# Using 2 controllers in Series



## rmay635703 (Oct 23, 2008)

Sorry, this is one of those dumb mental masturbation exercises, but is a step over overunity 

I had gotten this poorly made circuit a while ago and I promptly said it couldn't work because the timing of the controllers would never match but now that I look at again it looks like an inefficient but potential method of using 2 equally sized controllers to double up voltage, because of the bleed and supercap it shouldn't overvolt either controller but I think a contactor would need to be added between the controllers to keep the bleed resistor from leaking through the freewheel on the lower controller when idle.

I still think there must be several major glaring issues with this scenario I am missing. I do know the bleed resistor is needed to make the upper controller "turn on".

Any ideas if this could light up the place (on fire) or if it would work?

Because of the cap the controllers could mismatch on timing and also should not get exposed to lethal voltage, though spikes would be higher than average. (in both directions)

Cheers
Ryan


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## rmay635703 (Oct 23, 2008)

Since no one replied, the reason it can't work is that the center voltage is floating and if the lower controller does not push the same amperage as the upper the voltage difference on the upper controller increases and lets out the magic smoke.


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## GerhardRP (Nov 17, 2009)

rmay635703 said:


> Since no one replied, the reason it can't work is that the center voltage is floating and if the lower controller does not push the same amperage as the upper the voltage difference on the upper controller increases and lets out the magic smoke.


I don't think it can work. It is hard enough to make a controller behave with a well defined inductance as a load, but I that one controller seeing another in the load side would be impossible. Two in parallel for larger current might work, but two in series for higher voltage NOT.


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## dougingraham (Jul 26, 2011)

GerhardRP said:


> Two in parallel for larger current might work, but two in series for higher voltage NOT.


Neither will work. In the series case the one that turns on first will over voltage the one that does not turn on. And if you somehow manage to sync up the turn on the one with lower resistance will blow up the other one when both are turned on.

In the parallel case you could make it work if you designed it as a modular system with a master and slave arrangement but it would require that it be designed that way from the ground up. It isn't something you could just slap together.


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## HYPRDRV (Aug 20, 2009)

Ok If I could get some thought on this.

What if you have 2 motors and want to use 1 controller. Is it possible to operate this way? 
I have 2 Homewood group 4.5K motors on a prop shaft on a boat and each is controlled by an STI motor controller (#100A40). They no longer provide that controller but do have a replacement for it however I still would need 2 controllers for the 2 motors. Has anyone seen this dual setup with 1 controller?

Thanks,
Steve


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## arklan (Dec 10, 2012)

generally speaking
u can use 1 controller to power 2 motors no problem
u can do it in series and both motors will get half the volts or u can do it in paralel and both motors will get half the amps


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