Jump to content

Running two solar controllers / arrays


Featured Posts

What ho.  Another solar question please....  basically, any views on running two arrays through two MPPT controllers into the same leisure bank?

 

Long story short - we're upgrading solar capacity due to the need to work from home more.  We already had a solar installation but we can't easily upgrade that, so figure it is easier/as cheap to just install an additional set of solar panels with their own controller.  

 

Current set up is 440a/hr sealed battery bank, plus separate starter.  Mechanical split charge relay (needs to be swapped to VSR at some point ... next job...).  1000w sterling inverter. 

 

Original solar set up is a 320w Perlight mono panel into a 20amp EP Solar Tracer MPPT controller - this has been fine for our usage to date, summer cruising - few days stationary at a time, usually in good weather spells - rest of the time on hook-up.  Batteries have always remained well charged (albeit, we only have the monitor that comes with the solar charger, which never feels particularly accurate for indicating stage of charge...).   

 

Can't fit another of those big 320w panels on the roof, so got a pair of 100w Perlight monos.   Upgraded the controller to a 40amp Tracer...   However, now realise we can't just run all these panels through that one 40amp controller as the panels are mismatched.... (lesson: do more research before buying things on eBay after wine!). 

 

So - figured the easiest thing is to install both the controllers, run the 320w panel through the 40amp controller - and the two 100ws run in parallel into the 20amp controller - and both outputs go to the leisure bank.  Each of the controllers have separate LCD remote monitors.

 

I think that's okay to do?    Any thoughts....

 

Very specific query - do I need to connect both solar controller outputs onto the same battery terminals in the bank?  Or, does it not matter and I can put the charge cables onto different terminals within the leisure bank... (just thinking that I already have a few things on the terminal post so it may be a pain to put both controllers onto the same terminals).

 

Is there anything I have to do to make the controllers "talk to each other"?  Or is it fine to have these running as described...?

 

 

There's probably more queries to come!

 

Thanks in advance. 

 

 

 

 

Link to comment
Share on other sites

Hi, 

 

I have 2 separate solar arrays on mine. seems to work fine :)

 

My thoughts were if the first pair were under a tree when moored then hopefully the back pair would still be producing (or vice versa). The controllers don't talk to each other but do their own thing independent of each other.

 

 

 

Link to comment
Share on other sites

24 minutes ago, TandC said:

(just thinking that I already have a few things on the terminal post so it may be a pain to put both controllers onto the same terminals).

That could be another 'job on the list'.

Ideally all cables should run to a Bus-Bar and then a single cable runs from the bus-bar to the battery terminal posts.

It is not good practice to have multiple wires on a battery terminal.

 

Bus Bar 210A 8mm Stud Positive or Negative

Link to comment
Share on other sites

If you have 2 solar arrays and 2 controllers on one battery bank, at some state of charge the output from one array will cause the other controller  to go to float.  Provided the point of shut down leaves the remaining solar array still able to fully charge the battery, all will be well.  

I would want to set the controllers up so that in good light the smaller array shut down first.

 

That may need a little experimenting.

 

N

Link to comment
Share on other sites

49 minutes ago, Alan de Enfield said:

That could be another 'job on the list'.

Ideally all cables should run to a Bus-Bar and then a single cable runs from the bus-bar to the battery terminal posts.

It is not good practice to have multiple wires on a battery terminal.

 

Bus Bar 210A 8mm Stud Positive or Negative

 

Its not the brightest thing to connect direct to the battery terminal posts, too much opportunity for corrosion. Why not connect to the battery side of the master switch?

Link to comment
Share on other sites

1 hour ago, BEngo said:

If you have 2 solar arrays and 2 controllers on one battery bank, at some state of charge the output from one array will cause the other controller  to go to float.  Provided the point of shut down leaves the remaining solar array still able to fully charge the battery, all will be well.  

I would want to set the controllers up so that in good light the smaller array shut down first.

 

That may need a little experimenting.

 

N

I agree. We had a similar setup to the OP. 200W into a 30A MPPT and added another 2* 150W pannels so bought a new controller, so two panels in series to each controller. The two controllers 'fought' with each other so once up at 90% to95% full, one controller would go to float, wasting all that lovely power.

The solution, just wired to two sets of panels into the origina 30A controller. Never looked back. Only once last year did we see 30A from the 500W of panels.

I do not understand why the OP can't wire his 4 panels into one controller if he has 2S * 2P?

Link to comment
Share on other sites

I'm feeling a bit confused by all this solar elektrikery stuff, but I'll stick my oar in here. I have 2 arrays also, and at most times its the doggies. However, like as mentioned above, one controller takes president and t'other goes AWOL or float. In a nutshell though, I have been advised by an expert (un named of course) that my settings are OK. My 2 arrays are 400wts and 335Wts both into their own controller. As has been mentioned I concur, that this set up is indeed very handy for mooring along trees/buildings and their shading. So I say, go for it.

