New Victron MPPT Firmware

[RickG]

Originally Posted by TxCoastSailor

Where did you find the 1.5A value? Also is that 1.5A per battery? If you have 2 batteries in parallel would the tail current be 3A?

It's on page 3 of the manual:

"For a complete charge cycle, charge the G31 to 14.4V/L15+ to 4.8V with temperature compensation (bulk phase) and continue charging until the charging current drops to 1.5A for the G31 or 6A for the L15+ (absorption phase time will vary). You DO NOT need to fully charge the batteries each cycle in order to maintain the capacity and only need to perform a complete charge cycle when you want to maximize the capacity for the following discharge cycle."

https://oceanplanetenergy.com/wp-con...L15-180724.pdf

That would be n*1.5amps where n=# of batteries.

We are on the hard with batteries disconnected. We splash October 21 and I will upgrade the controllers and report on performance.

Cheers, RickG

[StoneCrab]

Please correct me if I am wrong, but it seems that there is a lot of theory here without the practical conclusions that if your house batteries are all wired together in parallel, and your multiple solar charge controllers are connected to those batteries, the voltage/current adjustments from the charge controllers can only raise and lower the volts and resulting amps to the collective whole.

If one of the charge controllers drops into float and the bank is still getting the 5 amps, it makes no difference if the split is 4 - 1 or 2.5 - 2.5. The voltage on the bank bus will be the same.

It seems to me that the advantage being able to adjust the tail current switch to float on a multiple charger system only exists in the capability to "sync" up the chargers for similar performance, without any real benefit.

RC hobby batteries can be charged with "balance chargers" which are able to charge the individual cells separately. This allows each cell to be charged to their full capacity. You can see this in the width of the battery sensor plugs that come on these batteries. A six cell battery will have seven wires going to the plug.

Charge controllers feeding a banked system like on a boat do not have this capacity. Even if you had a shunt at each battery, you couldn't control the charge unless you added a battery selector switch for each pair of batteries in your bank a voltage/current monitor for each battery and charge wires connected to each battery. At that point, you could manually balance charge the batteries in the bank by disconnecting individual batteries from the bank and monitoring their individual charge.

I don't see the harm in one of the charge controllers dropping to float early if the other one is still topping off the bank.

Am I missing something?

[noelex 77]

Originally Posted by StoneCrab

I don't see the harm in one of the charge controllers dropping to float early if the other one is still topping off the bank.

Am I missing something?

The harm is if the sun disappears behind cloud (or the load increases) there is a risk that the charge controller maintaining the absorption voltage will no longer be able to do this on its own. The second charge controller, if it has dropped to float early, will not contribute anything unless the battery voltage drops below the float voltage.

It is better if both charge controllers stay in absorption mode. In this case if one charge controller can no longer maintain the absorption voltage the second charge controller will add to its output.

[StoneCrab]

Originally Posted by noelex 77

The second charge controller, if it has dropped to float early, will not contribute anything unless the battery voltage drops below the float voltage.

There is a nuance that I am still not understanding.

The first charge controller will output as much as it can when the load comes up. Its contribution will either satisfy the load or it will contribute as much as it can and then the remaining current draw will lower the voltage of the batteries which will bring on the second charge controller (take it out of float). At that point, the voltage drop on the batteries will stop, and the combination of both controllers will either satisfy the load or it won't.

I'm pretty sure that the difference between meeting the load demand with one or both controllers remaining in "acceptance" would be measured in milliseconds. The controllers only react to battery voltage, so they go in and out of "float" as needed... as defined by the setpoint in the controllers setup.

[noelex 77]

If one controller has prematurely dropped to float it is trying to maintain the float voltage setting. It will not contribute anything if the battery voltage falls below the required absorption setting until the battery voltage drops further to the float voltage. It is not a matter of reaction time. The second controller is not in absorption mode so it will not try to maintain the absorption voltage. It is trying to maintain the lower, float voltage value.

The second controller will not be taken out of float until the battery return voltage (usually with a time delay) is reached. The battery return voltage is below the float voltage.

Thus while the available solar power from both controllers (not just one) may be enough to maintain the absorption voltage, because one controller is happy with a lower (float) voltage the absorption voltage will not be maintained.

[TxCoastSailor]

RickG,

Thanks, I found it in the manual. I had seen it before but forgotten about it because I couldn’t do anything about it. I will adjust mine to 4.5A since I have 3 batteries but honestly I’ve been running the DC system on solar only for over a year as is. Not sure what the default is but it seems to be OK.

[RickG]

Originally Posted by TxCoastSailor

RickG,

Thanks, I found it in the manual. I had seen it before but forgotten about it because I couldn’t do anything about it. I will adjust mine to 4.5A since I have 3 batteries but honestly I’ve been running the DC system on solar only for over a year as is. Not sure what the default is but it seems to be OK.

With Fireflys the default tail current has been fine me too. The problem has been early float; that is the main thing I am excited about.

Cheers, RickG

[TxCoastSailor]

RickG,

So if you want to delay float mode (longer absorption) you would lower the tail current. When I set mine the default was 2A so I had to raise it to comply with the Firefly 1.5A/battery guidance since I have 3 batteries. So it may actually spend less time in absorption mode. System is running now in bulk mode, we will see what happens this afternoon when it usually goes to float.

[RickG]

TxCoastSailor, let us know how it goes. I think we're going to need to tune things a bit to account for the working load.

Cheers, RickG

[admiralslater]

Is standing load taken into consideration when stetting tail current.

[rudykruger]

Thought I would resurrect this thread since great info was being shared, specifically for Firefly Oasis, and then stopped.

