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Old 02-08-2018, 09:11   #1
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Float voltage for Firefly batteries

We have a new bank of Firefly batteries with a second bank on order from Coastal Climate Control. Quite happy with them so far, but they are new. Charge is set at 14.4V and float at 13.2V on all charge sources. We will mostly be on the dock until September and then cruising on the hook/mooring for an extended period.

Details, after second bank added:
- house bank: 6 Firefly G31 116Ah per / 696Ah
- start battery: 1 Firefly G31
- solar: 660 watts
- charger: Sterling Pro 40amp, changing to Victron Multiplus 12/3000
- alternator: Balmar 110amp, mc-612 regulator
- solar charger: one Victron SmartSolar 100/30 per panel
- generator: Honda EU2000i

A couple of questions:

1) On the dock the batteries will be charged ~100% most of the time. Is there any benefit to lowering the float voltage below 13.2V on the shore charger?

2) For the externally regulated alternator, Balmar 110amp / mc-612, considering setting bulk to 14.4V and minimum bulk time to the lowest option of 10 minutes, absorption to 14.4V and minimum absorption time to 10 minutes, and float to 13.2V (or lower if advised above) and minimum time to the 10 minutes. I am looking to charge the batteries and then serve the house load while motoring. Does this make sense?

3) We are installing solar with Victron SmartSolar 100/30 controllers. Our daily amp budget is 150-200 amps. Is there any benefit to lowering the float voltage?

Cheers, RickG
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Old 02-08-2018, 09:13   #2
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Re: Float voltage for Firefly batteries

My understandind is firefly has raised their float voltage from original reconmations. . It's now more in the 13.4-5 range.

Lowering the bulk / absorb times will reduce your charging and chances of getting back to full. If you are always back at the dock to fully recharge. Less of issue. If out for a long time. I would raise them back up
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Old 02-08-2018, 11:00   #3
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Re: Float voltage for Firefly batteries

Why are you using a $500 deep cycle battery for your start battery? Strikes me as a waste. Mine is a plain old AGM from Battery Warehouse or whatever the nearest battery store was. It never gets deeply discharged. It starts the engine and then gets charged.
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Old 02-08-2018, 11:31   #4
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Re: Float voltage for Firefly batteries

As Firefly has a unique build, I would check directly with them for their current recommendations about voltages. There may be issues that contribute to longevity, that most users wouldn't see but the factory might be more aware of.
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Old 02-08-2018, 11:32   #5
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Re: Float voltage for Firefly batteries

Quote:
Originally Posted by RickG View Post
We have a new bank of Firefly batteries with a second bank on order from Coastal Climate Control. Quite happy with them so far, but they are new. Charge is set at 14.4V and float at 13.2V on all charge sources. We will mostly be on the dock until September and then cruising on the hook/mooring for an extended period.

Details, after second bank added:
- house bank: 6 Firefly G31 116Ah per / 696Ah
- start battery: 1 Firefly G31
- solar: 660 watts
- charger: Sterling Pro 40amp, changing to Victron Multiplus 12/3000
- alternator: Balmar 110amp, mc-612 regulator
- solar charger: one Victron SmartSolar 100/30 per panel
- generator: Honda EU2000i

A couple of questions:

1) On the dock the batteries will be charged ~100% most of the time. Is there any benefit to lowering the float voltage below 13.2V on the shore charger?

2) For the externally regulated alternator, Balmar 110amp / mc-612, considering setting bulk to 14.4V and minimum bulk time to the lowest option of 10 minutes, absorption to 14.4V and minimum absorption time to 10 minutes, and float to 13.2V (or lower if advised above) and minimum time to the 10 minutes. I am looking to charge the batteries and then serve the house load while motoring. Does this make sense?

3) We are installing solar with Victron SmartSolar 100/30 controllers. Our daily amp budget is 150-200 amps. Is there any benefit to lowering the float voltage?