Link to comment
Share on other sites

3 hours ago, TandC said:

Can't fit another of those big 320w panels on the roof, so got a pair of 100w Perlight monos.   Upgraded the controller to a 40amp Tracer...   However, now realise we can't just run all these panels through that one 40amp controller as the panels are mismatched.... (lesson: do more research before buying things on eBay after wine!). 

What is the open circuit voltage of the 320W and the 100W panels? There may be ways and means of running them all through the 40A controller. Which model of Tracer is it?

Jen

Link to comment
Share on other sites

Hmmm... dang it.  I  knew it'd be more complicated!  

 

Noted comments on optimum terminal points etc - trhat needs some attention then, which is easy enough to rectify.

 

 

But sticking with the panels/controllers etc: 

 

Jen-in-Wellies:  - if there is a way of running all through the 40amp controller that would be amazing...  but not sure it's doable without major losses that make it a bit of a waste of time/money.  The open circuit voltage on the 320w Perlight is 41.55v and the max open circuit voltage on the 100w panels is 22.8v (and there are two of them, being wired in parallel together).

 

Then there is a 20amp EP Solar Tracer (not sure of its model number without digging around in the cupboard), and the 40amp EPEVER Tracer - 4210EN is the model number.    I believe EP Solar changed the name...   they're both from China and the instructions are terrible/I struggle. 

 

Each one has its own LCD remote display... and I have never messed with the settings aside from I think I may have set up the battery bank size and type on the 20amp when I first installed it.

 

 

At only 45ft long, if the bow is in the shade more often than not so is the stern, so I wasn't really hoping to gain from different locations - it was more the increase of another 200w of charge power that I was pursuing - it's cost about £300 so far to buy the two 100w panels and the 40amp controller, so I hope that's not proved a massive mistake...

 

 

With regard the issue of one reaching float first....  obvs i want that to be the two 100ws going into the 20amp controller, so that the 320w is still able to go at it as long as it can/needs.   Is there a way of achieving that?

 

 

 

Link to comment
Share on other sites

2 hours ago, Dr Bob said:

I agree. We had a similar setup to the OP. 200W into a 30A MPPT and added another 2* 150W pannels so bought a new controller, so two panels in series to each controller. The two controllers 'fought' with each other so once up at 90% to95% full, one controller would go to float, wasting all that lovely power.

The solution, just wired to two sets of panels into the origina 30A controller. Never looked back. Only once last year did we see 30A from the 500W of panels.

I do not understand why the OP can't wire his 4 panels into one controller if he has 2S * 2P?

12v set up, not 24v.    The 320w panel just goes straight into the controller (currently the 20amp, but it will be swapped to go into the 40amp controller.   

 

The two 100w panels I was going to wire together in parallel, into the 20amp controller. 

 

My basic understanding was that you cannot put the 320w and the two 100w all in together as the mismatched voltages on the different panels creates big inefficiencies so it would make more sense to use the two controllers.  (i think).

 

 

Link to comment
Share on other sites

1 hour ago, TandC said:

My basic understanding was that you cannot put the 320w and the two 100w all in together as the mismatched voltages on the different panels creates big inefficiencies so it would make more sense to use the two controllers.  (i think).

I'll ask again. What are the open voltages of the panels? If they are the same, say around 19V on all, then they can be wired in parallel fine. If the 320W panel has twice the open circuit voltage of the 100W panels, then the two 100W's can be wired in series, then in parallel to the 320W. All in to one controller.

 

Link to comment
Share on other sites

1 hour ago, Jen-in-Wellies said:

I'll ask again. What are the open voltages of the panels? If they are the same, say around 19V on all, then they can be wired in parallel fine. If the 320W panel has twice the open circuit voltage of the 100W panels, then the two 100W's can be wired in series, then in parallel to the 320W. All in to one controller.

 

That sounds hopeful and starts to make sense to my small brain  .... just checked the panels now im on the boat - the 320w is open circuit voltage (VOC) 41.55v  and the 100w panels are 22.8v....  so yes, if the two 100w are in series that is very close to be equal voltage.  

 

Will that work without too much loss ? 

 

If that will run through the 40amp charger, that saves me messing about with the settings and having that faff.... means just one LCD display which is way more sensible/useful.... and means I have a spare 20amp controller/remote which I can repurpose for another project or keep as a spare.    Even if there are some small inefficiencies due to the slight difference in the voltages, it's worth it for all of these reasons.  

 

If the general view is that this is the most efficient/sensible way to approach it using this rather random selection of equipment, then that's what I;ll do.

 

 

(and I need to sort out the terminal arrangements too by the sound of things)

 


Thanks so much

 

 

 

 

 

 

Link to comment
Share on other sites

I think it should.

