MP4 Dual Driver problem

[Vipermn]

Hi. My name is Jack.As indicated  above I have a dual driver MP4. 26 inch front and rear motor. My problem is my front wheel  motor does not do anything. I have the dual driver cable and when I plug the front motor in to either connector nothing happens. When I plug the rear motor into either connector it works fine. Any ideas anyone? Thx

[Bikemad]

Hi Jack andto the forum.

If you are using a 24V or 36V battery, it could simply be that the front controller has the battery voltage set to a higher voltage than the rear one and the actual battery voltage is too low to allow the controller to work. If this is the case, you will need to use the USB programming cable and software to adjust the voltage setting to the correct value.

However, if you are using a 48V battery with the correct controller voltage settings, it could be a poor battery connection to the front motor, a fault with the Hall sensors, faulty controller or a fault with the front motor controller harness.

Check that the battery connectors are properly connected on the front motor harness, and if you have access to a voltmeter, check the actual voltage across the two connectors on the motor harness side. If it reads more than 50V and the motor doesn't work you will need to check that none of the four wires (Blue Yellow Black and Red) on the short unused cable coming from the motor harness are exposed and touching each other.

If there are no signs of touching wires, then I would say that the controller itself may need to be replaced, unless there is a problem with the hall sensors inside the motor.

Please let us know what you find.

Alan
 
 

[Kauaikit]

Hey Jack...welcome to the MP4 family.   

Your in good hands with Alan's advice.

It's a shame that GM doesn't install connector ends to the lights/horn wires instead of leaving them bare. As I also ordered 2 pairs of each f/r lights, and they came incomplete without the opposite connectors. So, that means I'll have to find the correct connectors and then too furnish wires to make them work. Though I also double checked to make sure none of these bare wires were touching each other while installing both MP4's.

This will be interesting to hear your test results with a dually using the newest MP4 setup.

What voltage and battery source are you going to be using?

Kit
S.CA USA

[Vipermn]

Hello Alan and Kit. Thanks so much for such a quick response! So  just so we are on the same page right now I have the rear motor unplugged and I have the power, the 5 pin connector(BAC) and 10 pin connector of  the front(not working) motor connected to the main harness. I have a small piece of shrink tubing on each individual wire of the unused connector from the controller I have 54.6 volts on the motor side of the harness. The lights on the twist throttle are all lit but the BAC reads 1 bar - no power. When I unplug the front motor and plug in the rear motor all is great. I don't get it. What could it be? By the way  I'm using 48v battery

[Bikemad]

Thanks for the additional info Jack.

If the BAC-601 Smart Display unit is connected to the front motor, check to see if it is also displaying an error code like this:



If it is displaying error code "8", the controller voltage setting is probably too low for the 48V battery. I don't know whether this would cause the battery gauge on the Smart Display unit to show the very low reading, but if the controller voltage was set to 24V or 36V, the motor would not run on a 48V battery because the default Over Voltage Protection value would be much too low for a fully charged 48V battery:



Try plugging the BAC-601 into the rear motor connector and see if all the bars are displayed correctly. If all the bars are showing on the rear but not on the front (with 54 volts on the motor harness) the front controller will either need to be reprogrammed to the correct battery voltage, or if all the voltage values are already set correctly, the controller may need to be replaced.

Unfortunately, you will be unable to check the controller settings if you don't have the necessary USB interface cable, but if you have the USB cable you will need to download the Vector Programming Software, if you haven't already done so.



Alan
 

[Vipermn]

Hi everyone. It's been a couple of weeks since I posted that problem and here is what has transpired. The motor was fried. When I wrote David at GM  about my problem he said it could be a bad connection between the controller and motor and said to remove controller then reinstall it. I was a bit apprehensive not being familiar with the controller and motor but 14 years as a Line Maint Tech for semiconductor fab equipment gave me some electro-mechanical experience so I gave it a shot. When I removed the controller I found the main wires from the controller going in to the motor were fried. Now keep in mind the fact that the positive and negative main wires from the battery all the way to the connection at the controller were not burnt and in fact looked totally normal. That rules out reverse polarity connection.There was never any smoke or anything that would indicate any burning and since David had just sent that dual driver harness to me I don't know what happened. But I took some pictures and sent them to David and the next day David sent me the tracking number for a new front motor kit he was sending me. Talk about customer service, I think GM has the best. Totally amazing. Anyways, the motor showed up about a week later installed with no problem- kinda. What I mean by that is that the motor works fine and together the front and rear perform beautifully but if I ride up a hill and then stop,  if I twist the throttle too quickly when I take off again the power drops out and won't come back on until I turn the key off then back on and then I must still roll the throttle very slowly or else the power will just drop out again. Any idea what that could be? It doesn't happen as often riding on level ground but if I get aggressive with my riding it happens more often.

[Ron]

I'm far from an expert but is your battery able to handle the load that 2 motors will put on it?  I'm thinking that the voltage sags below some cutoff point and the system shuts down to avoid damage to your battery.  It would either be the battery BMS or the main controller shutting the party down.




If I assume you have a 48v 10ah lifepo4 battery from GM the max continuous current is 30 amps or 48V*30Amp=1440 watts.  The max burst current would be 48*50=2400 watts.  If you do indeed have that battery you *might* need to upgrade battery your battery.


Let us know what you find out pls.

[Bikemad]

I'm far from an expert but is your battery able to handle the load that 2 motors will put on it?  I'm thinking that the voltage sags below some cutoff point and the system shuts down to avoid damage to your battery.  It would either be the battery BMS or the main controller shutting the party down.

Ron, you're absolutely right, the problem was indeed caused by the battery not being able to cope with the high power demand from both motors.

Let us know what you find out pls.

Check out this thread for full details, including the simple solution that has completely eliminated the cutting out problem.

Alan