Magic Controller does not allow enough current for motor

[Lkiss10]

Hello,

I am working on a starter-generator for a petrol engine of a model aircraft. The motor is self designed 12N14P and its power is about 1 kW. I had a selfmade controller for it, but it has more problems, so I have decided to use the Magic Controller BAC-028 with 48V LiPo battery. It works, it uses the Hall sensors, but the torque of the motor is too low. The used current is max. 6-7A, when I apply torque, even if the motor totally stops. The settings of the constant current is 25A. I could reach 40A-50A from 22V with the self made controller. The motor is just a little bit worm now. When I used the self made controller, it was very hot after a minutes usage, what is not a problem, because it is only a starter, so it will work for 2sec. But I need somehow higher torque.
Do you have any idea, what blocks the higher current input?

Thanks

Laszlo

[Lkiss10]

Hi,

I have found something: https://goldenmotor.com/SMF/index.php?topic=4072.msg28801#msg28801
Is it a typical issue with this controller? So I should change the resistor? Who has experience with this modification?

Laszlo

[Bikemad]

Hi Laszlo andto the forum.

I simply modified the shunt on an early Magic Pie internal controller (which is very similar in layout to the BAC-028 external controller) and I managed to increase the current from ~20 Amps max. to just over 56 Amps.



Check out this post and this post for more information.

I continued to gradually increase the thickness of the shunt until the controller finally died (shortly after it delivered the following current):


I also have another internal controller on an MPII that was modified over 5 years ago and is still going strong, and often delivers ~50 Amps under full load.

Alan
 

[Lkiss10]

Hi Alan,

Thank you for the info. I have done similar shunt tuning with the self made controller, but I have never believed it is necessary with this GM controller. It looks really professional with the nice housing, PC software tuning. Yesterday I have set 50A into the constant current field. It was possible in the software, I could store it in the controller, but of course the current was not increased in the reality. Then what is the meaning of this nice software?
So I will start to play with the shunt :-(

Did you get any feedback from GM regarding this theme? It is the official GM forum, correct? Have you ever got support, comment from GM on this forum?

Thank you again

Laszlo

[Bikemad]

Hi Laszlo,

I suspect your low current draw (max. 6-7A) may also be due to a higher resistance and inductance in your stator windings compared to the hubmotor that the controller was intended for.

With the exception off the more recent Vector controllers, the controller's stated maximum current has always been higher than the actual current draw, so perhaps the stated figures relate to Phase current instead of Battery current. 

In the past, we used to get a lot of posts from GM China representatives, but with the exception of Gary Salo (GM Canada) there has been very little response direct from GM on this forum in recent years.

Alan
 

[Lkiss10]

Hi Alan,

I will have time to try the new shunt on the weekend. I will double the wire in the first test to reduce the resistance to the half. As I sow from your try, I am far from the max. power of the controller, so I can not make big mistake.

How old is this controller model? Does GM have new version in the 1kW range? I could not find. Do you maybe know similar good quality controller brand?

Laszlo

[Bikemad]

How old is this controller model? Does GM have new version in the 1kW range? I could not find. Do you maybe know similar good quality controller brand?

The external BAC-028*P (Magic) controllers have been going for quite a long time. I joined the GM forum back in 2009, and it was one of two external controllers being used by GM at that time, the other being a regenerative mode controller that automatically engaged regen as the throttle was released:



I don't think that the regenerative mode controller is still available, but a slightly larger (and higher current) BAC-0501 external controller was introduced, which presumably produces more power and greater torque:



Unfortunately, I have no first-hand experience with other makes of controller, so I am unable to comment on their quality or reliability.

Alan
 

[Lkiss10]

Hi Alan,

It works well :-) I could reach 30A. The torque is enough now. Later I will try to push it even higher (till 50A-60A), then I can reduce the size of the motor.

Thanks for your help.

Laszlo