MPPT Solar Regulator - Duo?

multihullsailor6

multihullsailor6

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Due to space restrictions on my cat "Burnout" I have now fitted 2 x 2 flexible solar panels of different sizes port and starboard, i.e 1 x 68Wp and 1 x 34 Wp port and starboard. I have today been informed by a fellow sailor that I cannot wire them in parallel as I had planned as they are of different sizes and thus different electricity. I would thus need four solar panel regulators or two with twin inputs.

I have looked at two catalogues but have not come across a MPPT solar panel regulator with twin input - do they exist?
 
multihullsailor6 said:
Due to space restrictions on my cat "Burnout" I have now fitted 2 x 2 flexible solar panels of different sizes port and starboard, i.e 1 x 68Wp and 1 x 34 Wp port and starboard. I have today been informed by a fellow sailor that I cannot wire them in parallel as I had planned as they are of different sizes and thus different electricity. I would thus need four solar panel regulators or two with twin inputs.

I have looked at two catalogues but have not come across a MPPT solar panel regulator with twin input - do they exist?
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I do believe as long as the panels are the same voltage, you can run them in paralel, but check it out. Mind you, somebody will be along shortly with a deffinitive answer.
 
No experience with MPPT but I have had various panels wired in parallel - 38 watt semi flexible with a 32 watt flexible, currently an 85 and a 40 watt rigid. No problems whatsoever and in each case clearly delivering the required current.
 
MPPT cotroller

i have an MPPT controller and two solar panels different sizes ( combined rating 130 watt ) but same open circuit voltage . I wired them up in series to get about 2 amps max at a combined voltage of 36 volts . I understand that the beauty of the MPPT controller is that it works better at a higher input voltage up to a prescribed rating limit and that in series the current into the controller is low thus allowing the controller to make best use of the energy provided to convert it into 12 or 24 volt output instead of wasting some of it in heat as would an ordinary unit

Plenty capacity for later addition of more panels
 
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Me too. I have a mppt controller and 1 x 68 w panel and 2 x 34 w panels wired in parallel. No problems. Bright sunny days generates about 10A max in my experience.

Rob
 
I have just fitted a couple of 250W domestic panels (50v) in series and a Morning Star MPPT controller. Fantastic, seeing anywhere up to 35A on not the brightest days and (because of the high voltage) they start generating early, I was seeing 9A at 8:30 this morning :-)

Definitely the way to go!
 
SeamanStaines said:
I have just fitted a couple of 250W domestic panels (50v) in series and a Morning Star MPPT controller. Fantastic, seeing anywhere up to 35A on not the brightest days and (because of the high voltage) they start generating early, I was seeing 9A at 8:30 this morning :-)

Definitely the way to go!
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Not doubting your readings so may be a typo error. 250w x 2 in series is still 250w. I use a MPPT controller but it's not good to get out 35 amp!

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I think its correct

The panels are 250W each at a nominal 48v, coupled in series that gives a maximum voltage of 96v and (I am seeing at the moment 68v out of them). 500/96 = 5.2amp from the panels. The MPPT controller then converts that to 12v (well in fact around 13v depending on the battery state so, assuming 100% efficient (I know its only about 97%) that is 500/13 = 38amp at max output for charging. In fact, to get the 35amp I showed briefly I switched on the inverter with a 2kw load which dropped the battery voltage to around 12v which then equates to 500/12 to 41amps at max output so 35A is pretty good.

At present I am showing batteries at 12.8v with a solar panel voltage of 68v and an output current of 24A

Delighted :-)

Oh, just another thought, in much correspondance with the suppliers on these they always said that with an MMPT controller you need to wire in series (hence why I think that is how the ones at the start of this thread should be wired) since that gives you a higher input voltage into the MPPT which means less losses in the cable from the panels and greater efficiency on the controller (up to the maximum input voltage of the controller). You need to remember though that voltages over 50v 'hurt' if you ground them through you!
 
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SeamanStaines said:
I think its correct

The panels are 250W each at a nominal 48v, coupled in series that gives a maximum voltage of 96v and (I am seeing at the moment 68v out of them). 500/96 = 5.2amp from the panels. The MPPT controller then converts that to 12v (well in fact around 13v depending on the battery state so, assuming 100% efficient (I know its only about 97%) that is 500/13 = 38amp at max output for charging. In fact, to get the 35amp I showed briefly I switched on the inverter with a 2kw load which dropped the battery voltage to around 12v which then equates to 500/12 to 41amps at max output so 35A is pretty good.

At present I am showing batteries at 12.8v with a solar panel voltage of 68v and an output current of 24A

Delighted :-)

Oh, just another thought, in much correspondance with the suppliers on these they always said that with an MMPT controller you need to wire in series (hence why I think that is how the ones at the start of this thread should be wired) since that gives you a higher input voltage into the MPPT which means less losses in the cable from the panels and greater efficiency on the controller (up to the maximum input voltage of the controller). You need to remember though that voltages over 50v 'hurt' if you ground them through you!
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Surely to get 500w they must be in parallel, or have I got my Ohms Law wrong?

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Imagine two 12V Batteries. If each was producing 100A then if they where wired in parallel it would be 12V x (100A +100A) = 2400W or (12v x 100A) + (12v x 100A) + (12v x 100A) = 2400W

In this case we are series on the panels to give the 96v (or the 68v I see) its 500W at 96v. If we had done that in parallel it would have been 500W at 48V.
 
SeamanStaines said:
Imagine two 12V Batteries. If each was producing 100A then if they where wired in parallel it would be 12V x (100A +100A) = 2400W or (12v x 100A) + (12v x 100A) + (12v x 100A) = 2400W

In this case we are series on the panels to give the 96v (or the 68v I see) its 500W at 96v. If we had done that in parallel it would have been 500W at 48V.
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2 x 12v/100ah in series = 24v@100ah . . . 2 x 12v/100ah in parallel = 12v@200ah
Hence panels x 2 48v/250w in series = 96v@250w . . . . That's how I see it.

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Watts = Amps x Volts

Assume each solar panel produces 20 volts at 12.5 amps to give 20 x 12.5 = 250 watts


With two panels in series we have 40 volts at 12.5 amps to give 40 x 12.5 = 500 watts

With two panels in parrallel we have 20 volts at 25 amps to give 20 x 25 = 500 watts.

Either connection produces the same total power.

Think of it this way, if one solar panel is connected to a suitable heater it gets hot and we get warmer
With two solar panels each connected to a similar heater they both get hot and we get even warmer.


Connecting two solar panels in series means that a shadow on one of them will reduce the current available from the pair.

Connecting them in parallel with the shadow on one, the unshadowed one still produces its original power, the shadowed one produces less power.

So parallel connection is better for reducing the effect of shadowing.
But, MPPT controllers seem to prefer the higher voltage produced fron serial connection.

You didn't think that you could win did you !!
 
Ohms Law was never my strong point! :-) I have my two panels mounted on the bimini so one of them does get shaded from the boom for a part of the day, I still seem to be seeing around 65v most of the time though.

All I will say is that I am really excited about the setup I have just installed (I only switched it on for the first time yesterday). We are in Gibraltar and it is fairly sunny, according to the meter on the controller the panels produced 158 AH into the batteries today which more than covers my daily usage.

I used 2 x Sharp domestic panels which at 250W where around £200 each and a Morning Star controller at about £360. I had the advantage of being in Gibraltar so did not have to pay the VAT, only shipping.

Sorry to go on, just really pleased with myself :-)
 
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