I'm sure the CTEK chargers are fine, but just to close the loop on this, BMW's latest 'Advanced Charger' linked to in the second post has the part number 82-11-0-049-788, and the photo is wrong on the BMW website. It actually looks like this:
https://www.ecstuning.com/b-genuine-...35-space-~oeb/
And is nearly identical to the Deltran Battery Tender model here:
https://www.batterytender.com/Batter...-12V-4A-Select.
The only difference is that the Deltran model has a 6v / 12v option in addition to the Lithium / AGM option.
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2018 ///M2 LCI, LBB, 6MT...
Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings