FireFly Battery Long Term Users - Speakup

[Dave Lochner]

Originally Posted by sailorboy1

Just for the record:

In the 1.5 years I have had my FFI have NEVER done the recovery procedure. I have charged them with every source I have a couple of times, battery charger+alternator+solar, and even at 65% state of charge they would only accept 0.28C. They certainly aren't getting floated much and I now it has currently 2.5 months since they stayed at float. Evan when I have shore power I turn off the battery charger and go back to solar most of the time and the boat DC loads run off the batteries+solar.

Franky if people have experiencing FF batteries drying at the dock why did they even get FF batteries? The only reason the spend the money is for the PSOC protection and what do you need that for if you are going to plug in all/most of the time?

Interesting. Yesterday we started with the 2 FF at ~42% SOC. When we started motoring the batteries were taking about 105 amps or almost .5C.

We have 2 G31 FFs in parallel, a 165 amp Balmar Alternator with Belt Manager set at 60% with the 618 regulator and SG 200 monitor.

[mjgill1]

Originally Posted by Dave Lochner

Interesting. Yesterday we started with the 2 FF at ~42% SOC. When we started motoring the batteries were taking about 105 amps or almost .5C.

We have 2 G31 FFs in parallel, a 165 amp Balmar Alternator with Belt Manager set at 60% with the 618 regulator and SG 200 monitor.

Dave,
We have been thinking about going with 2 G31 FFs in parallel and a single AGM start battery. We have a similar set up for alternator, just different brand. How long have you had your FFs? Did you upgrade your shore power charger to be able to properly charge and float the ffs when at shore? In conversations with the folks at Ocean Planet, they were adamant about periodic high C charging and the 24 hours of float afterwards in order to stay in warranty. In the instructions and in conversation, they say once a week under heavy use and once a month for normal use. It just seems impossible to satisfy those requirements while cruising since after you reach 90% the amount of time to get to that float charge is quite a while and who wants to run the engine or a generator that long. It becomes counter productive. All of this in order to not void the warranty? Thus far, we have held off and are considering LiFePo4, but twice the price.
Not poo pooing here, just expressing my frustration. Love to hear more anecdotal experience like the OP requested. Thanks,

[dfelsent]

Finished the third season on 3x L15 4v 450 AH bank. Separate starting battery.
No shore power ever.
Freezer and fridge on in June , off in October.
Wind, solar, and alternator.
Hit 100% soc about once a month.
Leave them that way over winter. Don’t too up during the winter.
As far as I can tell, still at full capacity.
I am judging by the voltage when at what the victron monitor says is 50% or lower.
Run soc between 50 and 85% for the most part.
The bank will certainly accept over 100A when at 50%. This drops rapidly at 80%.
I have the regulators all set up to avoid over charge in float.
Quite pleased so far.
Another few years will tell the full story.

[MIRELOS]

I had eight (two house banks) just before the end of the third year one bank failed to hold voltage, The boat was always cruising or on a mooring. After the failure I followed Ocean Planets instructions for reconditioning them by fully discharge and super charge while hooked to a marina, it did not help. Luckily there was still some warranty and I replaced them with Victrons. I understand that some had quality control issues, hopefully they sorted it out.

[Peeew]

As I understand the manual the restoration process is recommended for use after significant deep discharge cycles. My pattern of use with solar and occasional engine or gen charging rarely sees my bank go below 70% SOC. So perhaps this is why I haven’t ever felt the need to do it. After three years and a few 6 month trips mine seem as good as new so far.
Overall I am very happy with the performance.

[Cthoops]

3 years of full-time cruising, not plugged into shore power even when docked (we removed it during our refit), zero issues. We ignore the batteries and have never done the deep discharge/fast charge as suggested. We do have solar panels and they get a good charge when we are motoring.

This winter the boat is on the hard in Connecticut so perhaps we’ll need to top them up in the spring, but the FF batteries have exceeded our expectations. We’d buy them again without hesitation.

[Dave Lochner]

Originally Posted by mjgill1

Dave,
We have been thinking about going with 2 G31 FFs in parallel and a single AGM start battery. We have a similar set up for alternator, just different brand. How long have you had your FFs? Did you upgrade your shore power charger to be able to properly charge and float the ffs when at shore? In conversations with the folks at Ocean Planet, they were adamant about periodic high C charging and the 24 hours of float afterwards in order to stay in warranty. In the instructions and in conversation, they say once a week under heavy use and once a month for normal use. It just seems impossible to satisfy those requirements while cruising since after you reach 90% the amount of time to get to that float charge is quite a while and who wants to run the engine or a generator that long. It becomes counter productive. All of this in order to not void the warranty? Thus far, we have held off and are considering LiFePo4, but twice the price.
Not poo pooing here, just expressing my frustration. Love to hear more anecdotal experience like the OP requested. Thanks,

We installed the FFs last July and have been living aboard and heading south since then.

