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larryjc

Solar panel wiring for MPPT and PWM

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Once again I are confused.  My new boat has a STECA PWM solar panel controller (2x 250 w panels).  Having used MPPT in the past I have seen how much more you can get out of the panels, I've bought a 40A Tracer from those nice peeps at Bimble.  They originally said that the panels should be wired in series for this controller and the STECA would be in parallel.  I spoke to another supplier and he disagreed with that so I went to the fount of all knowledge (google) and got even more confused.  Not one article I found said WHY you would want either connections system other than to say that in series you get higher voltage and the same current and that in parallel you get same voltage but higher current off the panels - er yes I understand that.  I don't care what volts /amps the panels are producing I want the max going into my batteries  out of the controller.  I queried this with Bimble and they said ' you can keep parallel' and then referred me to their web site link that shows MPPT controllers with panels all wired in series!

So is it that MPPTs are more efficient when working with higher input voltages?  Am I going to lose loads of lovely amps if I don't rewire the panels?  Frankly I would rather not do so as it will mean quite a lot of work sorting the wiring out as its all well conduited into the boat.

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Higher voltage series connections allow smaller cable to be used,but the panels can suffer from shading issues.

 

I would leave them as they are and wait for the solar season to start, see how you get on.

 

The limiting factor is often the panel voltage and controller max input values which may also determine the configuration.

Edited by rusty69

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Apparently the controller is up to 150v and I think the panels are 30v so should easily take the higher voltage if in series.  But if I had one 500w panel this would no be an issue so I'll just pretend thats what it is!!!!

 

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It's not going to make a massive difference either way, but I would be inclined to connect in series. There can be shading issues with panels in series but it depends on whether bypass diodes are fitted to each section of the panel, just to the entire panel, etc. I'm not familiar with those panels to have an opinion.

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The main advantages of series wiring is

1. Smaller cables as previously mentioned. 

2. A wider voltage swing for the controller to operate over. 

As you already have them wired in parallel and (presumably) already have thick cables then you might as well leave them like that. As Nick says, the difference in performance is unlikely to be anything other than negligible. 

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always wire in series, up to the maximum allowable voltage for the MPPT input.

I believe that on a cloudy day, if (nominal 20V) panels are wired in parallel the panel output voltage may not reach the minimum voltage demanded by the MPPT controller, so there will be no output.

Edited by Murflynn

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4 minutes ago, Murflynn said:

always wire in series, up to the maximum allowable voltage for the MPPT input.

Unless you have already done it in parallel.:D

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1 hour ago, rusty69 said:

Unless you have already done it in parallel.:D

I stick two wires in the top of the black control box thingy majig and two out the other end which go to the battery doobries via a thing called a fuse or somett. This puts ampy things into my batteries and Mr who looked at mi boat passed it for the BSS thingy so I am happy wiv that. :D

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7 minutes ago, mrsmelly said:

I stick two wires in the top of the black control box thingy majig and two out the other end which go to the battery doobries via a thing called a fuse or somett. This puts ampy things into my batteries and Mr who looked at mi boat passed it for the BSS thingy so I am happy wiv that. :D

Is that your version of what they call TechnoBabble?:D

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6 hours ago, larryjc said:

So is it that MPPTs are more efficient when working with higher input voltages?  Am I going to lose loads of lovely amps if I don't rewire the panels?  Frankly I would rather not do so as it will mean quite a lot of work sorting the wiring out as its all well conduited into the boat.

If anything it's the opposite, so there's probably little difference in most installs...

So just ignore 'the experts' and wire them how you like. :) Series probably has the edge for new installs if it avoids the need for MC4 splitters.

Interesting video here:

 

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42 minutes ago, mrsmelly said:

I stick two wires in the top of the black control box thingy majig and two out the other end which go to the battery doobries via a thing called a fuse or somett. This puts ampy things into my batteries and Mr who looked at mi boat passed it for the BSS thingy so I am happy wiv that. :D

Do you bother with the panel,or just connect the black box to another fully charged battery?:D

Edited by rusty69
Cos I forgot the smiley

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56 minutes ago, rusty69 said:

Do you bother with the panel,or just connect the black box to another fully charged battery?:D

:o Oh yeah 4got..... the other end of the two wires goes to a panel and then there are two more wires to another panel, so they are obviously wired in err umm err Togetherlell thats the term I fink togetherlell

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Well some really good advice here.  I think I'll just shove the wires into the new thingywhatnot as they are.  Oh and can I have a quaff of whatever Mr Smelly has been quaffing?

 

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Just now, larryjc said:

Well some really good advice here.  I think I'll just shove the wires into the new thingywhatnot as they are.  Oh and can I have a quaff of whatever Mr Smelly has been quaffing?

 

Probably battery acid!

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2 hours ago, larryjc said:

Well some really good advice here.  I think I'll just shove the wires into the new thingywhatnot as they are.  Oh and can I have a quaff of whatever Mr Smelly has been quaffing?

 

I'm never sure if the correct term of abuse address is Mrs Melly or Mr Smelly. :banned:

Edited by Murflynn

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20 hours ago, Murflynn said:

I'm never sure if the correct term of abuse address is Mrs Melly or Mr Smelly. :banned:

Mr smelly ( after the dog ) and its usualy wheat beer or G and T :D

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