Electric Propulsion Sailboat - LiFePO4 replacing SLAs


New Member
Apr 15, 2021
Hi Everyone - Thanks for creating a such a helpful resource.

I wanted to run my plan for a LiFePO4 installation into my 30' electric sailboat. It currently has some aging SLA's and I'm excited for more range!

Below is my wiring plan. I'll be using a WatchmonCore and Cellmate-K9. I am explicitly keeping the propulsion system outside of the BMS. I will add an audible alarm from the BMS for low voltage when running propulsion.

A few questions:
- Does it make sense to power the Batrium above the contactor and add some other low voltage protection? This would allow me to view the state of the system when critical while still maintaining discharge protection. How do people handle knowing what went wrong if the BMS power goes out with a fault?
- I see lots of nice marine fuse block/busbar combos (Bluesea, e.g.) but none seem rated for 48v. Most 48v fuse blocks are for much larger fuses than I want for a small MPPT or peripherals. Any ideas on 48v blocks I could use instead of the busbar and inline fuses?
- Any reason to go with Blockmons instead of the K9?
- Where am I missing fuses or more safety devices?
Any other comments?

Thank you!