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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Solar panels
Date: Sun, 2 Jun 2024 20:56:18 -0700
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On 6/2/2024 7:07 PM, KevinJ93 wrote:
> I understand what you are wishing to do.
> 
> Just putting the load across the battery that is being fed from a MPPT charge 
> controller may be all that you need.

The problem will be ensuring the battery voltage remains where I would like it
regardless of where I am sourcing (and sinking) power.  I.e., would I rather
use power to top off the battery -- or, feed a bigger load.  And, would that
power want to come from the mains (which has a price associated) or the PV
array (which has no such charge).

> By monitoring the state of charge you can then make decisions about how to 
> control the load to make best use of the available energy.
> 
> The only thing that is unusual about your application is that the battery would 
> be sized to be smaller than normal.

And the grid is never back fed *from* the array.  I.e., this just looks
like a regular electrical device that happens to use less power from
the grid than it actually uses.

One would typically size an array and its backup to handle arbitrary loads
as determined by occupants.  In my case, a machine determines the loading
so can better tolerate the variation in power availability.