Our charger is a ProMariner ProNautic 1250, 50 amp charger. It was installed to support the 4 6v GCs we had before the FFs. At 50 amp it is just over the .2C minimum charge. The charger is "smart" and will turn off once the batteries are charged and will not restart until the battery voltage drops a bit indicating a new charge is needed, it then launches into the Constant Current phase and puts out the whole 50 amps until the battery voltage reaches 14.4v and then it enters the Constant Voltage phase and tapers the current.

Ideally we would all follow the manufacturer's recommendation, I certainly have. (That's my story and I'm sticking to it!)

Reading between the lines of the many emails I exchanged with OPE, the reality is the more you deviate from the recommended charging/use protocol the fewer cycles you will get out of the battery. The FFs will yield many more charge/discharge cycles than AGMs and FLAs, losing a few cycles is not a big deal in exchange for the ability to deeply discharge them and their immunity to PSOC. If I recall correctly FFs are good for 2K cycles and the GCs about 400 cycles. That makes the break even point out 1K cycles for the FF.

I think the key to making FFs work well is the ability to rapidly charge them with a high current. That usually means a very high output alternator to quickly bulk charge them and then let the solar finish them off.

I wouldn't (didn't) waste money on an AGM starting battery. A generic Group 24 "deep cycle" battery will start most of our diesels and starting consumes very little total energy. With an ACR or similar the start battery will be quickly recharged and ready for the next start.

After 6 months of use, the SG200 State of Health reading is still at 100%. So far I'm happy.

[SoonerSailor]

I had a bank of three G31 Firefly’s for 3 years. Each tested over 100 Ah when new. Unfortunately, an accident last year resulted in complete discharge with continued load for three weeks. They recovered from this to about 70% of their original capacity. An expensive mistake!

[Dave Lochner]

Originally Posted by SoonerSailor

I had a bank of three G31 Firefly’s for 3 years. Each tested over 100 Ah when new. Unfortunately, an accident last year resulted in complete discharge with continued load for three weeks. They recovered from this to about 70% of their original capacity. An expensive mistake!

Maybe, but at least there was 70% left. AGMs and FLAs would be toast.

[GinoDelG]

We’ve had our 4 31s house for six years. We live aboard full time and have 350 watts of solar and a 160 amp alternator. We never plug in to shore power. We couldn’t be happier with the batteries. According to our Balmar SG200 monitor they are still at 100% state of health, and I have no reason to believe otherwise. Two years ago they started to lose their charge. So I fully discharged them and charged them individually to 100% (via shorepower because we didn’t have a high amp alternator at the time) but it didn’t help. So I did it again and they came back to full life. I would buy them again.

[PNWSalmon]

Originally Posted by sailorboy1

Well without details far as usefulness this is right up there with rumors. That is why i asked for USER feedback so questions of use can be asked.

We had a brand new bank of 3 31s in 2019. By November 2020 we had this failure, they all essentially died and there was nothing we could do to revive them. Firefly relaves all 3, it was just shy of the one year warranty. There was no problem there.

Now we are cruising full time since 2020 and the banks are strong. At the one year anniversary I was a little nervous but knock on wood they are doing okay. We are on shore power every few months, have a pretty high powered alternator and solar.

They biggest worry I have are the settings on the solar as it can't always be perfect in regards to voltages depending on the day.

[FlyingScot]

We had one set of 3 L15+ (450ah@12v nominal) fail. Just under a year IIRC. Either bad batch or possibly due to short cycling. I think you need to set you float setting high enough that there is always positive flow into the batteries. This presumes solar, not shore based charger, the difference being solar stops every day.

The warranty replacements came with a discount to buy 3 more for a total of 6 (900ah@12v). Working perfectly after 1.5 years.

There is no way we can charge at 0.4C. We can barely meet 0.2C with everything charging. We never plug into marinas so no long charging time.

What we do and I highly recommend is giving them a good boost in the morning then set you solar float charge to your absorption level and monitor trailing amps / tail current to ensure you get them to 100% SOC. We try to do this weekly but don't always succeed. Definitely every two weeks. Never capacity tested them but just keep an eye on voltage vs. SOC. My only complaint is weight.

