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Shudder on Regen with Tesla Small Drive Unit

Posted: Tue Nov 14, 2023 4:04 pm
by Kitlacey
Hi All,

I have a strange, occasional problem with my Tesla SDU. I'm in final stages of tweaking and occasionally, after rapid acceleration, I get a shudder on regen as I decelerate. It's not huge, and makes no difference if I'm off pedal regen, or on brake pedal. It also makes no difference what values I use

I've attached the file. If anyone can suggest where to start; it would be appreciated.

Re: Shudder on Regen with Tesla Small Drive Unit

Posted: Tue Nov 14, 2023 7:29 pm
by johu
Looks like Zero EV firmware. It is rather outdated so if you don't need the special features you should consider upgrading to 5.32.R

Apart from that it might be worthwhile to set udcnom to some midrange battery voltage. Regen raises the DC bus voltage so you may be saturating the stator or something. Setting udcnom will compensate for voltage changes

Re: Shudder on Regen with Tesla Small Drive Unit

Posted: Wed Nov 15, 2023 10:10 am
by Kitlacey
OK, so UDCnom is currently 0, but the nominal battery voltage is 350.4, so I should try setting it to that?

I'm due to finish the project this week so I don't want to mess with anything else at this stage.

Re: Shudder on Regen with Tesla Small Drive Unit

Posted: Wed Nov 15, 2023 10:36 am
by johu
Yes, try that. You can always revert the change

Re: Shudder on Regen with Tesla Small Drive Unit

Posted: Thu Sep 12, 2024 4:54 pm
by alexbeatle
I'm struggling with slow accel when starting uphil, which leads to steep temp rise on inverter. Do you have this issue too?
My parameters..
viewtopic.php?p=74742#p74742