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Forum Index : Solar : coupling controllers

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brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1439
Posted: 10:27pm 14 Sep 2020
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I've always wanted to minimise the number of cables running around a enclosure ,so.  

Heres the question-   Three different controllers, two are the same make and model, one is  my latest  MPPT .

Can I common the positive output from the "load ports". from these two common controllers .( all my negative cables are commoned onto a brass bar.) (saves cables and space).

or will the two common positive 's interfere with each controller and let the magic smoke out ????.   ( or can I insert a blocking Diode in both positive lines ??? )

Is there a good link I can access to obtain controller working information   -I've read a lot , but not yet satisfied.

Bruce
Bushboy
 
Solar Mike
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Joined: 08/02/2015
Location: New Zealand
Posts: 679
Posted: 12:02am 15 Sep 2020
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  brucedownunder2 said  
Can I common the positive output from the "load ports". from these two common controllers .( all my negative cables are commoned onto a brass bar.) (saves cables and space).... Bruce


By "Load Ports" do you mean +ve battery connection outputs or the controlled load switch output some controllers have; that gets turned off on low battery volts.

If its the main battery output connection, I would always run a separate CCB and cable connection from each controller back to the battery terminal. This prevents cable voltage drops affecting the other controller voltage sensing.

If the controlled "Load" connection, then I wouldn't combine them directly, if you want to use the load disconnection facility then take that output to a relay and series up the contacts with others, so any one could disable the output.


Cheers
Mike
 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1439
Posted: 04:49am 15 Sep 2020
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Thanks Mike.

 I'm attaching a photo of what I'm trying to describe.




 I've two of those black coloured controllers fitted , both 48 volts/ 60 amps .  


Just trying to electrically match them ,so either will be able to supply a light load from existing panels., - without interferring with each other.
The red unit is MPPT and will be for a seperate solar array.

The battery bank will be for primary supply -thats another story.
Thanks

Bruce
Bushboy
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 539
Posted: 04:02am 16 Sep 2020
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If what you are asking is what I think you are.....

When I started out with solar I set up a little Tiddly wink system I had about 1.5Kw of panels all in parallel wired to one of the controllers same as you have ( which I have found to be VERY good) and one of those cheap arse not nearly as good blue ones.  Because I had more power available than either controller could handle ( 30A ea) I simply connected them in parallel to the solar output.  

The controller outputs were also connected to a couple of car batteries with the idea being I could get all the power I was generating into the batteries when needed. The batteries ( 2x 12V N180 truck batteries)  were connected to a 2 Kw inverter and a 600W UPS.

I didn't have any trouble with any of it.
Mostly I ran a fridge off the 600w UPS and an Urn for hot water through a PWM controller to reduce the current for the 24V inverter.

Seemed logical to me you could parallel everything to take full advantage of the supply, charging and output. I didn't see any conflicts and both the the controllers are still perfect today. I spose I ran them in that setup well over 6 Months.
With the Inverter going flat out alone, both controllers were giving all they could back into the batteries and I had the outputs wired to the inverter terminals and longer cables back to the batteries to reduce any voltage drop when the inverter was running.  I only ever put any load on it during the day, at night the UPS just supplied the fridge when it kicked in.  Figured the supply current to the inverter was always going to be more than the charge current back into the batteries although I used car battery cable and they would carry the load ok without the solar.  

Since then, I have also done a similar thing with GTI's. I have a couple of arrays now that are side by side and I use standard 2.5 3 core cable to bring the power back to the inverters. The negs of the arrays are common and the positives go to each inverter.  Previously up the back I had 2x 2 Kw inverters on different phases sharing a common input.  I didn't see any problems with that setup either till I changed it a few months back.
 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1439
Posted: 12:44am 18 Sep 2020
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Thanks Solar Mike and Dave 99

sort of taking some time off for a while ..


Bruce
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