Matching SPD to MPPT

This is a question I have been discussing with colleagues (@JacoDeJongh @randomwalsh) and there seems no clear answer.

I have noted that most of the SPDs on the market are either Uc 600VDC, 1000VDC or 1500VDC. But our MPPTs are 150V MAX, 250V MAX or 450V MAX.

It seems thus, that a 600VDC SPD might protect something in the system against over voltage but that would not include the MPPT which would be exposed to over-voltage before the SPD had begun protecting (Uc).

Should we not be getting 145V, 245V and 445V SPDs manufactured which match the Victron products to properly protect MPPTs against over voltage? I have spoken to a manufacturer willing to do this but MOQ is 250 units which is a bit much for me to “test” the concept with.

Any insight would be valued.

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I suppose the question would be what the purpose is of the SPDs. Their purpose may not be to protect the rest of the installation, it might be to limit the energy levels and keep it out of whatever comes next (the grid?).

I don’t know, I’m just working from the established knowledge that the breakers in your DB doesn’t care about the appliance you have plugged in… it just protects the static part of the installation. The SPDs similarly probably don’t care about your MPPT… :slight_smile:

If you are willing to shop in China, I am sure they will offer a wider range of STD’s

I have these, one on my 150/35 (with VOC 120) and the other on my RS450 (with VOC 290V). The first one I bough from Sonop, me thinks, and the second my installer provided.


I am aware that there are these other options available eg. 220V Citel and the like.

To @plonkster’s point, usually the SPD is not intended to protect the MPPT. You will note in my original post, I said indicated the same. (“might protect something … but not … the MPPT”).

My question is not whether there are 200V or 300V etc SPDs on the market. The question is, if we were to develop a product like a 245V for use with 250V Victron MPPTs, would that be helpful? It seems to be this would help protect the MPPT from edge of cloud and the like as well as surges.

The challenge is we cannot test this without such SPDs being in existence. I will do some testing with 220V on a system that usually starts the morning in the 225V range and see what happens.

aah ok! I see where you are headed. Sorry, bit slow :slight_smile:

I’m not sure exactly what kind of tech is used in these SPDs. My first thought was to use a MOV, but it seems they have quite a bit of space between their operating voltage and their clamping voltage. Then there is the TVS option, don’t know that one all that well either.

In the back of my mind, I’ve always thought this would likely be a MOSFET with some heat dissipating material (to handle the ± 10A from an operating PV string, squared, times whatever its internal resistance is), and a crowbar circuit that activates just short of 150V/250V. But I’m not an electronic engineer.

I only saw this now - it made me chuckle :laughing: