I spent a while trying to figure out where to code the IBS. No luck.

I have never witnessed any of the voltage related issues described and I've always been aware of the car trying to keep the battery at 80%.

My understanding is that many of the systems run through a vintage regulator but possibly not the windows so that will be an interesting one to test.

AGM batteries are supposed to be very sensitive to over charging, there are very detailed notes about stopping charge when they get to a certain current level when charging. A non issue when charging to 80%, also non issue for your charging system if it's an AGM charger, but if you charge at home then drive away with IBS disconnected, you're effectively putting it on a dumb charger that is just applying ≈14v, and that sounds like a recipe for damage. (Unless you have a flooded battery in which case, your reasoning is solid).

I've been monitoring reports for years and with IBS I'm seeing far longer battery life than the days before. Eg typical 3-5 years on e53 and 6-7-8 and more years on the e70.

My understanding was the IBS was as much for battery life as cafe standards.

Wife's '15 F10 actually shows when it's "dynamic braking" on the dash and she's does get very good mpg. 24/25 typical vs. my 20/21 in my e70. Same motor, but 1000-1500# less weight to toss around

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)