Battery Monitors, Part 3—Calibration and Use


In Part 1 we chose the best type of monitor for each of us (voltage measuring or amp hour counting) and in Part 2 we selected an amp hour counting monitor from Victron for us control-freak nerds.

Now, in Part 3, I’m going to take a deep dive into how to calibrate and use an amp hour counting monitor.

We Got Work To Do

But, wait, these are pretty sophisticated devices. Surely we can just install them and read the state of charge of our battery right off the dial?

Sadly, not. In fact, the biggest bitch I hear about amp hour counting monitors is:

The state of charge is never even close to right.

That's bad enough, but I'm also betting there are a lot of cruisers out there managing their batteries based on false readings from their battery monitor because they are not even aware that there's a problem in the first place.

So what can we do about that?

Well, I have good news and better news:

  • The good: the monitor isn't broken.
  • The better: we can achieve acceptable accuracy fairly easily.

And, even better yet, in so doing we will often improve the efficiency of our electrical system and extend the life of our batteries, too—talk about a win, win, win.

Let’s dig in:

  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.

Subscribe
Notify of
27 Comments
Oldest
Newest
Inline Feedbacks
View all comments