Possible?: Dual Pies with Different Controllers on GM 48V

[Pwd]

Hello everyone, I could use some help... I'm so close to a 100% functioning dual pie.

I just soldered up my battery connection and throttle. The soldering job is pretty crappy (not very clean) but I tested both ends and I'm getting full voltage. I had split all three wires coming from my throttle and fitted another connector to plug both controllers in. I plug the throttle into both pies, the battery level into the front and connected both power cords. I turned it on and tapped the throttle and I could see that both motors were going. So I hop on and goto take off, and they both cut out. I tried accelerating very slowly, but it didn't seem to let me go past half throttle.

I then re-read a couple threads that state to only split the black(0V) and white(signal) wires from the throttle, so I disconnect the red wire from the one plug and it seems to go further without cutting out; it still did; but at pretty much full throttle. Why isn't the red wire used for the additional motor?

One thing I noted was that I cannot seem to get the rear motor to spin by itself. It seems that the throttle and power must be plugged into the front for the rear motor to work as-well. I also noticed that when I didn't have the throttle plugged into the front, it would beep 3 times as expected, but the rear motor would not do this at all. Any ideas?

I'm charging my battery right now and will try again in the morning, I really want to feel the power of the dual pie! Thanks in advance.

[Bikemad]

I then re-read a couple threads that state to only split the black(0V) and white(signal) wires from the throttle, so I disconnect the red wire from the one plug and it seems to go further without cutting out; it still did; but at pretty much full throttle. Why isn't the red wire used for the additional motor?

The Red wire is a 5V regulated supply from the controller. If only one controller was connected to the battery, it might put too much load on the powered up controller, and may even result in failure of the 5V regulator chip if it has been subjected to an excessive load.

I'm surprised that disconnecting one of the 5V supplies makes any difference at all to the cutting out, which I suspect is more likely to be the battery's management system (BMS) being unable to supply enough current for both motors under higher load.

Are you sure both motors are still working since you disconnected the red wire from the one plug?
 

One thing I noted was that I cannot seem to get the rear motor to spin by itself. It seems that the throttle and power must be plugged into the front for the rear motor to work as-well. I also noticed that when I didn't have the throttle plugged into the front, it would beep 3 times as expected, but the rear motor would not do this at all. Any ideas?

As long as the rear motor is being fed correctly from the battery, it should be able to run on its own without any problem, provided the throttle still has the required 5V supply.

If the rear motor's 5V supply has somehow become damaged, this might account for why it does not beep or run on its own.
It might be a goods idea to check the 5V supply by putting a voltmeter between the red and black throttle wires coming from the rear motor.

Alan
 

[Pwd]

Thanks Alan, I appreciate the help.

I just tested the rear motor with an extra throttle I had; it works fine. I connected only the white wire from the throttle to the rear and all three to the front; they both seem to be working fine. So to be clear, I just need the signal wire connected to the rear as long as all are connected to the front?

Not sure why, but my split throttle seems to be working fine now. I still can't get the rear motor to beep, but it does run. I'll be sure to test my 5V when I go back out to work on it.

If I acquired a USB cable do you think setting each motor back to 24V would prevent the motor from cutting out without sacrificing speed/torque?

[Bikemad]

If both motors are connected to the same battery, the black throttle ground cable should already be common, but it wouldn't hurt to join the front and rear black throttle wires together, just to make sure.

You'll probably find that both controllers are already set at 24V, but reducing the continuous and peak current should help.

The rated output of the GM batteries are as follows:
Max Discharge Current: 35A(12AH)/60A(16AH)
Max Continuous Discharge Current: 20A(12AH)/30A(16AH)
So you would ideally need to halve these figures for each motor to allow for their combined use, but this will obviously make it noticeably less powerful (when using just one motor) than it was before the second motor was added.

To experience the full power of the dual drive setup, you would need to upgrade the battery (or fit an additional one) to cope with the increased current consumption.

Alan
 

[GM Canada]

So I hop on and goto take off, and they both cut out. I tried accelerating very slowly, but it didn't seem to let me go past half throttle.

I'm charging my battery right now and will try again in the morning, I really want to feel the power of the dual pie! Thanks in advance.

I had this problem when I first hooked up dual pies in this thread..
 
http://goldenmotor.com/SMF/index.php?topic=2133.msg13893#msg13893

I had to use the usb cable to cut back how many amps they would draw and it solved it.

Gary

[Pwd]

Thanks guys, I've got time to think it over until the roads/weather improve. I also have to wait a couple weeks for pay day to buy a USB cable.

Cheers!

[Pwd]

So I got my USB cable last week.

On the weekend I managed to let a spoke get so loose, it almost fell off, so one new tire tube later(I popped the one while I was trying to fix the spoke) I'm back on the road.

Unfortunately both pies were already set to 24V... so I guess won't be seeing any increase in power with my current setup since my battery is doing all it can. I did expect there to be a little more torque with a dual pie setup than what I've got, but I do notice a difference in the mid range acceleration. Before I touch my bike with the USB cable to modify the settings... is there anything anyone would like me to test? I'm going to try setting them both to 48V and see what happens, then back to 24V...

[GM Canada]

I don't have any tests for you but if you do use that cable I would pull down the regen. My front wheel is at 25 percent and my rear at 50 percent. I don't know if regen is the culprit on controller failures but any failures I have had people report to me regen was on and at 100 percent. In other words, I have not had anyone with a controller failure tell me regen was off when it failed.

Plus I have found that 100 percent regen on the front wheel is very dangerous on slippery surfaces.
Gary

[DirtyGinge]

Using the cycle analyst, I found that even though the controller is limited to 13-15 amps power delivery when throttling, if you apply regen at 75% at 48V, you can generate 17 amps of regen, this can surely overpower the fets on the controller

Even more bizarre, I have a set of hope dual LED 8.4 volt lights, they have a low voltage cuttoff mode that flashes if the lights go below 7.4 volts, even for a second.....using a dc-dc converter, I converted 56 volts to 8.4 volts

anyway, without a battery connected at all, cycling at 12-15 mph, I can power these lights.......so the wheels without regen are generating 40-50 volts back down the battery line...

Just for info of course.......so lesson 1 kiddies, if the battery is not connected, don't put the battery feed on your groin and cycle, unless thats your kinda thing

[Pwd]

Thanks guys, ya the regen is quite strong with dual pies; so I'll definitely cut that back (probably around 40% front and 60%rear). I'll also report back when testing both pies on 48V.

[Pwd]

For the record, I used your wiring diagram Bikemad; and it works great! Although cutting off one motor doesn't seem to let me go further on a low battery (like I thought it would), its still kind of neat to have a selectable drive. My theory was that if the battery would begin to cut out, I could switch to use just one of the motors and draw less amps. I also don't seem to be getting better efficiency with the two motors, this surprised me aswell.

[DirtyGinge]

To be honest, using different controllers other than GM, I found the efficiency to be the same...it seems the efficiency gains from a dual pie setup are recouped from the "loss" of the controllers at the high amp end ( i.e. hilly areas)

Using controllers on a single wheel with IRB4110 mosfets, the draw seems to be the same as dual pies

If you have dual pies, I would suggest a switch to be able to switch the front off, so if conditions are wet, you can get more control

[MonkeyMagic]

Hey just regarding the GM batteries

The cells are rated at 2.5C continuous, so 30A continous, the most I've peaked my GM battery is 48A I assume it would do around 50 or so without issues, but cannot say the same for the BMS but if its similar to the other variants it could do 60

My dual drive up a mega steep hill will pull around 40A