# Zilla 1K controller bucking under constant throttle



## jordanleaman (Mar 30, 2021)

Hi all. I have a Zilla 1k controller that I recently installed in my '91 Miata conversion. I'm using a Hairball with a -P option and a HEPA pedal. Controller works great and delivers good power except for occasional "bucking" that mostly happens when on constant throttle between 80 and 300A. By bucking, I mean near total loss of power for a fraction of a second, and then near immediate recovery. All of this happens very quickly and then I'm back to normal power for whatever pedal position I'm holding.

I'm able to get instantaneous battery current draw from my BMS via canbus -> bluetooth OBD2 reader -> Torque Pro app on my phone. I'm able to see that the battery amps very suddenly drop off when this happens and then recover quickly.

Diagnostics so far:

I've triple checked my wiring and all of it is snug.
I have sufficient liquid cooling with a 2GPM pump and radiator. Temps are not an issue.
I don't believe my contactor is dropping, at least I think it should have failed by now if it had been interrupting that much current as many times as it has "bucked" on me. I'm using a Gigavac GX14BA and have a properly installed snubber diode across the contactor coil. Still need to verify before ruling out.
I have not one, but two deep cycle 12V batteries in parallel that are maintained by a sufficient (1000W) DC to DC converter, so I've ruled out any issues with low or unstable SLI voltage.
Checked error codes on Zilla, nothing unexpected.

Since this issue can only be exhibited while driving, it's been a bit hard to troubleshoot. Next steps will probably be wiring up a battery monitor to read voltage at B- and B+ on controller to check if the contactor is indeed dropping while driving. I was going to wait until after I had officially ruled that out before posting here, but wanted to get the ball rolling with any suggestions y'all might have


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## wjbitner (Apr 5, 2010)

jordanleaman said:


> Hi all. I have a Zilla 1k controller that I recently installed in my '91 Miata conversion. I'm using a Hairball with a -P option and a HEPA pedal. Controller works great and delivers good power except for occasional "bucking" that mostly happens when on constant throttle between 80 and 300A. By bucking, I mean near total loss of power for a fraction of a second, and then near immediate recovery. All of this happens very quickly and then I'm back to normal power for whatever pedal position I'm holding.
> 
> I'm able to get instantaneous battery current draw from my BMS via canbus -> bluetooth OBD2 reader -> Torque Pro app on my phone. I'm able to see that the battery amps very suddenly drop off when this happens and then recover quickly.
> 
> ...


Make sure it isn't the throttle pedal or its connections. That would be the first thing to check.


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## jwr813472 (Jun 1, 2010)

jordanleaman said:


> Hi all. I have a Zilla 1k controller that I recently installed in my '91 Miata conversion. I'm using a Hairball with a -P option and a HEPA pedal. Controller works great and delivers good power except for occasional "bucking" that mostly happens when on constant throttle between 80 and 300A. By bucking, I mean near total loss of power for a fraction of a second, and then near immediate recovery. All of this happens very quickly and then I'm back to normal power for whatever pedal position I'm holding.
> 
> I'm able to get instantaneous battery current draw from my BMS via canbus -> bluetooth OBD2 reader -> Torque Pro app on my phone. I'm able to see that the battery amps very suddenly drop off when this happens and then recover quickly.
> 
> ...


I had that problem when things started to really warm up. I re-seated the motor brushes. Actually swapped them around and the problem went away. Hope this helps.


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