Electric scooter 1500W controller cold temperatures cutting out

You've got 12 amp hours of a 2C cell with a maximum comfortable continuous output of 24A... but a 60A BMS... and i imagine 40-60A controller.

This is what the cell looks like when at 'room temperature'. The internal resistance of the battery pack will increase and this will be even worse in cold weather.



A real time display of voltage would probably reveal extreme voltage sag and the BMS repeatedly hitting low voltage cutoff. There is no way that battery can supply the power your scooter needs. At a minimum you need to either double the size of the pack, or redo the pack with the most powerful cell you can find.

Hello,

first of all, thank you for your reply..
The controller is 48V, 30A, so 1500W

I don't think the problem is in the battery.

I've rode more than 1000Km, with no problems with this battery. than the problem started to appear (only after 1000 Kilometers)

I have 4 cells parallel, and each cell is capable of 30A continous.
So I have 48V 120A continous.

Like I said, the controller cut's off when the controller is cold...

I've tried heating the controller with heat gun, and than it works flawlessly, I did not heat the battery up...

I've measured input voltage to controller, and it DOES NOT cut off..

There's got to be cold solder somewhere in the controller, but I was unable to find it!..
I do not know what else could cause the temperature dependence in controller...

Sincerely,
Jonathan

The cells are rated for 15A peak, not continuous.
You'll see on the graph that at 15A, they're a 3.4v nominal cell.

Remember that this is at room temperature. At freezing, this figure drops by about 1/4th.. therefore each cell is capable of 3.75A peak.. therefore the maximum peak output of your pack is 15A.
Let's say we are halfway to freezing.. well, your maximum peak is 30A then.

You are truly stretching the limits of your pack because there is zero headroom in it.. and it will always cut off early even at room temp due to the load you put on it. This will get worse as the pack ages. Because you are giving it a beating, it is going to age quicker also.


You might be right in that the controller is the issue. This can only be ruled out if you have a continuous watt/volt meter and observe the cutouts happening before the LVC hits. With a battery like yours, the voltage will vary +/- 10 volts when idle versus under load.. so this needs to be observed in realtime.


You probably have a cold or loose joint somewhere in the controller if the battery is not cutting out first. Having to heat the controller up is an important clue. Is this some cheap controller?

Hello,

Yep, the controller is cheap 1500W one..

I seriously doubt that the battery is the issue.

Like I said, when I start driving (cold controller), the cut off's happen.

When I drive for 10 minutes the controller warms up, and it start's to work flawlessly..

This theory is proven with heat gun (I heat controller a bit and it starts to work flawlesly)
This rules out the battery.

The voltage sag is not that bad.. it only drops 4-5V when on full load (up a hill)..

I probably need to buy new controller, but I do not want to buy the same crap controller..

I was looking into buying VESC ones (MAKER X MINI FOG), but it does not support LCD and battery readout

janzobanzo7 said:

Like I said, when I start driving (cold controller), the cut off's happen.

Click to expand...

When you initially put a load a cold battery, it draws peak amperage

Buy yourself a real time watt meter. You can get them as cheap as $25. It's a nice add on for any bike and a better 'fuel tank' than anything that comes with a controller, and you can wire it to anything:

https://hobbyking.com/en_us/turnigy...n=google_us_shopping&countrycode=US&gclsrc=ds

This $25 item will rule out my hypothesis versus yours.


But.. if your pack is 1/2 way freezing, your voltage drop could be as high as 10V which would probably trip the battery's low voltage cutoff. OR... your controller actually has a low voltage cutoff in it that isn't set correctly.
Another thing is that a cold controller has less resistance, so it draws more amps. Heating it will make a small change in this.

Is your quoted 4.5v drop a drop when cold, or warm? Because if we're talking warm, then at cold ( halfway to freezing ), that figure is probably >8v.

I may be overestimating your voltage drop but many people underestimate it greatly.

Thank you for your reply..

I should mention, that the cutoff happens independantly of the motor load..

So even if I run the motor in air (no load), the cutoff happens aswell!

So when running the motor without the load, the voltage dip is around 1V, so that disproves the battery problems (I think..)

Yeah sounds more like a loose connection. Perhaps tap the controller a bit when cold to see if you can reproduce it

I've thought about that..

I've already soldered tohether all the phase wires, and hall effect sensor wires.
didnt work, so I've tried:

soldering brake lines and LCD directly without connectors..

Same problem persists on and on.....

Hello,

I've found the issue! FINALLY

As it turns out, noone was right, it is not the controller nor the battery problem.

I've had a chance to test my friend's LCD (with throttle), and it works flawlessly with his LCD (brand new one).

Now I've started to troubleshoot the problem, and my hall effect sensor is somehow damaged on surface (magnet was rubbing against it).
I've checked it's output with oscilloscope and it still works, but the output has a lot of noise when the motor is running.. It does not have noise when the motor is still (makes sense..).

Today I will try to measure noise on my friend's LCD.

Jonathan

janzobanzo7 said:

Hello,

I've found the issue! FINALLY

As it turns out, noone was right, it is not the controller nor the battery problem.

I've had a chance to test my friend's LCD (with throttle), and it works flawlessly with his LCD (brand new one).

Now I've started to troubleshoot the problem, and my hall effect sensor is somehow damaged on surface (magnet was rubbing against it).
I've checked it's output with oscilloscope and it still works, but the output has a lot of noise when the motor is running.. It does not have noise when the motor is still (makes sense..).

Today I will try to measure noise on my friend's LCD.

Jonathan

Click to expand...

So your clue about heating the controller turned out to be a red herring. Glad you figured it out though.

Yeah I dont know why heating controller would help the problem, but I'm guessing the UART communication is broken between the LCD and controller... ...