Here's a photo of the battery compartment aboard my 2016 model. 

For space, I'd like to move the starter battery to allow more room in the battery box for various Victron kit. 

The most room available nearby would be under the bed in the starboard stateroom - only a few feet aft.  

I can follow the openings for the engine exhaust and or blower into the engine compartment and around into the battery compartment - but that's a long way around. 

I've previously run lines from the power board under the chart table, under the head, and starboard aft closet into the area under the bed, but that requires even more cable. And the compass would need to move. 

I'm tempted to open a passage aft of the battery box (where you can just barely see the start battery) - just under the cabin door -  go through the opening under the floor and into the space under the bed. Seems simple. Need to check ABYC about their battery box rules but I think this would be the easiest solution.

An alternate is to open a passage between the battery box and the engine compartment - and then follow the blower or exhaust openings into the compartment under the bed.  

Anyone have knowledge of what's inside this bulkhead under the cabin door? Any structural concerns? Have a call into my service advisor for their opinion but thought I'd present this issue here to the group. 

Any wisdom on this would be appreciated. 

According to my service advisor, that stringer between the battery compartment and starboard aft compartment floor is structural, but could withstand a hole up to 3" without issue. 

He warned that while the drawings do not show any lines along that stringer, there was always the chance that Hanse dropped a line in that space. If so, it would be enclosed in black plastic 'corrugated' material. He suggested a small pilot hole from one side, take a peek with a boroscope camera, and confirm the space is clear of wiring etc before opening up the hole to its maximum width from both sides. 

Will update with findings. 

I am surprised your house bank is under the cabin sole. This would be a potential problem if you had a flood of any great extent. I have a friend who has an old Oyster and he had a sounder unit give way and before they realised their bilges where full of water which included their house bank which meant no bilge pumps etc etc.  They almost lost the boat. 

Wayne,     My Hylas 49 (prior boat) had 2 8D's below the sole on either side of the companionway and 2 more 8Ds fore and aft (under the berth's) for a 4 battery bank.    Apparently it was fine for ABYC and CE ratings and has always been rated as one of the best offshore boats out there.   I can't speak to the complexities of a Lithium bank, however.    The only issue I had concern on was the distance for some of the runs and the potential for voltage loss.     Weight balance was great, but...

I had never actually thought too much about the battery placement until I saw this guys' Facebook video post on almost sinking his Oyster. I thought at the time it was good that Hanse had placed our 575 house bank batteries above the floor level. I have been on lots of commercial power boats (in survey) with batteries below the ER floor plates and that was completely acceptable.