purple_drank613
New here
Hi everyone,
I’m looking for some insight into a performance ceiling I’ve hit with my latest ebike build. Despite the specs, I can't seem to break past 42–44 mph, and I'm experiencing a "pulsing" sensation at wide-open throttle (WOT) that feels like a hard limiter or power cut.
The Build Specs:
Motor: 3000W 26-inch MTX rear hub motor.
Controller: JRAHK 3000W (36V–84V range). 3-mode (Square/Sine), 3-speed, single-line communication.
Modifications: Heavily shunt-modded controller.
Battery: 72V 65Ah pack. BMS is bypassed for discharge (BMS is only used for balance charging).
Wiring: 8AWG PTFE from battery to controller.
Safety: Breaker/fuse between battery and controller; throttle-mounted voltage meter for monitoring sag/low voltage.
Current Configuration:
Mode: Sensorless (running on phase only, no Hall sensors).
Waveform: Set to Sine Wave.
Speed Switch: Set to High.
The Issue:
Even with the shunt mod and the 72V pack, the bike tops out at ~43 mph. At full throttle, the power feels inconsistent—it pulses in and out rather than holding a smooth, high-RPM cruise.
Important Note on Controller Behavior:
I don't believe the controller is limiting based on sensing too much current from the shunt mod. I have another identical JRAHK controller on a Speedway Leger (MiniMotors), and I know how they behave when they hit a hard limit: if that motor spins faster than its Kv rating, it throws the controller into a "limp mode" that requires a full capacitor drain and hard reset to clear. This bike is not doing that. It just pulses at the top end without throwing an error or locking out.
My Questions:
Is it possible I’m hitting the E-RPM limit of the controller's processor in sensorless mode?
Could the "pulsing" be a result of the sensorless logic losing sync at high phase amps/high RPM?
Given this is a JRAHK controller, is there a hidden firmware speed limit or a physical jumper I might be overlooking beyond the 3-speed switch?
Since I'm running "sine wave" sensorless, would switching to "square wave" or hooking up the Hall sensors potentially resolve the sync/pulsing issue at high speed?
I’d appreciate any advice on whether I should try reverting to Hall sensors or if this is likely a physical limitation of the motor’s Kv rating at this voltage.
Thanks
in advance for the help
I’m looking for some insight into a performance ceiling I’ve hit with my latest ebike build. Despite the specs, I can't seem to break past 42–44 mph, and I'm experiencing a "pulsing" sensation at wide-open throttle (WOT) that feels like a hard limiter or power cut.
The Build Specs:
Motor: 3000W 26-inch MTX rear hub motor.
Controller: JRAHK 3000W (36V–84V range). 3-mode (Square/Sine), 3-speed, single-line communication.
Modifications: Heavily shunt-modded controller.
Battery: 72V 65Ah pack. BMS is bypassed for discharge (BMS is only used for balance charging).
Wiring: 8AWG PTFE from battery to controller.
Safety: Breaker/fuse between battery and controller; throttle-mounted voltage meter for monitoring sag/low voltage.
Current Configuration:
Mode: Sensorless (running on phase only, no Hall sensors).
Waveform: Set to Sine Wave.
Speed Switch: Set to High.
The Issue:
Even with the shunt mod and the 72V pack, the bike tops out at ~43 mph. At full throttle, the power feels inconsistent—it pulses in and out rather than holding a smooth, high-RPM cruise.
Important Note on Controller Behavior:
I don't believe the controller is limiting based on sensing too much current from the shunt mod. I have another identical JRAHK controller on a Speedway Leger (MiniMotors), and I know how they behave when they hit a hard limit: if that motor spins faster than its Kv rating, it throws the controller into a "limp mode" that requires a full capacitor drain and hard reset to clear. This bike is not doing that. It just pulses at the top end without throwing an error or locking out.
My Questions:
Is it possible I’m hitting the E-RPM limit of the controller's processor in sensorless mode?
Could the "pulsing" be a result of the sensorless logic losing sync at high phase amps/high RPM?
Given this is a JRAHK controller, is there a hidden firmware speed limit or a physical jumper I might be overlooking beyond the 3-speed switch?
Since I'm running "sine wave" sensorless, would switching to "square wave" or hooking up the Hall sensors potentially resolve the sync/pulsing issue at high speed?
I’d appreciate any advice on whether I should try reverting to Hall sensors or if this is likely a physical limitation of the motor’s Kv rating at this voltage.
Thanks
in advance for the help
