I think that Firefly’s are an excellent choice for part time boats. I just took out 8ea, 6v Lifeline’s (which were starting to bulge), and replaced with 4ea Firefly’s. With room for two more.
The one thing that you need to take in to account with Firefly’s is that they don’t like to be floated!
Both, the manufacturer and Bruce say that they are tolerant of a 13.4v float, but ideally charge and stop is the best. Hard to leave the boat
for long periods with out a constant charge source, but there are work
My solution was to retain the old 12v AGM
and design/build a DC selector panel that when we are away from the boat
, would electrically isolate the Firefly bank from the loads/charge sources and run everything to and from the start bank. This way the boat is never without a battery
bank connected and the Fireflys are not on “float” for weeks or months.
True the AGM start battery’s charge profile is a bit different then the Fireflys, and I am shorting it’s life by the wrong charge profile. But the start battery is cheap
compared to the Fireflys, so I have no problem with abusing it.
The dirt cheap
way to accomplish the same thing is to just physically move battery cables
around. But I wanted something a bit less, PITA!
Now full disclosure, I have all the tooling and equipment
to not only build the needed heavy gauge cables
(2/0 and 4/0 cables) but also to design and make the Selector panel. Meaning that I have a fraction of the cost invested compared to what most folks will have to spend.
You must take this into account when making the decision on which type of batteries