Shuddering under acceleration after replacing OBC snubber caps.

[Bebbetufs]

Thanks to the fantastic people contributing their expertise and time to the forum I've been able to repair the OBC by replacing the snubber caps. The work was done with the OBC in the car. It is now charging fine including the 12v.

I have no warning lights and all DTCs relating to charging has disappeared.

I've had the U1113 DTC for as long as I've had Hobbdrive and it is still present. The car has been running fine with it before.

After replacing the caps I now get a severe shudder when accelerating under load. Like going up hill at slow speed in backstreets the car seems to completely lose and regain drive for a series of instants. This causes the whole car to shudder severely. I searched the forums, but could not find anything similar.

Any thoughts?

 

[kiev]

Your car is having quite a strange problem. i don't think it has anything to do with the OBC since that is not operating while the car is in READY. To make a quick test for this you could remove the 20A fuse from the MCU to totally isolated the HV from the OBC and DCDC Converter. Of course the 12V battery would not be re-charged like this, but if it is a fresh and strong 12V then it would be fine for a short test drive.

This begs the question of what is the age and condition of the 12V battery? An old, weak or worn out 12V will cause all sorts of problems with a car and especially an EV.

i would recommend to monitor the HV pack while driving to see if some cell(s) may be getting pulled down and out of family with the rest of the pack when accelerating. Almost anything and everything that is not within normal specs will throw a DTC so it is strange that no code is stored...?

 

[Bebbetufs]

Thanks for your input.
I seem to remember reading about somone else having shuddering issues, but I can no longer find it.

I'll test your suggestions. I have a tiny thought that I might have forgotten to plug in the CANBUS plug in the OBC, but if that were the case I would surely get more error codes, or no charging?

The 12v battery has been on a maintenance charger for about 3 weeks, so it should be fine, but I'll look into it. I have an in-dash voltmeter connected to the 12V it seemd steady at around 14.4V.

The gear shift position sensor is out of whack. It won't register in the "C" position. The other positions work fine. Putting it in C makes the car go out of ready, but this sets a warning light. Restarting takes care of it. It has been like this for a long time, so I didn't suspect it, but I'll take a good look at it, but could it be related?

 

[kiev]

Yes the gear shift position sensor is a very likely candidate to cause your issue. It is a dual sensor with 2 sets of contacts for each gear, so it checks that they match as some sort of redundancy check.

 

[Bebbetufs]

Thanks. I'll take a look at it tomorrow. I'll get back with the results.

 

[jray3]

I believe a gear shuddering issue is actually fairly common, but under different circumstances. I can induce it pretty reliably by shifting into D while still slowly rolling backwards, or from a standstill if I 'blip the throttle', or depress and quickly release the accelerator and then push it down again. In both cases the motor will "clunka, clunka, clunka" back and forth for a couple of seconds. Thankfully, no apparent damage in 142k miles.
I had assumed the issue came from confusion/noise in the resolver signal that measures motor RPM.

On a sightly related tangent, EV motor company UQM was mainly selling wheelchair motors when they began their foray into roadgoing EVs. Their test mule was an aircooled VW station wagon, the 411. https://en.wikipedia.org/wiki/Volkswagen_Type_4
This rear-engined wagon enabled engineers to rig a Belted Alternator-Starter motor to the crankshaft without any body modifications, and also keep it out of the weather! From a firsthand testimonial, they managed to switch back and forth from motor power to regen with EVery cylinder firing while at low RPM, turning that churning reciprocating engine into an extremely smooth powerplant. I had asked for the gear to do the same to a Karmann Ghia, but they turned me down. So instead, I built the pure EV Karmann Eclectric! https://karmanneclectric.blogspot.com/search?q=make+a+what+outta+who

 

[Bebbetufs]

Last night I did a full test drive and depleted the battery. It went perfectly with no shuddering at all.

I then discovered that I'd forgotten to plug in the CAN plug on the top board in the OBC because the car would not charge. This triggered a fault code. Undid the lid and plugged it in. The charging went well and the fault code is gone.

Today the shuddering is back, although slightly less severe.
Still no fault codes.

 

[kiev]

The gear position sensor inspection results?

 

[Bebbetufs]

I went on a short trip for unrelated reasons yesterday and the shuddering was completely gone again. I now believe it to be unrelated to the charger repair.

Unfortunately, I haven't had time to look at the position switch. I'll report back once I have. I'm expecting the switch to be the culprit.