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lisaar avatar image
lisaar asked

BlueSolar end tail current with SCS

I have a system with a large AGM battery bank, monitored by a BMV 712 connected to a Octo GX (uncommon Venus OS device) with DVCC and SCS enabled. The Octo has three BlueSolar 75/15 MPPTs each with panels that get light at slightly different times (sailboat with shade limitations).

If I leave the default adaptive charge algorithm on the controllers, the first panel getting going in the morning sees the overnight voltage and picks a longer absorption time. Later panels see a higher voltage (since charging has started) and pick shorted absorption times. This tends to mean that they bulk charge together and enter absorption, two panels quickly drop out and go to float, leaving only one panel actually producing power. This then leads to a voltage drop that is well below specified absorption voltage and the batteries are under charged as a result.

My thought as to how to improve this would be to switch to the fixed charge algorithm, set a maximum absorption time and ending tail current to what my battery manufacture recommends. With SCS enabled (shows as being "Active" and has the correct BMV), each control SHOULD see what's happening at the battery and stay in absorption until either the max time is exceeded or the battery current drops while the absorption voltage is met. It however does not. If any panel sees its own output current drop below the configured end tail current, it drops to float, resulting in one panel only producing power.

My questions:

Is SCS actually supported on BlueSolar devices. I was told it was by the rep, but I kind of doubt that based on what I'm seeing.

If I replaced the MPPTs with SmartSolar equivalents and ran them like the above (VE.direct with DVCC and SCS, not BLE networked), would that work?

I've considered disabling ending tail current and just relying on maximum absorption time interval, but our power consumption can very based on things like running the water maker, so not a great choice.

We're adding panels, and without getting this resolved it's a waste as the Victron MPPTs are not playing well together so help on this is greatly appreciated.

Additional info: Venus OS 2.91, MPPT product id 0XA042 with firmware v1.63. SmartShunt in system to monitor starter battery and wind generator, but not selected as the battery monitor on the system setup page (the 712 is).

MPPT ControllersDVCC
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2 Answers
Alexandra avatar image
Alexandra answered ·

@LisaAR

I would use SVS since it is a voltage problem more than a current problem.

Even with DVCC on each charge controller follows its own internal set up when using not intelligent batteries. This is mentioned in the GX manuals. But if you need a longer absorption time then have it fixed rather than adaptive. Adaptive means the battery start voltage affects how long it runs absorption so if some are starting later than others then they will absolutely be in absorption for less time.

If you have a large bank and 3x15A of mppt you are not likely to be overamping on charge even at full production.

Set the 712 shunt as the system monitor, that is what it is there for. Do you have has dc system enabled as well with the shunt as a dc meter?

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JohnC avatar image JohnC ♦ commented ·

@Alexandra

My post crossed with yours. DVCC SCS should work here with these agms. There's no Octo manual, but it references CCGX's.. https://www.victronenergy.com/media/pg/CCGX/en/dvcc---distributed-voltage-and-current-control.html

See11.4.5

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Alexandra avatar image Alexandra ♦ JohnC ♦ commented ·
Yeah. I did think that after. I have not used an octo so never read the manual. Just assumed that the feature was across GXs though.
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lisaar avatar image lisaar commented ·
The 3x15A is the initial installation with at least three more panels being added. Using a fixed absorption time is not going to work well in our case and is why this was implemented in the first place.
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JohnC avatar image
JohnC answered ·

@LisaAR

This is supported by the Bluesolar units, no need to update. It works well on my own, but I don't have multiple mppts.

I can't really explain what you describe. Might be something like a VE.Direct cable not properly connecting (they're not very robust) and it doesn't take much time for the individual Tail conditions to be met if you lose comms. So check all that obvious stuff. I'd also update firmware on the Octo to the latest.

I also use a max fixed Absorb time, but the Tail never lets it get that far..

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lisaar avatar image lisaar commented ·

Cabling has been double checked and I've going in and looked at the communication error counts over MQTT and I'm not seeing any errors. That was my thoughts as well.


After much digging in documentation, I think I've found the issue though, in the release notes for the firmware that added SCS v1.47 there's the following:

  • Tail current mechanism improved: it can now use the real battery current. The current can be received via VE.Smart Networking (Bluetooth) as well as from a GX Device. Included for all SmartSolars and the following BlueSolars: 100/20, 100/20 48V, 100/30 rev2, 150/35 rev2, 100/50 rev2, 150/45, 150/60, 150/70, 150/85 and 150/100)

Note that the 75/15 is not in this list. Later 75/15 had a hardware revision that updated the processor, Rev 2, and maybe it was added there, but I have older versions.

Oddly the VE.Direct Protocol document lists the associated register (0x2013) as being SmartSolar only, which would sound incorrect based on the above and your experiences.

@JohnC , would you happen to know your HW version and model?

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JohnC avatar image JohnC ♦ lisaar commented ·
@LisaAR

I may have misled you. Mine's a Bluesolar, but a 150/100, not a 75/15. HQ1611 vintage, so more than 8yo. And after doing some research of my own, yes it appears the 75/ Bluesolars missed that update.

If you were to purchase more, make your dealer aware of your research, and only accept them if they are returnable if they don't honour the Tail. That changelog suggests the Smart units are ok, but you don't want to be doing this via BT alongside an Octo if that's what it really means.

I'll raise this up the ladder to see if someone can confirm.

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