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brianjonesphoto avatar image
brianjonesphoto asked

Smartsolar 100/50 load output no battery

I’m trying to put together an unconventional setup. I have a unique use case, a 24v portable battery and DC hot water diversion but since the battery is portable it’s not always connected to the Smartsolar 100/50. I think I have it mostly figured out, but I need some experienced Victron guidance.

I want this to work like this. Use the virtual load output set to turn on at .05v before the absorption voltage and stay on until just under float. The output would trigger a SSR that gets power from the panel before the SCC inputs.

I think this will create a diversion load situation that will be independent of having a battery connected to the SCC since it would take power straight from the panels. I plan to leave some head room in my diversion sizing for absorption charging. I did a test today once the battery got to float I could disconnect it and the load stayed triggered and the controller sat at 27v. I need to test tomorrow if I can find a voltage where the load turn on while the SCC is in bulk without a battery connected.

Just to be clear I an NOT trying to power the diversion load from the SCC output. The diversion would be powered in parallel to the SCC in controlled by a custom load algorithm on at 27.95v off at 26.9v. (28v and 27v bulk and absorption cut offs)

Has anyone ever tried used the output function while without a battery on the SCC?

Thanks. Brian.

MPPT Controllersvirtual switchHot Water Diversion
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5 Answers
mvas avatar image
mvas answered ·

I believe, Float mode is "working" without a battery because the Output Capacitor inside the MPPT is holding the voltage "steady". Like a miniature battery.

In the morning, with no battery connected, will the MPPT wake-up at sunrise?

Will the MPPT then enter Bulk mode, without a battery? If it does enter Bulk Mode, it should get to Absorb mode very quickly.

Absorb mode and Float are both constant voltage, so they have a better chance of operating without a battery.

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nickdb avatar image
nickdb answered ·

The load terminal is fed from the battery as I understand it, not convinced that can work without one.

There is a note in the docs about using an mppt as a power supply, it isn’t recommended but can be done.

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mvas avatar image mvas commented ·
He is not really using the MPPT as a "power supply" because his load is connected to the Solar Panel, not connected to the MPPT output.
He just needs the MPPT output voltage to remain "stable" when no battery is connected.
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nickdb avatar image nickdb ♦♦ mvas commented ·
On the basis that even optimisers aren’t supported panel-side, I can’t see a scenario where a load on the input side does not cause a conflict and instability in the mppt. Would make tracking exciting.
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mvas avatar image mvas nickdb ♦♦ commented ·

He is not using an optimizer or anything similar. When there is no-load, or is minimum load, on the output of the Solar Charge Controller, it is not using any Max Power Point Tracking logic.

When the SCC is in bulk mode and strictly enforcing MPPT logic, he does not apply any load to Solar Panel.

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klim8skeptic avatar image
klim8skeptic answered ·

@brianjonesphoto I would suggest you use a MPPT that has a programmable relay. Much more flexible options.

Set to switch relay upon float, adjust float voltage, re-bulk offset and minimum relay closed time to suit.

mppt-relay.png

Some one reported poor SSR switching via the VE Direct port a while back.


mppt-relay.png (43.4 KiB)
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mvas avatar image
mvas answered ·

If the voltage is not "stable" when the battery is removed then try adding a resistor, to allow a small amount of current to flow. Many Switch Mode Power Supplies ( ie the buck inverter inside the MPPT ) may require a minimum load for stable voltage.

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mvas avatar image
mvas answered ·

You stated, when / how you "enabled" your load. But you did not state, when / how you disable your load.

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