Online Book: Battery Installation & Maintenance, Chapter 16 of 18

LifeLine AGM Batteries—Final Report Card

JHH-iphone-6707-20160715-5In 2010  we installed a new house battery bank made up of two 8D AGM batteries kindly provided free of charge by LifeLine. At the time, we had been having problems with relatively short battery life, so this was part of a deal:

Our part was, and is, to write about the changes we made to our battery charging regime based on advice from Justin Godbar, a principal at LifeLine. These posts eventually became our Online Book, Battery Installation and Maintenance.

This spring, as part of our ongoing testing, we ran a discharge test on the batteries that showed that they were down to about half their original capacity and therefore it was time to replace them.

The batteries lasted six years. But it’s important to understand that’s a pretty meaningless statement. What matters when evaluating battery life is how many discharge cycles they have been subjected to. When measured this way we received good performance, since our usage was and is brutal due to our comparatively small bank size in relationship to our loads, often resulting in 1.5 to 2 cycles to 50% discharge a day. I would estimate that over their lives we deep cycled these batteries at least 1500 times.

Using this criteria these batteries yielded just about the life that Justin said they would. Had we paid for them, our cost of ownership would be about US$1.50 per deep cycle. Not too bad, given that we, like most voyagers who don’t spend much time in marinas, are regularly cycling between 50% and 80% of full charge, a violation of the first law of battery care: Fully charge the battery immediately after each discharge.

The key takeaway is that, by making a few simple changes to the way we treated our batteries, we reduced our per cycle costs to 25% of what they had been.

Another important point is that, although we made a bunch of small changes to the programming and use of our charging system, by far the biggest contributor to their improved life was regular equalization.

Coming Soon

Over the next few weeks I will be writing about our new and larger replacement house bank—our bank has always been too small in relation to our daily electrical usage—and changes we are making to further reduce our battery life cycle costs.

The Photograph

We were not happy trusting the rather flimsy-looking handles when removing the old batteries and were puzzling about a safer way to sling them when my friend Josh (in the photo) said, “Do you have a net?” After a moment’s thought it dawned on me: No net, but something a lot better: our Galerider storm drogue—worked a treat.

Further Reading


If you have questions, leave a comment, but please read the above first three linked chapters first. That way we won’t have to waste a lot of time covering stuff in the comments that I have already explained in detail.

Book Chapter Navigation:
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Battery Replacement—Resisting The Seduction of Perfection >>

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Meet the Author


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 twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

19 comments … add one
  • Geir ove Jul 16, 2016, 11:24 am

    Are you going to go Litium ? or stay with the good old batts.

    • John Jul 16, 2016, 11:48 am

      Hi Geir ove,

      Coming up in a couple of days.

  • Stedem Wood Jul 16, 2016, 10:19 pm

    I’m sure your batteries were fastidiously clean……..

    But it’s hard to clean old batteries in their locker and I’d be concerned about using a piece of my heavy-weather equipment anywhere near battery acid that may weaken the system…….


    • John Jul 17, 2016, 9:17 am

      Hi Stedem,

      That’s a good point I had not thought of because they were AGM batteries, so I didn’t think there was any acid there, but I will inspect the Galerider carefully. I’m thinking that any damage will show as discolouration. The other comfort is the Galerider I used is from our old boat and actually too small for MC. We carry a larger one and a Jordan Series Drogue for storm use.

      Anyway, yours is a good point, thanks.

      • Drew Frye Jul 19, 2016, 7:28 am

        The acid point is good, but…

        I’m pretty sure the Galerider is polyester, which is nearly unaffected by acid. Nylon, on the other hand, is melted in moments. In fact, this is a handy way to distinguish the 2 materials. I have a note in to the maker, asking.

        I like the Galerider hoist idea.

        • John Jul 19, 2016, 7:55 am

          Hi Drew,

          That’s comforting. I will be interested when you hear back.

        • Drew Frye Jul 20, 2016, 12:56 am

          From the maker:

          Hello Drew,

          The construction has little to no Nylon in it. The high strength webbing is polyester, the stitching and other components are Dacron polyester. All components are designed for long life, most of which spent in storage.

          • John Jul 20, 2016, 8:09 am

            Hi Drew,

            Thanks for doing the research.

  • Stedem Wood Jul 16, 2016, 10:23 pm

    I should have offered a solution……

    In the same situation, I’ve used an old piece of SCUBA weight belt wiggled underneath the battery as a strap that worked well with someone to steady the battery on to a dock cart.


  • Bill Koppe Jul 17, 2016, 10:05 am

    Hi John,
    Have you considered Firefly batteries, made in USA.
    They can be discharged to 20%, are 40% cheaper and almost half the weight.
    Have just ordered some for the new yacht.

    • John Jul 17, 2016, 10:40 am

      Hi Bill,

      Yes I have, more in the next post, where we can and will discuss this at length.

  • Marc Dacey Jul 17, 2016, 12:15 pm

    I just used a chain fall to place my six L-16s in their new space, while having the same squemishness about the look of the glorified strings that constituted the handles on the 55 kgs. individual batteries. We are taking very nearly the opposite tack to you, John, in that because our bank is fully accessible, we’ve stuck with lead-acid and have oversized the bank (but not beyond our ability to charge and to equalize, of course) in order to operate within a smaller band of discharge vs. cycles. The difference in terms of longevity before “used up” can be significant. I look forward to your next post on the topic, and its implications for the suggestion that you might be throttling back on your active cruising in Morgan’s Cloud, as of course, some battery types are better suited to inactivity/fewer cyclings than are others.

    • John Jul 17, 2016, 1:36 pm

      Hi Marc,

      Just to clarify, AGM, Gell, and liquid filled are all lead acid batteries. I think what you are referring to are liquid filled. And how do you know I have taken a different course? I haven’t revealed what I chose for replacement batteries yet. 😉

      As to using a chain fall, that’s fine, but what we were worried about was the handles failing as we swung them out of the boat on a halyard.

      • Marc Dacey Jul 17, 2016, 2:54 pm

        Yes, to clarify, I did indeed mean “flooded”, aka “liquid-filled”. As for the Gale Rider solution, I think it was a good idea as those little handles look severely undersized, even if they aren’t. We humped ours off a cart, onto the side decks and down into the pilot house by hand, which was somewhat daunting, but the final positioning was impossible without mechanical advantage, as I discovered when installing my engine. A chain fall or something similar is a good thing to have. I look forward to learn if you do indeed go “back to the future” with the new, embiggened bank.

  • Justin C Jul 18, 2016, 9:47 am

    Now you couldn’t do *that* with a Jordan Series Drogue!

  • Phil Aug 21, 2016, 6:08 pm

    John, can you tell us a bit more on the discharge test you did ? What load did you used, how you measured ? I am not very successful in finding information on this. Thanks

  • Bill Bailey Sep 5, 2016, 9:22 am

    Hi John,
    Thanks for the wealth of information on your site. I have found it very valuable. I have not seen a recommendation for storage of Lifeline AGM batteries. I replaced my batteries this year with Lifeline AGM’s and will be storing the boat for 6 months. I will not be able to get to the boat either for 6 months. Have you determined the best way to store them?
    Bill Bailey

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