About eight years ago, we switched to Absorbed Glass Mat (AGM) batteries on Morgan’s Cloud, to get the following benefits over liquid filled lead acid batteries:
- Shorter recharge times since AGM batteries accept a faster charge rate.
- No risk of the batteries freezing when we lay-up the boat unattended since AGM batteries have a very low self-discharge rate. (A fully charged battery won’t freeze but a flat one will.)
- About 10% more capacity in the same size battery.
However, our experience with AGM batteries was not good: We went through four sets of house batteries from two different manufacturers after the switch to AGM. When you consider that AGM batteries are as much as double the price of liquid filled batteries, that stung.
We should state at this point that we are tough on batteries, particularly at anchor when we are usually writing and working on photographs, using as much as 300 amp hours per day for lighting and computers.
However, we never discharge our batteries more than 50%, we installed chargers and a regulator that have temperature sensors and purport to be designed to properly charge AGM batteries, and we always recharge to at least 85%.
When the last set died after less than a year we had pretty much decided to go back to liquid filled batteries. However, before we did that we wrote to the manufacturer stating our concerns. What a pleasant surprise to get a helpful and concerned email from Justin Godber of Lifeline Batteries. A big contrast to the usual blow off, or worse yet, dead silence, that we are used to getting when we complain about gear that has not met our needs.
Set Up To Fail
As we conducted a technical and detailed email exchange with Justin to try and figure out what had killed our batteries so early and how to avoid it happening again, it soon became apparent that we liveaboard voyagers are set up to fail as caretakers of any lead-acid batteries, not just AGM :
- The yachting press and most battery experts, including Justin’s largest competitor, have told us that you should not equalize AGM batteries. Wrong—any lead acid battery of any type will sulfate with typical liveaboard use and eventually fail if you don’t get rid of that sulfation regularly with equalization. So, if you can’t equalize a battery, it does not belong on a voyaging boat.
- Many, perhaps most, chargers and voltage regulators are programmed incorrectly as they come from the factory.
- Many chargers simply don’t behave the way they say they do in their own brochures and manuals; yes, even the fancy three stage ones.
Worse still, the general instruction from manufacturers and battery experts, that all you need to do to enjoy a long life from lead-acid batteries is to fully charge them after every discharge, is completely impractical. Here’s why: It takes two hours of generator or main engine time on Morgan’s Cloud to bring our house bank from a 50% discharge state to a 85% charge, but five more hours of charging to get from 85% to 100%. This same basic fact will apply no matter how you charge your batteries, since the limiting factor is the amount of current (amps) that a battery can accept for the last 20% of its charge cycle—not much.
So the standard wisdom is fine if you are in a marina and can plug in but totally impractical on a voyaging sailboat that may not see shorepower for months at a time and that discharges the batteries by 50% on most days at anchor or at sea.
Yes, wind and/or solar power will help. That is, if we are willing to use almost no power for the six to ten hours it would probably take those methods to top the batteries up to 100%, and that assumes a two hour generator run first.
So, we cut a deal with Justin: He provided us with a new set of AGM batteries for free and committed to advising us on their care and feeding. Our part was to write about the experience and develop a real-world set of recommendations, a manual if you will, on the use and care of lead acid batteries on a voyaging boat—this Online Book is the result.
Justin bought one of my prints for his office wall and he, as stated above, provided two 8D AGM batteries at no cost to us. Those are the only benefits we have received from Lifeline Batteries.