However , I loathe to spend extra money on a new charger whilst there is a perfectly good charger built into the Growatt which I am not allowed to connect to the grid.
Surely just connecting a load to the grid is perfectly fine?
As far as I can tell this unit does not even have the capability to back feed the grid in the sense a grid-tied inverter would. It has an AC input which can be a grid power supply or other suitable AC supply such as an inverter generator. This AC input connection does not back feed the grid. It presents as a load only.
It's the AC output side which will be up to you to ensure is not connected to the grid.
If it is only supplying a dedicated off-grid distribution board, then you have zero concerns with any back feeding of the grid being possible.
In my case my AIO inverter also supplies my home's circuits but via a transfer switch and it is the transfer switch which ensures the grid supply and the AIO inverter supply are never ever connected. It's a 3-position "break before make" switch.
Like the Growatt, my AIO inverter is an off-grid only unit, with an AC input and an AC output. The difference (apart from capacity/quality, mine is a cheap 48V/4kW Voltronic clone) is mine requires a battery to operate. I think that Growatt model can operate without a battery.
In my case the 230V AC input is normally a grid supply and I have the AIO input connected to a 20A plug which is plugged into a 20A grid supply power outlet. I did this rather than hardwire the grid to the AC input so I can choose to unplug from the grid outlet and instead connect my Yamaha inverter generator into the AIO to charge batteries if needed (e.g. if we have a very long grid outage with poor solar conditions).
I constructed a separate DB for the off grid Growatt and transferred some of the loads from the grid DB to this one.
Same. My off-grid AIO inverter feeds a small AC distribution panel with a common current protection breaker and two output circuit breakers - one RCBO for the off-grid power outlet (which the pool pump uses) and regular current limiting circuit breaker connected to the 20A power inlet which in turn supplies the home's main panel transfer switch. The main panel already is chock full of RCBOs. The 20A power inlet for the transfer switch and the 20A socket connected to the AIO AC input are the same type of socket so I can connect the generator to the AIO inverter or just directly feed the house if needed. I like the multiple redundancy.
The 48v 100Ah battery bank is thus only charged from PV during the day and if the battery is not optimally charged by the time the sun sets then I run out of power in the early hours of the morning. The problem is that , during the day , I re-direct the PV to heat up the 150lt hot water tank and once on temp it is directed back to charging the battery.
Yeah hot water sucks a lot of energy. It's a really good use of excess solar PV but does need a bit of load management when supply is limited and you want to prioritise supply to other loads.
Another option is a heat pump HW system which will draw way less power to heat water than a regular resistive element tank. If ambient air temp is no super sub freezing cold then you can expect your HW energy draw to be no more than 1/3rd to 1/4 of what a resistive element HW tank would use. Whether it's a suitable option will depend on your climate (and budget - as they are somewhat more expensive).
Our hot water will remain grid connected and is currently on a dedicated off-peak circuit controlled by the energy distributor but I am considering changing that to a regular anytime supply circuit and using a smart diverter so my excess grid-tied solar PV can power it instead. This would not be much of a money saver as the off-grid tariff is pretty good but it would reduce carbon emissions (our night time grid is coal/carbon intensive) and importantly it will help to lower our daytime grid voltages which are high enough to regularly cause my grid-tied inverter to throttle output and occasionally shut down if it exceeds 258V for too long. Adding load really helps keep our supply voltages down.
I must admit that this set-up is totally experimental and not optimal as yet
As is mine. It was a lockdown project. I have a thread where I describe it and what I've since done:
Greetings from down under. I live in a home near the small town of Bellingen, in northern NSW, Australia. Glorious country: That's our home at left centre, and obscured by the tree and slightly off the left of the image is a secondary dwelling where my Mum lives. 12 acres, behind our home (to...
diysolarforum.com
At this stage lighting and TV / fibre router only but want to add fridge and freezer soon.
I've only moved my pool pump to off-grid supply (and a few small sundry items like pool robot cleaner, a power tool charger), the rest of the household I am not as yet going to operate via the off grid. I would except:
- my 48V 18.2kWh battery bank is sealed lead acid (second hand data centre backup units) and so it's actually well suited to doing very little but being there when needed. I would need to add some LiFePO4 to that for regular cycling duties.
- because the main panel backup circuits also supply two other buildings (a second dwelling and my mancave) via sub-circuit boards there are a couple of high power circuits (oven/stove in the dwelling and a large aircon unit) in those other buildings which are too much for my AIO to manage. Being sub-boards I can't bypass individual circuits so easily.
