Escooter conversion : 350 Watt controller paired with 250 watt battery

Submitted by sergio on Tue, 02/04/2020 - 18:06

Hey guys !
I'm trying to do a scooter conversion, I have a 250 watt battery (36 v) and a 350 watt chinese generic controller. The thing is, when going uphill the battery shuts off. I think that maybe due to the current draw being too high. Does anybody know how to fix this issue ? Can I limit the draw current in anyway besides buying a new controller? Sorry for my english and for my poor knowlege of electronics I'm just starting, thanks for the help !

Hey, the current draw on these controllers is limited for a reason, if you draw more current you might either destroy the controller or the battery itself.

But if you want to do this for some experimental purpose, then this is how you do it.

1. Open the controller to examine the PCB board

2. You should notice a shunt resistor which will normally be in silver colour. It might look like a thick jumper/connector  wire, you can google "PCB Metal shunt wire" to get images of that

3. The voltage drop across this shunt resistor decides how much max current you controller can allow. In order to decrease the voltage drop just scratch the metal shunt resistor and add some solder do decrease the resistivity

4. Pack the controller again and now try your load.

Again, you have been warned. If you remove over current protection, your controller and battery pack might get destroyed when you draw way too much current 

  Joined August 16, 2016      997
Tuesday at 12:29 AM

Thanks for the suggestion but I think I didnt explain myself very well ! What I want to do is the opposite, I want the controller to draw less current, because i think its already pulling too much current from the battery ( when going uphill it starts flashing and theres no power to the motor) 

  Joined February 04, 2020      2
Tuesday at 06:01 PM

the battery is actually rated at 720 watt, i dont know whats the issue 

  Joined February 04, 2020      2
Tuesday at 06:01 PM

When you EV climbs a hill, it will consume more current as the load increase. This high current will damage your controller and battery and hence the controller has a built-in protection feature to shut-down. 

You can avoid this problem by decreasing the current consumed by the motor. Do do this increase the operating voltage from 36 to 48, by adding another 12V battery is series. Also, make sure your controller and motor can operate on 48V. 

  Joined August 16, 2016      997
Tuesday at 12:29 AM