Cheers, RickG
We went thru the same exercise when we launched in the Spring. From Ocean Planet we set buik to 14.4 and bulk time to 30 min. Absorption to 14.2 and absorption time 30 min. Float was set to 6 hours at 13.4. We have a 150 amp hour alternator and have set the belt manager to "2' but it never gets above 64 C. Going forward I plan to reduce the belt manager to 1 and then monitor its performance. We too have been very satisfied with the Firefly batteries but there are early days.
Attached Files
File Type: pdf Balmar Settings for OPE-Li3_F.Fly.pdf (102.2 KB, 241 views)
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Old 02-08-2018, 12:06   #6
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Re: Float voltage for Firefly batteries

Quote:
Originally Posted by Suijin View Post
Why are you using a $500 deep cycle battery for your start battery? Strikes me as a waste. Mine is a plain old AGM from Battery Warehouse or whatever the nearest battery store was. It never gets deeply discharged. It starts the engine and then gets charged.
Simple reason, keeping all batteries the same chemistry simplifies charging. I can add a simple start battery later if I need more house capacity.

Cheers, RickG
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Old 02-08-2018, 12:15   #7
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Re: Float voltage for Firefly batteries

Quote:
Originally Posted by sogin View Post
We went thru the same exercise when we launched in the Spring. From Ocean Planet we set buik to 14.4 and bulk time to 30 min. Absorption to 14.2 and absorption time 30 min. Float was set to 6 hours at 13.4. We have a 150 amp hour alternator and have set the belt manager to "2' but it never gets above 64 C. Going forward I plan to reduce the belt manager to 1 and then monitor its performance. We too have been very satisfied with the Firefly batteries but there are early days.
Excellent and exactly answers my alternator question, I have not come across this and my retailer did not provide this. I see OceanPlanet posting this as recently as May 2018.

13.4V float I had seen second hand as a recommendation from "factory representative" for "technical reasons." This is the first time I have seen it from a definitive source.

Cheers, RickG
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Old 02-08-2018, 15:35   #8
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Re: Float voltage for Firefly batteries

RickG

We have almost the exact same set up, Except I used a Sterling 50A charger.

When I installed my FireFlies, I too was confused by conflicting Float voltages. 13.2V vs 13.4V.

I contacted Peoria for the final answer.
They told me that the 13.2V was the original recommended float voltage. But it was upped to 13.4V a few years ago because some installations were not fully charging.

They also told me that they really don't recommend the bank being held at 13.4V for an indefinite amount time. A few days or weeks at this higher voltage, will cause no real measurable harm. But they recommend disconnecting the bank for extended float times. I.E. weeks or months.

What I did to solve this problem is modify my battery selection panel so that when we are away for long periods, the house loads and all charging sources are transferred to the start bank.

Which by the way are nothing more than 2ea, old AGM's that came out of the old house bank.
The start bank will maintain all, needed demands (bilge pumps, alarms and vessel monitors) for weeks on end, with out any charge sources.


FWIW, all of my charging sources are set for 14.4A bulk and 13.4V float.
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Old 03-08-2018, 05:34   #9
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Re: Float voltage for Firefly batteries

Quote:
Originally Posted by missourisailor View Post
RickG

We have almost the exact same set up, Except I used a Sterling 50A charger.

When I installed my FireFlies, I too was confused by conflicting Float voltages. 13.2V vs 13.4V.

I contacted Peoria for the final answer.
They told me that the 13.2V was the original recommended float voltage. But it was upped to 13.4V a few years ago because some installations were not fully charging.

They also told me that they really don't recommend the bank being held at 13.4V for an indefinite amount time. A few days or weeks at this higher voltage, will cause no real measurable harm. But they recommend disconnecting the bank for extended float times. I.E. weeks or months.

What I did to solve this problem is modify my battery selection panel so that when we are away for long periods, the house loads and all charging sources are transferred to the start bank.

Which by the way are nothing more than 2ea, old AGM's that came out of the old house bank.
The start bank will maintain all, needed demands (bilge pumps, alarms and vessel monitors) for weeks on end, with out any charge sources.


FWIW, all of my charging sources are set for 14.4A bulk and 13.4V float.
Thanks so much for the details. You're the second person to mention a good source for the 13.4V float - the manufacture and OceanPlanet. My reseller points to the documented 13.2V float. I am changing float to 13.4V today.

