Update to the Update..
As of today (mid-May-2022) it looks like Firefly is a victim of the economic turmoil of the COVD age. A quick search finds that all of the USA based distributers have dropped them from their vendor list, and nobody has them in stock. It’s unfortunate, because I still think they had a good cost effective alternative to lithium batteries.
If anybody has alternative information, please leave a comment…
I have previously described some of the issues that a cruising boat has with batteries. As our batteries have started to show their age, we replaced them with what we hope to be a long term solution.
Firefly Battery Update
We have had our Firefly batteries in full-time cruising service for over a year, and think we can give a preliminary report on the results we see vs. what we expected. After 20 years and nearly continuous cruising, our Onan genset–with over 7000 hours–is aging. Given that replacement of the genset is a very expensive proposition, reducing its run time will postpone the day when that trigger needs to be pulled.
We have an older Amel Super Maramu (hull #160) with a 24 volt house bank assembled from eight Group31 12 volt batteries. Our charging sources are:
- a 630 W solar array with a Victron MPPT controller;
- the 220V genset powers a very sophisticated 70 Amp Victron Inverter/Charger, and 100 amp charger from Quick;
- And finally, a 50 Amp internally regulated alternator on the main engine.
Where we started
Our previous battery bank used Lifeline AGM batteries. They worked well for 7 years, but had lost about 30% of their original capacity. They were not in a rapid decline, but were slowly fading.
With that system, our routine was to run the generator for about 90 minutes each morning. The stopping point was when the accepted charge current dropped below 18 amps in the absorption phase of the charge cycle, which corresponded to about 83% charged. The solar panels then took over, and the batteries were typically at 95%–or better–state of charge by the end of a solar charging day. This process kept the batteries well charged, with minimal potential for undercharge leading to sulfation.
The downside was that the solar panels spent most of the day in absorption phase of charging, meaning their full potential output was not available to be stored in the batteries and we were running the genset more than we really wanted to. Typically we saw about 50% of the potential energy available from the panels was discarded in the absorption or float stages of the charge cycle.
Our usage of electricity is dominated by our two refrigerators and one freezer, and our watermaker.
Our reason for going with the Firefly batteries was centered on the claim that they do not need to be brought to near 100% charge to avoid sulfating. They can be operated routinely and constantly in a partial state of charge with out long-term damage. If true, this meant that the normal daily charge could be kept below the point where the solar panels were current-limited by their controller. All, or nearly all, of the capacity of the panels would be able to be stored in the batteries, thereby reducing the need for generator run time.
This has worked exactly as we expected. Our generator time has been cut by more than 1/2. We now run the generator routinely every other day for no more 60 to 90 minutes. If the weather is especially sunny we can easily go two days. If we did not run the watermaker, we’d be running the generator only for stretches of cloudy days. If this change in generator run cycle postpones buying a new generator for one year, the extra cost of the batteries will have been worth it even if they only live five years.
The actual stored output from the solar panels is now higher because they are no longer throttled by the ability of the batteries to accept amps. The batteries routinely cycle between 60% and 85% state of charge over two days.
Our conclusion is that the batteries are delivering the benefits we had hoped for in the short-term. The still unknown factor is: will they have the full expected life span when operated under a nearly constant state of partial charge—as the manufacturer claims? Only time will tell…
While working in the battery box in August of 2018, I happened to notice that one of the eight batteries was significantly hotter to touch than the others. After some back and forth with Ocean Planet Energy, and some simple diagnostic tests, we agreed that the battery had developed an internal short, and needed to be replaced. Firefly and Ocean Planet delivered a new battery under warrantee, with no cost to me, quickly, and with no hassle. After installation and preliminary charging, the new battery was found to be venting gas and a little bit of acid from the valves. Once again, back to Ocean Planet and Firefly. They quickly diagnose the problem as bad valves. They ship me new valves and all is happy.
The moral of this story is that Firefly is very responsive to issues. But it is another anecdote that supports the rumors that the India based manufacturer is having some quality issues in their production.
And One More Thing…
Because of the way we use these batteries, frequently keeping them below full charge for extended periods, they do not often get the kind of prolonged absorption cycles that automatically balance the voltages of the series pairs. To solve this issue we added Victron Battery Balancers, and all is now happy. You can read a lot more detail about this issue here:
And After Two Years…
We periodically do what Firefly called a “Recovery Charge.” This involves discharging the batteries all the way to empty (10.5V) and then recharging them quickly. We discharge them at a rather steady rate, in about 10 hours. The original specification sheet for this batteries listed the C10 capacity as 440 Amp-hours. Here are the results so far from these discharges:
- APR-21 458.9 Amp-hours
- SEP-21 453.2 Amp-hours
- JAN-22 481.6 Amp-hours
- MAY-22 456.5 Amp-hours
- OCT-22 461.3 Amp-hours(opens in a new tab)
So far pretty impressive. All results at 5% to 10% BETTER than the original specification, and no obvious trend downward at all.