question

nohertz avatar image
nohertz asked

SmartSolar MPPT 100 volt /20 amp VS 1,000 watts of solar panel

Gday,


Im thinking about buying a victron SmartSolar MPPT 100 volt /20 amp to use with four 235 watt

Trina Solar TSM-235PA05 Solar Panels


technical specifications

Peak Power 235W
PTC Rating 213.6
Power Output Tolerance 0/+3%
Maximum Power Voltage 29.3V
Maximum Power Current 8.03A
Open Circuit Voltage 37.2V
Short Circuit Current 8.55
Module Efficiency 14.4%
Values at Standard Test Conditions STC (air Mass aM1.5, irradiance 1000W/m²,
Cell Temperature 25°C). Power measurement tolerance: ±3%


This would be taking place in Sydney Australia where the temperature is above 5c when the sun strats shining


Would this work?

Is there a down side to this plan?


Thanks

MPPT Controllers
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3 Answers
wkirby avatar image
wkirby answered ·

You didn't mention your battery Voltage. As you probably know, this controller charges the battery at 20A. With a 12V battery this controller will charge at a maximum power of ~240W. With a 24V battery it will charge at ~480W

You can put 1KW of panels into the charge controller, but it will only take the maximum power from the panels like I said above. There is.nothing wrong with this and will help on cloudy days.

Just make sure not to exceed the 100V input Voltage limit. Arrange those panels in 2 series 2 parallel and she'll be right.

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marin avatar image
marin answered ·

"Would this work?"

I agree with the solution of WKirby, connecting 4 pannels would work most reliable in a 2x2 configuration, since the PV voltage is a strict limit which shouldn't be exceeded under any circumstance ( can damage the controller).

"Is there a down side to this plan?"

The downside is the controller can't utilize all the available PV power: e.g. it doesnt give you the option of using the ~1 KW of power during the day, without draining the battery.

Also after a long periods of low sun (when the battery gets drained), the sunny day won't be optimized to its full potential. So in case the battery can stand higher charging currents then 20A, a slightly larger model of MPPT might be worth looking at (e.g. 150/35; then 35 A of charging).


Basicly the question, if it is a downside, depends moslty on when you want to use the power.

If you plan to switch on extra consumers, on a sunny day, a bigger controller might be a good idea to optimally use the solar power.


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wkirby avatar image wkirby ♦♦ commented ·

It can actually be an advantage in low light because you have more PV panels but the overall PV power at that time is inside the controller's capacity.
You are only really "loosing out" in super good shiney sun.

However, I do always maintain that you should go with the largest capacity charge controller that you can afford. Then it can grow with you as you upgrade.

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nohertz avatar image
nohertz answered ·

Thanks guys,


I did use the Victron MPPT Calculator Excel sheet ( www.victronenergy.com/support-and-downloads/software#mppt-calculator-excel-sheet )


But I wanted to be sure there was not something I was missing.


I do like the sound of Victron gear, The 5 year warranty is a good start.

Ive read Energy Unlimited (Revision 9, June 2011) by Reinout Vader of Victron Energy

( www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf )



Im looking at the Victron SmartSolar MPPT 100 volt /20 amp as its the largest I can see with load control built it, I know there is a 48 volt model, But Im still thinking 12 or 24 battery voltage should be fine for me


So far the only thing I own is the four 235 watt Trina Solar TSM-235PA05 Solar Panels


So thats where Im starting



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wkirby avatar image wkirby ♦♦ commented ·

Good, what a place to start. Not far off from where I started.

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boekel avatar image boekel ♦ commented ·

What kind of system are you building?
small / big / mobile / offgrid / etc can make different advice.

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wkirby avatar image wkirby ♦♦ boekel ♦ commented ·

Some of us (myself) don't have a clue. We buy what we can, when we can and we build up experience along the way.
We don't have a project plan or a system spec. We just love the idea and want to get involved.

@Boekel no disrespect to you or your profession is meant :)

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boekel avatar image boekel ♦ wkirby ♦♦ commented ·

Haha yes I've started somewhere too, all second hand stuff...

reason for asking: 48 volt makes a lot of sense for a lot of applications, but not for all (mostly when charging from an engine mounted alternator is involved, or for very small systems)

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