Final decision on my solar panels and controller

[Christianonthecut]

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[Paul C]

Its a well known fact, that the larger the typeface, the more sure you are on a prospective purchase.

[DeanS]

LOL. There's a long way to go yet. Top boxes to build, tilt mechanisms, fuses, wiring it up....THERE'S MORE QUESTIONS TO COME

 

but...at least I wired up my alternator.

and at least I bought a clamp meter.

and at least I got an invertor that powers the fridge

and.... now it's solar time.

[Paul C]

You're in danger of actually matching the electricity you consume, with the amount you generate, soon!

[smileypete]

Phew!

[George94]

It's worth remembering that a bad decision is very frequently better than no decision at all.

 

And I am not saying this is a bad decision. I wouldn't know.

[Naughty Cal]

You're in danger of actually matching the electricity you consume, with the amount you generate, soon!

Never....

[DeanS]

Never....

 

ye of little faith

[Naughty Cal]

Im a realist not an optimist

[Titan]

Dean for what its worth. I have 1 tracer 45A controller and 2 x 235w pannells coupled to 4x6v T105 batts approx 1000 amps. Recently whilst on the boat ive seen on sunny days between (on the higher side ) between 26 and 33 Amps going into the batts, Just a thought, rather than go to the exspense of huge pannells and huge controller, would it not be possible to go with a simillar set up but employ a second battery bank ie reserve bank ?? ax2 6v cells would be in the area of475A. two pannells charging one bank, then alternate to the other ?... i did find a 20 amp mppt controller which would match A sigle 235w pannel on ebay for around the 80.00 mark. So when were counting pennies two banks 2 pannells and two inexspesive controllers maybe a possability. my thinking that a good cyclic pattern between each bank may well prove healthy for the batts ?? one set just on charge one set on charge and on duty, then swop duty set via a switch every other day ?? did i make sense ?? regards Martin

 

Thought ? if you had two controllers feeding the same bank? would they not possibly counteract each other? ie one output of 30a sees another supply of 30 and close down ?? just a thought and its late, my reasoning is the moment i start my engine the mppt controller closes down as it sences /detects alternator output

Edited May 4, 2013 by Titan

[smileypete]

Thought ? if you had two controllers feeding the same bank? would they not possibly counteract each other? ie one output of 30a sees another supply of 30 and close down ?? just a thought and its late, my reasoning is the moment i start my engine the mppt controller closes down as it sences /detects alternator output

Sounds like your alt reg voltage is higher than the MPPT set voltage, and the alt can provide much more current than the batts can take at that voltage, so effectively takes over from the MPPT.

 

If you'd prefer the MPPT to provide charge instead and save on diesel, maybe find some way of disabling the alt temporarily, like disconnecting the charge warning light from the D+ terminal. But bear in mind the charge warning light also has a very important secondary function to warn of belt failure and consequent engine overheating...

 

cheers, Pete.

~smpt~

[matty40s]

Added another 240.w sanyo this week for £20 which brings me up to 540w. Batteries on float by 9.30

[Grace and Favour]

Added another 240.w sanyo this week for £20 which brings me up to 540w. Batteries on float by 9.30

Cheap as (silicon) chips

[matty40s]

no typo.....Panel with cracked glass, couldnt see it get skipped.

[Nickhlx]

Re the max handling of controllers...

 

We have 3920 Wp of panels on the house roof and a SMA Sunny controller which is rated at 3800 watts.. The monitor always "tops out" at 3800 ( but occasionally 3810 watts) and nowhere near the peak of the day or the year, so I am convinced it is limiting itself.. I was about to take it up with the installer ( who probably will justify it by saying the percentage "loss" per year does not justify the cost of the next size up to take advantage of the full generation.

 

Had I known at the time I would have shelled out for the next size up as it was only a hundred or two pounds more..

 

Having said all that, I am staggered at the last week's generation of some 125 kWh, and it is only early May - panels face due south and aren't even optimised for the elevation of the sun at this time of the year ( roof angle )..

 

We have had for now approaching 3 years and the annual generation has exceeded forecasts significantly at about 3550 kWh / year, against 3200 kWh/year that was forecast... It is particularly good for us as we have a high demand in summer so use much more than the 50% assumed and payback is on track to be about a year earlier than the 7 years forecast..

 

Nick

[Justme]

Had I known at the time I would have shelled out for the next size up as it was only a hundred or two pounds more..

 

 

Nick

 

 

And you would have wasted your money.

 

The thing you are forgetting is the efficiency of the different inverters when at different loading points.

 

In most cases you will still get a larger total amount of energy produced over the year with a slightly under sized inverter.

[smileypete]

Worth remembering they can output more than nominal rating at cold temperatures and on top of that can have an output tolerance, sometimes up to +5%. On the other hand the output declines about 1% long term.

 

So you could probably get well over rated output depending on age, tolerance and temperature, but some of that does depends on the panels manufacture, and it'll drop year on year.

 

Look on the bright side , if it's doing well now it should maintain at least rated output for some years to come.

 

Do you know yet what sort of output you get in high summer temperatures? I can quite understand the installers POV, the average person doesn't always really understand 'negative temperature coefficient' so it's better to go for slightly oversized panels maybe with a better tolerance, than spend the money on an slightly oversized controller.

 

cheers, Pete.

~smpt~

Edited May 6, 2013 by smileypete

[Nickhlx]

I haven't found claims of efficiency at different loads - the overall figure is " 97.6% " or thereabouts in the specs...

 

I have noticed that the best output is when its not very hot, e.g. best when its clear skies with occasional clouds passing, when it shoots up to 3.810 kW immediately after the sun comes out from behind a cloud...

 

If its a long hot clear day like a few last week ( here at least) then it settles down at around 3.2 kW, presumably because the panels are running at a high temp and with their neg temp coefficient are only able to output less...

 

I gather there are now ( or shortly) to be available combination panels for solar thermal and solar photovoltaic, where the water jacket behind the solar panel is helping to cool the panel and enhance its output, at the same time as heating the DHW cylinder - ideal for limited roof area applications !

 

Nick