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BlueStringPudding

MPPT controller question

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Can two separate MPPT controllers be connected to the same battery bank from two separate arrays of solar panels (meaning two simultaneous charging inputs)?

 

Or do the two solar panel arrays have to be joined together and fed through one single big controller to the battery bank?

 

Thanks.

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Yes, I have the panels on the port side going through one Voltage Regulator and those on the starboard going through another. The theory being that with the curve of the roof there will normally be a difference between the two and if going through one Voltage Regulator the whole system will be pulled down. 

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Yes......but....

We had two separate controllers for our 4 panels. 2 in series times two.

We started with only 2 panels with a 30A mppt. Added another 2 panels one a new charger. The problem though was getting power from both when batteries over 90% charge. The were always fighting each other. One would be in bulk putting out 14.1 V so the other would go into float.

I tried all combinations of bulk and float voltages but no real success. 

Gave up this year and all 4 panels are on one 30A mppt and working so much better. The total power is 500W and the 30A controller copes with 25A the max I have seen from it.

I blame the duck.

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My two tracers tried to cook the batteries dont know why but I now have a midnite controller these can be put together with link leads

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1 hour ago, Dr Bob said:

The problem though was getting power from both when batteries over 90% charge. The were always fighting each other.

But that’s not a problem. At that point in the charge curve the batteries no longer need the output from both controllers. Hence one of them will switch off. 

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I wondered this some time ago and was informed (on here) that it would be no problem to have two controllers (although I haven't needed to add the second one yet).

Don't the Tracers just do what they do? Ie 14.something for two hours, regardless?

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1 hour ago, WotEver said:

But that’s not a problem. At that point in the charge curve the batteries no longer need the output from both controllers. Hence one of them will switch off. 

But it is. The final 10% is 60Ahrs and it's no use if one controller is putting in 10A and the other one nothing. If you put a heavy load on for a minute then the one in float goes back to bulk and then you get 20A till it starts decreasing.

It's a faff having to do that. The final 10% is a lot easier with just one controller. 

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12 hours ago, BlueStringPudding said:

Can two separate MPPT controllers be connected to the same battery bank from two separate arrays of solar panels (meaning two simultaneous charging inputs)?

 

Or do the two solar panel arrays have to be joined together and fed through one single big controller to the battery bank?

 

Thanks.

Perfect timing ?, I am installing our solar atm, as in right now. I've got 3 panels on with one more to go and am planning on wiring them in pairs as you have described with 2 separate controllers. I bought the kit from bimble solar and they were very helpful and said the above system would be absolutely fine. 

 

We were lucky in that bimble are only a few miles from home and it was well worth the visit to chat things through face to face. 

 

 

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On 14/05/2019 at 11:34, Dr Bob said:

But it is. The final 10% is 60Ahrs and it's no use if one controller is putting in 10A and the other one nothing. If you put a heavy load on for a minute then the one in float goes back to bulk and then you get 20A till it starts decreasing.

It's a faff having to do that. The final 10% is a lot easier with just one controller. 

I had 3 tracer bn controllers going into one battery bank to partialy overcome the problem you refer to I simple fed false dates into 2 of them, this gave the, 'end of the month' bulk charge on different real dates. Simply put all 3 of the controllers had a different calendar 2 of which didn't match the actual external calendar. 

 

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10 hours ago, reg said:

I had 3 tracer bn controllers going into one battery bank to partialy overcome the problem you refer to I simple fed false dates into 2 of them, this gave the, 'end of the month' bulk charge on different real dates. Simply put all 3 of the controllers had a different calendar 2 of which didn't match the actual external calendar. 

 

What date do the Tracers perform the equalize charge?

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26 minutes ago, jenevers said:

What date do the Tracers perform the equalize charge?

I think mine does it every 28th of the month.

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1 hour ago, Richard10002 said:

I think mine does it every 28th of the month.

I believe that is correct. 

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I now have my two controllers and PV arrays.

 

The Sunsaver MPPT Controller and PV Array #1 is already installed and has been working fine for a few years.

 

I have yet to install the Victron MPPT Controller and PV Array #2. Looking at my diagram below, is it correct that I should connect cable E to cable C (outputs that run from each controller to the positive battery terminal). And cable F to cable D (outputs that run from each controller to the negative battery terminal) - using a bus bar or similar?

 

Or will that make batteries/controllers go boom-boom? 

20190614_160806.jpg

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5 minutes ago, BlueStringPudding said:

Looking at my diagram below, is it correct that I should connect cable E to cable C <snip>. And cable F to cable D

Yes :)

 

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3 minutes ago, WotEver said:

Yes :)

 

If one array was in shade but the other one wasn't wouldn't this set up mean that the array in shade would pull down the array that wasn't in shade? 

 

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Trying to get my head around this. Is my thinking wrong here. 

First array is passing 2 amps to controller battery output terminals. 

Second array is passing 4 amps to controller ouput terminal. 

So actual current passed through connections to battery bank will only be 2 amps? 

I'm thinking of the scenario where solar panels of different currents are wired in series such as shown here 

Solar Panels in Series of Different Currents

http://www.alternative-energy-tutorials.com/energy-articles/connecting-solar-panels-together.html

 

Edited by reg
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The controllers will be in parallel. With parallel connections you add the amps but the volts stay the same.

 

The only slight problem might be that with well charged batteries if one controller has a higher voltage it might persuade the other to go into float or shut down but as soon as a decent load was applied they should both work again.

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11 minutes ago, reg said:

Is my thinking wrong here. 

Yup. 

 

We’re paralleling controller outputs, not panels. 

Just now, Tony Brooks said:

The only slight problem might be that with well charged batteries if one controller has a higher voltage it might persuade the other to go into float or shut down but as soon as a decent load was applied they should both work again.

Yup, but as this will only happen with well charged batteries it’s not particularly significant. 

28 minutes ago, reg said:

If one array was in shade but the other one wasn't wouldn't this set up mean that the array in shade would pull down the array that wasn't in shade? 

Nope. 

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12 minutes ago, WotEver said:

Yup. 

 

We’re paralleling controller outputs, not panels. 

Though I was getting the fundamentals wrong, can see it now as we are, as you point out, talking post controller output so solar input is to all intents out of the equation. 

I already have a similar setup but I ran separate output cable runs to the battery from each controller, won't be changing it now but I could of saved my self a few pound in cabling if I'd thought it through. 

Thanks both. 

 

Edited by reg

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3 hours ago, reg said:

Though I was getting the fundamentals wrong, can see it now as we are, as you point out, talking post controller output so solar input is to all intents out of the equation. 

I already have a similar setup but I ran separate output cable runs to the battery from each controller, won't be changing it now but I could of saved my self a few pound in cabling if I'd thought it through. 

Thanks both. 

 

I initially thought about running another set of cables to the batteries but then I thought once they reach the batteries they're basically part of the same "terminal" so I might as well join the cables further up and save some money on cable length. 

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Special thanks to the Monkey man for my early birthday present of these extra panels and charger  ♥️🐵 I'll be happy to sell any spare electricity back to him at a very reasonable rate ;)

And as my birthday isn't till August, I'm taking this as permission to celebrate my birthday for two whole months starting today  :D🎂

 

 

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