Just thinking: Charge controloers

[Gordon]

Just thinking here. That's about all I can do right now.
About a future homebrew solar power system. And the
necessary charge controler.

What is the common wisdom on charge controlers?
Is the panal just disconnected from the battery
when full charge is reached?

Or can the panal be connected to a dump (diversion)
load.

If a diversion load is used, is the battery
disconnected at full charge? Or is the
diversion load connected across the battery/panal
combination.
If the diversion load has the same rating as the
panal, it should keep the battery from receiving
additional charge. The only problem I can see is
if the diversion load should drop out. That would
cause the battery to over charge.

 

[vaughn]

Just thinking here. That's about all I can do right now.
About a future homebrew solar power system. And the
necessary charge controler.

What is the common wisdom on charge controlers?
Is the panal just disconnected from the battery
when full charge is reached?

Or can the panal be connected to a dump (diversion)
load.

If a diversion load is used, is the battery
disconnected at full charge? Or is the
diversion load connected across the battery/panal
combination.

In a perfect world, the charge controller would be smart enough to allow the
panels to continue to supply just enough power to supply system loads while
preserving the full charge in the battery. Sometimes residual uses are
found for the heat from a dump load (such as water heating) but other than
that, nobody has yet explained to me the reasons for a dump load in a PV
system. The panel can hardly overspeed like an unloaded wind turbine. I
have never heard of a panel being damaged by its own open-circuit voltage,
but perhaps someone here will educate me.

My controller seems to put a partial load on my panels when full charge has
been achieved. I assume that the controller is just shorting out the panels
intermittently with a PWM arrangement, thus the panel's internal resistance
is serving as the dump load, but I don't (yet) know why they bother.

Vaughn

 

[Gordon]

In a perfect world, the charge controller would be smart enough to
allow the panels to continue to supply just enough power to supply
system loads while preserving the full charge in the battery.
Sometimes residual uses are found for the heat from a dump load (such
as water heating) but other than that, nobody has yet explained to me
the reasons for a dump load in a PV system. The panel can hardly
overspeed like an unloaded wind turbine. I have never heard of a
panel being damaged by its own open-circuit voltage, but perhaps
someone here will educate me.

My controller seems to put a partial load on my panels when full
charge has been achieved. I assume that the controller is just
shorting out the panels intermittently with a PWM arrangement, thus
the panel's internal resistance is serving as the dump load, but I
don't (yet) know why they bother.

Vaughn

I'm mystified by that too.
But what really gets me is the idea that there is power to be
harvested and it has no where to go. I suppose that's the
attraction of grid tie systems; you can dump as much power
as you have into the grid.

I suppose that on a stand alone system, I could just switch in
another battery.