Is my controller 'bad'? Severe loss of power at low SoC?

[bob2.0]

I've decided that this drop in power at low SoC is 'severe'.

I mean, it has always done this and I first assumed it was the controller or BMS protecting the battery.

You guys said it was just a drop in voltage.

But, I get a much bigger drop in power than the drop in voltage, they do not go down together.

Fully charged at 84V I get strong, 'nice' performance.

At around 74V it drops off so much that it's barely adequate.

At below 72V it's dangerous, and only a mad person would ride it. Which, I do all the time!

I do a regular 75 mile trip on it, taking back roads because in that lower half of the battery, it literally cannot pull off on a hill. There is a point in my trip where I have to stop at lights pointing up hill. If I mis-time the lights, I literally have to peddle and push the bike forward to get it going, it can't do it on its own.

One day, maybe someone in a car will not be as kind to me as they usually are, and will just drive over me. I have to be so careful.

So, here is my question; how low SoC do you guys take your bikes, and do you find the loss of power is 'severe'?

I bought a spare controller, if you recall, and I am wondering if there is any sort of fault with the controllers that might cause this, and I should swap it out? I have resisted doing it because I did not think it would help, but, I don't know.

[bob2.0]

I did a long ride out this weekend and it seems to be worse.

it might be my perception, but I was at around 40%, still 5~6 bars, and it would barely accelerate up a gentle gradient.

It is basically in 'tortoise' mode from 6~7 bars, as if the battery is totally flat, but it is still >40%.

So, I think it is the controller, and that it is an error mistake measuring the battery voltage.

'chatgpt' suggested some component failure in a resistor divider circuit. Perhaps a signal smoothing capacitor that has cracked and leaking, pulling the voltage down.

This makes sense.

I need to get that computer reading feature going. I have a hard wire lead julet connector but I can't find the thread explaining the steps connecting it up.

I have a replacement controller with bluetooth cable connection. But I worry replacing it all in one go, making too many changes.

Does this failure mode make sense? If the controller software reports a lower voltage than actual, then I think that could explain everything.

[jeff-jordan]

--- sorry, double post ---

[jeff-jordan]

Please connect* your controller via bluetooth & fardriver app.

In the "Graph" screen, you can monitor the voltage (the one that the controller "thinks" the battery has).
Compare this value with the voltage you measure with a precise multimeter at the charging port.
The values should be roughly identical (+/- 1%).

Maybe you need to adjust the "-Protect" parameters: LowVolProtect (LowVolRestore will be adjusted automatically to LowVolProtect + 2V).
The LowVol... values define when the bike gets into turtle mode.
You can even switch off the turtle mode when you set the LowVolProtect value to 60V or below, but I won't recommend that.

I recommend to drive with a smartphone holder and an (old) android phone running the fardriver app, connected to the controller.
Then you can monitor what happens if you loose power.

But maybe the problem is the controller temperature?
I had this last year, because the cooling of my ND72530 was not adequate (before I installed a fan above my ND72530).

_____________________________


*) To figure out the correct pinout of the small julet connector (which comes with random colors!) and make a connection to the bluetooth dongle with the 4x 2.8mm automotive connector, just figure out between which pins of the julet connector you can measure about +5V, using your multimeter.
If you then connect the +5V to the purple wire of the dongle and GND to the black wire of the dongle, the red LED at the dongle should start to blink slowly (approx. once every second).
You then should be able to "see" the dongle with a bluetooth monitor (as described here).
To communicate now with the controller/dongle, you can connect the two remaining pins to the two remaining wires of the dongle (red and blue).
There are two possibilities to do so.
You can try out both without damaging anything.
At one of the possibilities you should be able to connect to the controller via fardriver app and bob's your uncle .

[bob2.0]

Thank you nicely for your reply. I appreciate the direction towards bluetooth, I was hoping to avoid rewiring things. I have a julet to usb connection.

I should have done this and sorted it before and last year. Funny, that the machine rolling at 45mph max speed was not a problem for me, I can at least say it makes the range better!

But this lack of acceleration is a big problem now.

It remains poor on acceleration even after the controller has cooled down. So, maybe not that. But perhaps that has 'also' gone bad now, too. I often seem to suffer dual, simultaneous failures that make problems a total mystery. It is meant to be rare. I am now convinced The Gods of machines play with me, just for their amusement. They like seeing me shouting at inanimate machines that refuse to be fixed.

[bob2.0]

The USB lead I had seemed to work fine with my PC so I just plugged it in to the motorcycle and it all worked fine.

I cannot see any issues, apart from the motor temp is reading zero, which I can't see why that would cause a restriction as the battery voltage drops.

Battery voltage is slightly under what I think it is, but by fractions of a volt.

Controller temp seems fine.

These settings, this current battery charge, 'couldn't pull skin of custard'. Well, it can, just.

So, I am none the wiser.

At least now I have all the settings, so I can go ahead and swap with the new controller I have. Then, we'll see if it is some strange MOSFET failure, and not opening the gate fully.

If you can take anything out of these screen shots, I can give you any from the other menus.

'Mystery'.