Bicycle that turns off after only a few kilometers of use

J

Jay-Cee

100 mW
Joined
Jul 7, 2024
Messages
45
Location
France
Hello everyone!
I own a fatbike equipped with a 750W motor and a 48V / 25Ah battery. It has 3 speeds (via the throttle): 1- 15 km/h max | 2- 30 km/h max | 3- 40 km/h max. The assistance (PAS) blocks me at a max of 23 km/h.

For some time now, when I use my bike only with the throttle "wide open" in speeds 2 and/or 3 (speed 1 not tested), it suddenly turns off after about 2.5 km. The box where the controller and battery are located does not show signs of heat. However, I can restart it immediately and continue on my way, then if I continue to ride with the throttle "wide open" it cuts out again after a few kilometers.

At first I thought it was coming from the battery, it has been checked and 5 cells have been rebalanced but the problem persists.

Would anyone have an idea of what is happening? Or could help me establish a diagnosis to solve my problem. Thank you in advance for your feedback.
 
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hmm, you rebalanced cells, how far were they disbalanced?
How old is the bike/battery pack?

Does your screen show a great amount of voltage drop when it cuts out, or is everything appearing as normal when it's happening?
 
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neptronix said:
hmm, you rebalanced cells, how far were they disbalanced?
How old is the bike/battery pack?

Does your screen show a great amount of voltage drop when it cuts out, or is everything appearing as normal when it's happening?
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I cannot answer you precisely because it was not me who did the work, but I know there was not an enormous difference.
The battery and the bike are almost a year and a half old.

When the problem occurs, the screen turns off, as if I was turning off the ignition. I press the on/off button of the screen to restart the bike, then I continue my journey
 
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E-HP said:
Have it checked to see if it’s still (re)balanced. “Not an enormous difference” is not a very precise description
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Sorry, I am French and I am using a translator. The battery is properly balanced. After doing the rebalancing, he used the bike for several kilometers and then he did another test of the cells and there was no more problem.
 
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E-HP said:
Model of bike and any links? Pic of the “ box”.
I’d remove the cover of the “box” to allow air flow to the controller and retest.
Click to expand...
Link of my bike : Fiido T1 Pro - Vélo électrique Fatbike Cargo

I cannot remove the controller that is inside the box (circled in red) because the battery rests on the lid of the box. Furthermore, after my bike has turned off, I place my hand on the box and it does not emit any heat.

IMG_9137.jpg
tempImage0UWe7V.jpg
 
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Jay-Cee said:
@E-HP do you think it comes from the controller?
Click to expand...
Does it happen when you don't ride full throttle? The two areas that come to mind that may cause the symptom are the battery or the controller getting too hot. There isn't a way for the controller heat to efficiently transfer to the "box", so touching the box won't tell you much.
 
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E-HP said:
Does it happen when you don't ride full throttle? The two areas that come to mind that may cause the symptom are the battery or the controller getting too hot. There isn't a way for the controller heat to efficiently transfer to the "box", so touching the box won't tell you much.
Click to expand...
For comparison, when I ride solely with electric assistance (PAS), this does not occur. I have the impression that the motor is not being exploited 100%. But as soon as I start using the throttle and fully soliciting the motor, after a certain time, it stops as if it is putting itself in safety mode because it is overheating. However, I can restart it immediately and fully solicit the motor again until it cuts out after a few kilometers.
 
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I have an additional problem: the pedal assist no longer works, nor does the odometer and the total distance traveled. I deduced that my PAS sensor was faulty, but I changed it yesterday and the assist still doesn't work. How can I test if my new PAS sensor is functioning properly?
 
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New pedal assist does not work but throttle still works? Probably a sensor install problem.

Most PAS sensors are not a simple install. First they may mix the wires. Second, they must be installed on the proper side of the pedals, with the sensor facing a certain direction, and often with the magnet disk mounted properly too.

All of this should be checked by trial and error during the install.

Your other problem sounds like throttle use runs the battery down far enough to shut off. Then it bounces back and you are able tor ride a little further. Older worn out batteries can do this. Perhaps your battery repair guy can lend you a good battery to test this statement.
 
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docw009 said:
New pedal assist does not work but throttle still works? Probably a sensor install problem.

Most PAS sensors are not a simple install. First they may mix the wires. Second, they must be installed on the proper side of the pedals, with the sensor facing a certain direction, and often with the magnet disk mounted properly too.

All of this should be checked by trial and error during the install.

Your other problem sounds like throttle use runs the battery down far enough to shut off. Then it bounces back and you are able tor ride a little further. Older worn out batteries can do this. Perhaps your battery repair guy can lend you a good battery to test this statement.
Click to expand...
I think I have installed the PAS correctly as it's a model that fits into the "bottom bracket frame," but I will check the wires. Indeed, you are right about the possibility that the wires might be reversed.

IMG_0854.jpeg

As for the throttle, yes, it still works.

Unfortunately, my battery repair person doesn't have the type of battery I own. Would you know how I can determine if my cells are worn out?
 
