM?

Post a “diff all” file to see if we can find the culprit


#9

diff all

Betaflight / BETAFLIGHTF3 (BFF3) 3.2.0 Sep 28 2017 / 16:16:50 (ceb6f70) MSP API: 1.36

defaults nosave
name Bruno75

feature -TELEMETRY
feature MOTOR_STOP
feature DYNAMIC_FILTER
beeper -GYRO_CALIBRATED
beeper -RX_LOST
beeper -RX_LOST_LANDING
beeper -DISARMING
beeper -ARMING
beeper -ARMING_GPS_FIX
beeper -BAT_CRIT_LOW
beeper -BAT_LOW
beeper -RX_SET
beeper -ACC_CALIBRATION
beeper -ACC_CALIBRATION_FAIL
beeper -READY_BEEP
beeper -DISARM_REPEAT
beeper -ARMED
beeper -SYSTEM_INIT
beeper -ON_USB
beeper -BLACKBOX_ERASE
map TAER1234
aux 0 0 0 900 1300
aux 1 1 1 1300 2100
aux 2 2 1 900 1275
rxrange 0 1094 1945
rxrange 1 1094 1945
rxrange 2 1094 1945
rxrange 3 1094 1945
set gyro_notch1_hz = 0
set gyro_notch2_hz = 0
set acc_trim_roll = 4
set rc_interp = OFF
set use_unsynced_pwm = ON
set motor_pwm_protocol = BRUSHED
set motor_pwm_rate = 16000
set bat_capacity = 450
set vbat_max_cell_voltage = 44
set vbat_min_cell_voltage = 31
set vbat_warning_cell_voltage = 31
set pid_process_denom = 2
set osd_rssi_pos = 40
set osd_flymode_pos = 2497
set osd_throttle_pos = 225
set osd_vtx_channel_pos = 2520
set osd_ah_sbar = 200
set osd_ah_pos = 200
set osd_current_pos = 385
set osd_mah_drawn_pos = 353
set osd_craft_name_pos = 2508
set osd_gps_speed_pos = 218
set osd_gps_lon_pos = 82
set osd_gps_lat_pos = 65
set osd_gps_sats_pos = 51
set osd_home_dir_pos = 302
set osd_home_dist_pos = 303
set osd_compass_bar_pos = 266
set osd_altitude_pos = 247
set osd_pid_roll_pos = 423
set osd_pid_pitch_pos = 455
set osd_pid_yaw_pos = 487
set osd_debug_pos = 1
set osd_power_pos = 321
set osd_pidrate_profile_pos = 345
set osd_warnings_pos = 329
set osd_avg_cell_voltage_pos = 76
set osd_pit_ang_pos = 257
set osd_rol_ang_pos = 289
set osd_battery_usage_pos = 392
set osd_nheading_pos = 311
set osd_nvario_pos = 279
set osd_esc_tmp_pos = 82
set osd_esc_rpm_pos = 83
set osd_stat_min_rssi = OFF
profile 0

set dterm_lowpass_type = PT1
set dterm_notch_hz = 0
set dterm_setpoint_weight = 254
set p_pitch = 100
set i_pitch = 130
set d_pitch = 60
set p_roll = 90
set i_roll = 110
set d_roll = 60
set p_yaw = 180
set i_yaw = 120
set p_level = 120
profile 1

profile 2

profile 0
rateprofile 0

set rc_rate = 0
set rc_rate_yaw = 200
rateprofile 1

rateprofile 2

rateprofile 0
save


#10

Put ALL your filters back on and use BIQUAD. (Cause of heat #1)

Remove RC Interpolation (receiver tab) for better response

Your “I” is insanely high - you should never have to go past 70. Start at 60. (Cause of heat #2)

47grams for a 7mm build is a bit on the heavy side - those are more like 8.5mm motor with 750mah lipos weights.

Shed the weight if possible (Cause of heat #3)


#11

I followed the Project Mockingbird recipe for an “Angle Only” setup which specifically calls for turning off all filters and suggests high “i” (as a starting point), Though I don’t know if they were meant to work on a 75mm frame/ 7X20mm motor build. I have six other whoop-style quads with Project Mockingbird settings - 65mm frame/6X15mm motor and 65mm frame/7X16mm motors - all with filters turned off, and high “I”. None of them come down with motors that are anything more than barely warm.

Maybe it’s a 75mm/7X20mm thing… but there’s not a lot I can do to shed weight. This is basically how the factory builds these, minus the 4-blade props (they go with tri-blades). As soon as I can get my hands on some 40mm tri-blade props, I will give those a try. Then my setup will be essentially 100% stock.


#12

I reflashed the FC to BF 3.3.1 and left the PID’s stock, and did not implement any of the Project Mockingbird settings. Just made a few basic changes.

Also installed Rakon-Heli 40mm Tri-blades,

Ran it with a MyLipo DE 255mAh HV this time to save some weight. AUW with this battery is 40.07 grams.

Got right around 3:00 mins flight time. Motors came down hot again. Maybe a touch less scorching, but still way hot compared to what I’m used to on all my other quads.

The quad also makes a weird “tone” upon being armed. It’s not motor whine. Just a mono-tone that doesn’t change pitch or volume when the motors spin faster.

Here’s my new DIFF after flashing to BF 3.3.1

diff

Betaflight / BETAFLIGHTF3 (BFF3) 3.3.1 Apr 3 2018 / 09:26:40 (4b7eaf79d) MSP API: 1.37

name Bruno75

feature -TELEMETRY
feature DYNAMIC_FILTER
beeper -GYRO_CALIBRATED
beeper -RX_LOST
beeper -RX_LOST_LANDING
beeper -DISARMING
beeper -ARMING
beeper -ARMING_GPS_FIX
beeper -BAT_CRIT_LOW
beeper -BAT_LOW
beeper -RX_SET
beeper -ACC_CALIBRATION
beeper -ACC_CALIBRATION_FAIL
beeper -READY_BEEP
beeper -DISARM_REPEAT
beeper -ARMED
beeper -SYSTEM_INIT
beeper -ON_USB
beeper -BLACKBOX_ERASE
map TAER1234
aux 0 0 0 925 1200 0
aux 1 1 1 1700 2100 0
aux 2 2 1 1300 1700 0
aux 3 28 1 900 1300 0
rxrange 0 1093 1946
rxrange 1 1094 1945
rxrange 2 1094 1945
rxrange 3 1093 1946
set gyro_sync_denom = 2
set rc_interp = OFF
set motor_pwm_protocol = BRUSHED
set bat_capacity = 500
set vbat_min_cell_voltage = 30
set vbat_warning_cell_voltage = 31
set deadband = 5
set yaw_deadband = 10
set pid_process_denom = 1
set osd_vbat_pos = 2102
set osd_tim_1_pos = 2499
set osd_flymode_pos = 2519
set osd_vtx_channel_pos = 2085
set osd_crosshairs_pos = 2282
set osd_craft_name_pos = 2508
set osd_warnings_pos = 329
profile 0

rateprofile 0

Any other ideas?


#13

What’s your motor PWM? The fact that it didn’t appear in the diff means that it is at default PWM - Bring it back up between 8k and 32k