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Exceeding 'Rated" input of a MPPT PV Controller


pilchard

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I need some advice as to if I can safely exceed the input to my 10Amp MPPT solar charge controller.

It is rated at 130W max, but will it take 140W or even 160W without any related problems?

 

I installed 2 solar panels to my campervan roof ( 50W & 80W) with a total rated output of 130W, and installed at the same time a 10Amp MPPT controler rated at 130W max... bought from the same supplier.

Both panels were either defective when installed, or failed shortly after. I never discovered this until, a month or so later on an extended holiday in Italy doing some off-grid camping and doing minimal driving, the leisure battery failed and I replaced it. But soon after, the new battery was drained and I then realized the battery was seing no benefit from the PV system. The suppliers have, after months of email exchanges requiring me to perform a range of quite technical tests, admitted both panels are goosed and the have agreed to replace them.

The trouble is that this supplier no longer stocks that range of solar panels (I wonder why?) and have offered me ("reinforced") replacement panels from a limited range of output and sizes that are not identical to the originals. The upshot is that, given the limited available space on the van roof, I could end up with 2 panels totalling either 120W, 140W, or 160W.

Having planned for and paid for a minimum of 130W there is no way I'd go for 120W.

 

Re the 140W option, the supplier has assured me the MPPT-130W controller "can actually take a higher solar input than rated, as there is a function within it that allows it take a bit more power, so the 10W addition won’t be a problem".... that they also sell a 150W package using the same controller... and have pointed out in its instruction manual that the "Max.PV Array Power = 390W/12V".

 

I am still trying to get an answer from them regarding if the above advice would still apply if I chose my preferred option of 160W, but I'm also looking for informed second opinions from any techie folk here

 

Should I believe that a controller advertized, rated, and sold as a max 130W... will give many years of trouble free service despite being used beyond it's "rated" range?

I could ask the company to put it in writing, but that would only cover 1 year of warranty and then diminishing consumer protection to a max of 6 years, beyond which I would be on my own if damage related to exceeding that 130W should occur to controller or panels.

 

Any electronics experts out there?

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It is unlikely you will ever see the maximum power from the panels unless you go far south during winter and/or angle the panel towards the sun. Put another way, I have a 120W panel and haven't seen more than 110W coming out of it. More commonly see a max 90-100W. So 140 panel should be OK under normal conditions. Also, the excess power, if ever seen, will likely only be converted to heat. Whether that becomes damaging probably depends on the controller.

 

 

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Thanks Spirou for that reassurance.

That was kind of the conclusion I had been veering towards, although Its a shame the supplier seems unwilling to answer exactly the same question.

 

They are also now playing hard-ball re allowing an upgrade to 160W... which I think considering the huge additional expense I have been put to, loss of use, delay, and time spent testing and writing emails, and next, removal of bonded on panels and re-bonding new ones on with expensive tubes of Sikaflex... they really do owe me as an absolute minimum.

They claim they will only replace based on the same or closest output: company policy. Company policy...PISH!

 

They also say that the faults the tests they instructed me to perform produce results they have never seen before. Basically... "we have never had a complaint like that before". How many times have we heard that?!!!

 

I will eventually mention this supplier's name... if they continue to fail me.

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Ideally your controller (all controllers) should be somewhere that is well ventilated and not stuck in a top cupboard, mine are low down near to the battery box where cool air from the gas drop vents can circulate, they're also on heatsinks.
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Some Solar regulators are rated at the maximum Solar panel size they will support, not necessarily the number of watts going in to it from the panel.

It is therefore likely to make an allowance for the inefficiencies of the installation.

 

For evidence of how the budgets are so often mis-described, go on eBay and look at the 'generics' that are the same regulator from the same manufacturer, Then checkout how the descriptions from the different suppliers vary.

Some you will see are described as MPPT controllers when they aren't even basic PWM technology.

When we tackled one UK supplier after opening up what was a very basic shunt model they said, "MPPT is not the technology it uses, it is the manufacturers 'model' name".

 

 

If yours is a quality controller like Schaudt, Victron or Votronic then it might last a bit longer, but pushing any electronic device to it's maximum isn't a good idea. To deliberately drive it beyond it's rating isn't the way to a reliable system.

 

We repair Chargers every day, and you can tell the failed ones that have been driven hard.

 

I don't know what Solar panels you fitted, but I am guessing that because you have had two panels fail so soon that they are 'Flexi' panels with a plastic top layer, not glass?

Maybe you should be made aware that there are a rising number of Flexi panels that either don't work from installation or fail soon after.

