# Dual Controllers setup, how to do?



## major (Apr 4, 2008)

LotusEV said:


> Hi,
> I'm trying to get a controller that is capable of receiving my high voltage input (345 nominal) and run 2 motors in series... Now I'm thinking if it were possible maybe I should just get 2 controllers instead of one, I assume wiring the two controllers in series configuration would give 1/2 of the Voltage at each controller and therefore I could use 2 Zilla's or Soliton Jr's...
> 
> Does anyone have experience with this or any technical advice on how/if this could work? I could split the pack into two sections but I'm having trouble with schematics and figuring out how to get the single on-board charger to charge the full pack and have the drivetrain separately break the pack in half...
> ...


That's a big can of worms  As far as I know, 2 controllers will NOT work in series. And you should NOT charge the battery as a whole (in series) when the two halves are separately discharged.


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## LotusEV (Sep 8, 2012)

That is not good news... I'm wondering why the two controllers won't work in series though?

Is there a way to fractionally reduce voltage (without losing batteries)? I need to knock 10-20% off of my peak voltage output and still be able to run 200A peak out of the batteries.


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## LotusEV (Sep 8, 2012)

LotusEV said:


> That is not good news... I'm wondering why the two controllers won't work in series though?
> 
> Is there a way to fractionally reduce voltage (without losing batteries)? I need to knock 10-20% off of my peak voltage output and still be able to run 200A peak out of the batteries.


I should say; any experience with doing this, I know there is a way to do it with 2 resistors but I don't think it would survive the high current situation...


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## major (Apr 4, 2008)

LotusEV said:


> That is not good news... I'm wondering why the two controllers won't work in series though?


How about a simple explanation? The controller is a switch. Put 2 switches in series. Can you imagine that? If the 2 switches are both off, no current passes. If both switches are on, current can pass. If only one is on and the other is off (either way), no current can pass. 

See the problem? The only way it would work is to have the two switches (controllers) synchronized and that would mean no independent control. Which means that each controller would have to be rated for full voltage and current. Meaning one of the two controllers is fully redundant.


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## major (Apr 4, 2008)

LotusEV said:


> Is there a way to fractionally reduce voltage (without losing batteries)? I need to knock 10-20% off of my peak voltage output and still be able to run 200A peak out of the batteries.


That is what the motor controller does.


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## frodus (Apr 12, 2008)

major said:


> How about a simple explanation? The controller is a switch. Put 2 switches in series. Can you imagine that? If the 2 switches are both off, no current passes. If both switches are on, current can pass. If only one is on and the other is off (either way), no current can pass.
> 
> See the problem? The only way it would work is to have the two switches (controllers) synchronized and that would mean no independent control. Which means that each controller would have to be rated for full voltage and current. Meaning one of the two controllers is fully redundant.


Well, as I understood his explanation:

If he taps each controller off each half of the pack, and ran one controller to the upper and one off the lower, he could charge with one HV controller. Each controller gets half the voltage because of the tap. The controller and their respective pack are independant, but the bottom of pack 2 and the top of pack 1 are connected so you can charge them.

The issue here, as Major explained, is that you are not equally discharging each half of the pack.

What would be better is to get one higher power controller and run the series wound motors in series.


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## Zak650 (Sep 20, 2008)

I'm trying to do the same thing with two sevcon AC controllers and twin AC motors so I could run overall higher pack voltage. I'm not an electronics guy but from what I've been able to glean if the throttle drove two isolated op-amps, then the two independant op-amps could feed the throttle info to the two controllers. They would have to be wired in series with a mid pack tap between the two. Perhaps something like the Lee Heart battery monitor could keep the two half packs balanced if it fed information to the op-amp circuitry.


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## iop95 (Sep 4, 2012)

What type of motor is? For series filed coil DC motor is possible to link them in series and use a single controller; this motor type have filed coil in series with rotor and this lead to a very good mechanical curve for traction like high torque at slow speed and as speed increase, torque decrease. In car traction may arise same issue when motor's speed it's different (slip or curves if put on front train). At extreme, when one motor is locked, the other must support almost entire converter output voltage, or may put a circuit to detect speed imbalance and reduce output voltage in such way to protect motor. If motor nominal voltage are the same with controller no need for this.


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## major (Apr 4, 2008)

frodus said:


> If he taps each controller off each half of the pack, and ran one controller to the upper and one off the lower, he could charge with one HV controller. Each controller gets half the voltage because of the tap. The controller and their respective pack are independant, but the bottom of pack 2 and the top of pack 1 are connected so you can charge them.





Zak650 said:


> I'm trying to do the same thing with two sevcon AC controllers and twin AC motors so I could run overall higher pack voltage..........They would have to be wired in series with a mid pack tap between the two.


frod, Zak,

The center tap is a bad idea. It then is not running the 2 controllers in series. And not quite independent either. If you want to run half pack to each controller, lose the center connection and run 2 separate packs. But don't connect the 2 packs in series to charge, at least not with Lithium.

major


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## Zak650 (Sep 20, 2008)

major said:


> frod, Zak,
> 
> The center tap is a bad idea. It then is not running the 2 controllers in series. And not quite independent either. If you want to run half pack to each controller, lose the center connection and run 2 separate packs. But don't connect the 2 packs in series to charge, at least not with Lithium.
> 
> major


I can see how that could present some problems with balancing the two half packs. My main goal is to facilitate faster charging at public J1772 charging stations. Each half pack would consist of 34 CALB CA100 cells. So getting the cell count up higher speeds up that process a lot. By the way Jack Rickards latest CALB CA cell charging video is pretty interesting as far as fast charging goes.


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## major (Apr 4, 2008)

Zak650 said:


> I can see how that could present some problems with balancing the two half packs. My main goal is to facilitate faster charging at public J1772 charging stations. Each half pack would consist of 34 CALB CA100 cells. So getting the cell count up higher speeds up that process a lot. By the way Jack Rickards latest CALB CA cell charging video is pretty interesting as far as fast charging goes.


Let's not hijack this thread, but I fail to see what cell count has to do with charging stations.


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