What is likely to happen with an undersize MPPT reg? (1 Viewer)

Jun 10, 2010
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Now Ive removed my chocolate teapot satelite dish, I have a big space to put another solar panel. What I'm considering doing is to pair a new 200w panel to one of my existing 185w panels to run through one of my 350w Votronic MPPT regs. I know that the house people regularly undersize inverters but unlike them I can find myself in Southern Europe. What I'm wondering is that IF I get perfect conditions and am generating 385 watts will the regulator blow a fuse or seriously damage itself in some way?
 
Dec 17, 2016
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The Votronic has a standard blade fuse (30A in your case?) on the front that protects the unit. It would be easy to replace if it blew. I think Raul has said that good quality units like Votronic it shouldn't be a problem? If it blows you could always put a blanket over one of them!
 
Apr 27, 2008
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I think you will have to get much nearer to the equator to get anything like full output from your panels. I wouldn't worry.
The sun won't be directly overhead except well down in Africa and midsummer midday.
 

funflair

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Dec 11, 2013
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Hi Jon

I think the Victron kit just ignores what it can't convert, up to a point of course but the numbers you are talking about would be OK, likewise my guess is that you will get away with it on your Votronic.

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Dec 2, 2019
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Now Ive removed my chocolate teapot satelite dish, I have a big space to put another solar panel. What I'm considering doing is to pair a new 200w panel to one of my existing 185w panels to run through one of my 350w Votronic MPPT regs. I know that the house people regularly undersize inverters but unlike them I can find myself in Southern Europe. What I'm wondering is that IF I get perfect conditions and am generating 385 watts will the regulator blow a fuse or seriously damage itself in some way?
There are two things to consider: voc limit of your controller, and max DC amps in. If you wire them in series, the voc of the panels added up, should not exceed controller limit. If you wire them in parallel, the DC amps from your panels added up, should not exceed controller max amps in. Both this limits will be documented in the controller manual.
If one of this limits are exceeded, risk of burning the controller is very high.
 

makems

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I remember when "The fat man" (old Morocco hands will know who I mean) fitted panels for me he reckoned that even in Morocco in Summer you would be unlikely to see much more than 2/3 of their rated output.
 
Dec 2, 2019
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Votronic do not recomended connecting more solar than the unit is rated at, Victron say its OK.
I remember somewhere mentioned that votronic gives a max dc voltage something like 45-50v max. Very little flexibility, forcing you into 36cell panels only. If the rating is given in Watts only, that’s not sufficient data info. The power can be made up of various combinations of amps x volts. A controller has a absolute limit on those two limits mentioned above. If rating is given in Watts only, is assumed you are using 36cel panels. The world moved on, so 36cell is not the only choice. Hence victron provides a higher voc limit, comprehensive data for voc and amps-in limit, so you can over-panel and still stay within controller capability to modulate the power. You wire the panels wrong and trips you over the limit, rest assured you can burn the victron to. They are sensitive to voc, 1-2 volts over goes into alarm and does not charge. Any higher will see smoke.
 

Steve and Denise

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Sep 26, 2011
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Early this year we up graded our solar panels from 2x175 in parallel to 3x 175 in series through a 100/30 Victron and up to now all has been ok.
I know we are over panelled but in the summer we don’t need all the power from the solar and can’t use it in our van.
The Victron regulator just limits the output to 30amps no problem.
although makes a fair difference out of the summer season that is not ever so long in the UK

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Hoovie

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May 16, 2021
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I think you will have to get much nearer to the equator to get anything like full output from your panels. I wouldn't worry.
The sun won't be directly overhead except well down in Africa and midsummer midday.
You can get >100% of the rated power of a Solar Panel when you are in the UK in the summer actually.
The rating is based on a specific solar irradiation value of 1000mW/M2 and that can be achieved anywhere on occasion. I've hit over 100% in Scotland in the summer (this time of year be lucky to get to 10% mind).
It may not be an everyday thing by any means, but contrary to apparent popular opinion, yes it is very possible.


It is important generally to avoid exceeding the Input Current and Input Voltage as Raul says. Some controllers whilst having that limitation are happy to have panels exceed the rated power and they will just cap the output at the rated power level. For example, the Victron 100/20 MPPT .... upto 100V and upto 20A input current. That doesn't mean it will output 2000W though - it is limited to a 20A Output, which equates to 290W on a 12V system, 580W on a 24V system or 1160W on a 48V system. But it CAN handle upto 2000W input if you very weirdly decided to do that.

You do get the odd controller that can handle overvoltage by cutting out but most (including the Victron) will be damaged.
 

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