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If i was in your position, i'd throw out al the electronics except the battery and motor and run a third party programmable controller that's well known and supported instead of some random controller with no support and no diagnostic capabilities to help you rule out what the problem is.

ebike manufacturers constantly cheap out on controllers, ship them poorly tuned, don't keep a particular model on bikes long enough to know it's quirks and faults, etc. Displays are sometimes in charge of the controller and are built to lower standards than controllers.

Of course this could also be your BMS. This is an unlikely fault for a BMS. A battery tripping a low voltage cutoff early would happen at an increasing frequency the longer the bike is ridden. A BMS shutting off for reasons other than over or under voltage, a short, or overcurrent is possible but unlikely.
 
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neptronix said:
If i was in your position, i'd throw out al the electronics except the battery and motor and run a third party programmable controller that's well known and supported instead of some random controller with no support and no diagnostic capabilities to help you rule out what the problem is.

ebike manufacturers constantly cheap out on controllers, ship them poorly tuned, don't keep a particular model on bikes long enough to know it's quirks and faults, etc. Displays are sometimes in charge of the controller and are built to lower standards than controllers.

Of course this could also be your BMS. This is an unlikely fault for a BMS. A battery tripping a low voltage cutoff early would happen at an increasing frequency the longer the bike is ridden. A BMS shutting off for reasons other than over or under voltage, a short, or overcurrent is possible but unlikely.
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That's what is planned, but I'm stuck on certain connectors that don't match my current wiring. Perhaps you could help me, I've created a post on the subject here : Connector Compatibility Issue for Replacing a Generic Controller
 
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The only other thing that comes to mind is a flaky connection between the battery and controller can cause the controller to shut off spontaneously while under load. I had a 20A sinewave controller that would sometimes shut down completely at full throttle; in other cases, I would temporarily lose my throttle with the LCD display registering 0W even fully engaged. Since the problem was transient, it was difficult at first to pinpoint. These shutdowns tended to occur when the motor was under highest load, such as on hills or if I stopped pedaling. In my case, fixing a damaged connector on the positive connection solved the problem completely. There was some heating of the wires from the increased resistance at the damaged site, which helped me narrow down the problem.
 
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molybdenum said:
The only other thing that comes to mind is a flaky connection between the battery and controller can cause the controller to shut off spontaneously while under load. I had a 20A sinewave controller that would sometimes shut down completely at full throttle; in other cases, I would temporarily lose my throttle with the LCD display registering 0W even fully engaged. Since the problem was transient, it was difficult at first to pinpoint. These shutdowns tended to occur when the motor was under highest load, such as on hills or if I stopped pedaling. In my case, fixing a damaged connector on the positive connection solved the problem completely. There was some heating of the wires from the increased resistance at the damaged site, which helped me narrow down the problem.
Click to expand...
I am gathering as much information as possible through my two posts here and here, as I am going to change my controller, which involves modifying my connectors because some elements do not match. To help me find out what the wires were transmitting, I opened my original controller.

Even though I think my battery is partly responsible for this unexpected shutdown problem, it still needs to be proven by conducting power measurement tests. My controller, on the other hand, is far from clean. I had to cut the blue phase wire to remove it because the connector had melted inside (impossible to notice from the outside). The insulation on the red and black battery wires (which were inside the controller) is cracked for several centimeters.

I can't wait to change it! Thank you for your feedback.
 
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E-HP said:
The one neptronix linked to doesn't require an external power supply so is less of a hassle to use. (y)
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Yes, that's true! I've seen a tutorial that explained how to insert a battery, but what I find interesting is being able to place the screen on my handlebars to see how my battery is performing along the way.

In any case, my choice is not final. The idea is there, but I still need to do more research as I've only skimmed the surface of my searches. I've focused primarily on my project to change my controller.
 
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Yes it's not good for that, it's a basic tool, really it would be ideal to have a standalone cycle analyst if you're serious about this hobby.

Middle ground option is very long battery cables, lol.

I have a standalone cycle analyst i've been using since 2010 in all kinds of conditions, it's a great long term thinking purchase.
 
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I used one of these for a while. Using a shunt lets you have the display on your bars without having to run high current cables to the front for the meter. Another feature I liked it that it can retain the readings/data even after shutting it off, so when measuring Ah for instance, it will be cumulative until you reset it.
 
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neptronix said:
Yes it's not good for that, it's a basic tool, really it would be ideal to have a standalone cycle analyst if you're serious about this hobby.

Middle ground option is very long battery cables, lol.

I have a standalone cycle analyst i've been using since 2010 in all kinds of conditions, it's a great long term thinking purchase.
Click to expand...
For me, the purpose of buying a watt meter is to determine if the cells in my battery are exhausted. 30€ seems reasonable to me for getting this information, and it will always be useful in the future, considering that I don't know everything I can do with it. There might be other functions that I could exploit.
 
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E-HP said:
I used one of these for a while. Using a shunt lets you have the display on your bars without having to run high current cables to the front for the meter. Another feature I liked it that it can retain the readings/data even after shutting it off, so when measuring Ah for instance, it will be cumulative until you reset it.
Click to expand...
It looks like it's great! How does it work and how should it be physically installed?
 
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