7 Checks To Stop Our DC Electrical System From Burning Our Boat

Not Fused

Before we dig into how to upgrade our boat's DC electrical system, we need to check for potential boat-burners.

Two thoughts on that:

  1. I'm pretty sure that fires started by 12- and 24-volt battery-supplied systems are a common cause of boat losses.
  2. I would also bet that more fires are started by 12- and 24-volt systems than by shore power 120- or 240-volt systems.

No, I don't have accurate statistics on this, and I'm guessing that, as is typical around recreational boating, no one does due to poor or non-existent reporting requirements. But using poor reporting as an excuse for inaction would be stupid...err...unwise. (If you know of useful stats on this, please leave a comment.)

What do I base this on?

The current (amps) in even a single small 12-volt lead-acid battery can turn any conductor with low resistance (think a length of wire) red hot, thereby starting a fire.

And the amount of dangerous amps lurking in the huge battery banks we see on modern cruising boats is positively mind blowing.

This battery bank on our McCurdy and Rhodes 56 is rated at 2190 cold crank amps, meaning it can produce that current for 30 seconds at at least 7.2 volts. That's plenty to heat up even a piece of AWG 2/0 cable, not to speak of the probable case rupture of the battery if it's called upon to produce that much current for long.

Wait, it gets worse. On many boats, even ones built comparatively recently, like our new-to-us J/109 (2004), the only over-current (short-circuit) protection is on a breaker/fuse panel, leaving the high-current conductors connecting batteries and alternators completely unprotected.

Contrast that to the shore power system that typically carries ten to twenty times less current (amps) and is pretty much always properly protected against a short-circuit-started fire by fuses and/or breakers.

(Shore power systems kill people, but that's another article.)

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