No Regen After Numerous Standard Mode Charging Top-Offs

[Roadster]

Scenario: I go on a trip for two weeks and leave my car plugged in to charge in Standard mode. The timer is set for the charging to start at 2am nightly. I come back home and the car is fully charged but seems to have 10 more ideal miles of range than it normally does with my daily top-offs (normally 175 but now showing 185 miles). CAC has also increased by five (normally 146 but now at 151).

Symptom: I take the car for a drive and immediately notice there's no regen and there's also no dash "Regen" indicator on either. Checking logs, it appears the car got a slight top-off each day and the ESS inched up near 95% charge. I end up having to drive the car down to approximately 100 miles of remaining range before regen starts to come back into effect. I assume the car is having sheet balancing issues so I proceed to do two full power cycles (down to 8% then back up to 80% 2x). No luck. Even now, a month later, I still have to drive the car down to 100 miles remaining before regen returns. Worse, the CAC has dropped to 144 with 172 ideal miles after each charge.

Question: Is there a way to recalibrate the system so I'm not without regen for the first 1/3 - 1/2 of my range?

 

[Marius]

Maybe I can not help you since my standard maximum charge is limited to 108 miles but anyway I notice that you have the JdeMo charge unit?
This unit messes up the software of the car and it can sometimes take 4 or 5 charges before regen has returned after intensive JdeMo use.

 

[Roadster]

Ah, thx Marius. This makes sense as I did have a JdeMO session recently that was performed after the battery was run very far down. Mind you, the car was already exhibiting the aforementioned symptoms prior to this session.

Below is an excerpt from the JdeMO for the Roadster? thread that seems to suggest this condition is indeed created by frequent DCFC charging and can be remedied by a few full ESS cycles on AC. Paging @TonyWilliams for his thoughts (thx Tony):

Moreover, the pattern of absent regeneration stuck with the car after next AC-charging cycle too. Still did not regain regeneration until there was only 150-180 km Ideal range left. When I got home, I found that it took three full charge cycles on AC for the car to normalize the regeneration when driving.

However, I only occasionally DCFC my car and almost exclusively use 240V/32A for daily charging. I'm curious if anyone has left their car plugged in and had the vehicle top-off past 80% if left for multiple days on the charging timer. If so, this might be a software bug. If not, perhaps a JdeMO update is needed to prevent the car from continuing to charge past the 80% standard threshold when charging on AC?

 

[Marius]

Maybe disconnect the JdeMo from the CAN bus and see what happens

 

[Roadster]

I texted Tony and he replied confirmed the AC and regen charging systems are autonomous so, unfortunately, disconnecting JdeMO won't have any effect. Any other thoughts on how to reset/recalibrate things? It seems the car is charging past the 80% cut-off and up to 95-100% in Standard mode.

 

[gregd]

The only thing I can think of is to consider the wall "charger" (connector) behavior. I had an occasion to use a Clipper Creek HCS-40 public charging station in town, and it had a habit of cycling a bunch (dozens) of very short (few seconds to a minute) charging cycles after the initial charging session completed. Not a lot of charge each time, but I expect it could add up over time.

 

[X.l.r.8]

It was my understanding (not from roadster bms) that balancing takes place in the upper end of the cycle, above 80% and was given to believe a range charge at low amperage over a long time would balance the pack, driving down to low power and recharge only helped with the displayed/ calculated range. If you have one brick/sheet over saturated it would stop regen so maybe look at brick level rather than pack level.

 

[Marius]

Try software reset. Go into the VMS screen with the pin as you can find in the newsletter of Gruber and do a reset. VMS screen goes dark for 1 minute and maybe the situation improves.

 

[Roadster]

I'm not aware of a software reset option in the diagnostic mode. If it's a VMS reset you're referring to, doesn't that require disconnecting the power connector from the unit in the passenger wheel well?

 

[markwj]

Can you show us the DIAG mode ESS screen from your car after a full standard mode charge? I am interested in values for CAC and SOC LIM, MAX. That should give us some idea of balancing status.

 

[Roadster]

Success! Full regen has returned after a simple VMS reset. You don't realize just how integral regenerative braking is to the enjoyment and safety of driving the Roadster until you're coasting down the highway having to rely on the standard Elise/Brembo setup like I've been for over a month. Well, I guess if there's any good news, whatever glaze was on my pads has been removed

 

[Marius]

It is worth to try if this reset also works to overcome the issues with regen and JdeMo.
After a long JdeMo charge reset VMS could solve the regen issue?

 

[Roadster]

It certainly wouldn’t hurt to try. Paging @RuneTR who originally encountered the JdeMO issue (though, it’s been over a year since their last activity on TMC).

REMINDER: make sure to download your logs before performing the VMS power cycle as they’ll get cleared on reset