On Fri, 9 Mar 2018 14:25:59 -0500, "Jim Wilkins"
wrote:

"Larry Jaques" wrote in message
.. .
On Fri, 9 Mar 2018 08:19:07 -0500, "Jim Wilkins"
wrote:
Indeed. You don't want dueling PSes on your hands.

The intent is for them to cooperate, with the higher of the two
outputs, PS or solar, charging the battery. The series diode keeps
higher voltage from backfeeding into the 13.8V PS and solar
controllers are built to accept battery voltage on their output when
their input fails.

How does this differ from the diodes attached to most solar panels
nowadays? You chose the exact schottky voltage you wanted?

https://www.allaboutcircuits.com/tex...hing-circuits/

Figure (d) shows a diode switch that passes the higher of battery or
power supply voltage to the load while isolating them from each other.
The diode in series with the lower voltage source is reverse biased.

I have the battery directly connected to the load and use diodes to
select the higher of power supply or solar controller voltage. The
power supply provides 13.5V through its diode, the solar controller
limits itself at 13.9V if there's enough sun. The solar controller's
series diode is internal, to keep battery voltage out of the panels
and wiring. That diode shorted in my HF controller.

On a partly cloudy day like today the solar controller supplies
whatever current the panels can produce and the power supply provides
the rest of the load's demand. I can watch the power supply's input
wattage rise and fall on a Kill-A-Watt as the sun dims and brightens.
Sometimes the KAW Watt display goes to 0.0 and the system is purely
solar powered, although the power supply is still connected and turned
on.

When neither the solar panels nor the grid can provide power it
reverts to the battery, all automatically.

Good explanation, and I grok it now. Thank you.

--
Silence is more musical than any song.
-- Christina Rossetti