Boat Electrics

I am currently weather bound in Scotland waiting for a chance to sail to St Kilda, its been a week already (excepting a couple of day sails for shopping) and  am likely to be here for much of the next 10 days or more so having done all the odd jobs I can on the boat I am writing up some guidance on boat electrics.

Which turned into a fairly major job and in late July is still not finished!

Disclaimer: My first career was in electronics and at one time I was a member (I.Eng) of the Institution of Electronics and Electrical Incorporated Engineers, (now merged with others to be the Institution of Incorporated Engineers) but that was a long time ago, similarly I once worked for the worlds largest manufacturer of industrial Lead Acid batteries but as IT Director not on the produce side so no responsibility is accepted or implied by anything written on this web site, use at you own risk and take advice from a currently qualified expert as you think appropriate, particular regards shore power.

Overview of Sancerre's electrics as evolved to 2023.
Click on this pic and others to enlarge.

Sancerre's primary power distribution and switching diagram
including automatic charge control for two domestic battery
banks and the starter battery.

Examples are often from my boat showing the equipment I used or inherited, other makes and types are available. I have explained some of the alternates but not all, this is a blog not a book! 

Click on the main heading to read that section.

• Fusing, cabling & mains power on board:
• Fusing.
• Cables.
• Consumer units.
• Galvanic Isolators (Zinc savers).
• Types of Battery.
• By use: Traction, Reserve Power, Starter, Dual Purpose (Leisure).
• By Technology: Flooded, Valve Regulated (VRLA), Absorbent Glass Mat (AGM), Thin Plate (TPLA).
• I have not researched Lithium batteries in depth, they may well be the way forward being light, compact, quick charging and long lasting but they are still very, very expensive and largely unproven in a marine environment, and beware adverts often have misleading comparisons assuming 50% DoD levels for Lead Acid batteries whereas some newer  technologies can go to 80% (e.g. AGM) or 90% for TPPL.
• Things to check when buying a battery.
• How much battery?
• Engine start.
• Service / domestic.
• Rules for connecting batteries in parallel and in series.
• Switching.
• Traditional.
• Manual charge control.
• Automatic charge control by DVSR.
• Charging using Diodes and intelligent splitters.
• Integrating solar and / or wind generators.
• Blocking diodes.
• Controllers.
• Getting more from your Alternator.
• Battery management.
• Battery Monitoring.
• Battery charging strategies.
• What would I do differently starting now?

See also my post:

• Rebuilding the Navigators Area, the Electrics & Electronics.
• Upgrading the Battery compartment wiring.