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Old 11-05-2022, 08:47   #1
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Firefly not reaching 13.2 volts, not resetting to 100% SOC

I have all Victron solar chargers and battery monitors. 5 Firefly G31 batteries.
The absorption voltage is set to 14.4, tail current 2.5 amps, float voltage is 13.4. In the battery monitor the "charged voltage" is set to 13.2 and the tail current is .5%.

Also have 870 watts of solar and a wind generator.

A few months ago I'd hit 100% SOC periodically but I haven't managed more than 91% recently. The system usually enters float mode in late morning and has great sun the rest of the day. During float mode the voltage sits at 13.1 most of the time, occasionally touching 13.2, but not for long enough to reset the SOC to 100%.

Is this batteries aging? Do I need to do a "restoration" charge? Or are my settings just wrong?
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Old 11-05-2022, 09:43   #2
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

What's the battery temperature? And how much current are the batteries accepting towards the end of the day before the sun starts to go down?
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Old 11-05-2022, 10:08   #3
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

Quote:
Originally Posted by sailingunity View Post
I have all Victron solar chargers and battery monitors. 5 Firefly G31 batteries.
The absorption voltage is set to 14.4, tail current 2.5 amps, float voltage is 13.4. In the battery monitor the "charged voltage" is set to 13.2 and the tail current is .5%.

Also have 870 watts of solar and a wind generator.

A few months ago I'd hit 100% SOC periodically but I haven't managed more than 91% recently. The system usually enters float mode in late morning and has great sun the rest of the day. During float mode the voltage sits at 13.1 most of the time, occasionally touching 13.2, but not for long enough to reset the SOC to 100%.

Is this batteries aging? Do I need to do a "restoration" charge? Or are my settings just wrong?
You have voltages and time too low. The battery monitor charge voltage should be 14.4 and the batteries not rset till they get to that 0.5% at 14.4. Mine normally get to 0 amp hours out after about 3-4 hours of solar absorption.

Doesn't sound like your solar is staying at 14.4 long enough.
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Old 11-05-2022, 11:37   #4
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

It fluctuates a little but they are generally accepting about 2-3 amps.

@sailorboy1 are you saying it should flip to 100% charged while they are still in the absorption cycle?
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Old 11-05-2022, 11:38   #5
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

My max absorption time is 6 hours.
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Old 11-05-2022, 12:12   #6
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

Many times problems like this are due to a bad connection(s).

You should first reseat (redo, loosen/tighten) all your connections.
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Old 11-05-2022, 13:16   #7
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

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It fluctuates a little but they are generally accepting about 2-3 amps.

@sailorboy1 are you saying it should flip to 100% charged while they are still in the absorption cycle?
The battery monitor should reset at whatever you have programed at. Which should be 14.4v and 0.5% acceptance. I have mine set for this, but never see the 0.5%. If you have it set for 13.2 that is way too low. Set your bm to 14.4 and the tail current to 0.5%, which is 2.9 amps if your programed for 5 G31 FF batteries.

Now the bm resetting has nothing to do with the solar.

Your solar needs to be set for an absorption voltage of 14.4V. I Have mine set to stay in absorption for 6 hours then drop into float. I have an amp setting in my controller that will drop it sooner than the 6 hours, but if you arent on shore power i wouldn't worry about this.

So reset the fully charged setting in your battery to 14.4 v and 0.5% tail current. Set your solar to do 14.4v and to hold it for 6 hours. Check your bm for how many amps the batteries are accepting at 14.4 after they have been there 4-6 hours to see if maybe you should do shorter or longer.

Click my user name and search threads by me. There are few about FireFly batteries
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Old 11-05-2022, 16:16   #8
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

Firefly periodically need to be drawn down and provided with a high amperage charge current. FF recommends .4C.

When I have been only using solar for a long time the batteries have trouble getting to 100%. Once the batteries have been given high charge currents in rapid succession they are able to reach 100%.

Draw the batteries down to 30-40% SOC and then give them a full charge starting at .4C. If I did the math in my head correctly that would be around 200 amps for the whole bank.
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Old 11-05-2022, 16:48   #9
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

To test or "restore" the battery, put on shore power, minimum 8 hours assuming plenty of amps.
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Old 12-05-2022, 07:06   #10
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

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Originally Posted by Dave Lochner View Post
Firefly periodically need to be drawn down and provided with a high amperage charge current. FF recommends .4C.

When I have been only using solar for a long time the batteries have trouble getting to 100%. Once the batteries have been given high charge currents in rapid succession they are able to reach 100%.

