As others have mentioned, I've seen numerous alerts in the EVIC pertaining to failures of the Stop/Start system on my 2016 Latitude 6 cyl. This first happened last fall on a trip to upstate NY; the "Service Stop/Start" message appeared, then about 30 minutes later, I began to smell sulfuric acid fumes coming from the battery, which had severely overheated. The following day, I found a dealer near Rochester who flashed some firmware updates that were supposed to correct the problem. He showed me the battery test results, which indicated that it "passed" and was therefore ineligible for replacement under warranty.
I got through the winter without major issues, although sometimes I wondered if the Intelligent Battery Sensor (IBS) was functioning properly. For example, once the engine warmed up about ten minutes after a cold start, ESS would begin operating correctly -- but then, after 30 minutes of daytime highway driving with very little load on the electrical system, the EVIC would show a "Stop/Start Not Ready - Battery Charging" message, which didn't make much sense, since the battery sensor had apparently seen sufficient charge earlier.
Last week, the "Service Stop/Start" warning popped up again after several hours of highway driving and about an hour later, I began smelling battery fumes. Fortunately, I was only 3 miles from home -- so once in the driveway, I recorded this 2 minute video as proof of the problem. Same symptoms as before; battery was very hot and vapors were venting from the negative side. Next morning, I checked the voltage with a DVM and it was down to 12.19 V.
I discussed this with my local dealer yesterday and set up an appointment to have it serviced on Monday. Has anyone had similar problems with overheated AGM batteries? Are there any service bulletins that require IBS replacement? Thank you for any advice you can offer.