Do controllers have overvoltage protection?

[Stephan Linn]

I am working on a client's SMLRO Ebike (https://smlrobikes.com/product/s11.html). The bike will not run with a fully charged battery( 54 V ). I unfolded it and connected it to a power supply set at 48V and it ran. Through a very scientific method of slowly increasing the voltage, it cut out at 52 V. I then had a look at the controller P-settings but no setting was near 52 V. The manual only describes unboxing and operation, and the company does not respond with requests for tech support. In fact they refer one to the "dealer or distributor", which is a dodge, since it was bought from Amazon.
Anyone know what is happening? Is the max voltage programmable? Perhaps a bad resistor?

 

[docw009]

These displays often have an option for a 48 or 36 V setting, but I think the general protocol is that the controller senses the voltage and sends a data packet to the display. In other words, there must be a resistor divider in the controller that must be reading it wrong. Good luck in finding it,

No, I don't recall even running up against an overvoltage protect on my discrete controllers. The mid drive motors had them. I did have a brainpower controller that had a 36V and 48V jumper on the circuit board. I recall I had to set it for 36V to be able to use a 36V battery with it,

 

[DonL]

Most China made controllers are over rated to the max power. Always look for the continuous rating and never exceed it.

 

[Stephan Linn]

These displays often have an option for a 48 or 36 V setting, but I think the general protocol is that the controller senses the voltage and sends a data packet to the display. In other words, there must be a resistor divider in the controller that must be reading it wrong. Good luck in finding it,

No, I don't recall even running up against an overvoltage protect on my discrete controllers. The mid drive motors had them. I did have a brainpower controller that had a 36V and 48V jumper on the circuit board. I recall I had to set it for 36V to be able to use a 36V battery with it,

Thanks for your response. The controller to display reading is very close to the voltmeter value of the battery, so the measurement seems correct. The software comparator seems to shut things down????

 

[docw009]

Some guys here mapped out the BMSbattery S06 controller, which is a small 6 FET KT controller. There's no overvoltage protection on it. Just a resistor bridge, 15K and 1.2K in the battery. I've run variations of this KT controller up to 60V.

You probably know how to run the controller w/o a display? COuld be circuitry in the display shutting you down. Try doing that and see if it will start up and run at 55 volts.

 

[Hwy89]

I had a KT controller that would shut down above 55 volts. It was on a dual motor cargo bike so the other motor and identical controller would get me along until the voltage dropped below 55v then everything worked fine.

 

[Stephan Linn]

Some guys here mapped out the BMSbattery S06 controller, which is a small 6 FET KT controller. There's no overvoltage protection on it. Just a resistor bridge, 15K and 1.2K in the battery. I've run variations of this KT controller up to 60V.

You probably know how to run the controller w/o a display? COuld be circuitry in the display shutting you down. Try doing that and see if it will start up and run at 55 volts.

"You probably know how to run the controller w/o a display?"
Actually, I dont? I usually swap the display. Do tell?
SLL

 

[docw009]

Brainpower S866, SW900m and KT displays all work the same way, The 5 pin connector has battery and ground, a start lead, TXs and Rxd data. when you turn on the display, it raises the start lead to battery level. Bafang displays works the same way too,

If you look at the schematic, the start lead on the controller (Vin) will power up the onboard DC-DC converters and power up the controller logic and sensors. Most controllers will have an active throttle and a default PAS. At least the ones I have tried will do so. KT, Brainpower, Bafang and an unknown brand,

To run without a display on controllers that use the above design, take battery voltage to the start lead. Here's the KT documentaion, You probably don't need to ground the data lead,.



,You do have to verify the pinout on other style connectors. Don't apply battery voltage randomly. If applied anywhere but the start lead, it will blow something up,






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