Two independent inverters on same DC bus

Inverters Axpert-Mecer-RTC-King
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What would happen if you were to put two independent Axpert inverters on the same DC bus?

Here’s the scenario:
We have an Axpert 5kW inverter at the office (Kodak OG 5.48) that has 3.5kW of solar panels and is connected to 4 x US2000 batteries (soon to be 7 x US2000). There’s no communication between the inverter and batteries (nor between the batteries), and the inverter is set to SUB (solar-utility-battery) mode, so it only dips into the battery when there’s loadshedding and insufficient solar.

The 5kW currently available is proving to be a bit limiting, so we’re contemplating adding another 5kW (because it is cheaper than buying a 10kW inverter). The problem is these inverters cannot be paralleled, so the idea is to just connect them both to the same DC bus, and split the loads more-or-less equally on their outputs.

Is this a non-starter? If not, are there any special considerations if we were to go this route?

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It should work just fine. Of course, if the battery voltage drops out (and you have a low battery disconnect voltage), one of them will let go before the other. If both are charging (via solar, grid), one will stop before the other. And all those things. But in general it should perfectly fine.

There is somewhat of a question of what happens if the BMS disconnects (assuming it is a Lithium battery). Then you have two inverters potentially pushing DC into each other, and the result of that is of course undefined.

At least with Victron inverters, it is actually fairly common place to have two inverters on the same bus. In some boats, people are fond of having a second smaller inverter for the “night time” loads.

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