bora avatar image
bora asked

Firefly Oasis 12V Profiles


I'll shortly be installing 5x Firefly Oasis G31 as my house bank, are there any plans to create a firefly specific profile for the following equipment?

- BMV-712

- Phoenix Smart Charger 3+1 50A

- MPPT 150/60

Or can someone share the settings that they currenty use?

MPPT ControllersBMV Battery Monitorcharger
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4 Answers
wkirby avatar image
wkirby answered ·

It's always best to consult the battery manfacturer to obtain the charge parameters from them directly. Then set up your equipment to match the parameters that they give you.

Use the "User defined" profile to save your specific profile for your batteries.

With any luck there is someone out there who already uses the same batteries as you plan to use who is willing to share.

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bora avatar image
bora answered ·

Here's what I got from their tech guys regarding the smart charger, waiting on the BMV and MPPT but could probaly copy most.

I hope it is for 5 Nos .12 V Batteries in Parallel.

4 nos . in Parallel only is Recommended.

If 5 are to be used , ensure uniform current flow in all parallel cables during

charge as well as discharge.

For a 12 V System ,

Bulk & Absorption Voltage : 14.40 V

Float voltage : 13.50 V

Storage voltage : 13.20 V

Temperature compensation : + /- 0.050 V / deg.C ( For 12 V Battery @ 0.004V/Cell)

: For Higher Temperature above 25 deg.C – to be Applied.

: Lower Temperature below 25 deg.C , + to be Applied.

Bulk Time Limit : 10 hrs.

Re Bulk voltage : I am not clear. To be set with help from Supplier. note from manual "

Reset to bulk phase: for programmable charging sources, adjust the “reset to bulk

phase” to occur if the battery voltage drops below 12.0V for >1 minute"

Maximum Absorption Time : 4 hrs

Repeated Absorption : Once in 7 days.

Recondition Current : 8 %

Recondition Stop : Automatic on voltage

Recondition Time : when in auto as above , Not required.

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billknny avatar image
billknny answered ·


I am not sure what your question is, since you have the official numbers from Firefly. The numbers for you MPPT should be the same as your charger. The numbers you posted are the same as I have used with my Firefly bank. You have to be careful with Firefly's recommendations, especially about Float voltage, and reconditioning charges. Numbers have changed. Float used to be 13.2, then moved to 13.4, your quote above is the first time i have seen 13.5. Always be sure you are using the latest info, and check back for updates as they learn more.

The only reason to make them different: If you set the MPPT at an absorption value of 14.4V and the battery charger at 14.2V or 14.3V, the solar will preferentially charge the batteries during the absorption phase, saving a bit of what ever source power feeds the Charger. If this is a good idea depends on your application, cost of shore power, etc.

Assuming your are going to be running a 12V system, the capacity you will enter into the BMV will be 5*116 = 580Ah. With a solar system, I set the charge end voltage at 14.2V, and the tail current at 2% of C20, or 11.6A. (Victron default here is 4% of C20, I think that is too high, but your mileage might vary!) Note that when the BMV reports 100% the batteries will NOT be fully charged. That doesn't happen until the tail current reaches 0.5% of C20 at 14.4V, or for your system about 3A.

Also, note that Firefly has consistently recommended against storing the batteries under "Float" conditions. They suggest if they are not being used to disconnected from loads and chargers and just let them sit. Some of us have no choice, if we are connected to shore power and using power, we need to float them. My compromise if I am tied to the dock for a while is to disconnect shore power and cycle the batteries once a week, and do a reconditioning charge once a month.

Be very careful with the "Reconditioning" charge. Make SURE you read the latest version of the Firefly manual and follow those instructions exactly. If your equipment doesn't allow you to do so, communicate with Firefly to get their approval for an alternative procedure.

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Ramsey avatar image
Ramsey answered ·

Has anyone got a clear Firefly profile yet and is willing to share? Ive set up my solar array and plugged in the batteries but a little unsure about a couple of things.

When I apply the firefly recommended amounts the charger stays mostly in Bulk mode even when batteries are full. It says bulk but I know its not charging. If I go back to a factory preset it immediately says absorbtion.

Also why is the rebulk only below 12v (for more than a minute) this means draining the battery to 30% depth of discharge! Why so low?

Any help or fresh info greatly welcome. I will post here too once I have enough experience and a clear profile

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