voltage to run mptt? (1 Viewer)

mick noe

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bought a shiny new mppt a victron75 15 but read in the instructions that it needs 5v above battery voltage to start charging, should I now rewire my two 100w panels in series to make this work correctly?
 
Aug 10, 2012
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That wasn't my understanding of mppt
See this https://en.m.wikipedia.org/wiki/Maximum_power_point_tracking

I 'think' the maximum power point tracking controller steps up the voltage as required
As you can't push voltage up hill i.e. 12 v won't go in to a 12.5 v batt.
So it inverts it to AC and steps it up , enabling it to put the current in at a 'synthetically ' higher voltage

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Derbyshire wanderer

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Mar 30, 2014
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It will work just fine with the panels in parallel. As the day starts it needs the extra 5v to start its cycle but as said above the single panel voltage will be a little over 20v at peak output.
Mine is wired this way and it works perfectly.
The extra voltage is converted into extra watts by transforming the available input in the most effect way it can.
BTW, it is best to remove the jumper plug and let it charge your battery bank with the algorithm that uses the clever voltage cut off to enable complete charging every few days. Not so useful in summer but in winter it will make a big difference to maximising you battery life and output.
 
Feb 9, 2008
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Peak output on a panel can be as high as 30v or more.
 
Sep 23, 2013
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bought a shiny new mppt a victron75 15 but read in the instructions that it needs 5v above battery voltage to start charging, should I now rewire my two 100w panels in series to make this work correctly?
It will work fine either way. There is a theoretical advantage to wiring the panels in series, because the panel output voltage is then doubled & so the controller will switch on slightly earlier in the morning & will keep producing a small amount of power on an overcast January day when parallel connected panels may never reach the 17 - 18v required to start the controller's charging process.

This advantage is cancelled out if you get partial shading of a panel. On a parallel circuit, you will lose most of the output of the shaded panel, but the one in full sun will continue unaffected. In series, the partial shading of one panel drastically reduces the output from the pair.

Which is best for you will depend on when & where you use the van & whether you have access to EHU while it is not being used.

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Last edited:
Aug 6, 2013
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It will work fine either way. There is a theoretical advantage to wiring the panels in series, because the panel output voltage is then doubled & so the controller will switch on slightly earlier in the morning & will keep producing a small amount of power on an overcast January day when parallel connected panels may never reach the 17 - 18v required to start the controller's charging process.

This advantage is cancelled out if you get partial shading of a panel. On a parallel circuit, you will lose most of the output of the shaded panel, but the one in full sun will continue unaffected. In series, the partial shading of one panel drastically reduces the output from the pair.

Which is best for you will depend on when & where you use the van & whether you have access to EHU while it is not being used.
Bypass diodes should prevent that although I agree there's not much if any advantage anyway in series connection.
 

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