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Biggles

MPPT Paralleling

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Hi All.

 

Back for some advice please and suggestions.

I've just fitted an extra 500w of solar to my boat making 1000w in total.  I'm not entirely sure the current MPPT has capacity for 1000w at 12v.  I have an identical MPPT as a spare and I know these can be run in parallel with feeds from each 500w array, but the wiring in the boat prevents this as a possibility. The MPPT's don't communicate with each other.

 

So I am wondering with my limited knowledge of wiring if the same could be achieved by paralleling the 2 MPPT's together instead.  In my head I think this is would have the same effect of halving the load each was handling.

 

If this is not possible then I would need suggestions for an MPPT that could do1000w at 12v with an solar input of 37v

 

Kevin

Edited by Biggles

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Hey Kev, long time no see :)

 

Just wire the outputs of the two controllers straight to the batteries in parallel. Once the two of them have handled the bulk charge between them one of them will switch to float, leaving the other on Absorption for a while before it too switches to float. 

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Hi 

 

Yes I'm still around.  Bobbing my way through France.

 

This is what I had in mind, do you concur?

20190525_121359_resized.jpg

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I suspect one just makes 2 parallel systems, panels, mppt, battery. 

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2 hours ago, Jim Riley said:

I suspect one just makes 2 parallel systems, panels, mppt, battery. 

I can't do that because all the panel wires feed into 2 16mm wires which end up at the the first MPPT  I'v shown them as 10mm but they are actually 16mm now I come to think if it.

 

Seeing as how the current MPPT is supposedly rated at 30amps this is the reading I'm currently getting.  See pic below.

20190525_161515_resized.jpg

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Firstly, I wouldn’t put two MPPTs in parallel to the same set of solar panels. It is OK to parallel the outputs to the battery, but I would say that paralleling the inputs is “uncharted territory”.

 

the MPPT will have more current on the output to the batteries than on the input from the panels. The 30A spec may refer to the input current. If the panel voltage is higher than 12-14v, the output current to the batteries will be more, maybe much more, than the 30A input rating. 1000w at 37v is 27A so you will be fine with just the one controller if the 30A is the panel current. What is the exact make and model of the controller?

Edited by nicknorman

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4 minutes ago, nicknorman said:

Firstly, I wouldn’t put two MPPTs in parallel to the same set of solar panels. It is OK to parallel the outputs to the battery, but I would say that paralleling the inputs is “uncharted territory”.

 

the MPPT will have more current on the output to the batteries than on the input from the panels. The 30A spec refers to the input current. If the panel voltage is higher than 12-14v, the output current to the batteries will be more, maybe much more, than the 30A input rating. 1000w at 37v is 27A so you will be fine with just the one controller.

I agree with all this. I think I misunderstood the original question. 

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6 minutes ago, WotEver said:

I agree with all this. I think I misunderstood the original question. 

I edited it because I am not clear if the 30A limit is the panel current or the battery current. Bearing in mind it’s putting 46A into the batteries it seems likely that it’s the panel current, but we can’t be sure without knowing exactly which controller it is.

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21 minutes ago, nicknorman said:

Bearing in mind it’s putting 46A into the batteries it seems likely that it’s the panel current

Agreed. The ‘limit’ only means that it won’t put out any more than that anyhow. It won’t be damaged by too much solar. 

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Hi and thanks or the input and discussion.

 

This is the make and model and some specs.  I have to say its a lot bigger and heavier than a modern one I fitter to a friends barge a few weeks ago.

 

Uncharted territory?  Do you think it would do any harm to try?  Perhaps make it a bit less uncharted? 

 

Kevin

 

 

20190525_205019_resized.jpg

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It does seem to imply that the max charging current is 30A, and yet yours is showing 46A. On the other hand it says it has automatic overcurrent protection (by disconnecting the panels). 46A at 13.4v is 616W which is not bad - you will never in reality get 1000w from a 1000w panel array.

 

As you say, nothing will be damaged by connecting 2 controllers to one set of panels, but I suspect it may make the max power point tracking misbehave. Only one way to find out!

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Even by what's written as its specs it shouldn't be able to handle 500w of solar but it has for the past 6 years.   But again getting 500w is very unlikely..

 

I'll watch what happens when I have continuous sun.

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13 hours ago, nicknorman said:

I edited it because I am not clear if the 30A limit is the panel current or the battery current. Bearing in mind it’s putting 46A into the batteries it seems likely that it’s the panel current, but we can’t be sure without knowing exactly which controller it is.

All the panels are 8.3 amps max output, so even on the best day just a bit over 32 amps at 37v panel output. if that helps

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OK I have put them together, nothing bad has happened as far as I can tell.

 

They certainly aren't sharing the work as can be seen by the two gauge. The one with the thumb is  the second MPPT.  As it can be seen the two closely add up to the total the Victon is saying, but that actually says more.

 

So I'm not sure if there is any harm or benefit.  I have tried disconnecting and reconnecting the 2nd MPPT and there is no significant change on the victron, but the individual meters are bouncing all over the show albeit slowly.  They seem to be sharing the work, and certainly the first unit is cooler and each are the same temperature.  Perhapas as said it messing with the max power point tracking.

 

Thoughts please

20190526_130921_resized.jpg

20190526_131011_resized.jpg

20190526_131016_resized.jpg

20190526_131138.jpg

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I can’t see how this will work. An MPPT controller works by varying the load on the panel until it finds the maximum power output. With two of them attempting to do the same thing... I dunno. 

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Hello All

 

So the results are in.  It doesn't work.  The best I got with them connected together was 36amps   46amps is however regular when the sun is good and the batteries need it.

It would seem there is a huge additional capacity in the 1st MPPT.

The good news is I went 5 straight days without starting the engine.  My biggest draw is the full size domestic fridge freezer on 240v.

 

while I was messing about with things my 1160A/h battery bank went down to 76%, but once I had everything running optimally I got back to 100% in a day.

Nothing ventured nothing gained.  Thanks for you interest.

Kevin

  • Greenie 2

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5 hours ago, Biggles said:

So the results are in.  It doesn't work

Thanks for the feedback :)

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