A Simple, Efficient and Inexpensive¹ 12 or 24 Volt DC Electrical System

This setup in our J/109, as she came to us, is actually better than many—at least the cables are correctly, in fact a bit over, sized—but it still needs a complete makeover. How many violations of ABYC recommendations can you spot? Leave a comment. Photo kindness of the surveyor.

Our new-to-us J/109, like most production boats, came to us with an electrical system, installed in 2004, that is not even close to ABYC compliant. Said system also had some dangerous defects.

And on top of that, the system as installed by the builders, while adequate for the light usage they envisioned, is horribly inefficient, and will be very frustrating, not to speak of environmentally destructive, to live with once away from shore power for more than a few hours—think running the engine for hours, and often, to charge the batteries.


The Way It Is

But here's the thing, our experience is the norm, not an aberration, and the older the boat we buy is, the worse the system will be, so there's no point in wasting time pissing and moaning, rather, we need to fix it.

Two Tips for Buyers

But before we get into that, two tips for those of us buying a secondhand boat, as we did:

  • The boat will almost certainly require significant rewiring and electrical upgrades, so we better budget time and money to do that.
  • The survey will probably not warn us of this impending expense and hassle, so even with a clean survey we need to leave money in the budget for this project.

A Survey Won't Save Us

On the second point. Yes, I know, most surveyors claim to be ABYC trained and claim they survey to that standard. And maybe some do.

But the fact is that, during the process of buying our J/109, I read through three surveys on the class—two on the boat we bought, and one on another boat—and not one even pointed out that the batteries were not fused, a fundamental code violation and a potential boat-burner.

I also read through several other surveys on other types of boats, and not one had more than one or two trivial mentions of ABYC-compliance violations, and all completely missed problems and omissions that I could see at a glance in photos, like the one at the top of this article.

A North American Problem?

I'm guessing, but do not know, that the situation in Europe, and probably Australia and New Zealand, will be better, at least for boats built comparatively recently, both because in those countries regulations are backed up by the rule of law, rather than just being recommendations as ABYC's are, and, further, it seems that surveyors in these countries are, as a rule, more thorough.

But even so, our experience and what we are doing about it will still be of use to those of you in those countries who are buying boats that are over about 20-years old, or boats that have suffered from electrical systems modifications from a series of owners equipped with a lot more enthusiasm than knowledge.


So what the heck are we to do about this state of affairs?

What about hiring a boatyard to fix the problems and upgrade the system to ABYC? Generally a bad idea for three reasons:

  • Most boatyard staff are woefully ignorant of basic electrical theory and the applicable standards; yes, including the ones that are ABYC certified—the courses they take are a joke.
  • Even if the yard has a person who does understand ABYC or CE, the likelihood is that they will have absolutely no idea how to make the system more efficient for cruising away from shore power.
  • High cost. More on that in a minute

How bad are the first two issues? Really, really, bad. For example, I know of just one guy here in Nova Scotia and one in Maine who I would trust to rewire my boat to be both compliant and efficient.

Gotta Take Responsibility

Given the deplorable state of training and knowledge among most boatyard "professionals" and even boatbuilders, particularly in North America, even if we can afford to delegate the actual work, we owners have to get at least a basic understanding so that we can check it's being done right.

The other problem is that even if you can find someone competent (look for independent contractors, not boatyards), you will probably have to wait ages before they can help you. The good people are invariably snowed under.

Don't believe it's that bad? OK, read on:

  1. One Simple Law That Makes Electrical Systems Easy to Understand
  2. How Batteries Charge (Multiple Charging Sources Too)
  3. How Hard Can We Charge Our Lead Acid Batteries?
  4. Cruising Boat Electrical System Design, Part 1—Loads and Conservation
  5. Cruising Boat Electrical System Design, Part 2—Thinking About Systems
  6. Cruising Boat Electrical System Design, Part 3—Specifying Optimal Battery Bank Size
  7. The Danger of Voltage Drops From High Current (Amp) Loads
  8. How Lead Acid Batteries Get Wrecked and What To Do About It
  9. 11 Steps To Better Lead Acid Battery Life
  10. 10 Tips To Install An Alternator
  11. Stupid Alternator Regulators Get Smarter…Finally
  12. WakeSpeed WS500—Best Alternator Regulator for Lead Acid¹ and Lithium Batteries
  13. Smart Chargers Are Not That Smart
  14. Equalizing Batteries, The Reality
  15. Battery Monitors, Part 1—Which Type Is Right For You?
  16. Battery Monitors, Part 2—Recommended Unit
  17. Battery Monitors, Part 3—Calibration and Use
  18. Do You Need A Generator?
  19. Efficient Generator-Based Electrical Systems For Yachts
  20. Battery Bank Size and Generator Run Time, A Case Study
  21. Battery Options, Part 1—Lithium
  22. Battery Options, Part 2—Lead Acid
  23. Why Lithium Battery Load Dumps Matter
  24. 8 Tips To Prevent Lithium Battery Load Dumps
  25. Lithium Ion Batteries Explained
  26. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 1
  27. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 2
  28. Q&A—Are Battery Desulphators a Good Idea?
  29. Renewable Power
  30. Wind Generators
  31. Solar Power
  32. Hydro Power
  33. Watt & Sea Hydro Generator Review
  34. A Simple, Efficient and Inexpensive¹ 12 or 24 Volt DC Electrical System
  35. 8 Checks To Stop Our DC Electrical System From Burning Our Boat

John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for 25 years, first in yachting magazines and, for the last 20 years, as co-editor/publisher of AAC.

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