We are liveaboard. I see my batteries every day. We are off the dock this weekend for a bit of 'camping' for the weekend in a nearby quiet creek; too much debris in the Chesapeake for much sailing. We've been on the dock a lot lately doing major engine work, solar install, new electronics, etc.; it is easy enough for me to turn the battery charger off for 24 hours once a week.

What I would really like to do on shore power is to fully charge the Fireflys and then discharge the bank to 30% DOD before going into bulk/absorb again. We are off the dock September 2018 and cruising for the next 5+ years and we will be more or less doing that with solar each day. So, I think I'll leave the shore charger at 14.4V/13.4V and manually turn off the shore charger once a week to get down to 30%-50% DOD.

For now, it's a bit of an experiment.

Cheers, Rick
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Old 03-08-2018, 06:15   #10
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Re: Float voltage for Firefly batteries

Check that Ocean Planet source again. I think I remember him waffling a bit about the need for float at all on these batteries somewhere on this forum. I took away that it was probably not something that makes a huge difference. I have mine set at 13.1 or 13.2 but I do what you are planning by turning the charger off for a day or two and then recharge every week or so when I am in marina. I haven’t noticed anything but the truth is I wouldn’t know what to look for to see if it was working since the batteries seem to be just like new even though I hardly ever get them charged fully. I am the definition of PSOC abuse. [emoji3]

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Old 03-08-2018, 07:13   #11
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Re: Float voltage for Firefly batteries

jkleins, I have emails into Firefly International Energy and https://www.bruceschwab.com/ on current recommendations. I've found plenty of anecdotes from Michael Kepros and Bruce has great comments here and elsewhere as does MaineSail.

Here is one that sticks in my mind from MaineSail in 2016

"The main concern around float with the Firefly is long term dockside or continual daily solar floating. The inventor would actually prefer it if they were never floated but concedes to 13.2V as a good compromise. The batteries are designed to be cycled...."

Voltage regulator Firefly Batteries - Gear Anarchy - Sailing Anarchy Forums

Maybe I should just take the following as gospel and never float. I'd be okay with 24 years of battery life.

"30% DOD - 9000-13500 cycles"

http://fireflyenergy.com/wp-content/...e-SPI-LV-1.pdf

Cheers, RickG
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Old 03-08-2018, 07:41   #12
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Re: Float voltage for Firefly batteries

It pays to ask questions. Bruce Schwab from Ocean Planet responded briskly and very cordially - I have my definitive answers, for now. Bruce forwarded the updated July 2018 User's Manual and the Balmar settings file that sogin posted. I am pleased.

These documents recommend:
- 14.4V charge at 0.4C+ until current drops to 1.5amps
- No float required, but 13.4V if you must
- Reset to bulk/14.4V charge as above if voltage drops below 12V for > 1 minute

Cheers, RickG
Attached Files
File Type: pdf _Firefly User's Manual G31 & L15+ 180724.pdf (153.2 KB, 137 views)
File Type: pdf _Balmar Settings for OPE-Li3_F.Fly - 180803.pdf (80.5 KB, 116 views)
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Old 03-08-2018, 11:01   #13
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Re: Float voltage for Firefly batteries

RickG wrote

- charger: Sterling Pro 40amp, changing to Victron Multiplus 12/3000

Why are you changing? I might be interested in the Sterling Pro 40 amp. How new?
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Old 03-08-2018, 11:59   #14
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Re: Float voltage for Firefly batteries

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RickG wrote

- charger: Sterling Pro 40amp, changing to Victron Multiplus 12/3000

Why are you changing? I might be interested in the Sterling Pro 40 amp. How new?
I'm quite happy with the Sterling Pro, but it does not put out enough amps for 700 amp/hours of Firefly batteries. I haven't decided whether to leave it in place as a spare or not. If I decide to let it go I'll ping you.

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Old 03-08-2018, 12:31   #15
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Float voltage for Firefly batteries

You can use several Sterling Pro chargers, they will all play together nicely, and of course that gives you redundancy. Buy a 60 amp or two to get what you want.
Another way is an inverter / Charger. I have a Magnum MS2812 at 125 amps, it along with my 60 amp Sterling gives me 185 amps, and that is about all my 30 amp Boat can support.
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