Batteries that support "islanding" during power cuts

Qyburn

Hi,
I believe Tesla batteries can provide backup power during a power cut. I'm not sure if that also means it would keep the solar inverter running as well. Do any other battery brands give this backup function?

Thanks.

Bianchiintenso

Sunsynk batteries/hybrid inverters provide this feature, I’m sure there will be a quite a few others as well

Mikeyboy01443

My solax inverter/battery has an EPS output so i can change over in the event of power failure 

Heedtheadvice

Unless you are considering  ' batteries ' as a whole system then it is usually the inverter part that provides that functionality.

LUX also provide that in addition to the above I.e. as a UPS

You need to also consider how you will operate it ( automatic switch over of circuits or manual or plug in when required) and therefore if you need an electrician to do that installation, plus what power/duration you wish to draw from the UPS  facility.

With a separate inverters: Usually the solar Inverter requires an AC feed from the grid to keep working for safety reasons much  in the same way as an AC battery inverter. The UPS/EPS does not - must not!- feed back into to the grid.

With a hybrid inverter ( one that performs inverter functions for both solar and the batteries) even though the grid connection will be disabled when the grid fails and you then want the backup feature it is possible that the solar DC generation can then be used by the inverter it's battery charge mode to good effect.

All features depend upon the individual inverter functionality!

EPS = EMERGENCY POWER SUPPLY (Possibly switched when required)

UPS= UNINTERRUPTIBLE POWER SUPPLY (Available at all times)

BossBob

I’ve had freezers/fridges/fish tank, power to the kitchen for kettle, and networking for the house put on a separate circuit as UPS, which runs off the battery in the event of a power cut, all happening automatically via an extra box by the meter which cuts off the house from the grid. When power is restored it all goes back to normal.

[Deleted User]

Qyburn said:

Hi,
I believe Tesla batteries can provide backup power during a power cut. I'm not sure if that also means it would keep the solar inverter running as well. Do any other battery brands give this backup function?

Thanks.

The Tesla Powerwall 2 and Gateway provide islanding. The panels continue to output solar provided there is headroom in the battery and/or a power demand. For example, my Powerwall 2 is currently at 100% SOC and my house demand is 200W. The panels are outputting 4kW so clearly they cannot continue to output at that rate if there was a power cut.

I should add that the Gateway also monitors the Grid input. In the event of high/low voltage/frequency, the Gateway will disconnect the prooerty from the Grid. It will then monitor the situation for 5 minutes before attempting to reconnect to the Grid supply.

Qyburn

Thanks. Ideally I would have backup power available to the whole house, and just avoid doing anything stupid like using the electric shower or cooker/kettle. Our essential loads are scattered around the house and outbuildings so can't really be separated.  Off the top of my head these would be the freezer, water pump, electric fence charger. Maybe incubator and/or heat lamp if it was Spring rather than Winter. Nice to have would be the heating, Internet, lights.

The alternative is something like 4kVA generator, but that's inefficient to run for a long time to handle intermittent and generally light loads. Freezer is a case in point, it has a start load of around 1500W but only take 45W or so while running. And needs to run around 8 to 10 hours a day.

One disappointment already is I'm told the Tesla battery can't be topped up by a generator.

Qyburn

But on a more positive note although Tesla is the only battery from this particular installer which supports islanding, there are others which I can look for elsewhere.

DougMLancs

Givenergy are soon to be releasing their all-in-one as an alternative to the powerwall which will do whole house backup too.

scubajoe

Solaredge have recently introduced their new Home Hub Inverter that can be used with their new backup interface.

propnut

You could always build your own off grid as I have done. I have a full PV system with 13.2KW of storage and can put an EPS on there but I built this before all of that and just kept it. I have 12 x 12v 110AH Leisure batteries configured as 6 x 24 in parallel giving around 6KW storage. These are then connected to a 4KW 24v Inverter (8KW peak). It is a completely off grid so I can just run an extension from it to run whatever I need to during a power failure. Teh batteries are charged off the main PV system using 2 x 24V heavy duty chargers. I use this to mow the lawn, vacuum the cars, run my garage tools etc as well as a full failure backup system. 

There are 2 x Y&H 600W grid tied inverters there but I don't use them anymore. They are redundant due to the main PV system.