XW6048 / MPPT80-600, Opportunity loads?

Rossman

Hi All,

After reviewing the documentation for both the XW and the charge controllers, I can't figure out if there is a way to run an "opportunity load" after the batteries finish Absorb and go into Float.  Right now after it goes to Float, any power generated goes nowhere (off-grid here).

Any suggestions?

Thanks,
mark

mike95490

"Waste Not" is a setting in Midnight Classic that activates an AUX relay.   I don't have an XW controller.

Vic

Rossman said:

Hi All,

After reviewing the documentation for both the XW and the charge controllers, I can't figure out if there is a way to run an "opportunity load" after the batteries finish Absorb and go into Float.  Right now after it goes to Float, any power generated goes nowhere (off-grid here).

Any suggestions?

Thanks,
mark

Hi Rossman,

YES,  more than five years ago,  I did mention to Schneider Tech folks,  that their simple-minded SCC (60 A/150 volt MPPT CC)  really needed more Aux functions,  beginning with the very simple Aux output  -- " CC has entered Float".

They seemed astonished that anyone would need such a "useless function".   They wanted to know if any other CCs had this needless level of functionality.  I noted the ones that I knew of,  and this tech person mentioned that this would be forwarded to the Product Manager for the product ...  have heard nothing in reply,  yet.

Have not looked at the Aux functions in the current version of the SCC,  but assume that Schneider is into making as many $$ as they can,  and programming,  documenting,  and Tech supporting very many functions is just too tedious for them,  and it would cost them a few additional Marks to add anything to this very,  very basic CC.

MidNite CCs have many useful Aux functions for using excess RE power.  Both the Classic,  and the KID CCs have two Aux outputs.  One of the Classic Auxes can be an Analog input,  as well as an output.  Believe that both of the KID CC's Auxes can be Analog or Digital.

There is a rumor that the MidNite Classic might support communications on the Xantrex Comm buss,  IIRC.

The XW SCC (their old name for this product),  is quite dated,  as well as being quite limited.  BUT,  for an integrated,  Grid Interactive system,  if could still,  possibly be the best choice.   Am unconvinced that it would be the best for off-grid users.

Just from my personal experience with a very buggy XW SCC.  YMMV,   Vic

Dave Angelini

A better way to use the XW  aux is to use Voltage set-points. Waiting for float can waste hours of energy in large systems.
You are lucky Mr. Rossman as there are things on the horizon for you. Buy a Fujitsu mini-split for your load!

Vic

Dave Angelini said:

A better way to use the XW  aux is to use Voltage set-points. Waiting for float can waste hours of energy in large systems.
You are lucky Mr. Rossman as there are things on the horizon for you. Buy a Fujitsu mini-split for your load!

First,  I was simply asking Schneider to implement the simplest of Aux functions that off-grid users might benefit from,  but even that seemed too difficult or complex for them.  Really,  off-grid is a small segment,  and am sure that this is of no interest to them.

YES,  waiting for Float will reduce the amount of opportunity load power harvested,  but it is a start,  and would be better than nothing.

Using "Voltage set-points"  seems quite ineffective to me,  as Absorb is a Constant Voltage stage.  Reaching Absorb,  and waiting some programmable amount of time would help,  but would bet that the XW CCs might not compensate the voltage set-point,  and so on.

As mike mentioned,  the MidNite Classic has a full suite of Aux1,   AND Aux2 functions,  including PWMing Aux outputs to allow control of the energy available to Resistive loads.

Classic Manual is here:
http://www.midnitesolar.com/pdfs/Classic_manual_REV_2056.pdf

On pages 37 through 45,  the Aux1 and Aux2 functions are described.

MidNite is not Schneider,  and visa versa,  but Schneider does not even try to support a range of customer needs,  they know what is correct for everyone,   IMO.

You like Schneider,  and some of the rest of us do not,  particularly.  If I needed to replace a Xantrex SW+ 5548 Inverter,  today,  for off-grid use,  I might choose Schneider XWs,  but  MidNite is working on a covey of Inverters,  and bet that they will be much less Grey in nature.

AND,  I do realize that Rossman owns the HV MPPT 600-80 CC,  so there are not that many choices in this segment of the market.

Just my opinions,   FWIW,   Vic

Dave Angelini

Well good for you Vic and we all know your story here so thanks for filling me in, again.
It must be 50 miles of CAVU here, go out and take a look, much, much better than electronics!

Rossman

Thanks for the feedback folks, I appreciate it.

It's too bad SE doesn't give better options for off-grid programming, to be sure.  Having a "Entering float" aux trigger, to start an opportunity load, and another trigger like "less than X watts incoming from array" (where X was configurable) to terminate the running of an opportunity load, would be some kind of ideal but I guess I live in Never-never land 

In my case I want the chargers to complete the absorb ahead of any opportunity loads so that I can be sure it will get to completion, it's no good to trigger off absorb voltage because then my opportunity load might not let the batteries get their full charge.

We do all our heating with propane - radiant heat and fireplaces - so I was thinking if I could preheat the radiant heat system water with an electric water heater as an opportunity load this would be awesome....maybe one day!

Dave Angelini

You are facing more of a problem of latitude. You have to insure you complete charge and the whole strategy of using voltage set-points really is about stretching out the absorb time to run loads early in the solar day. I will just tell you that entering float to run loads can cause problems if clouds and poor solar conditions persist. The whole system needs to be smarter and all I can tell you is hang on.
Of course the easy answer for you is more solar. It is the buffer that will allow more options. Heating water for radiant really is much better when the sun is directly heating the water up north.

