xw6848 with two mppt60 charge controllers, hunting not good

[keepsake]

Schneider/Electric
Issue I have today ... got the xw6848 with TWO mppt60 units.
One of them will not migrate to the mppt voltage and current that is maximum.
In fact it's like 40% off the max.
How can I force the unit to stay at a fixed voltage and let the current fall where it will ?
My gateway has two Xanbus paths.
When I put the second mppt60 on a separate Xanbus I can get better results than when they are both on the same Xanbus.

So in other words, the 'hunt' works better splitting the mppt60 apart on Xanbus.

 

[keepsake]

Still an issue three days later. What setting can be used to force each mppt to produce 100% and perform proper tracking ???
Too much technology is OUT OF CONTROL. The designers think they know more than the users and the end goal IS NOT BEING MET. Energy is BEING WASTED and LOST.

 

[timselectric]

I don't know enough about xanbus to help in that regard. But I will say that solar only produces what is needed. If all loads are covered, it's not going to produce anything more.

 

[keepsake]

I'm seeing one of the mppt's skewing the pv voltage so high and reducing the mppt output to close to only 10% of the other one.
I'd be happy if I could SET the voltage goal for the pv side. I am talking a sell-to-grid situation most of the time where all pv energy needs to be harvested at all times. All standalone grid tie inverters do this automatically. Like Sunny Boy, etc.

 

[Tecnodave]

If you do not have separate array’s on each controller they will fight each other for control. Using two MPPT controllers they MUST HAVE SEPARATE ARRAY’s You cannot connect two controllers in parallel to one array. Each MPPT controller MUST HAVE.......it’s own array to control.

When MPPT controllers are tied in parallel to one array the first controller will sweep the solar input voltage from vmax to v=zero which will cause the second controller to sweep to find the MPPT which is hidden by the first controller sweeping.

Both the positive and negative of each array must go directly to the controller which is controlling that array and NO WHERE ELSE.....

A common mistake

 

[timselectric]

I'm seeing one of the mppt's skewing the pv voltage so high and reducing the mppt output to close to only 10% of the other one.

Not sure how this could happen. Unless both MPPT's are connected to the same solar panels.

 

[Solar Guppy]

The XW-mppt60 ( Xantrex and now Schneider ) are very mature products ( released in 2007 ) so the issue is likely in your installation configuration.

Can you describe from array(s) to batteries what/how your system is configured as? this would help on pointing to the cause of your issues.

As already mentioned, you need harvested energy to be demanded, either by filling batteries or selling to the grid and each charge controller must be on its own solar arrays.

 

[Tecnodave]

Not sure how this could happen. Unless both MPPT's are connected to the same solar panels.

That is exactly what I am talking about, a very common beginner mistake and assumption.

MANY...controllers measure current on the negative conductor

I have two Midnight Classic 150, two Midnight beta Kid , one Morningstar MPPT controller, and one Morningstar PWM controller all on the same network , sometimes charging the same bank, but always with a dedicated array connected to that controller

I do have different battery types, both FLA and LFP, thus controllers to charge all. I do have POCO power but I do not sell to power co.

 

[keepsake]

I had a grid tie inverter smoke last week. So I had to shift panels to a new path.
Long story short. Each mppt60 is fed from a totally isolated set of panels in strings not to exceed 120 volts.
I just need each mppt, on its own, to hunt the best voltage/current ratio, independent of the XW6848 that is selling to grid at the same time.
I might be at a happy point right now. Have XW GSV sell 0.3 of a volt below the mppt bulk goal voltages. Mid day both mppt's say Float while feeding energy for sell-to-grid purpose.

 

[Solar Guppy]

I just need each mppt, on its own, to hunt the best voltage/current ratio, independent of the XW6848 that is selling to grid at the same time.

Well that's the issue, there isn't an mppt unit in the world that can be be independent of the load.

If there is no place to send energy, the array can't be loaded ( full batteries , XW not configured to sell all excess energy to grid )

This is an issue of setting up the XW inverters grid sell values correctly, there are many threads on this forum to do that.

 

[keepsake]

All working fine now. Ticket was to keep second mppt60 on separate XanBus.

Does anyone know how to adjust XW to better and more rapidly track cloud-to-sun transistions ? Grid-tie inverters do this 10 times faster than the 6848 does. I see my battery currents surge to 50 amps as I go from cloud to sun and vice-versa. After a good 30 second all is in balance.