Wired like this:

 

     ______________________ To controller + in

     +                      |

  100W                  |

     -                       +

     +                    320W

  100W                  -

     -                       |

     --------------------------------------- To controller - in

 

Drawn in ASCIICAD (tm)

Jen

Link to comment
Share on other sites

5 hours ago, Dr Bob said:

The two controllers 'fought' with each other so once up at 90% to95% full, one controller would go to float, wasting all that lovely power.

Nothings being wasted - at 95% the batteries are taking a very small current that one controller is quite capable of providing all on its own.

4 hours ago, ditchcrawler said:

One will always go into float first but when it does is the other still giving maximum input or has the current dropped back because your batteries are getting full.

Yes, and yes.  Otherwise the other controller wouldn't have dropped out :)

  • Greenie 1
Link to comment
Share on other sites

22 minutes ago, WotEver said:

Nothings being wasted - at 95% the batteries are taking a very small current that one controller is quite capable of providing all on its own.

Yes, and yes.  Otherwise the other controller wouldn't have dropped out :)

I know that but does the OP who is trying to fix a problem that doesn't exist 

Link to comment
Share on other sites

Okay - these are good points, and now I appreciate then that if running two controllers at the same time, if one goes into float then it really doesn't matter a great deal.  

 

However.... 

 

Practically - I would prefer to run just the single 40amp controller for a variety of reasons (space and temperatures in the cupboard, not needing to install more cabling for the extra controller to the batteries, not having two remote screens, I can liberate the spare 20amp controller to a neighbour/other project)  - , if what Jen has suggested is an acceptable approach as that sounds like a winner... but I can't work out how to compare the two outputs. 

 

The choice remains - use two controllers, and obtain the maximum possible  charge current from 520watts.  Or use one controller, with the pair of 100ws wired in series, then paralleled with the 320 into a single controller.... but I can't work out in my head how to then compare that output....  does it create significant losses that would outweigh all those practical reasons, when the whole point of doing this is to get a decent uplift in charging capacity...?

 

I've tried to find the formula to work it out, using the information on the technical specification labels, but am not grasping it!

 

Oh dear.  I am a bear of very little brain

Edited by TandC
clarification
Link to comment
Share on other sites

2 minutes ago, TandC said:

I've tried to find the formula to work it out...

What are you trying to work out?  A 40A controller can give a maximum output of 40A.  Your panels have a theoretical combined power of 520W, which is 520/12 = 43.33A.  So on a bright but cool summers day in full sun the output should approach 40A (if the batteries are sufficiently depleted) but the reality is that you'll rarely see above 20A in the UK.

Link to comment
Share on other sites

5 minutes ago, WotEver said:

What are you trying to work out?  A 40A controller can give a maximum output of 40A.  Your panels have a theoretical combined power of 520W, which is 520/12 = 43.33A.  So on a bright but cool summers day in full sun the output should approach 40A (if the batteries are sufficiently depleted) but the reality is that you'll rarely see above 20A in the UK.

I didn't think it was that straightforward when you mix panels of different sizes....  lots of web content explaining why it introduces losses... hence me starting this whole sorry saga in the first place...!     

 

 

 

Link to comment
Share on other sites

40 minutes ago, TandC said:

I didn't think it was that straightforward when you mix panels of different sizes....  lots of web content explaining why it introduces losses... hence me starting this whole sorry saga in the first place...!     

 

 

Remember that 41.55V & 22.8V are open circuit vltage, when the panels arr working into a load both will be supplying a lower voltage than this. Check your panel voltage on the controller at random times throught the day. I bet you won't see 41.55V

Link to comment
Share on other sites

3 hours ago, WotEver said:

Nothings being wasted - at 95% the batteries are taking a very small current that one controller is quite capable of providing all on its own.

 

Not quite what I said.

I said at 90-95% full. In practice what I had was two controllers each pushing 10A into the batteries, then at 90% full (based on Ahrs out - so not very accurate), one controller would go into float so I was only getting 10A in rather than 20A. If I repeated the same on a subsequent day, but changing the float voltage settings to 14.4V on both controllers, both would continue to push in 10A until they both started to decrease due to the batteries controlling what they were taking. If you are topping up in the afternoon, then that extra 10A is wasted if one controller gets to float until the batteries started to cut the Amps back.

The charging was quicker once I ditched the new controller and went back to just one. This was with the lead acids before I went to Li's.

Link to comment
Share on other sites

14 hours ago, TandC said:

I didn't think it was that straightforward when you mix panels of different sizes.... 

If the voltages are the same (as would be the case (more or less) with the proposed series/parallel arrangement) then you'll gain more than you'll lose by using a single controller.

11 hours ago, Dr Bob said:

The charging was quicker once I ditched the new controller and went back to just one.

Yes, it would be.
 

 

Edited by WotEver
Missing parenthesis.
  • Greenie 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.