> If you're trying to determine what information would be available
> when using MDI/GDS on the Volt, I could probably take some
> screenshots and post them.
Thanks, that would be great. It might be helpful if I describe what I would like to be able to do with a Volt diagnostic tool. The best way I can do that is to give the background of what I have been doing in that respect with my two 2002 Toyota RAV4-EVs and relate it to that.
For the last 5 and a half years, I have possessed and been using a Toyota dealer’s handheld tester/scantool (made by Vetronix) together with the special RAV4-EV datacard (inserted into the side slot on the scantool) that only authorized RAV4-EV servicing dealers have (24 Toyota dealers in California and 2 in the NYC area). This special RAV4-EV datacard allows EV-specific and battery-specific data to be read on the scantool, and without that special RAV4-EV datacard, the EV-specific and battery-specific data can’t be read. So even my own local Toyota dealer (which is not an authorized RAV4-EV servicing dealer) is not able to read the EV and battery data with their diagnostic equipment, as I am able to do. Regular Toyota dealers can only read the more generic (non-EV-specific) DTCs that are common to both EVs and conventional ICEVs. (BTW, many other individual RAV4-EV owners have the Toyota dealer’s HHT/scantool w/ RAV4-EV datacard.)
The scantool plugs into the OBDII port underneath the driver’s-side instrument panel. It provides a real-time digital readout of such useful things as:
-- Pack voltage
-- Amperage in/out of the pack
-- 3 temperatures -- one in each of the three rows of the battery
compartment (front, middle, and rear), plus ambient temperature
-- Individual voltages of the 24 battery modules
-- Internal resistance values (in mOhm) of each of the 24 battery modules
(calculated by the battery ECU as a long-term moving average,
over the entire SOC range that the driver uses, of many ΔV/ΔI
calculations while driving)
While driving, one can occasionally glance at these data values, which change in real-time as one drives.
My scantool can also be used to reprogram or change the configuration and settings of the various electronic control modules in the car, but I have never done that and would never attempt to do so in the RAV4-EV, just as I would never attempt to do so in the Volt. Other than very rarely checking DTCs, which is useful if there’s some rare anomaly in the operation of the car, the only thing I use the scantool for is just to read the battery data values listed above.
Similarly, this is exactly what I would hope to be able to do in the Volt -- to acquire some sort of scantool which can read and display the same kind of battery data listed above, in real-time while driving. From the list that you gave of the 27 electronic control modules in the Volt, it looks like I would only need to access and tap into just two of those ECMs in order to read and display the battery data I’m interested in -- those being the “Battery Energy Control Module” and the “Coolant Heater Control Module”.
[I don’t know whether the Volt’s “Battery Energy Control Module” calculates and stores long-term moving averages of internal resistance values for individual cells or modules, but I’m not really too concerned with that in the Volt as I am in the RAV4-EV and in fact is really crucial in the RAV4-EV. I don’t think that’s going to be all that crucial in the Volt, for various reasons, which I won’t bother to elaborate here (unless anyone is particularly interested in an explanation of salient differences between the RAV4-EV’s TMS and the Volt’s TMS). I think pack-level IR is probably sufficient in the Volt and don’t think more granularity than that is likely needed. Pack-level IR calculations can easily be manually done on a periodic basis, say, once every 3 months, as long as one can get a digital readout of pack voltage and amperage on a real-time basis while driving. That is the primary metric of how one measures and keeps track of battery condition and health and the rate of degradation and ageing over time. But in the case of not having an automated battery ECU-calculated long-term moving average of IR, where in the absence of that one is going to do a pack-level IR calculation manually on a periodic basis, ... in order to have a valid, consistent basis of comparison over time, one must make sure to always run the IR calculation driving test (full acceleration, in Sport mode) at the same SOC every time and at the same battery temperature every time. In the Volt, I would suggest doing it at around 30% SOC in CD mode (CD mode runs from 85% SOC down to 20% SOC). Holding the temperature constant should be easy, as the Volt’s TMS apparently keeps the batteries between 20 and 22 degrees C while driving.]