Australia - Best approach to add batteries to existing 5kw grid tied system?

[jjslody]

Hi All,

Fantastic resource here - lots of info to be absorbed!

I live in Victoria and have a 5kw grid tied Goodwe inverter with approx 5.5kw of panels. I'd like to add 10-15kw of batteries to further reduce my consumption from the grid. I'd also like to have black out protection in the (very rare) scenario that the grid goes out.

I also want to make sure everything is 'above board' as I'm still going to be grid connected.

From my research, it seems I have the following options:

Batteries:
In Australia we have a CEC list of 'approved batteries'. It seems to me, that this 'approved list' is only showing which batteries can receive a state government rebate if they are installed.

It seems I can install any LifePo4 battery, to a grid tied system - it doesn't need to be on the CEC list. It's hard getting any good advice from installers, they all tend to default to Tesla powerwalls.

Replace current inverter with Hybrid inverter:
Seems the easiest option is to simply replace my current inverter with a hybrid inverter. I would need to make sure it would be compatible with the batteries I want to choose.
I would have backup during a grid failure (although seems most hybrids max out at 3kw draw from batteries) and also allow the option of panels still charging batteries even if there is a grid failure. This system will also be more efficient, as there is no DC > AC > DC conversion happening.

Keep current inverter and install Victron Multiplus 2
Another option is to AC Couple a Victron Multiplus 2 to my current system. This won't be as efficient when charging batteries due to going from DC > AC > DC.

It does allow me the option of adding additional solar panels down the line by purchasing a MPPT to also charge the batteries

One thing I'm not 100% sure is what happens during a grid failure. I know batteries will be used (up to 5kw draw), but I'm unclear if the panels will still be able to charge the batteries, as I assume the Goodwe would switch off and thus no power


Looking forward to any suggestions, especially from fellow Aussies who have gone down this route!

 

[ncsolarelectric]

If you want the battery inverter to backfeed to the grid as well, you need a hybrid inverter but you could also switch everything to Enphase IQ8 Microinverters, and Encharge batteries. That would be a top-of-the-line system.

 

[wattmatters]

Looking forward to any suggestions, especially from fellow Aussies

Adding new inverter (and solar PV) capacity for a grid tied system in Australia will require DNSP approval and work done/signed off by a qualified electrician.

Being in Victoria it could be any one of five DNSPs, and they may have different approval limits/process so you'll need to know their requirements to begin with.

Personally I don't think grid-tied anything in Australia is really within the realm of DIY.

The simplest solution is to get a solar battery installer to quote and install a Tesla Powerwall 2 + Gateway. That will do everything you ask of it. It will also relieve of $15-16k of your money, although there is a (up to) $3.5k battery subsidy scheme in Victoria you can use to reduce that pain a little (unless you have already used the Vic state solar subsidy).

Solar battery rebate | Solar Victoria

Eligible households can claim a discount on the cost of installing a solar battery system.

www.solar.vic.gov.au

The reason PW2 is the default installer solution is because installers have recognised it as the most trouble free, consistent solution. It just works. Just look at the hassles many are dealing with the LG and similar battery recalls at the moment.

If the PW2 is a bit beyond your budget you might consider an Alpha ESS system:

AlphaESS

www.alpha-ess.com

 

[jjslody]

Yes - this would go through all the formal approval processes and work done by qualified electrician.

I can't justify spending $15K for a PW2, so what I am hoping to achieve (in the spirit of DIY) is to figure out a system that will work for my setup.

The next challenge would then be finding a qualified electrician who has both the license for solar + battery installs (this is very well where I may fail).

There is too much risk DIYing for a grid tied system.

 

[wattmatters]

I can't justify spending $15K for a PW2

Yeah, that I can understand. Grid tied battery is a PITA and expensive. I have an 11 kW grid tied PV system but doubt I'll go with a grid tied battery.

I have a DIY off-grid solar / battery system for outage backup (via transfer switch) and it also powers a few loads via a dedicated off-grid distribution panel (pool pump and office).

I'm planning to expand the loads managed via the off-grid but will leave the high power draw stuff on grid supply only (ovens, large aircon, induction stove, hot water).

Essentially move to 24x7 operation via the backup system. I have some server rack batteries coming to supplement my backup banks and I'll need to upgrade the off-grid inverter and have my main panel upgraded/reorganised as well. I could make the current panel work as is but I'd rather it was a tidied up / reorganised.