In 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.
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.
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.
- More detail on how cycles and charging profile effect battery life.
- 11 steps to Better Battery Life.
- More on equalization, why and how.
- Full details on our improved charging regime and system.
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.