Gday all
I have lived where I am atm since 1997 and have not been connected to grid the entire time,had no idea what power was worth or when it was off.Not completely smooth sailing but have been very happy with my system.
Lead acid battteries originally but now 24v 900amp lithium cells wired by myself.
We have purchased a property in a different location for when we eventually retire and it is grid connected with no solar at all.
My plan if possible and leagal……?
*Get heap of  used panels,still can’t fathom how cheap they are .My first 3 64w panels cost me $750 each😲

*set up 48v battery bank,not sure if I’ll make my own or go server rack or similar

*this is where I have no idea,I’d like to have my system run the house but have grid power as either a straight swap(automatically)or as a backup battery charger.From what I’ve read the Victron multi plus units can do this job for me but is it leagal and safe.Can it be set so NO power can get back to the grid.I have no want or need to export to grid.
My current system has a diesel engine that is direct coupled to a special 24v alternator which starts automatically at 25% soc and off at 30%.works fantastic and I’d simply like similar set up at new place but just use grid to do same thing if possible?

Any thoughts or tips greatly appreciated
Cheers Bush

Hello Bush. I don't know about legal stuff but I do know that if a new system is installed they usually want to have new panels and inverters etc.
By doing it yourself with second hand panels you would save money but you will need a licenced electrician to wire the inverter into the switchboard.
A Hybrid inverter can do what you want, they can run off batteries to run the house and also feed back into the grid.
Or you could have a manual change over switch fitted by an electrician to the switchboard and use any gear you want. It would just mean that when you wanted to run off the grid that you change the switch over manually and then nothing can go back to the grid at all. A double pole changeover switch is what is needed to do that.
I am fully off grid and have been now for over 40 years so don't bother with grid stuff.
But I do know that it is legal to have a changeover switch fitted to the switchboard to use either a generator or off grid system to power the house.
There are many hybrid inverters around that will do what you want.
From what i have seen of Victron gear is it not easy to repair if things go wrong.
Good luck
pete

Gday Pete
Thanks for the reply
Yes have thought about basic manual change over but it would very much limit the potential of the system.
It would be far more user friendly and get the most out of the system if I could get the system to change over automatically on battery state of charge.Battery drops to  25% system flicks to grid,battery rises to 30% clicks back to battery.
I don’t want to feed power to grid at all,so happy to have change over switch but hopefully be able to automate.
Cheers Bush

Gday Bush,

I agree with Pete, I also had a change over switch on the house when we bought the place, it was grid and generator With hi and low power generator inputs 32A and 15A, we used the generator one quite abit when we had grid power that often blacked out, since removing the grid connection and cutting the power pole, the change over switch on some occasions gets used, I wanted to replace the main switch before the inverter, so just plugged the shed power into the gen input on the changeover switch, so no outage of any sort.

I'm sure there are many hybrid inverters that will switch back to grid with a low battery, most of the older design's used battery voltage parameters to trigger, will have to check which inverters use SOC to determine when to switch back to grid and charge....and you would likely need a battery with communication cable to the inverter, so lily a rack mount battery would do this, there should be some types of BMS that would also do this if building your on battery setup.  

My other dislike is the ability for a lightning strike to come along the Grid connection and screw the whole thing up.........YES had it happen.



Edit:
It might be better to have a decent quality standalone inverter, away from the grid and a battery charger that is connected to grid and only triggered to charge the battery at your desired set point.
Edited 2025-09-16 10:32 by Revlac

Gday Aaron,
Thanks for the suggestions,yes I have thought about a separate battery charger and it could be a good possibility
Cheers Bush

It seems these 48v battery chargers are still expensive and low amperage, there are forklift chargers and I have some old Telecom battery chargers 50A don't see them for sale much anymore.

However there is plenty of "48V Solar Hybrid Inverter Charger Off Grid" most of them are 80A charging or more and also a solar charger built in, those that don't feed to grid might be a cheap option if they cater for charging at user defined SOC, perhaps in a program or they might have a phone APP don't know, if you use your own inverter and one of these as a charger from grid there would be no interruption to your main inverter when charging switches on and off.
I have an old PIP4048HS and it gas a grid or gen input for pass through or battery charging but have never used that for charging, but I think these new types would work almost the same way.
See what you find anyway.

