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Adding additional panels via seperate MPPT charge controller


Douw G. Gerber

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Hi all,

If you have an existing all-in-one inverter where the existing panels connect to, can you add a second dedicated charge controller and panels connected directly to the battery bank via a DC busbar?

In the event that the batteries are fully charged woul the inverter draw power from these additional panels during the day?

What would the pro's and cons be of doing this?

Edited by Douw G. Gerber
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21 hours ago, Douw G. Gerber said:

If you have an existing all-in-one inverter where the existing panels connect to, can you add a second dedicated charge controller and panels connected directly to the battery bank via a DC busbar?

Yes. I used to do this myself.

21 hours ago, Douw G. Gerber said:

In the event that the batteries are fully charged would the inverter draw power from these additional panels during the day?

Yes. It will draw power from the extra panels even when the battery isn't full, in preference to drawing the battery down.

21 hours ago, Douw G. Gerber said:

What would the pro's and cons be of doing this?

Well there is the cost and installation of the extra gear, of course. The niggle I found is that the inverter sometimes got a bit confused near the end of the absorb stage. But you can avoid that problem by setting the absorb voltage setting for the external MPPT just a little lower than the inverter's. Adjust a little if the calibrations aren't perfect. That way, the external MPPT helps most of the time, just not at the very end of the charge, but then the battery current is low anyway.

I even had my monitoring system (written 99% by a colleague) figure out what power must be coming from the external MPPT, and graph that separately from the inverter's charge power. It got that wrong when the loads changed sharply, but most of the time it worked really well.

I only changed the system when I found I needed more power, so I added another inverter in parallel, and that had another MPPT. So I just swapped the panels to the new inverter.

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22 hours ago, Douw G. Gerber said:

Hi all,

If you have an existing all-in-one inverter where the existing panels connect to, can you add a second dedicated charge controller and panels connected directly to the battery bank via a DC busbar?

In the event that the batteries are fully charged woul the inverter draw power from these additional panels during the day?

What would the pro's and cons be of doing this?

If your inverter has a gen input you could also use a separate string inverter

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Can you guys perhaps suggest a decent MPPT charge controller (30A) that wont break the bank?

Would this one work as an example?

https://shop.thesunpays.co.za/products/epever-xtra-solar-charge-controller-30a-mppt?variant=39474339676231&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZzOASkGUQ4AZg7PnQ5JDdUrRj7RjK8ivrfZ3gRRFyCZ4eWpeVhlV4kaAimqEALw_wcB

My household rarely goes over 50A at present - I assume the inverter will pull from wherever it can to deliver say 60A if required.  What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

Edited by Douw G. Gerber
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8 minutes ago, Douw G. Gerber said:

Can you guys perhaps suggest a decent MPPT charge controller (30A) that wont break the bank?

Would this one work as an example?

https://shop.thesunpays.co.za/products/epever-xtra-solar-charge-controller-30a-mppt?variant=39474339676231&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZzOASkGUQ4AZg7PnQ5JDdUrRj7RjK8ivrfZ3gRRFyCZ4eWpeVhlV4kaAimqEALw_wcB

My household rarely goes over 50A at present - I assume the inverter will pull from wherever it can to deliver say 60A if required.  What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

Decent would be victron

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28 minutes ago, Chris Louw said:

Buy the communication cable for programming mppt. Can be used with Lithuim batteries. Only had good feedback 

@Chris Louwwhere did you buy the comms cable? I agree very capable Mppt's i also use the Epever Xtra 150v 40a works like a charm

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54 minutes ago, Chris Louw said:

The Epever Mppt 30A is a good option. Currently run 2 in parallel with Axpert inverter. Buy the communication cable for programming mppt. Can be used with Lithuim batteries. Only had good feedback from Forum members using Epever Mppt. 

This is a vital point for expansion that you can parallel the Epever after loading the same settings on both. 😀

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3 hours ago, Douw G. Gerber said:

What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

It should just throttle back, and the  battery has to supply the shortfall. It decides how much to push into the battery, you don't "pull" from the solar charger.

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4 hours ago, Douw G. Gerber said:

Can you guys perhaps suggest a decent MPPT charge controller (30A) that wont break the bank?

Would this one work as an example?

https://shop.thesunpays.co.za/products/epever-xtra-solar-charge-controller-30a-mppt?variant=39474339676231&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZzOASkGUQ4AZg7PnQ5JDdUrRj7RjK8ivrfZ3gRRFyCZ4eWpeVhlV4kaAimqEALw_wcB

My household rarely goes over 50A at present - I assume the inverter will pull from wherever it can to deliver say 60A if required.  What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

Here is an example of my Epever. Mine does over read by 10%+. Single panel charging 24V battery. 

IMG_20230504_153305.thumb.jpg.8c4bb7ed565e304f154b3b4c9e9b8179.jpg

 

 

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  • 9 months later...

Good day,

 

So if I am understanding this thread correctly.

 

The Separate MPPT Controller and batteries get added to a DC busbar and not the inverter?

 

Which busbar is the right one to get? 

 

Also can anyone show a wiring diagram of this setup? 

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