[vonBlitz]

Hey, how did you connect to the cable into the relay?

I have that question as well, as I've not yet obtained an official BMW supplementary harness ( @Meese ? ) but have looked at the relay connector without seeing an obvious or easy sanitary way to add another set of conductors alongside the OEM leads.

In fact I have this question in relation to the installation of the supplementary harness as well -- apparently that harness is intended to replace rather than augment the existing OEM harness?

Often relays have dual parallel contacts that would make this easy, but that is not the case here.

 

[vonBlitz]

I've looked through the garage and storage, and haven't yet found the supplementary battery harness.

Sorry for the hassle.

Thanks for looking!

If you think you'll come across it in the relatively near future I'll hold off on ordering one... and I'm still considering the possibility of the far cheaper approach of just adding my own few buck's worth of 8 AWG wire in parallel, which has reportedly worked for at least one other owner, if I can devise a clean connection method to the relay.

 

[vonBlitz]

...I had pretty good luck by switching to an Odyssey PC680 battery which cranked hard hot or cold. But the quality on those seems to have gone down, or at least they don't seem to last as long for me as they used to.

I'm not an electrical engineer but my gut and experience makes me think the battery compartment size imposes a limit such that anything that fits will be barely capable of the required service.

Which is OK for weight reasons if nothing else, but only as long as tolerance stack-up doesn't fall into the inadequate zone and in-storage maintenance is performed competently -- which is something I keep screwing up, but at least for a different reason each time.