question

I go with borderline and depending on usage. The battery is rated for 400A continous and recommended for 200A continous. Thats around 10kVA and 5kVA. Two units will exceed 400A when fully loaded at 12kVA startup, lower when battery is down on voltage, 2 times 2.4kW is what they can uphold at length if kept cool. So thats spot on. If you have heavy AC Compressors or the likes, likely the battery will shut off if maxed out. AGM can deliver way more current than the LiFePo that is limited by the internal BMS. AGM doesnt last long could mean abusive high currents or a very warm place. The latter isnt good for the LiFepo either, the former might be an indication, that it wont work.

Since you dont seem to acttually use the capacity, its almost a waste of a huge battery sitting fully charged all day at the worst spot state of charge wise as far as longevity goes. Best to run it between 20 and 80% or have it sitting at 50% If you have a specified load I would go as small as practical or use other more potent Lipo. They have discharge rates of 4 to 8C rather than 1 or 2. Saves even more weight.

Be aware if you do drain the battery, she takes what she can off the alternators if directly connected. Likely these will overheat and give up. Voltage is wrong too, so the alternator including regulator might need changing.

So the boats 24v anyway, and yes I’m thinking of 1200 watts of Orion tr DC to DC for the moment

probably supplemented later by a second alternator mounted on one engine with a wake speed regulator.

1200 watt is enough to keep up with normal demand should mean the generator only starts when we make tea. And if we are running a deficient then it can start at 50% soc

We have the 6000 watts of power as there last a remote possibility that if we had generator failure abs had something to winch up using the ac deck winch we could but we could also parallel the other batteries for that circumstance temporarily

The other reason is the compartment can get quite hot in the summer so we needed the assurance the units will carry on running without risking overload.

looking at VRM and our biggest load was 4kva in the last 6 months. Too much for one 3000 but not stretching the two by any means

I guess I could fuse at 400 since that would give 9,600 watt anyway. And stay within spec.