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MPPT 250 / 100 - Tr Question

I'm running a two-week test to prove compatibility of a module level rapid shutdown system with DC/DC converter at the recommendation of the manufacturer. Circuit = PV -- DC/DC -- MPPT -- LFP Battery -- Loadbank (as needed to keep room in the battery). PV is 10X 235W panels. DC/DC is 500kW (I know those don't match in real life). MPPT is Victron 250-100 which is built into a 60 KVA energy storage system which is serving as the load in this test. I don't care about efficiently as we will be dumping the power. My Victron related question is: Will the Victron MPPT fault with the third party DC/DC between the PV and MPPT? Basically, the DC/DC converter will act like a DC power supply. We will set the output voltage and it will supply the MPPT at varying amps but fixed voltage depending on the PV output. The DC/DC converter does the MPPT. The test needs this specific DC/DC as this is what we are looking to prove the rooftop module level rapid shutdown. As such, the Victron MPPT will not be able to move input voltage like it normally would. Problem or no? I realize I'm doing something with the MPPT that it was not strictly designed to do but am hoping it will work as it is all equipment we have on hand. Collective wisdom appreciated.

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JohnC answered ·

Hi @Sten Levin

There's probably quite a few people out there who feed an mppt with a DC/DC converter. Should be ok providing you don't exceed the voltage and input current limits of the mppt. But you must have at least a 5V difference between the mppt input and battery V, or the mppt won't start up.

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Alexandra avatar image Alexandra ♦ commented ·

And it needs to be able to handle a short circuit. The mppt can short its input terminals if it needs to protect the battery. (And you are not exceeding the short circuit ability of the mppt.) Or the mppt will kill itself.

Couple of things though, the mppts are not compatible with optimisers or similar devices before them on the pv side. So it is not a recommended/supported setup. (Partly because of tracking among others.)

The 250/100s have a remote on off port, this can be connected to an emergency switch to shutdown charging.

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