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blue-sails asked

Connecting a smaller charge controller instead of a VE.CAN controller

I have a common, main DC bus bar.

I am sending 48VDC to it from various energy sources: solar, wind, hydro, a DC generator, and AC energy converted to 48VDC.

To avoid overcharging the batteries after the 48VDC bus bar, I am using VE.CAN chargers that are connected between them as a master with slaves.

One of the problems I have is that each solar panel is connected to a single VE.CAN MPPT charger. The solar panel is too small in relation to the smallest MPPT charger.

Due to shading issues I cannot connect more than one solar panel per MPPT charger.

Is there a way to connect the solar panel to a smaller MPPT charge controller without interfering with the current arrangement of not overcharging the battery or having chargers in standby?

Could a GX display or some other device help me to achieve this? Could up to six solar panels be connected through a GX display, for instance, and could this group (solar panels and device) become a slave of the master MPPT charge controller?

I thank you in advance for any assistance.

Venus GX - VGXVE.DirectVE.Busgx deviceVE.Can
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JohnC avatar image
JohnC answered ·

Hi @Blue sails

It's very hard to answer this without having more info. It sounds a lot like you're using multiple dc sources (not just solar) and syncing them through/with CAN mppt's. Is that the case?

Agreed that your can mppt's are oversized for single panels, but they should still work ok, just like smaller ones. Changing them out for smaller may achieve nothing.

Frankly, without a GX box and a BMV/Smartshunt batt monitor I'd be lost. And there's a number of things can be achieved there control-wise too. But we don't know what you want to do.

Do you have managed batts, with a bms? CAN linked?

Sorry for not answering your questions directly, but there may be a lot more to getting this right than just spouting uninformed answers.

Please tell us more.



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blue-sails avatar image blue-sails commented ·

Hi John C.,

I APPRECIATE YOUR RECENT RESPONSE.


It's very hard to answer this without having more info. It sounds a lot like you're using multiple dc sources (not just solar) and syncing them through/with CAN mppt's. Is that the case?


YES. This is correct.


Agreed that your can mppt's are oversized for single panels, but they should still work ok, just like smaller ones. Changing them out for smaller may achieve nothing.


YES. They will work but not optimally.


Frankly, without a GX box and a BMV/Smartshunt batt monitor I'd be lost. And there's a number of things can be achieved there control-wise too. But we don't know what you want to do.


==========================================================

ANSWER


I am guessing that perhaps I could add a smaller more optimal MPPT charge controller to each solar panel, and before connecting these to the DC bar bus I could group them together under a separate device able to take charge controllers as VE.direct devices and join the other VE.CAN charge controllers as a new slave device.


I am guessing that one of these devices could be GX device.


However, I am not familiar enough with all Victron devices and the communication options that are available. Therefore, this is pure speculation on my part.


The motivation for this is that I do not want to introduce a separate source of charging that will work independently of the synchronized charge controllers, and at the same time I want to explore the possibility of increasing the efficiency of the solar panels.


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JohnC avatar image
JohnC answered ·

@Blue sails. Addressing your motivations..

The smallest Victron mppt that can charge 48V is the '100/20-48', with a nominal max of 1160W. Still oversize for a single panel. And I very much doubt there'd be a measurable performance difference from your /70's (?).

Syncing is irrelevant until you reach the target Absorb/Float stages. All your kit will go as hard as it can up til then. So to test your panel capability do it before that's reached, even if you have to switch off the 'competitors'.

I think you have too much kit to be without a GX box. Give it some www/VRM, and you have full graphing and email warnings of any issues that might arise. Not to mention prioritization of charge sources, autostart of auxiliary non-green sources, and much more. The functionality 'apps' come free.

A BMV or Smartshunt would also be a great addition, and complement everything.

And I say all this without knowing your batt type?, offgrid?, want to export power? Or loads? It doesn't really matter either way, just considerations that need dealing with.

And syncing charge sources once you're there will fade in importance. To almost insignificance..

Please don't waste your money on new mppt's. There's far better ways to spend it, even if it's burning a hole in your pocket.. :)




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blue-sails avatar image
blue-sails answered ·

Hi John C.,

I appreciate the suggestion, and I will look into using a GX box alongside the charge controllers.

Kind regards,

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Related Resources

Venus GX manual

Venus GX product page

VE.Direct protocol FAQ

What is VE.Bus?

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