Since these batteries are a specialized AGM but in many ways behave like low resistance Lithium - definitely somewhat unique - and they are expensive, I was hoping that Firefly would provide more clarity with instructions, something akin to Battle Born Batteries' excellent solar charge setup instructions (Victron examples https://battlebornbatteries.com/prog...ge-controller/ and https://battlebornbatteries.com/conf...etooth-dongle/ ). But that's not the case.

I'll condense requests I've sent to Firefly, eMarine and Ocean Planet Energy - since I seemingly experience early float with my 900Ah bank of six FF Oasis L15+ at 4V each. The six batteries are set up 3+3 series parallel. In the 3 months since install they've clocked only 5 cycles, with most daily SoC varying between 85% overnight to 100% mid to late morning.

I am open to the suggestion that I simply don't have enough charging capability for the size of FF Oasis bank. Solar panels are 12 years old and replacing with modern higher yield panels can more than double installed capacity to over 2000W in the same footprint.

Charging infrastructure is Victron apart from alternators, everything running latest available firmware. My Victron Centaur battery chargers (100A + 50A) are not programmable with only a basic AGM dip setting being used. However, the battery bank spends 99% of it's life being charged by a Victron SmartSolar 150/80 MPPT charge controller with a Victron BMV-712 battery monitor combined on a Victron VE Smart Network with temperature sensor. My solar panels will typically produce an actual maximum of around 700-750W around mid day at the moment (early March in Bahamas).

I also have a Balmar SG200 monitor on board, recently installed to get a second set of eyes on the bank since it has a carbon foam battery preset, and hopefully give me a decent SoH calculation. At the moment, with typical shallow discharges of 10-15% overnight the SG200 tracks the Victron BMV closely.

Basic MPPT setup follows the "Firefly User’s Manual for the “OASIS” G31 & the L15+ June 2019" document provided to me by eMarine who provided the batteries (but also available on Cruisersforum in various threads). It is set up with absorption voltage at 14.4V and float voltage 13.4V. I currently have absorption stage set to adaptive with maximum absorption set to 5 hours and tail current set to 6 Amps, half the recommendation (the user manual states 6 Amps for the L15+ at 4V which would be 12 amps for my 12V series/parallel bank, but this lower tail current is an attempt to avoid early float).

The BMV-712 has a charged voltage of 14.2V, tail current at 1.3% (which corresponds to a 12A tail current - pretty meaningless anyways as the boat's base load varies between 5 and 20 amps depending on which of 3 fridges are running and two 2000 inverters sucking up some juice in the background), and charge detection 10 minutes. These are the current settings, I tinker with them basically weekly.

I find that my solar MPPT controller typically goes into float:

(1) If the bank is drawn down to 60% SoC for example, float happens while the BMV still reports only 80-85% state of charge. The BMV usually syncs to 100%, but after these deeper discharges it will show SoC slowly build to 80-85% and then, boom, sync to 100%. I've not had a deeper than 80% SoC discharge since installing the Balmar SG200 and cannot compare it's behavior.

(2) If the bank is drawn down 10-15% overnight (which is typical), float happens mid-to-late morning but a few times when I changed the MPPT's float voltage to the 14.4V absorption level - for the sake of experimenting - the batteries would sometimes soak up the full 50-60 amps from my charge controller - which to me looks like they did not spend enough time in absorption.

I guess I'm looking for some recent learnings from other Victron MPPT and FF Oasis owners, specifically around absorption and float settings and behavior.

[Jim Cate]

The expert mode with my 100/30 keeps turning itself off. Is this a common flaw and is there a fix known?

Jim

[RickG]

Given the charging recommendations from Firefly, I don't see a need for directions from Firefly on setting up Victron products? It is pretty straightforward using the smart phone app.

The only time I see the solar controllers go into float early, with the most recent firmware, is when motoring for long periods. After turning the engine off the controllers go back to bulk or absorption eventually. I turn the controllers off and on again to make them go to bulk/absorb faster if I remember.

The controllers stay in expert mode as long I am connected to a controller. When I reconnect, I need to select expert mode to see the additional settings, but the settings persist.

Cheers, RickG

[rudykruger]

Originally Posted by RickG

Given the charging recommendations from Firefly, I don't see a need for directions from Firefly on setting up Victron products? It is pretty straightforward using the smart phone app.

The only time I see the solar controllers go into float early, with the most recent firmware, is when motoring for long periods. After turning the engine off the controllers go back to bulk or absorption eventually. I turn the controllers off and on again to make them go to bulk/absorb faster if I remember.

The controllers stay in expert mode as long I am connected to a controller. When I reconnect, I need to select expert mode to see the additional settings, but the settings persist.

Cheers, RickG

Have you attempted to verify your FF's are actually truly in float when the charge controller says they are, for example on a day with variable clouds? When a battery bank that's just flipped over to float on a partly cloudy day gobbles up 50A when I adjust the MPPT float voltage to 14.4V it's not there yet.

Maybe it's an impossible mission to set an adaptive absorption rule when clouds probably cause the net charging amps to drop low enough for long enough that float is "induced". Just speculating.

[rudykruger]

To add to my own last post in this thread, I also wonder how closely these carbon foam batteries charging profile match regular AGM's. Firefly says charging infrastructure should ideally push 0.4C or higher (40A per 100Ah installed capacity) which translates to 360A charge rate for my 900Ah bank. Clearly these batteries like to be punched hard during charge, much like lithium.

Prior to firmware 1.42, Victron MPPT had an identical adaptive absorption charge scheme for lithium and lead acid. Post 1.42 it defaults to a fixed 2h absorption for lithium presets.