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Hi Dala!


Let me see if I understand you correctly. You are going to try to modify the CAN message
0x1D4 that is sent to the inverter from the VCM?
I have a a Leaf motor and am chatting with the stock inverter via CAN messages.
see bbitnerblogs.com/e-miata
There is a maximum requested torque in the 1D4 message. Have you seen evidence
that the VCM is not sending the maximum requested torque when you have pressed the acclerator fully? Thanks..

P.S. I wonder if the inverter might perform differently in Diagnostic mode? I know it has
some temperature limits..

Bill Bitner
 

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Hi Dala!


Let me see if I understand you correctly. You are going to try to modify the CAN message
0x1D4 that is sent to the inverter from the VCM?
I have a a Leaf motor and am chatting with the stock inverter via CAN messages.
see bbitnerblogs.com/e-miata
There is a maximum requested torque in the 1D4 message. Have you seen evidence
that the VCM is not sending the maximum requested torque when you have pressed the acclerator fully? Thanks..

P.S. I wonder if the inverter might perform differently in Diagnostic mode? I know it has
some temperature limits..

Bill Bitner

Yes, the demand message in 0x1D4 is a signed 12-bit value with 0.25 factor. This would put the upper demand limit possible to write as 511.75 Nm


The response message that the inverter sends back is a signed 11-bit value with a 0.5 factor. This would put the highest value it can theoretically send back as 511.5


Please correct my calculations if I'm wrong! I store the findings here https://github.com/dalathegreat/leaf_can_bus_messages


I've been told that the inverter firmware is the limiting factor. How much we will soon see. Oh, and it is possible to increase regen this way!
 

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Yes, the demand message in 0x1D4 is a signed 12-bit value with 0.25 factor. This would put the upper demand limit possible to write as 511.75 Nm


The response message that the inverter sends back is a signed 11-bit value with a 0.5 factor. This would put the highest value it can theoretically send back as 511.5


Please correct my calculations if I'm wrong! I store the findings here https://github.com/dalathegreat/leaf_can_bus_messages


I've been told that the inverter firmware is the limiting factor. How much we will soon see. Oh, and it is possible to increase regen this way!
Hi Dala! This is great information. When you perform your experiments, I would pay close attention to the inverter voltage. As you say, you can increase the regen. However, this may either charge the batteries with more current than they are rated for or increase the inverter voltage past the 403 volt limit, which causes the inverter to fault. If the VCM is not commanding full torque in some cases, it may be because increasing the torque will cause the inverter voltage to go down lower than 240, where again the inverter will fault. Both of those faults are not permanent, but I'm not sure how they can be reset other than removing power from the inverter, or most likely, clearing them with a diagnostic code reader.. I look forward to hearing more about your experiments.. :)

Bill Bitner
 

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My initial attempts at persuading the inverter to output more power was a failure. Check this screenshot



In this screenshot I added 10Nm to the demand when it went above 253Nm. So it seems like the inverter firmware clamps to some hardcoded value to keep 80kW, which is a damn shame. I might try some other tricks, but it feels like either firmware needs to change (incredibly difficult) or an inverter swap from a newer Leaf (never done afaik)?


I got some additional info from a friend, "The inverter firmware limits torque to 254Nm (EM61) or 225ish (EM57)"
 

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Hi Dala!

I think swapping the inverter from a new leaf would be quite a challenge. There are some values from the resolver (on the motor) that have to be entered into the new inverter to make it work properly. If you are skilled enough to do that, altering the firmware may be the next step.. I'd be much more inclined to put a different logic board in the inverter to
get more power. If you did that, the next challenge would likely be keeping the inverter cool.
Have fun and keep up the great work.

Bill Bitner
 

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Do you have the throttle position and motor RPM that you could also plot with the torque demand and torque generated?

Is there a current limit in the inverter that might be holding the generated torque?
 
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