MPPT selection

DIY
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@havoc

Regardless of this…

If your panels don’t break the two hard rules for Victron mppts, you can connect them how you want to.

Rule 1 - input voltage must remain under the mppt VOC max. (This includes overshoot like cloud edge effect.)

Rule 2 - ISC input current limit for the mppt must not be broken.

(All information is in the tech specs)

{Using NOCT or STC is an often argued choice. I usually play it safe as there are some circumstances where panels can over perform.}

How many mppts you add will depend on if your battery can take the amps or not.

Correct. The online mppt calculator will agree. The next size up will be 150\ possibly 60A. Or maybe

This is also sound advice. As you can add more mppts and with a GX then set a charge amps limit using the GX to co ordinate them all.

This is good advice as well.

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  1. But what effect gives me use of two MPPTs connected to cooperate versus two MPPTs not connected? Limit charge current or something else?
  2. Are these Victron MPPTs able “synchronize” charging using built in Bluetooth or GX controller is only option.
33

Havoc, for small installs you can use ve.smart networking, which is bluetooth based. No GX required, and you shouldn’t mix bluetooth networking and a wired GX, one or the other.
The GX provides additional benefits like VRM, DVCC for system control, managed batteries etc, how relevant this is depends on your requirements.
Basic BT networking does allow them to share sensor information if you are using a shunt, for example, and to synchronise, but is limited compared to a GX.
I would encourage you to do the free training, it helps answer these fundamental questions.

34

The response of @pwfarnell on the link below.
And considering that the MPPT will try to find the optimum (maximum) power point, almost always will settle on the unshaded one, so the option number 2 from pwfarnell explanation.
In other words, the stronger string delivers, the weaker is ignored, as @Ludo said.

https://communityarchive.victronenergy.com/questions/138628/2-strings-in-parallel-with-diferent-shading.html

36

Do they need to synchronise if they are facing different ways. Surely that is when you don’t want that? You would want the best or most power out of each one as it can and not waste anything.

For mppts voltage (besides algorithm) is how they determine what they should be doing and when in stand alone. I have see it work quite well like that.
If both need to produce in bulk they both do. For top end charging & smaller loads the “stronger” as some have referred to will produce. At this point it is not necessary for them to be both working.

In short if your battery doesn’t need charging and loads are being covered, synchronisation is not necessary.
If you are really wanting to be serious then a GX.

You can smart network but ideally then a shunt would be added.

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@alexpescaru
A bit offtopic, so brief. Peter didn’t say anything like " the weaker is ignored". He knows better, and was acknowledging the effect of poorer performing strings on the weighted average power used to determine the optimum mpp.
If you really want to discuss this constructively, start a fresh thread and call me. Happy to oblige.

1 Like
38

Got answer from colleague, who has practical experience. Both panels will work with same voltage, so they will work according voltage of less illuminated panel. As voltage dependance from illumination is more or less logarithmic, in real conditions panels oriented in different directions and connected in parallel will be quite efficient until one of panels is not totally blinded (by covering with non transparent material).
What do you think?