Draw the batteries down to 30-40% SOC and then give them a full charge starting at .4C. If I did the math in my head correctly that would be around 200 amps for the whole bank.
This has also been a quandary for me, not quite understanding the .4C rate of charging. I have three FF Group 31 batteries which also are not holding a full charge. Shoreside charger is a 40-amp Sterling, and for the three years since new have never given the batts a restoration charge cycle. Do I have a woefully under-powered shoreside charger?
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Old 12-05-2022, 08:06   #11
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

Quote:
Originally Posted by sailingunity View Post
I have all Victron solar chargers and battery monitors. 5 Firefly G31 batteries.
The absorption voltage is set to 14.4, tail current 2.5 amps, float voltage is 13.4. In the battery monitor the "charged voltage" is set to 13.2 and the tail current is .5%.

Also have 870 watts of solar and a wind generator.

A few months ago I'd hit 100% SOC periodically but I haven't managed more than 91% recently. The system usually enters float mode in late morning and has great sun the rest of the day. During float mode the voltage sits at 13.1 most of the time, occasionally touching 13.2, but not for long enough to reset the SOC to 100%.

Is this batteries aging? Do I need to do a "restoration" charge? Or are my settings just wrong?
If the battery voltage on float is 13.1v, but the solar charger is set for 13.4v, providing there is enough sun this indicates there is around a 0.3v volt loss between the charge controller and the batteries, or the temperature is high enough to reduce the voltage set points by this amount.

If you have one of the popular Victron chargers, an inexpensive solution is to install the Victron battery sense. This will correct for voltage loss in the cabling (although if you have a 0.3v voltage loss when on float the cable size is too small). It will also measure the temperature correctly at the battery rather than at the solar controller, which is often considerably hotter.
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Old 12-05-2022, 08:07   #12
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

I have 6 Fireflys on my lake boat,
4 configured for 48V re: electric drive, 2 for 12V re: House.
I use 2 X 15amp Sterling Chargers for the 48V, and 1X30 amp Sterling for the house set.

I believe your 40a is sufficient for 12V setup and although I haven't had your issue, I agree with the advice of Thom225 as well as Dave Lochner as first steps.
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Old 12-05-2022, 09:46   #13
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

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Originally Posted by Skipper Lee View Post
I have 6 Fireflys on my lake boat,
4 configured for 48V re: electric drive, 2 for 12V re: House.
I use 2 X 15amp Sterling Chargers for the 48V, and 1X30 amp Sterling for the house set.

I believe your 40a is sufficient for 12V setup and although I haven't had your issue, I agree with the advice of Thom225 as well as Dave Lochner as first steps.
According to what I have read you need 48 amps of charging power for each battery for a restoration charge. I suspect your batteries are gradually loosing capacity.
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Old 12-05-2022, 09:48   #14
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

Have you created a Bluetooth network so the solar can use the voltage from the bvm?

Is the solar controller mounted near the battery and What is the current temp? They will adjust voltage based on the temp of the controller not the battery. . So don’t mount them somewhere hot. (Unless you have them linked to a battery temp source).

The batteries not hitting voltage is a charger or wiring issue.

I would set the float to 14.4v for a day and see what happens That will force them to fully charge instead of droping to float to early.

Victron specifies the reset voltage should be 0.2v below float so you are current. Despite all the answers above. If it’s not resetting now at 13.2 setting it certainly will never reset at 14.4v setting
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Old 12-05-2022, 10:27   #15
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Re: Firefly not reaching 13.2 volts, not resetting to 100% SOC

While not exceeding voltage recommendation from FF, current is more important. If current is not sufficient or the batteries are left charging for too long without a high current charge, they will lose capacity. How much depends on how undercharged they are.

The FF Manual is explicit in its instructions to charge at .4C and as high as .5C. From my experience, this is especially important when the batteries have been on solar only for more than a couple of weeks.

To get the most out of FFs there needs to be a high amperage charging source. Solar won't work well here because the current is too variable due to clouds and such and the high current can't be provided for long enough periods of time unless one has acres of solar panels. To reach .4C the panels will need to provide 45 amps per battery and be able to maintain that until the absorption voltage is reached. That's about 600 watts of solar per battery.

On Second Star we have 2 G31 FFs, 300 watts of solar, a 50 amp Smart Charger, and a 165 amp Alternator. It is the alternator that does the big charges. The system is working well. After 10 months of full time live aboard and cruising, we seldom use shore power and rarely run the diesel to simply charge the batteries. At idle, the alternator will put out ~90 amps, just shy of .4C and in an hour or less can restore as much as 30% of SOC. When needed we just start the motor a little early before weighing anchor, take our time setting the sails and then motor sail for a while. That takes care of the big charges.

Stock internally regulated alternators are not a good match for FFs, they don't put out enough current.

Solar is fine for later in the absorption phase and for float, but they can't put out enough current at the optimal voltage for the bulk phase of charging. The greater the deviation from the recommended charge protocol, the shorter the life span of the battery. That's true for all batteries.
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