Hi there,

Some time ago i bought an electric skateboard from daibot, (aliexpress) and since they are no help at all, i hope some of you might know the issue.
I was dumb enough to drive trough the rain with the skateboard, and it actually had a lil bit of corrosion, at that point it would turn on, but had problems driving the motors. Now i was able to clean up the corrosion, and get it functioning again.
When i'm not riding it myself, or not too long at least it works fine. But it seems that when it draws too much power, it turns off.
I did some testing and measured the voltage across the battery while powering the motors, at first the voltage stays quite steady, but when the motors draw more load (holding the motors for testing purposes) everything turns off, and the battery will give a voltage of about 6 volts, before very slowly ramping back up (electronics won't turn on at that point). If i disconnect the battery the voltage rises right back up to about 24.5.
I've attached a picture of the electronics and as far as i could reach of the BMS, the battery is a 7S battery, using 18650cells.

 

holding the motors for testing purposes

If the motor is stalled, or close to stalling, it draws a LOT more current than when running freely. Holding it like that will risk burning out the motor or its controller, unless the controller is smart enough to shut down and protect itself. It sounds as though your controller is shutting down.

 

Yes that is true, but the exact same thing happens when i ride it.
And as i mentioned, when measuring the battery voltage, it's voltage goes down to 6V which to me sounds more like a problem with the BMS

 

Did you check the back side of the circuit board for corrosion? I am guessing that the problem is that the batteries are not being charged enough, at least that would give such a symptom. And the stuff left behind when water dries off an energized circuit can certainly cause problems. At least that is one thing to check and it is cheap to do and not that hard. But disconnect the battery power befor cleaning the circuit board.

 

I did check the backside of the main pcb, but not of the bms yet, i guess i'll give that a try!

 

So i checked the BMS and it's totally fine, all battery terminals are clean as well.

 

When the battery is on charge does it reach the correct fully charged voltage?

 

Yes it does, i checked with multimeter and battery voltage is correct when charged, i also have a batttery meter with shows it in percentage, an also correctly displays 100% when fully charged

 

The one thing not yet checked then is the motors themselves. Water, especially with assorted contamination, can cause problems in motors. I am not familiar with that board, so I don't know if the motors are brush types or not.

 

From what i can find, they appear to be brushless motors.
If what you say is true, would it be possible that the motors still work, but only fail at a certain treshold?
I might be able to take the motors apart as they are screwed together.

 

From what i can find, they appear to be brushless motors.
If what you say is true, would it be possible that the motors still work, but only fail at a certain treshold?
I might be able to take the motors apart as they are screwed together.

I think the batteries my be the problem. I have found that if I leave fully charged batteries in my RC planes and helicopters for several months, unattended, they behave in the same way. When I charge them, switch on and increase the power, they reach a point where thy suddenly shut down. I have not figured out why. I have cycled the batteries and tried slower charging but nothing seems to recover them. It appears that the internal resistance of the batteries has increased. I must check that and try again to find a solution. Batteries are expensive!

 

this might be the answer, i was able to open the motors and clean em out, there was some corrosion on the magnets but nothing severe, but it didn't change the behaviour.
I did have any extra battery pack on it that i made myself, though i took it apart, but it might be that the battery had this problem before but that i didn't notice it because of the extra pack.
I do still have those batteries so i should be able to replace the cells.

 

this might be the answer, i was able to open the motors and clean em out, there was some corrosion on the magnets but nothing severe, but it didn't change the behaviour.
I did have any extra battery pack on it that i made myself, though i took it apart, but it might be that the battery had this problem before but that i didn't notice it because of the extra pack.
I do still have those batteries so i should be able to replace the cells.

I hope that solves your problem.