sorry to disagree. there are 2 entries for check battery. One is for the 12 volt battery and is in every service list (1, 2, 3). Service 3 has a separate entry for, what I presume is the main EV traction battery.
Could be as simple as a software (BMS) check, as well as physical inspection of the connectors to the HV pack front end- only visualized with the bottom covers off. The second part you could do yourself, while the first part would be done using a diagnostic tool only the dealers would have access to. I don't recall seeing this as part of the regular maintenance, at least in my 21 manual, but it can't hurt to have it done.
My question is technical. For example for a regular 12 volt battery you do load tests and alternator voltage tests. How would a garage do a load test on an EV Traction battery? I suspect that everything needed is actually on the car already. I cannot see connecting a load to the traction battery. Normal use of the car should gather such info.
The BMS contains a "precision shunt" which measures current in real time, both in and out separately. Along with the related pack voltage measurement, that data integrated over time counts cumulative coulombs and cumulative energy and places the values in the four registers readable over OBD. Battery capacity can be closely estimated by logging and plotting the data, then adding a linear trendline to extrapolate that over the full 0% to 100% displayed SoC and to determine the rate of change (the slope). You would drain the battery by driving and the wider the range you can span the more accurate the results will be. If you could actually manage 0-100% you could change the word estimated above to measured. It matters little how you drive because you're only doing that as a convenient way to drain off the energy. I took this data December 2021 and as I expected obtained the advertised capacity of 180 Ah and 64 kWh to within 1%. The thin black linear trendlines follow the data so closely you can barely see them in the graph below.
thanks, very cool that you can get this out of OBD, but this does not answer the question of exactly what the dealer does to "check battery condition" in order to justify taking your money, and what, if anything they can do. Is there a point in reduced capacity where the warranty will replace the battery? Would the driver not be able to get battery condition from the dash? Or do you have to do your data extraction and excel linear curve fit. (I am an electrial engineer, I know what you are doing. )
The dealer's equipment as best as the community knows only tells them if it's 100% or under 70% SoH, which is the warranty threshold in regions that specify that explicitly. No one has reported the existence of any other test other than cell balance, certainly not a "load" test. There have never been capacity related issues reported on forums - most common is an error light that indicates a general issue, presumably either low isolation resistance or excess (0.1 V) cell voltage imbalance. There is no indicator on the dash. An owner using any one of many available apps and an OBD dongle can check the current SoH but it's almost always 100%, as mine is at fours years old. The only other seen recently under 100% was 98.6% at 230,000 km. The theoretical life down to 80% SoH is double that.