One van we worked on was on his second flexi, before he finally insisted on a solid frame panel.

 

.

 

 

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To add to good post of Alans, its certainly wise to buy a good controller from a reputable supplier, there are many fake ones and YouTube has videos showing copy's that have been opened to reveal the old technology shunt controller.
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Thanks for all the replies and what sounds like very good advice.

 

 

Having hit a brick wall with the supplier, as they will not allow me to fully utilize roofspace by going for a larger panel for one of the two panels they are replacing, I am having to settle for a total of 140W.

By the sounds of things (as per your replies) that's possibly no bad thing if I'm sticking with the 130W rated MPPT Controller supplied by them.

 

I sited my controller in an easily visible spot high up about 40cm below the van ceiling in a well-ventilated place, but I think I'll bear the heat situation in mind, keep an eye (or hand) on it and put an aluminium plate behind it if in any doubt.

 

The term MPPT isn't just used as a label on this, but fully explored in their website "overview" text. But that's no saying it isn't a pile of rubbish. It was cheap at £59.99, but all the others seemed far too overspecified for the simple leisure battery charging I require. I used to go OTTD/ belt and braces, but these days (specifically re stuff outside my knowledge base) I go more basic... but not rubbish... on the basis that if it turns out it isn't so good, then I haven't thrown too much money away.

 

This supplier of panels, controller, and bits etc, is one whose name was constantly cropping up on motorhome forums at the time I was doing my research. Everyone felt they were the dogs gonads.

But you are right... they were the semi-flexible type of panels, chosen for a variety of reasons... lightweight, thin, easily bonded to a slightly curving roof, tough enough to be fixed to a boat deck walked on (apparently), and even the claim they had superior efficiency to the older glass panels. This is the first time I've heard that this type could have a high or rapid fail-rate.

 

Anyway, the replacements are a "reinforced" type with "German solar cells". I have no idea if this reinforcement, achieved with the addition of a thin sheet of aluminium embedded within it, will make damn-all difference for my application. But, as I am stuck with this supplier and it's products, I am forced to suck it and see. If it all starts to go wrong again though... they'll be getting the whole lot back and I think I'd be justified in insisting on a refund.

 

One thing has occured to me though..... The new panels should be arriving in a few days, and I'll plug them in and test them (this time) on the system before I bond them down. If the MPPT Controller (which no-one has suggested I test) should be faulty, and because of this it kills the new panels (if that's possible), then I'll be back to square one.

Anyone know if my new worry is baseless.

 

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Have a read of our solar panels web page : http://www.aandncaravanservices.co.uk/solar-panels.php

 

I would suggest at £59 it is one of the better ones and probably is genuine MPPT.

 

If you read the Solar Hints and Tips page, we don't do Solar so it's not Sales motivated, it gives info on where to site the Solar regulator and why : http://www.aandncaravanservices.co.uk/solar-power.php

 

 

Note :

Being close to Conwy Marina and the nearby Conwy Harbour we have in the past done a lot of Boat Solar or seen lots of Boat electrical systems/chargers.

You will find if you have a marina near you and ask around that the 'myth' of flexi panels being able to be walked on and last any length of time is marketing hype.

The surface has got to be perfectly level and smooth, with the mastic applied with such smooth precision and you might then get a away with a two year old in slippers walking on it once or twice.

 

 

They are not at all robust, need very gentle handling, etc. From the ones we have seen that don't work from new, we would guess they might have been damaged in transit.

 

.

 

 

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Will have a good read of those recommended web pages as well as the hints and tips tomorrow when I have a little more time.... so thanks for that.

 

Seems like I have started from a position of abject ignorance and been taken in by the sales hype. But having said that, the PV marketplace is literally rammed full of semi-flexi panels... can they all really be complete rubbish? My supplier is currently showing on it's website 28 semi-flexible panels and 28 rigid framed panels... would they really have half of their PV panels of a type that they are going to get thrown back at them?

 

I had no need or wish to walk on my panels, so I ignored all that hype.

I was also very aware of, and took on board, warnings they needed careful handling. I handled them like Ming vases. I also suspect they may have been treated neglectfully in transit, but seem to remember the supplier saying they send them by a specialist courier familiar with the panels fragility. They arrived in pristine boxes with sufficient polystyrene padding.

 

Anyway, I am stuck going down my chosen route and all I can hope to do is make the best I can of it and hope for the best. If these replacements fail prematurely, then I'll be sending the lot back for a refund and go to small claims if need be.

This time though, I will at least conduct some testing before I install them.

 

 

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