Battery change

[Popski]

Morning all. An easy question I hope. It’s time for me to change the service and engine batteries on my beneteau Antare 30 fly. Both are sited under the companionway however it’s not in anyway marked as which is engine and service battery. One battery however has a positive lead which is much greater diameter than the other therefore I am assuming this is engine. I know the simplest way is to disconnect each in turn then see what power is available but before doing this I just wanted to know if anyone here know if right battery is engine etc. Thanks

 

[Rocksteadee]

I would guess heavier cables being start battery.
You have the right idea to disconnect one and see what doesn’t work.
Can you trace wiring? I like to have a drawing of everything, always useful when you have 8’ waves breaking over the fly bridge and she won’t start

 

[baldyash]

Rf picture .Looking towards stern left battery,domestic,right battery engine start.Changed mine last year . As an aside watch the battery charger (dolphin) which has in internal 30a fuse.Mine has blown twice,melting the green plastic! Also my b744v transducer failed so no speed or temp( common fault evidently).Depth was still ok so I have just replaced with an active insert from Airmar. Going back in tomorrow so fingers crossed! This is all on my a30. Had to replace my bow thruster battery as well!! They were all 2010 !

 

[Springfieldcq]

There's a digression, to ensure the engine could always function, a spring starter might help a lot by providing mechanical starting methods to launch the engine in an emergency.