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chrigu asked

Multiplus 24/800 DC-coupled ESS

Hey

I got a used Multiplus 24/800 with a couple of AGM batteries for a good price.

I want to use that as an energy storage system. I also have two 350W solar panels, at the moment hooked up to a 600W micro inverter. I plan on changing this to a Victron MPPT charger, to charge the batteries with it directly.

Now the, maybe, tricky part. Can i set up the Multiplus in a way that it will use the battery optimisation mechanism, but feeds 100W of power continuous (if batteries are full enough) into the grid?

Reason is, i dont have an energy meter than counts backwards or counts the export seperately. So any power fed back is a gift to the power company.
So i would like to cover my base usage of around 200W as much as possible troughout the full 24hrs of a day.

I would like to not install an extra power meter or a GX device. There will also be no loads hooked up to the AC out of the multiplus.

Is that possible?

MultiPlus Quattro Inverter ChargerESS
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1 Answer
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chrigu answered ·

To answer myself on this, if anyone is curious, i ended up using the microinverter that was previously used directly on the panels (Hoymiles HM600).

Using AhoyDTU and homeassistant, im currently regulating the inverters power depending on the battery voltage. Not the most elegant solution, but so far works since a few months.

From two 350W panels im able to (on average over 30 days) feed back 86W constantly, 24hrs a day. Since output power is regulated by battery voltage, the actual power will vary up to 150W (arbitrary limit i set, but seems to work) and down to 30W (lower limit of the inverter).

I chose a 36V battery setup since i had three of the same batteries at hand. 170Ah nominal, but who knows how much they have left after five years of service as UPS batteries. 38V means 75W output, 42V means 150W output. Below 38V and inbetween is interpolated linearly.

The inverter is fed by a Relay, that in turn is controlled by the load output of the MPPT 100/20. I tried to feed the inverter directly from the load output, and although on paper 600W at 42V is only about 14A, the load output did not like it and stayed disabled. My guess is that the inrush current of the inverters DC side tripped the overload protection on the load output. Should the battery voltage drop too low, the MPPT will cut the Inverter. BatteryLife algorithm is enabled, but so far it never needed to cut out.

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