Motor not working under load

[Always Learning]

I got an ebike from my friend who had some work done on it (upgraded the controller) a few years back, the bike ran great for some time and then he didnt need it anymore so he just let it sit for a year or two. I took the bike from him and it right off the bat felt very jumpy accelerating up hills. I didnt think much of it and took the bike home and fully charged up the battery. The next time I rode it I discovered that when accelerating from a stop the bike works fine when I accelerate slowly, however if I give full throttle rite away it kinda jumps, meaning it gives short bursts of power and then catches. Either way once I hit around 12 MPH the bike goes back to only giving short bursts of power. Unloaded the bike gives the same problem when accelerating, but once it catches it goes to top speed no problem. I checked all the connections and they seem tight. Battery voltage is around the same (48-52.3V) loaded or unloaded. The battery is 48V/20A and the motor is a 500W brushless geared hub motor. Any help would be great.

 

[99t4]

I checked all the connections and they seem tight.

How did you check them? With a meter? Sometimes if they are minimally corroded or dirty, disconnecting/reconnecting them several times can "wipe" away the foreign matter. Also look closely for damaged wire.

Concentrate first on the throttle and its wiring. They are not so robust. WARNING: One of the throttle's failure modes is full throttle (runaway mode), so be prepared for that.

Battery voltage is around the same (48-52.3V) loaded or unloaded.

Really? Usually heavy load will cause some voltage sag, especially for older batteries. How are you measuring the voltage?

 

[amberwolf]

The usual problem is either connections between motor and controller for hall sensors (or phases).

The next usual problem is the battery (sagging in voltage under load causing controller to hiccup at it's LVC), but if you are watching it with a voltmeter during the moments you have the problem and see no voltage fluctuation, then that's not very likely.
If it sat outside unused, it could ahve collected water inside things and corroded connections, wires, even electronics (like hall sensors in the motor, or parts inside the controller, etc).

 

[Always Learning]

How did you check them? With a meter? Sometimes if they are minimally corroded or dirty, disconnecting/reconnecting them several times can "wipe" away the foreign matter. Also look closely for damaged wire.

I dont have a meter so I pretty much just looked at them and made sure they were clean and making full contact.

Concentrate first on the throttle and its wiring. They are not so robust. WARNING: One of the throttle's failure modes is full throttle (runaway mode), so be prepared for that.

Could the throttle be causing it to fail only under load?

Really? Usually heavy load will cause some voltage sag, especially for older batteries. How are you measuring the voltage?

I measured the voltage just by looking at the display on the bike. I could be remembering wrong though, I'll check again.

 

[Always Learning]

The usual problem is either connections between motor and controller for hall sensors (or phases).

In that case what should I do?

The next usual problem is the battery (sagging in voltage under load causing controller to hiccup at it's LVC), but if you are watching it with a voltmeter during the moments you have the problem and see no voltage fluctuation, then that's not very likely.
If it sat outside unused, it could ahve collected water inside things and corroded connections, wires, even electronics (like hall sensors in the motor, or parts inside the controller, etc).

It was covered while it was kept outside so that probably protected it from most of the elements.

 

[B_c]

I had a few situations like you described, and when I changed the battery, everything worked properly again.

It would be good if you could borrow from someone and test their battery before getting a new one.

 

[Always Learning]

So I checked the throttle sensor and all its wiring, all seems good. I know more about cars than bikes but it feels like maybe the clutch is worn?? Is that a possibility? It is a geared motor so... LMK

 

[Always Learning]

I had a few situations like you described, and when I changed the battery, everything worked properly again.

It would be good if you could borrow from someone and test their battery before getting a new one.

Good idea Ill try that

 

[K.K]

Hello bro, I would like to know if you have done the above test, whether it is because of the battery caused the problem?

 

[knightrider]

I have had that issue on one of my builds awhile back. The bike ran great for about 100 miles and then started a jerky on and off situation with throttle use or above pas 1 setting. Bike was good on the stand with no load. Checked everything as display, wheel sensors and connections along with changing out to another batt. Removed motor from bottom bracket and found that a hard bend in wiring was the culprit. The torque put on the wiring above the pas 1 and touching the throttle was the strain on the system.