Gday Aaron
I thanks again for your ideas and yes I think inverter charger may well be the way to go.
Cheers bush

Hi Bush, I don't know where you are, but I have a 5kw 48 volt inverter/charger  sitting in my shed if you want it.
No charge, but it is really heavy, something like 30kg or more.
I live in Tasmania so depending on where you are freight may be a killer.
Unless you know someone who could pick it up for you.
It is a verson of the Powerstar W7 inverter chargers. It has two EI transformers in it so weighs heaps.
I was given it as it needed repairs, but it was only a broken weld on the battery terminal that I needed to fix.
I use 24 volts so don't have a need for it.
They are a fairly power hungry inverter but as a charger they are fine.
I had a 24 volt version of the W7 and it dumped near 100 watts in idle power.
cheers
Pete

Hi Bush yes mate an idea where this new property is a good idea for all of us trying to help  

A few months ago I priced up 2 volt 1000AH Ceil traction batteries and 12 of them worked out to 5K where 24 of them were double the price.

Like Pete I'm also on 24 volts mainly as when I bought the farm in '03 48 volt systems were unheard of.

I got a couple of free 24 volt traction batteries in 2012 and they are still going today and I do think I will get another decade out of them.

Traction batteries are designed to give 100's of amps out for a 8 hour period and when there is solar input they do take on a new life and with the right charging system they will be on float around lunchtime each day.

Now solar panels on FB market place does have some bargains and I picked up 6.3Kw for $1,800 and I have seen the same go for $1000 too.

Now mate if you want to follow my inverter build I do have a spare board that you could have so you can make your own inverter. The parts list does addup to a bit but in all it is still way cheaper than to buy the same inverter type for the money spent by a long shot. The best part is as you built it if something does go wrong you are in a place to fix it and try your best NOT to come member of the blown Fet club  

Regards Bryan
Edited 2025-09-23 17:49 by Bryan1

Welcome to the forum Bush. Just to give you some idea of what can be done, I am like Bryan and a fan of forklift batteries.

I bought my first one, a 48V 980aH for $500 (scrap value)

I installed 19kW of secondhand panels and built 4 MPPT charge controllers  ...  see Poida's thread

I built a 15kW Warpverter , though that is a fairly major undertaking  ...  but there are a lot more options nowadays for hybrid inverters.

We have an all electric home except for gas hot water, two ovens and a pool etc  ...  all power hungry devices.

I also added another 10kW Goodwe inverter ac-coupled to the Warpverter (cost me $200 and only a year or two old).

Because we regularly have far more power than we can really use, I have connected up two underfloor heaters that were here when we bought the place  ...  but would never have dared hooking up.

It's not unusual for us to have over 10kW of heating turned on for 6-8 hours a day if the sun is cooperating.

Now I definitely have to manage the system and keep an eye on charge levels and all that sort of stuff  ...  but the rest of the family lives exactly like we were on the grid  ...  they simply have no clue or understanding or interest even in what's going on in the background.

Our last 5 quarterly bills have come in at less than $50 all up since we've been off grid. We can still use the grid for backup or charging if the weather is not good  ...  but we do not feed into it and have an auto changeover switch that keeps us totally seperated unless the inverter fails or we switch it off  ...  then we seamlessly drop back to grid power.

I have since bought some more forklift batteries to add to the mix, so we can use more heating early mornings and in the evenings.

We used to average 20-22kWh/day  ...  but now are up around 40kWh coz it's free and we can find uses for it.

So far the Warpverter has generated 17MWh since March last year  ...  and the four MPPTs have supplied just over 19MWh. The ac-coupled Goodwe is not included in those numbers.

Let us know where you are located and what sort of outcome you really want to achieve.

Gday Gents
Thank you all for your very generous offers,I will give it all some more thought as to which way to go.
I currently live in nth west Vic but moving to Nagambie post retirement.
As mentioned my current property has never been grid connected so never needed to have any knowledge of grid connected systems but new place is on grid but no solar at all at t(e moment.No interest in selling to grid so definitely looking at second hand solar panels and wiring all but inverter to house myself.
Have had FLA batteries for over twenty years but now on lifepo4 cells again wired with bms myself.Hadnt thought about used forklift batteries but will definitely give that some consideration as well.
Cheers bush