Overview - I have for along time wondered if there are any significant consequences to failing to perform the Battery Sensor Module Calibration Procedure in cases where a battery was replaced, charged outside of the car, or improperly charged. I think the answer is mostly no, very little consequence most of the time. But I did run across some info in the Service Manual about the alleged consequences, and thought I would share it. So, here goes. The first part is just a review of what the Battery Sensor Module and the BSM Calibration Procedure for those that did not know about. it. The info regarding the potential isses (which I think are minimal) is really in the attached clips.

Background
As some/many/most may know, the Stingray with the FLA battery has a Battery Sensor Module (BSM) that is attached directly to the negative terminal of the battery. The negative battery cable connects to the BSM - so all current that flows out of the battery or into the battery flows through, and is measured by the BSM. That along with measuring "resting" voltage is how the Body Control Module (BCM) estimates the battery state of charge, which it then uses to select the system charging mode and also can use that for load shedding. There is an additional connector on the BSM which is how it communicates the info it collect to the BCM.

As a result there are two "semi important" things to be aware of (again I think many/most know this part too). And they are 1) when using a charger the negative lead of the charger cable must be connected to chassis ground and not directly to the negative battery post. Otherwise you will bypass the BSM and its estimate of the battery SOC will be skewed. If you charge via the port in the frunk, then it is properly connected, no problem. And 2) If the battery was replaced or charged out of the car or improperly charged, the Service Manual indicates that the BSM need to be "calibrated". The procedure is extremely simple - just shut the car off and leave it undisturbed for at least 4 hours.

What Happens the Calibration get Out of Whack?
With that as background - here's why am writing about this. I really wondered if this calibration step is essential. As far as I know, when someone installs a new battery, themselves or even at the dealer, it does not seem as if anyone observes the calibration as urgent. I just had a new battery put in my car at a dealer, and I drove it around - it did not sit for 4 hours until much later. So.....is there really any consequence to delaying the calibration step? I don't think so - not very much. But I did stumble across some info about it in the Service Manual that indicates some situations where it might be a (minor) issue (to make a short story long). Just thought I would share it. You can tell its a "generic" GM description, because it mentions Start-Stop, and although Erays have that feature, this description has been in the manual since 2020. But what I found interesting and potentially relevant to us is that improper charging might cause the BSM to indicate a default SOC of 65% and prevent an OTA.

 

One comment I'll add. Some internet places say if you replace a flooded lead acid battery on a GM car you need to use a scan tool to update the charging profile for an AGM battery. However it doesn't appear that is an option on the C8 Corvette, or at least it isn't clear in the service manual nor is it clear whether or not the C8 learns this during the calibration cycle. One website I stumbled on said the Battery Sensor Module is different for a car that comes from the factory with an AGM battery.

 

Hmm. Well, actually there is scan tool parameter to indicate the battery type. But it is set to default, not to flooded lead acid. And I have never found anything in the Service Manual about changing the setting for different battery type. I attached the portion of the scan tool list showing that. The list of battery parameters is lengthy and interesting. You can find it in the LEMON manual by using find in page, with the expanded index, and searching for scan tool information, then selection Body Control Module Scan Tool Information.

And, I have found nothing about if or how the charging system adapts to the battery type. I do know its possible, though I have no reason to think that the C8 does all that. The new CTEK flagship charger does not need to be told anything about the battery , but will charge FLA, AGM, and Li batteries.
https://www.ctek.com/us/battery-char...one-(gen-2)-na

 

I thought this was interesting enough to post. It implies that the system can measure quite a lot of information about the battery and the state of the system.