I have a 48v LiFePO4 bank that is charged with a big genny.
I am soon changing the 12v house bank to lithium as well.
Here: https://www.victronenergy.com/live/drafts:mppt_faq Q7 it is mentioned that the MPPT can be used as a DC-DC charger.
The rationale is that a buck converter has no lithium specific/programmable charging algo but the MPPT has this csapability hence when not on shore power we would have this scenario: Genny -> 48v bank -> mppt -> 12v bank.
The problem is that all grounds are common on a boat as per code. The MPPT documentation mentions this: "WARNING: DC (PV) INPUT NOT ISOLATED FROM BATTERY CIRCUIT." -> no problem, we have a common ground anyway,
Then more problematic apparently: -> "The plus and minus of the PV array should not be grounded. Ground the frame of the PV panels to reduce the impact of lightning."
In our case the PV is the 48v bank which shares the same common ground as per code for the whole boat, which essentially is the... sea.
Is the FAQ right? Can someone from staff tells us the lowdown please?