Vic

Quote - "Thanks for the feedback folks, I appreciate it.

It's too bad SE doesn't give better options for off-grid programming, to be sure.  Having a "Entering float" aux trigger, to start an opportunity load, and another trigger like "less than X watts incoming from array" (where X was configurable) to terminate the running of an opportunity load, would be some kind of ideal but I guess I live in Never-never land 

In my case I want the chargers to complete the absorb ahead of any opportunity loads so that I can be sure it will get to completion, it's no good to trigger off absorb voltage because then my opportunity load might not let the batteries get their full charge.

We do all our heating with propane - radiant heat and fireplaces - so I was thinking if I could preheat the radiant heat system water with an electric water heater as an opportunity load this would be awesome....maybe one day! "

Right now,  the Quote function does not work on this computer ...   am sure that this is a problem for this computer not the Forum SW  ...

Hi Mark,

YES,  that would be very nice if/when SE implements this function.

On the venerable Outback MX-60s,  this "CC IS in Float" was a useful function,  and it was only active when the CC WAS in Float,  and when the CC could no longer maintain Vflt,  this Aux signal switched OFF,  to avoid discharging the batteries much at all.

The MidNite Classics also have this function,  as well as the ability to make the Aux output PWM,  for better control of the amount of power delivered to a Resistive load  -- these are called, "Waste Not",  as Mike mentioned.

In the Classics,  the "CC IS in Float" Aux output remains active until Vflt drops 0.30 V below Vflt,  when this Aux signal switches OFF.  So,  it is not a simple voltage detector,  and therefore,  it is temperature compensated for the actual Vflt required for the temperature of the battery  --  it is keyed to the Float function,  not just a voltage setting.

Being able to use excess power,  in the later stages of Absorb,  would allow more PV power to be harvested by Opportunity loads,  as the battery charge current tapers,  from diminishing Charge Acceptance.  Using simple voltage setpoints for this is less useful.   Although a set voltage,  plus a programmable delay time could help accomplish this function.

FWIW,    Vic

Rossman

On the venerable Outback MX-60s,  this "CC IS in Float" was a useful function,  and it was only active when the CC WAS in Float,  and when the CC could no longer maintain Vflt,  this Aux signal switched OFF,  to avoid discharging the batteries much at all.

That seems like the ideal!!  Oh well.  Maybe another alternative will present itself 

Dave Angelini

I had three customers that had MX-60's go off in sweep mode and not output power for a minute or so every hour with 3kw loads running. Not happy about that one still. 
  I also worked on the last beta for Outback on the MX and there just was not enough memory to fix this. It was great for it's time but the FM series from Outback replaced it for other good reasons also like overly complicated for average humans.
 If anyone needs one I have a pile of them in my shed that all need fans.

I also have a client up your way with radiant.  He logged his propane use and there was very little difference with pre-heat.
People in the southwest can do this but even there if you want to really do this right and save propane you need to heat the water with the sun.

Vic

The MXes Swept quite slowly,  AND,  the higher PV input voltage,  the longer the Sweep time.   One could probably Park  the input at a given point to alleviate the Sweep time,  but one would lose some of the CC's flexibility.

It is the FM CCs that apparently have NO memory left.  Like the Schneider  150-60 SCC,  the FM CCs are long-in-the-tooth.  For example,  it appears that the FM CCs have a FIXED battery temp comp value of --5mV/C.  Believe that the comp can be turned OFF and ON,  but for many battery types,  --3mV  is called for ...

The MXes are still great CCs,  with the proper fan inside,  or a simple 120 MM fan blowing into the Wiring Compartment.

A friend may well be interested in some of your bone-pile MXes,   Dave.

Vic

Rossman

Dave Angelini said:

I also have a client up your way with radiant.  He logged his propane use and there was very little difference with pre-heat.
People in the southwest can do this but even there if you want to really do this right and save propane you need to heat the water with the sun.

Thanks for the feedback Dave.  I've noticed our propane water heaters actually use very little propane so perhaps another load can be contrived.  We'll see how we are this summer maybe a mini split for cooling would be nice on the hot days 

Dave Angelini

They do make a heat pump water heater that 2 of my "buddies" use for radiant. The problem with it, (that I can tell) is that they are not like the mini-split in their use of energy.  They seem to just be on or off where the mini-split varies it's energy use as the programmed temp gets close to the actual room. For heating the split  can use your excess energy and the amount is controllable. Even though you do not need it it could take some of the load off the radiant/propane or give you a hot spot in winter. Their use in spring keeps the pollen out and is very acceptable to keeping the dusting down for the homemaker.

You might want to read the string I started on the splits over in the sticky section of energy.

The use of the AUX will get better on your controllers.  Think of it as not turning on a solenoid or relay but rather actually telling the load
to turn itself on/off or raising/lowering  the differential to keep the battery always charged. Or. maybe sending an e-mail/text that the aux has changed state.  I am doing this already for some clients but it will get mainstream in the XW and soon. Your controllers have had zero firmware updates since I first got the chance to beta test them. There was a very good chance then that the great recession would cause it to be cancelled. The most valuable tool in my tool box is that controller, well next to common sense.....