Electrical System
The working design for Swallow's 12-volt and 120-volt systems, including the dual battery banks, shore power, protection, distribution and Victron Energy monitoring.
From working plan to as-built drawing
This is the design that we are using for the electrical rebuild. It combines a lithium house bank with a separate AGM starting battery, keeps the alternator away from the lithium battery, and replaces the original daisy-chained distribution panel with proper bus-bar distribution and individual circuit protection.
The shore-power section includes the SmartPlug inlet and galvanic isolator that are already installed. The DC rebuild and panel change are still in progress. The drawing will change as installation settles the remaining routing and connection details; when the work is finished, this page will become the as-built record.
The architecture in brief
The alternator charges the AGM starting battery and nothing else. Each battery then has its own shore charger, because the two chemistries want different voltages and a dual-output charger runs a single algorithm across both of its outputs. Set for lithium, it would have left the AGM permanently undercharged — which is the most likely reason the batteries that came with the boat were dead. So the house bank gets a Victron Smart IP43 on a lithium profile, and the starting battery gets its own Blue Smart IP67 on an AGM profile. In normal operation the two banks remain isolated; the battery switch can combine them briefly if the starting battery ever needs help.
The boat retains 30-amp shore hardware, but the DCYC slip supplies 20 amps. That makes load management part of the design. The selected Mabru SC09VI air conditioner draws between 1.3 and 5.2 amps, leaving enough room for charging and ordinary cabin loads without asking the dock circuit to do more than it can.
Shore power now arrives through a leakage detector. It compares the current coming in on the live conductor with the current going back out on the neutral, and opens both of them if 30 milliamps goes missing — the missing current being electricity that has found another way home, through the water or through a person. The socket on the dock already does this, and at a lower threshold, but it only does it at this dock. Fitting one aboard makes the protection a property of the boat rather than of the berth.
The device is a Blue Sea 8100, and it is a 30-amp main breaker as well as a leakage detector. The panel it feeds has no main of its own, so the 8100 is the only one — which makes it the shore-power disconnect by construction, since switching it off kills the feed to everything behind it. It also carries a reverse-polarity light, which tells you something about the dock you are plugged into before you find out the hard way.
- House bank
- Epoch 12105A-H · 105 Ah LiFePO₄
- Start battery
- Odyssey ODX-AGM24M
- Main switch
- Blue Sea 6011 Dual Circuit Plus
- House charger
- Victron Smart IP43 12/30
- Start charger
- Victron Blue Smart IP67 12/17
- Monitoring
- Cerbo GX MK2 · GX Touch 50 · SmartShunt
- Shore inlet
- SmartPlug 30 A / 125 V
- Shore protection
- Blue Sea 8100 ELCI main · galvanic isolator
- AC panel
- Blue Sea 8097 · 6 position
- DC panel
- Blue Sea 8377 · 16 position
Where the DC side goes next
The sheet above is the design, not the boat. What is fitted today is a single combined panel; what is drawn is its replacement — split in two, everything mains in one and everything twelve-volt in the other — with the battery compartment emptied of all but the batteries, their fuses and the shunt. The reasoning is in the log.
This second sheet is the routing plan that came out of that, and it is drawn on the shape of the boat rather than as a schematic. The question it exists to answer is not what connects to what, which was never in doubt, but how far each heavy cable actually has to travel — and which of them end up crossing a hinge.
It is a working plan. Nothing on it is fitted, the assumptions it rests on are listed at the bottom of the sheet, and the block ground is marked unconfirmed for a reason.