question

blue-sails avatar image

Can I use a Multiplus the same way that a Tesla Powerwall 2 works?

A Powerwall can be connected to existing grid tie inverter regardless of the PV array size or the inverter size (no 1.0 factor rule).

A Powerwall can be connected to a single phase of a three phase system.

If the grid fails, the existing PV array continues to provide the battery with energy.

Can a Multiplus meet all of the above criteria for one installation?

ESSAC PV Couplinggrid3 phasemultiplus-ii gx
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2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Blue sails

Both Victron MultiPlus and Tesla Powerwall can use any size, existing or new, AC PV array on the GRID side.

The Tesla powerwall DOES have a PV array factor sizing limitation if you want the PV to continue to provide power to loads and charge the battery during an outage - documented here on Tesla site.

Victron does as well, as do ALL battery inverters (as far as I know). This is a fundamental limitation of the design.

Victron does not have a limit on DC solar with our MPPTs though, so for very large no-grid PV solar systems, that is the way to go.

3 Phase

As far as I know, Powerwall does NOT provide backup power to 3 phase circuits, only single phase. Even if you have 3 of them, with one on each circuit, they will not synchronise to 3 phase when the grid is out.

3 x Victron Multiplus DO backup 3 phase circuits, this is important if you have 3 phase loads, or 3 phase AC PV inverters.



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blue-sails avatar image
blue-sails answered ·

Guy,

I very much appreciate your help.

I was unaware of the sizing rule for Powerwalls (“.... at least one Powerwall is required for each 7.6 kW AC of solar included in the backup circuit.“).

I thought of adding a Victron Multiplus II GX to one of the phases of an existing 3-Ph, 220V, 50Hz, FIT, SE15K, 16.4-K array, grid tie installation with two grid meters (consumption & production). The existing grid is robust with few blackout periods.

The purpose of this new installation was to use the existing PV installation when the grid went down and to obtain battery backup particularly for night use. Peace of mind.

The existing SE15K does have the ability to connect to StorEdge and use a high 400V battery such as LG. However, I wanted to instead use NiFe 48V batteries mainly for their reliability, longevity, and cost.

In order not to provide additional PV power, I decided to use a less efficient method than DC coupling to the existing system.

However, one of my goals is apparently not feasible due to the sizing rule. I had apparently thought naively that since I would be applying the Multiplus to a single phase that I could divide the array size by three.

Again, I appreciate your comment.

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As far as I know a 3-phase gird tie PV inverter needs all 3 phases to operate. So with only one Multi/Powerwall the PV inverter will shut down in case of a grid blackout.