Choosing & Installing Battery Switches

I can't tell you the number of times I have started to write about the simple, efficient and inexpensive (relatively) DC electrical system that I designed and have recently finished (just about) installing in our new-to-us J/109, only to find that there's a major issue I need to cover first.

Today it happened again. I was going along fine only to get dragged down the rabbit hole of how to choose battery master switches and install them.

And that lead to charging both engine and house banks at the same time.

Which was all complex enough five years ago, but now we have lithium to deal with.

If I could just say, "This is the best way, now do it", it would be easy. But I can't. Like most things around cruising boats, there is no best way, just the best way for each of us, which depends on our usage profile, and how techie we are or wish to be.

So, after thinking about all of the above, I realize that my design is a lot less useful than I thought it would be. Better to spend my time, and yours, exploring the options, so we can all come up with our individual best, rather than jamming a design that works for Phyllis and me down your throat—YouTube presenters take note. That said, I will publish said design eventually, since it will be useful to some of you as is, and to more of you as a starting point for your own system.

I will cover battery switches in this chapter of our Online Book Electrical Systems for Cruising Boats and cross-bank charging in the next.

There are three usable battery switch options and one that, though very common, no one should go near.

  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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