Advice on which Inverter/equipment to purchase for existing grid tied system

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doog asked Oct 10, '23

Advice on which Inverter/equipment to purchase for existing grid tied system

Hi everyone first time post for myself, I have already purchased a 14kw lithium Ion battery and want to install an AC coupled system with my current solar grid tied system.

I am wanting an inverter that will supplement grid power rather than import from the grid and also use the batteries overnight and during bad weather. I have kept track of my usage for the past 12 months and my average draw from the grid daily is 9kw. In the spring and summer I can produce 50kw or more per day and in winter as little as 14kw on a bad day and around 22kw on a sunny day.

I am starting with a14kw battery with a view to adding more if I am happy with the results.

I was thinking the Multiplus II which I think can only be linked via one inverter which would be the 6.6kw panel system.

Any advice would be appreciated as I am still uncertain about what will be needed such as ESS etc.

I am located in Australia 240v Grid single phase

Current System

2 x Sungrow SG5K-d inverters

9500 watt panels.

Smart meter installed

thanks

AC PV Coupling

2 |3000

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Answer 1 · 2023-10-10T11:16:45Z

Hi,

I also live in Aust (WA) you need to look at the "Factor 1" rule. This says that the Solar inverter cant be bigger than the Victron Multiplus if used on Output 1. So before you put cash on the table you need to make 2 decisions.

1. Am I happy to go it alone and only have the grid as backup using a 240v to X volt battery charger.

2. Do I still want to export power to the grid?

You also need to look to ensure youu PV invereters can be used in a Microgrid setup. Without knowing a lot more info about your setup its hard to say exactly what you need and what will work. But Id give a couple of the larger Victron vendors a call or email and talk directly to them about your situation. I have chatted to Solar4RVs they are one of the bigger Victron agents in Aust along with mygenerator and outback marine. SOlar4 RV have been very helpful when I have spoken to them.

Right now in Australia, the only answer here is yes to option 1 if you want to use Victron as the Multiplus 2 units dont comply to AS4777.2 as yet. Its in the wind and due any week now. Depending on which state you live in you can do other things, ie put additional disconnection devices infront of the Multiplus to make it legal. I live in WA and they dont allow this in WA...and here i was thinking we were one country with one set of rules...silly me!

A possible solution for you: (Only an idea as I dont know your full scenario and there are lots of unanswered questions)

In your case if you stayed connected to the grid with one Solar Array, an run say your Home AC of the grid or the electric oven the high power appliances youd likely stay in credit. Then connect a 240v to 48v battery charger with say 20amp output to your battery as a backup for winter. Connect a 5000VA multiplus to a sub board which all your lights and power points are fed by you would likely be ok. Assuming your battery is 16S aka 48v nominal. for (WA prices) 365 dollar a year grid connection fee is a cheap reliable generator(battery charger), for those peace of mind times. I have also assumed your PV inverters are actually 5000va and the array is 6.6kw. So the factor 1 rule applies, but put a lot of effort into making sure your PV inverters are on the list of those that a multiplus can throttle, and are sized correctly. Alternatively over size the Multiplus to a 48/10000 unit if your pv inverter is infact a 5000w or larger. Watts and VA are not the same. 5000va is aprox 4000wats.

you need to take your time come up with a few options ask heaps of questions and make sure everything fits before moving forward. Once done you wont look back. I have jsut done mine, whilst I still have a few teething issues I run an entire house and an EV from a Multiplus 2 and a 30kw battery. with 6.6kw solar north facing. I need about another 4kw of Solar for winter time, but at the mo the battery is 100% mid afternoon ready for the next night. We get down to 40% most nights some time as low as 15%. Family of 4.

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