I feel this is the good choice when you can't charge them fast.

[Training Wheels]

Originally Posted by FlyingScot

We had one set of 3 L15+ (450ah@12v nominal) fail. Just under a year IIRC. Either bad batch or possibly due to short cycling. I think you need to set you float setting high enough that there is always positive flow into the batteries. This presumes solar, not shore based charger, the difference being solar stops every day.

The warranty replacements came with a discount to buy 3 more for a total of 6 (900ah@12v). Working perfectly after 1.5 years.

There is no way we can charge at 0.4C. We can barely meet 0.2C with everything charging. We never plug into marinas so no long charging time.

What we do and I highly recommend is giving them a good boost in the morning then set you solar float charge to your absorption level and monitor trailing amps / tail current to ensure you get them to 100% SOC. We try to do this weekly but don't always succeed. Definitely every two weeks. Never capacity tested them but just keep an eye on voltage vs. SOC. My only complaint is weight.

I feel this is the good choice when you can't charge them fast.

I’m certainly no expert and tend to be wrong more than right, but my understanding is the opposite of yours. I have the float voltage low so as to not boil off the electrolyte. I seem remember reading that overcharging at float voltage is the main failure mode. Of course, I’m probably mistaken!

[Dave Lochner]

Originally Posted by Training Wheels

I’m certainly no expert and tend to be wrong more than right, but my understanding is the opposite of yours. I have the float voltage low so as to not boil off the electrolyte. I seem remember reading that overcharging at float voltage is the main failure mode. Of course, I’m probably mistaken!

From the FireFly manual:

Charge V Settings: Charge the G31 to 14.4V & the 4V/450AH to 4.8V with temperature compensation (bulk phase) and continue charging until the charging current drops to 0.5A for the G31 or 3A for the 4V/450AH (absorption phase time will vary). You DO NOT need to fully charge the batteries each cycle in order to maintain the capacity however see the section below on periodic fast & complete charge cycle recommendations.

● Float-Charging: For charging sources that may be charging the battery for an extended period of time (solar, or an alternator if motoring for a while); set the float voltage to 13.4V or 13.5V for the G31 and 4.5V for the 4V 950Ah model. Firefly batteries do not require a float charge on a regular basis. However, if you are float charging, due to their longer projected lifespan, it is important to keep the float voltage at 13.4V or 13.5V (4.5V for each 4V/450AH) to ensure the battery lasts for as many cycles as possible. For this reason, Firefly batteries are not recommended for applications using internally regulated alternators.

Note it does not mention leaving the battery on a charger that goes into a long term float stage. On Second Star, we don't turn the charger on until the battery is down to about a 40% SOC. The charger (a ProMariner ProNautic 1250) has the California Emissions Control which will shut the charger down after reaching a float voltage.

[Jetx]

We're on our second set of 8x G31 Fireflies. The first set died after 1 year, having been connected to shore power and kept on float most of that time. We carried out the FF recommended restoration procedure several times, but the batteries didn't recover. To their credit, OPE and Firefly acknowledged these were from a bad manufacturing batch, and they were replaced under warranty.

Now, 18 months later, our second set is showing signs of reduced capacity, although not nearly as pronounced as before. This set of batteries was PSOC cycled between roughly 45%-85% for most of the past 18 months. During 8 months of cruising this year, they were only fully charged 4 or 5 days. (Flexible solar panels died, and we chose not to rack up the generator hours that would be required to get through absorption to 100%.) We performed the restoration procedure multiple times again at the dock, and the batteries recovered somewhat, but definitely not all the way back to original. Based on voltage sag, I'm guessing they've lost about 20% of nameplate capacity.

I admit these batteries have been abused, and we didn't come close to following Firefly's recommendations -- periodic fast charging at 0.4C, and a full charge every 2 weeks. Run-of-the-mill AGM batteries would likely have been destroyed by the treatment we've given these Fireflies. Still, given that PSOC operation is what FF batteries are meant for, I had hoped for better. My conclusion is that the Fireflies hold up very well under extended PSOC cycling, much better than most lead acid batteries would, but even FFs will permanently lose capacity if they're not fully charged often enough.

If you have enough solar capacity, or get to the dock often enough to charge them to 100% at least every few weeks, Fireflies will probably work beautifully. But if you don't, then LFP is probably a better solution.