question

The 35mm² positive output cable from a BlueSolar 150/70 MPPT is currently connected to the positive terminal of the middle battery of a 3P 810Ah 12V AGM House bank on my boat. I'd like to eliminate this battery terminal connection. I have two options and would appreciate advice on which of these should be preferred:

1. Extend (or simply replace) the MPPT's 2.5m long positive output cable by about 0.5m so it reaches an existing positive charge/loads busbar that is turn is connected to the House bank; or
2. Connect the MPPT to a nearby (~1.5m) 3000/120-50 Multiplus and then 'share' the Multi's 120mm² positive cable to the same positive bus-bar. The Multi is charge-limited to 90A and the MPPT to 70A so a max of 160A charging current would flow through the shared cable section. The max load on the Multi when inverting doesn't exceed 200A, so I think there's no problem with the Multi & MPPT sharing this cable for a 4.5m round-trip. Only one of the Multi's two positive DC studs is being utilized now, so it would be easy to connect the MPPT positive to the spare DC positive stud on the Multi.

Both the Multi and the MPPT negative cables (120mm² and 35mm² respectively) are connected to a shared negative bus and I don't propose to change that. Both the Multi and the MPPT get their voltage sense and temp data from a SmartShunt now (via a CCGX) and that also wouldn't change. The Multi is grid- and generator-connected from time to time.

I have a slight preference for Option 2, piggy-backing on the Multi's cabling....but given the Multi inverts as well as charges, I wondered if any damage to the MPPT could occur by this arrangement? And am I missing anything on the negative cabling front? I COULD tie into the Multi's negative cable too, but this seems like unnecessary work given the MPPT's negative is already off the battery and on a negative bus.

Thanks for any comments.