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run inverter off panel without battery?

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Robert Morein

Jan 1, 1970
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Is it possible to run an inverter off a panel without a battery? The purpose
would be to greatly extend the permissible length between the panels and the
battery bank, by using a battery charger at the other end.

I'm concerned about the possibility of inductive kickback from the inverter,
when turning of/on, that would normally be absorbed by the capacitance of
the battery.

It seems to me that spikes of both polarities must be considered, so it's
not simply a question of the reverse breakdown voltage of the panel.

It's not enough to know that while running, an inverter produces no
kickback. The possibility of accidental disconnection or turnoff is always
there.

One could put a car stereo capacitor across the panels, and it might help
starting the inverter, but I'd like to know if this is of any real concern.
 
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Robert Morein

Jan 1, 1970
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Thanks.
I had forgotten that the 12V nominal panel voltage does not represent the
actual swing that occurs.
The inverter may refuse to start, simply because the open circuit voltage of
the panel is much higher.
 
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steve

Jan 1, 1970
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My expectation is that at best the transient load regulation performance
of the inverter would be degraded without a nice low impedance at the
inverter D.C. power input.

At worst the inverter could possibly become unstable, even if it started.

The other concerns regarding momentary drop of panel voltage or
excessive panel output voltage making inverter startup impossible also
seem valid to me.

This is not a scheme I would attempt if I had expensive equipment
running at the output of the inverter!

With CAREFUL investigation regarding the inverter specifications (input
DC source characteristic requirements, OV / UV limits, etc) it could
accomplish what you are looking for, but it sounds like a bit of a
science project to me :)

Steve
 
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Robert Morein

Jan 1, 1970
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steve said:
My expectation is that at best the transient load regulation performance
of the inverter would be degraded without a nice low impedance at the
inverter D.C. power input.

At worst the inverter could possibly become unstable, even if it started.

The other concerns regarding momentary drop of panel voltage or
excessive panel output voltage making inverter startup impossible also
seem valid to me.

This is not a scheme I would attempt if I had expensive equipment
running at the output of the inverter!
All of your objections are valid.
The only thing at the other end would be a two-stage battery charger, such
as a Samlex, that can simultaneously charge a battery and run an inverter.
 
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Steve Spence

Jan 1, 1970
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1. PV output voltage tracks battery voltage. No "regulator" needed. Charge
controller needed if panel can exceed battery charge rate. small panels
usually don't. I don't use a charge controller with my 115ah battery and 15
watt panel on the camper.

2. The battery is the buffer between the inverter and the pv panel. You can
pull more watts from the battery than the pv panel supplies. That's the
point of the battery.



--
Steve Spence
Renewable energy and sustainable living
http://www.green-trust.org
Discuss vegetable oil and biodiesel
powered diesels at
http://www.veggievan.org/discuss/
 
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Steve Spence

Jan 1, 1970
0
I did not see where he was foregoing a battery. I apologize if I missed it.
Not a good move if I may say so. Put a battery in there. Even on my son's
solar cars, we put a small NiCad or cap to level out momentary shading.

--
Steve Spence
Renewable energy and sustainable living
http://www.green-trust.org
Discuss vegetable oil and biodiesel
powered diesels at
http://www.veggievan.org/discuss/
 
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Robert Morein

Jan 1, 1970
0
Thank you Steve, John, Steven Spence.

It appears that the best answer is an MPPT charger, and the best of them is
the Outback MX-60.
With this charger, I can run the three panels in series at 36V, reducing
both transmission losses and power point mismatch.
 
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boB

Jan 1, 1970
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I disagree. Robert is considering running an inverter directly off the PV
panel without a battery, so there is nothing to load the solar panel down
to decrease its voltage. An inverter directly connected to a solar panel
will not start because the solar panel voltage is above the inverter's 15
volt maximum input rating. Of course if you were using a battery it would
all run smoothly.

John

You should use at least a small battery connected to the inverter
battery terminals, for one, to act as a filter (ripple voltage) and
also to start the controller, since most controllers will not start up
with PV input alone.

That might work OK.

boB
 
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Robert Morein

Jan 1, 1970
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N. Thornton said:
"Robert Morein" <[email protected]> wrote in message inverter.


Every conversion process loses you power: the invertor, and the
charger. Why not run the panels in series and eliminate those power
losses? Just how far do you want to transport your power?

Regards, NT

I bought a 12V inverter, because of the flexible options with respect to
hooking up to cars.

But your point is correct, and I have solved it in the following manner: The
charge controller will be an Outback MX-60, which auto-senses the panel
voltage. I can string two or three panels in series, and keep the battery
bank voltage at nominal 12V.
 
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