question

the main thing is see is you took off the diode between the alternator and the lifepo batteries , assuming to stop over charging for the lifepo and you replaced it with a 30 B2B charger. this means your lifepo won't get the possible 80amp from the alternator. not quite sure how the alternator is regulated at this setup??

if you do not use your engine often too charge your battery that should not be an issue , if you mostly rely on charging your battery with the engine it makes a difference between 30 and maybe 70 amps.

i do not see a BMS in this system. do the batteries have internal BMS.

(I dont know why there is a GND swtich on the original setup, any Idea ? installed factory by Beneteau)

maybe the idea is to disconnect the battery completely from the

engine (and usually some ground to the keel and metal thru hulls)

if you leave your boat stored in salty water.... so electrolysis and the potential damage of a lighting strike maybe being reduced by not having the electric system connected to the water thru the engine /shaft/saildrive....

i which case your diagram or setup is not right.....
one house battery is going thru the GND beaker the other one not?

the startermotor is going thru the GND breaker the alternator not?

and in your second diagramm the alternator is permanently connected to your starter battery that can't be right??

Assuming you're adding a battery monitor, suggest you use the BMV712 and monitor starter battery voltage as well. Common negative must remain connected for this to work.

@Ingo21 commented on the B2B. It's not clear whether you're charging starter or leisure with it. One can infer, but... If you want bi-directional, you'll need two.

Wow, that’s a very clear description of your plans. Have you started your project yet @kevgermany and if so how did it go?

I am about to do exactly the same thing and had more or less exactly the same plan as you. The exception was that I did not think about moving the anchor winch to the starter battery, which is obviously the right thing to do.

Anyways, any experience you might have had from this conversions are very welcome.

I'm super happy with my new setup.

I did this summer a 230nm trip, 36H at sea (without solar panel connected) with fridge, autopilot, electronics, ... and I had 53% battery left at arrival.

I've change a little bit the initial setup, As I had a crisstec mosfet isolator already in place. I kept it.

The B2B charger is configured to start after 10 minutes (typically the time to warm up the engine et reach a crusing speed). I try to avoid to run the engine at low rpm as this can cook the alternator.

Lifepo4 batteries are really impressive !

Thanks! I also have an existing isolator but was thinking about removing it, and am really interested in why you kept it. I guess it will prevent the starter battery from being drained by the service batteries, but can you not also program the B2B to prevent that? Or is there another reason?

The isolator prevent draining of the engine battery by any miss-configuration / malfunction of the B2B charger.

Moreover I use the B2 output (connected to the B2B input) to power a small 12v fan as the victron B2B charger heat a lot. Once the engine is stopped, the fan stop.

Hi Feeling
I am interested in your schema as I have very similar plan this spring.
Just wondering if you have more feedback after a longer period in use?