Do three-phase households require three-phase batteries?

Apr. 28, 2024

Today's conversation highlights that no matter how hard you try to push, a boat with a hole just won't sail.Likewise, a mono-phase battery is incapable of powering appliances requiring three phases.This means, regardless of operating a high-capacity high volume kitchen extractor fans, mid-sized CNC machines, or compact commercial conveyors, typical battery backup platforms aren't able to support a simultaneous 3-phase load.Naturally, there exist a few deviations to this common situation, which we'll delve into later...



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What Exactly Is Three Phase?

You might have heard people discussing electricity in phases. They're referring to the number of active supplies your property receives from the grid, be it 1, 2, or 3. Although most of the appliances in your household operate on a single phase, there might be some significant ones, such as your heating, ventilation, and air conditioning system or electric vehicle chargers, which utilize all three supplies. These are your 3 phase appliances.


One of the initial points a skilful solar dealer may question you about, and to provide clarity, we have put together this convenient guide in our very beneficial FAQ segment.Perhaps we should label it as CAQ, standing for Often Responded Questions, as they are not just unnecessary additions to a webpage. They are legitimate questions from real individuals for which we have crafted insightful responses.


Single Phase Batteries Are Straightforward

Single-phase systems encompass the widest range of models and brands. Actually, high-quality brands like Enphase batteries and Tesla Powerwalls don't even provide three-phase units.


The key advantage of a single-phase, battery-backed system is its high power surge capacity. Regardless of the capacity specified, all of its power is focused on one output. This is critical when attempting to start a motor such as a refrigerator compressor or a rainwater pump.To tell you the truth, most individuals living in a 3-phase home will be quite content only backing up a single "essential" phase during a power outage.


Three Phase Batteries Are Less Prevalent.
Although they were earlier quite rare, as we pointed out recently, a much wider variety is now available.Usually, people don't aspire to back up three-phase appliances. These appliances tend to be large energy consumers that would require a considerable and costly battery capacity.


However, if the layout of your buildings or the location of your switchboard necessitates a three-phase battery system, then rewiring the entire house may not be a feasible option.Most 3-phase battery systems have a limited surge rating because only approximately one-third would be available to power any given single-phase circuit. For instance, a 10kW nameplate will only deliver 4kW for 5 seconds to an unbalanced load.

A Single-Phase Battery Cannot Backup A 3-Phase Solar Inverter
If you have a 3-phase solar inverter and a single-phase Tesla Powerwall, a prolonged grid outage would still pose a problem since the Powerwall, even if you bought three of them, can't establish a synchronous 3-phase supply to restart the solar inverter. This holds true for any single-phase battery that's AC connected to a 3-phase solar system.


When the grid shuts down, you're left with whatever energy is stored in the battery, and it won’t get replenished until the main power is back on.However, if your solar power is generated from a single-phase inverter, the Powerwall will gladly continue supplying power to that solar inverter, as long as the equipment is rated below 5kW or is properly managed by the commissioning electrician.

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SUNESS 3Phase Inverter—HIS10248

A Single-Phase Battery Can Backup All The Single-Phase Loads In A Three Phase House
If you live in a 3-phase house but are willing to forego the use of your 3-phase loads during an outage, an astute electrician can set up an arrangement with a contactor that allows all your wiring to be backed up by a single-phase battery system.
You can think of it as removing the back wheels of your tricycle and positioning them next to the front wheel. You'll need to balance carefully, but it's possible to ride it like a unicycle.


The same principle can be applied to a 3-phase EV charger. It would be possible to charge your EV when the sun is shining, though I would recommend a manual switch-over arrangement for this, as it could easily end up draining the house battery into the car.However, it's simpler to just put all your essential loads on one phase and back up solely that phase.


Do You Really Need A 3-Phase Battery System?
Though the Australian grid is required by law to be 99% dependable, many individuals are exploring battery options for both financial and security reasons.
If you have a 3-phase house, you should seriously contemplate whether you need a 3-phase battery system. Could you place your vital loads on the same phase and comfortably manage outages with only that phase backed up?Your decision will hinge on whether your solar inverter is single or three-phase, the significance of your 3-phase appliances, and the amount of money you're willing to invest.


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