Well, there goes my theory! Your battery looks very good.
Now I'm confused as to why Reduced Propulsion is invoked. I can't see a cell going bad momentarily and then getting back into perfect shape.
Are there other reasons for Reduced Propulsion...anyone?
Are you saying that Reduced Propulsion comes and goes? I guess that you did say that. Perhaps a momentary break in connection at a connector is being interpreted as being "low voltage". I would begin checking connections, beginning with the last known connection problem that was "fixed".
Let’s see... If you run out of gas while driving in Hold Mode, you’ll trigger a Propulsion Power Reduced episode. If you drive up a steep mountain road at 80-90 mph while driving with a fully depleted battery, you’ll likely trigger a PPR episode. If you are driving a Gen 1 Volt with a fully depleted battery that has lost 10% or more of its full capacity over the years and stop to run an errand, if the engine is still running when you turn off the car, you may trigger a PPR episode by pulling power from the battery when you try to restart the engine.
PPR episodes, especially when not accompanied by a malfunction light, are kind of like stubbing your toe or banging your elbow... unlike arthritis in the joints, there’s nothing really wrong with your toe or your elbow, you just did something that caused a sharp pain in your toe or elbow that’s warning you not to repeat what you did that resulted in the stubbing of your toe or the banging of your elbow... The PPR is the vehicle’s method of telling you to not do something (don’t run out of gas, don’t keep so little power in the battery buffer when driving aggressively while extending the range)... and if it’s accompanied by a malfunction light, then the conditions under which it occurred should help locate the problem that triggered the PPR. Metasys Tech’s battery cells appear to be in decent shape, so it almost appears as if the PPRs could be triggered by the same problem that is triggering the CEL (perhaps a code reader would provide a clue). Perhaps a momentary break in connection at a connector is being interpreted as a loss of battery access, so performance is reduced to allow the car to be driven to where the problem can be repaired.
I’ve finally relocated a comment I once read in an old thread that seems to be applicable to Jaryd’s 121 mV spread limit...
In a thread started in January of 2015 discussing the gm battery degradation test procedures, WopOnTour, a very knowledgeable forum participant, responded to the question, "wouldn't differences in the cell voltages I mentioned be a good indicator of a bad cells problem?" by saying:
" No generally they would not .
Observing a 0.01-0.03V variation on a scan tool and especially in the absence of triggered voltage DTCs, would be considered perfectly normal. In fact, depending on conditions even as much as a 0.05V or more observed variation might be considered OK. This is because it will depend on exactly WHEN this instance was indicated , where within the pack the variation is observed, and under what specific conditions.
Was it during charging? discharging? hot/cold soak? before/after cell balancing occurred? etc etc
ALL of these can affect the observed cell group's (triplet) differential voltage and therefore ALL of these conditions are taken into account within the diagnostic routines used to establish when there actually IS an issue. So in a nutshell IF your Volt wasn't triggering cell variation DTCs THEN there isn't any significant variation present WHEN IT MATTERS."
As I understand WOT's comments, the system is constantly gathering data and running diagnostic routines to monitor the operation of the car. At any given time, the readings might be anywhere... so a greater than 121 mV variation will trigger a DTC only if it happens WHEN IT MATTERS. If it happens at other times, it does not. (I offer this example: your engine is running, you drive over a speed bump rapidly, and bam! The gas sensor jumps with the bumping, and the system interprets the interruption in the data as saying there’s no gas in the tank, but instead of triggering a PPR episode because you just ran out of gas, the data obtained at that moment DID NOT MATTER, so no PPR episode.)
Another question is asked, "What are some of the data indicators of battery pack problems?" and WopOnTour responds:
"Quite simply as far as individually monitored PIDs that one might be able to monitor on GDS2 and scan tool or some other CAN device, and used as a metric representing pack, group, or cell state of health- THERE REALLY ISNT ANY! The process is simply too complex to rely on simple point-and-shoot analysis if such individual data points.
Once a DTC is triggered however, that's when we KNOW something abnormal WAS observed under a precise set of enabling and failure criteria. Then and only then might some of these PIDs be used, but only under the conditions as detailed by the diagnostic and often only as a technician observable verification/corroboration of the diagnostic software's indicated detected fault."
Further information is available in this 2015 thread on battery degradation, and more information on cell balancing can be found in a 2014 thread:
OK everyone, this is kinda urgent -- my car is in the shop today. It literally is about to go over to 100k and I took it in to get the main traction battery checked, and some other, minor problems. The dealer service department called and said that they checked for error codes and that the...
www.gm-volt.com
After being parked at the airport for 12 days, when I was 1/2 mile from home, my 2011 Volt went into charge sustaining (CS) mode, with over 10 miles of EV range left. A message of "propulsion power reduced" came up, along with a check engine light. The engine was running, and the air...
www.gm-volt.com
