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Old 12-10-2015, 09:18   #1
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MPPT Controller operation

I have a question, can an MPPT controller increase voltage ? So for example , if one had a 12v panel but a 24v battery, would the MPPT controller take the panels 12v output and increase it so as to charge the battery at 24v ?

I know it works the other way around, i.e. if the panel were putting out at 18v, and there was a 12 v battery, then the MPPT controller would reduce this output voltage to meet battery voltage (12v ) .

If it is the case that the MPPT controller does increase 12v output to meet the demands of a 24v battery, what is the downside, presumably a reduction in Amps being put into the battery ?

This question arises because I have a 24v battery bank, and I am trying to decide whether to ;

a. get 12v panels and keep them at 12v, utilising an MPPT controller to increase the output to 24v, or,

b. to wire two 12v panels in series to get 24v....or,

c. to buy a 24v panel at the outset

I have space on the boat for two good sized panels (I mean dimensionally good -size Length x width )

d. then to confuse the whole issue I read on this forum a lot of people have each panel connected to its own standalone controller so that should one panel be shaded the other can keep functioning.

e. Maybe two 12v panels connected in Series/ that a good idea ? what are the pros and cons ?

Many thanks
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Old 13-10-2015, 12:41   #2
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Location: Boat: West coast of Norway Winter: Höllviken, Skåne, Sweden
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Re: MPPT Controller operation

The easiest way is to have two 12 V panels that are connected in series to 24 V. Do there not exists 24 V solar panel controllers? If there do, use that. The controller will not know that you have two 12 V panels. If you have separate controllers to each panel you can maybe get 5% more power.

A MPPT is only one part of a regulator that determines at what voltage will the solar panel give the highest power. Then there is an other part that transforms the incoming voltage to the level that the batteries want. That part is in a solar regulator made for taking down the voltage, but technically you can also rise the voltage. I feed my laptop with a unit that take 12 V up to the 18 V my laptop want. If the MPPT part finds the max power point of the panel it will get out 10% more power than without the controller, but you lose 5% in the transformer. If you rise the voltage you will lose 10% and then you have no use of the MPPT.
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