JM,
Have to be careful with the 343 circuitry. Initially, there were many reported problems with the batteries discharging.
On 343's equipped with a windlass, Beneteau installed relays to combine the starter & house bank to ensure maximum amperage to operate the windlass. I found out the hard way on a chartered 343 that it can be a problem if not operated correctly. The charter boat had a 4D house bank and separate starter battery. Upon leaving the home base marina, both battery switches were "ON", I turned the starter battery switch to "OFF" and sailed for approximately 5 - 6 hours with the refrigerator, instruments, radios on. When I turned the starter battery switch "ON", the starter battery had discharged to the point that the engine would not start! No combination of switching provided enough amps to start the engine. Not going to go into detail as to what happened next; however, I investigated the matter further and found that unless both the starter and house battery switches are simultaneously switched "OFF" to de-energize the relay, the relay stays on and the batteries remain combined. To de-energize the relay and uncouple the house & starter batteries, both switches need to be turned off simultaneously and then the house bank switch can be turned "ON" without the relay combining the banks. There were several owners who initially had this happen. I think that Beneteau eventually published a revised wiring scheme. On my boat, I removed the relay. I know that I need to turn all the batteries on and run the engine to provide the amps necessary to operate the windlass. Actually, my house bank is big enough to operate the windlass; however, I want to discharge them as little as possible; therefore, I run the engine. So check out your wiring scheme, you may have this relay issue that could cause a problem.