Load sharing among Multiple XW-60MMPT-150 controllers.

[deacon]

Just upgraded my system from 800 watts to 5.3K.
I have had plenty of time to Monitor MY XW-SCP watching the (3) XW-60-150's at work. It's been too hot to go outside much.
I can't figure how the controllers decide who provides what current at any given time.
Some times #1 is almost at 200 watts, while #2 is showing 500 and #3 is showing 1100. They always work together providing the right Wattage that I am using plus floating the batteries after they are charged.
One thing that seems constant is that #3 always seems to be the hardest working, then #2, followed by SCC #1
One really odd thing I noticed is that SCC #2 is always showing less input wattage then output wattage, unlike the other 2 SCCs.
I checked the arrays at the combiner the voltages were the same for all the arrays.

Xantrex experts, anyone know the theory of operation as far as load sharing on multiple SCC's?
The new system is working so well that I ordered another portable 14,000 BTU heat pump.
I have a small 2 bedroom ranch home with a huge living room (1000 SQ FT). The single 14,000 unit I having running off the solar keeps the living room @ 74*- 75* when it is in the 90*'s outside.
These units only use ~1250 watts, So I am adding another one and will be able to use them in the winter for heaters. They are considered 1 ton heat pumps based on their output.
Rich

[RCinFLA]

It is every man for itself. Each PV controller will push as much as its PV input is providing.

When battery reaches absorb voltage regulation there may be some variance due to small calibration variations between controller. Same goes with float voltage. This assumes all controller have the same settings.

I assume each controller has it own set of PV panels. You don't want same set of panels connected to two different controllers as the MPPT search of the two unit will disrupt each other.

If you are getting less from one controller it is because of its PV panels. One reason for multiple controllers, besides amperage limits on CC, is to collect from panels facing different directions.

[deacon]

Thanks.
I have 2 strings of (4) 190 watt panels going to combiner boxes for each controller.
So each controller gets a manufacturer panel rating of 1520 watts before derating.

My batteries spend most of the day in float mode, because the most I have taken them down is 20% discharge. Toward the end of the day I do a force bulk from the SCCs to top them off.

I might just try facing a string S-SE and one S-SW just to see if I pick up anything, good idea.
Rich
Before March of this year, I never so much as wired an electrical outlet, so this has been an adventure.
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