Converting 12V house battery to 24V - what about grounding?

[fxykty]

Our boat is a catamaran with 2 AGM 12V engine start batteries (one per engine, can be paralleled) and 2x LFP 12V batteries (each 4S 3.2V cells) in parallel to create a 12V house bank. Common DC ground is to the port engine block. Starboard engine room DC ground is to the starboard engine block.

We are considering converting our two 12V LFP batteries into a single 24V battery, putting the 3.2V cells into a 2P4S configuration. We will need to use DC 24-12 converters to provide us with the 100W of12V power that most of our DC system will need. Alternators, windlass motor, wind generator and Quattro inverter/charger will be converted to 24V models.

In a DC system with both 12V and 24V batteries, is there still a common ground regardless of voltage?

As an aside, any lessons learned from those who have converted from 12V house to 24V house?

[GordMay]

Yes, there is still a common ground, in a DC system with both 12V and 24V batteries.
FWIW: A ‘2P4S’ battery configuration has two cells in parallel, for twice the current, and four in series, for 4X the voltage.