question

jman avatar image

What happens if you add more solar wattage than the max Nominal PV Power?

Hello,


My victron mppt 100/50 in 12V mode says Nominal max is 700W, but down the bottom it says "If more PV power is connected, the controller will limit input power. "

What happens If I hook up 900Watts of solar to controller? & This is the full 900watts noon summertime.


Does it simple take in 700W & the rest is wasted/left? Will doing this damage the controller?


thanks

MPPT - Solar Charge Controllersolar sizing
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2 Answers
Paul B avatar image
Paul B answered ·

NO issue/problem at all with putting 900 watts on a 700 watt reg victron blue ort smart solar MPPT unit

The unit will only accept the 700 watts and the rest is left

WARNING do not exceed the max PV voltage of the regulator so as long as you stay well under (at least 10% just for a margin thats all)

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Hi Paul, they recommend not going over the short circuit current rating which is 60A for my victron, by the looks when you increase solar wattage you inevitable increase short circuit current. For example with my 3x 300watt portable fold panels each have 22A short circuit rating, so does that mean the whole lot is 66A when wired parallel into controller? and thus over the limit?


Stefanie avatar image
Stefanie answered ·

I've had a similar question a couple of weeks ago and got told that as long you don't go beyond the max. PV voltage of your MPPT 100/50, which is 100V, you don't do any harm to them. The MPPT limits the output to its maximum current of like 50A (or what you have set via VictronConnect).

But I wonder why you want to hook up 900W to a 700W MPPT?. That sounds a bit odd because it's quite a waste of power. If it were for a tiny bit more of wattage, I wouldn't ask.

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Hi Stef. Where it is useful is outside the optimal couple of hours in the middle of the day when panel spec sheets *might* get close. And there's actually many reasons for doing it - short cloudy winter days, shade, clouds, suboptimal panel angles, and it goes on. Extending the length of hours for charging Pb's is a biggie too.

It's not really a 'waste' of power if you're offgrid, more a saving of genny fuel, and getting what power you need over a longer day to largely look after your batts.

Like Sean sez, many experienced offgridders will design it in. 'Clipping' of pv output comes with the territory when you're charging batts, and is actually your target to reach..

There's deeper technical reasons for not going too far though, but I won't go there just now.


Hi John, I didn't look at it from this point of view. Makes totally sense. Thanks :-)

especially nowadays with panels being very cheap and the MPPT's therefor -relatively- expensive, if you have space for more panels, it's more economical to buy some extra panels.

That's fairly common practice as it'll maximise low sun production.

Hi stefanie, 900watts in winter only equates to about 700ish watts from my tests, in summer its close to 900watts, so taking out a whole panel would leave me too short.