Power or Power not? That is the question!

[n4zi]

Solar Friends,

   Being the curious sort that I am, I know a lot of solar installations are off grid. In this
case they use what energy they need and once their batteries are topped off there is no where
for the energy to go and the Classics start resting. Is this hard on the charger controllers?
Currently I am able to pull all the energy that comes off my panels and either use it or push it
to the grid.
Which is harder on the solar panels?
Which is harder on the Charger controllers?
I know it's probably harder on my inverter, but it seems to run at nameplate with ease!
It is definitely easier on the batteries to grid tie as I seem to only drop about 7 ah
between charging sessions!

Your thoughts are appreciated!

Thanks and 73,

  N4ZI

[TomW]

N4;

I am pretty sure that resting will NOT harm the Classic controller, I believe it just disconnects the PV and that should  not harm the PV or the controller.

Maybe one of the Midnite guys will chime in.

Tom

KD0YTD

[vtmaps]

Which is harder on the solar panels?

The solar panels like to be loaded... they run cooler when they are loaded.  Thus when your classic is resting, it is harder on the panels.   btw, the toughest thing for your panels (other than lightning and meteors) is partial shade (like a leaf or bird dropping).  Partial shade causes the bypass diodes to be stressed.

As for your other questions.... don't know the answer, but if you have an infrared thermometer you can find the answer yourself.... whatever makes the controller run cooler is better for the controller.

--vtMaps

[boB]

Actually, I DID hear of a particular PV module type that did NOT like to be left open circuited for a long period of time.

Can't remember which one though...

The Classic doesn't care one way or the other.

boB

[vtmaps]

Actually, I DID hear of a particular PV module type that did NOT like to be left open circuited for a long period of time.

Can't remember which one though...

You're thinking of Cadmium Telluride ( CdTe ).

--vtMaps

[boB]

Actually, I DID hear of a particular PV module type that did NOT like to be left open circuited for a long period of time.

Can't remember which one though...

You're thinking of Cadmium Telluride ( CdTe ).

--vtMaps

Ahhhhh yes.

Thanks !

[laszlo]

Solar Friends,

   Being the curious sort that I am, I know a lot of solar installations are off grid. In this
case they use what energy they need and once their batteries are topped off there is no where
for the energy to go and the Classics start resting. Is this hard on the charger controllers?
Currently I am able to pull all the energy that comes off my panels and either use it or push it
to the grid.
Which is harder on the solar panels?
Which is harder on the Charger controllers?
I know it's probably harder on my inverter, but it seems to run at nameplate with ease!
It is definitely easier on the batteries to grid tie as I seem to only drop about 7 ah
between charging sessions!

Your thoughts are appreciated!

Thanks and 73,

  N4ZI

When the charger needs to limits array power, it does not disconnect from the array, but  raises the array voltage to a point on the I/V curve that meets the load. There is no stress on the charger from this. The I/V curve is the fancy graph that should come with your your panels that shows how many amps the panel can produce at certain voltage at a given temperature.

[kitestrings]

I know a lot of solar installations are off grid. In this
case they use what energy they need and once their batteries are topped off there is no where
for the energy to go

This is where the Classic's options for load diversion work very well.  It takes a bit more consideration of matching the power available to an appropriate load, but the "harvest" of energy can be considerably better if you divert excess to a "opportunity" load.  We pre-heat water, but there are other load diversion schemes here.  It works very well, it's useful, and it costs less than more batteries.

If you're grid-tied this pretty much goes away - the grid will always take all the power your panels can produce - but for off grid the folks at MS loaded this thing with some very useful tools.

~ks