Battery Monitor


What the heck is a BMK?  How does it work?  Why is it so important to have one?  Right before we moved aboard Curiosity we shot this video.  We’re no experts by any stretch of the imagination, but we did our best to show you our BMK in use and answer those questions.

In our RV we had the magnum but decided to go with this very affordable Xantrex link pro for the sailboat.  Here are a few specs:

  • Link lite Battery monitor
  • Displays time remaining
  • Communication/expansion port
  • Stores a wide range of history events in internal memory
  • Advanced programmable alarm Relay

Want to see the link pro in action?  Check out this video:



  1. John Turner

    Question if you removed the generator and it was sitting on the dock what would it be worth? What would the cost of the larger alternators and 5 additional solar panels.

  2. james meyer

    I have some question that you didn’t cover, and its a little more detailed than you have gone over, My wife and I follow you for the last couple years, we have a monohull and IM considering switching from lead-acid batties to? lithium or AEG, I bought a solar panel and IM installing them now.
    so my question is
    – what monitors the charging of the batties so it goes from one to the next one? what happens to the charge once everyone is charged up?

    we have a peasron 424 ketch and I had always been told by our old yard that I had some kind of monitoring system and that the charge would go from one battery on to the next one however I have fried 2 batteries over the years so, I don’t think that what’s happening

    • Curious Minion

      If you’re installing solar panels you’re going to need a solar charge controller. The charge controller monitors the charge state of your batteries (whichever kind you choose) and it shuts off charging from the panels to keep them from being overcharged and frying. Also, I’m not sure what you mean by moving the charging from one battery to the next, because the system charges all the batteries at the same time. Solar charge controllers have several built in battery profiles, so if you buy AGM batteries you need to choose the AGM charging profile, or the lithium profile if you buy lithium. The Wynns have an overview of how a solar system works here, with links to all kinds of gear (including solar charge controller):

      You also mentioned a battery monitoring system, and that is a great idea in addition to the solar controller. The battery monitor lets you see the current state of charge of your batteries, you can see how many amp hours you are actually using at any given time, and lots more info. If you’ve been using the simple voltage monitor that comes with most RVs and probably most boats, that is a wildly inaccurate measure of the actual state of charge and might be why you’ve fried a couple of batteries.

      And finally, for a little more info on battery choices, you can check this post out: If you are living aboard the boat and can afford lithium you’ll never be sorry. They charge so much faster (so less generator time if it’s cloudy) and you can pull more of the energy out of a lithium battery than either an AGM or lead acid.

      The “off the grid” section of the blog has a lot more info on solar, including videos on charging the batteries, more info on solar gear, etc. Check it out here:
      Hope this helps!
      Curious Minion

  3. David N.

    Hi, I was looking into a currant generator, but every one says to put it thru the boat, build a scoop, and so on. I asked the dealer why does it and why i couldn’t put it into a bucket with a water pump for continuous use. as long as that pump is pushing water thru the tubes and turning the turbine, its making electric. Connect the wtr pump directly into the battery, Put it all on a switch to turn on and off. Now you can use fresh water and with a cover on it , and never spill a drop. This is something that I’ve been thinking of for a while. I live on my Searay and hate the fact of connecting to shore power all the time. When i go out i still need an efficient way of making pwr.

  4. Mark Russell

    Watching your video on recharging your batteries I found it interesting and informative. One of the things you mentioned was not liking the current generator set up due to weight and placement in the boat. The weight puts the the boat gives it a bit of a list which is not a good thing. I have what I think is a good idea and a bad idea at the same time. The bad part of it has to do with the fuel required to run it. Honda makes generators that are VERY efficient. I don’t know all of the math but I will tell you what I do know.

    First, there are two models worth exploring. The 2200 watt and the 3,000 watt. The 2200 watt will run for 3 hours at full load and 8 hours on 1/4 load. The 3,000 watt will run 20 at 1/4 load and 7 hours at rated load on 3.5 gallons of fuel. One of the things that is cool about these generators is that you can link them together with a kit that doubles the watts. The other cool thing about these generators is they are both VERY quiet about 57 db at rated load. The weight is low for the work they can do. The 3,000 watt is 150 pounds and the smaller ones are 50 pounds. There is a 7,000 watt version that can also be linked with another unit again doubling the power output. This one also supplies 240 volts as well. It is considerably heavier at 270 pounds.

    The big draw back for either of these is the fuel. They run on gasoline which means that you would need another fuel source which is space which is… the list never ends. But with the fuel economy and depending on how often you need to run them and distance between ports of call 10 gallons of gas might last you quite a while. The 2200 watt units are really small and take up a very small foot print and two of them together making 4,000 watts is quite a bit of power for a small unit. Cannot run a lot at one time but.. that is part of small living off gird.. power management is key.

    Just some thoughts.

    Oh, and wind generators. My brother works for the power company in Wisconsin. They have a lot of wind power up there. According to him they are NOT efficient and not worth having. But, in the media and for the many that don’t know it “looks” good.

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