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[motordavid]

Are you describing the Battery Tender sold by BMW?

If so, it's "no better" other than the cig lighter plug in
and that BMW Roundel...

Edit: Ah, I think you are talking about a new batt.
I'd pass on the Stlr version: no "better" than aftermkt,
and an utter rip.

If you get a new batt., I'd hook it up to your handy dandy
new Batt Tender for a day or two, if you can manage it.
Or, install it and hook up Batt Tender to the lugs when not
driving it, to get it fully charged, slowly.
GL,mD