Any AC coupled system experience or advice.

J

Jon

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Aug 20, 2017
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Hi
Because of the layout of our house roof and shading we have recently installed a microinverter PV system, 22 of 275Wpanels with 235W Enphasemicros.
We're happy with the way the system is performing and have load shifted as much as practical with simple timers.
This is an average day for us

image_btcjgu.jpg

Above the lineis produced power, light blue is produced and used, dark blue is produced and exported.
Below the line is used power, light orange is produced andused, dark Orange is imported and used.

image_ilcvev.jpg


We're running Heat Pump Hot Water andPool pump during the day only, computers, stereo etcthe hours we're home and awake and have put most of our24hour stuff like TV, Blue ray, cordlesss phone, WIFI etc in on area that we've run off a 1500W24v UPS as a test (not running on this day) that I'm going to build the firstbattery packs for. (7S100P)
When it's settled I'll run the fridge as well (that's most of the lumps on night time power usage, a couple are the blower on sewage treatment system that runs all day and for 15 minute blocks every 3 hours overnight)

Slowly collecting and testing cells.

Stage2 will beto build another 7 of 100p packs and run the whole a whole of house system which brings me to my question.

All the systems im seeing are DC coupled with hybrid inverters, is anyone running an AC coupled system or have any advice on one?
Thanks
Jon
 
You need them to be DC coupled to work with battery doesnt you? :) Or am I missing something?
 
The easiest way is DC coupled with a hybrid inverter.
If you don't have a hybrid inverter you can run a add on inverter charger, most are DC coupled, I've seen a few advertised that are are AC coupled.
Enphase batteries are AC coupled for example.
The only additional piece of hardware is the AC battery charger I think.
 
One option might be to use a grid tied inverter with a limiter, that should allow you to run a inverter off a battery bank with a AC charger that is timed to only charge when the solar is producing enough power and / or when the batteries needs a charge up.

I've been thinking of doing just that as I already have a 4kW SolarEdge inverter with 16 x 245W solar panels each with their own micro-inverter on the back of the solar panels. The nominal voltage on the solar string is 350vDC so obviously outside of what I would want to work on myself...


While you _can_ get a battery solution integrated with the SolarEdge inverters it's way too expensive unless you go out and buy a Tesla PowerWall 2 and even then you have to invest another 1000+ to get the right bits so obviously that's out of the question.

I am thinking about getting a inverter with a limiter configured to use all of my solar power onsite via a battery bank and a AC coupled charger on timers / controls to only charge when there's solar power to back this up or when the bank is empty. I am looking at this one now: https://midsummerwholesale.co.uk/buy/sofar-storage/sofar-me3000sp.html

Here in the UK we can still get Economy 7 plans (https://www.uswitch.com/gas-electricity/guides/economy-7/) thatg basically gives you cheaper electricity rates at night for stuff like electric heating, I was thinking of using that to charge the battery bank up over night...

Having a Ac tied system also gives you independent systems which can be a bonus I think as not everything is running through one inverter and adding bits to it or upgrading is a lot easier although you may need to search a bit to find exactly what you want that can play well with others...
 
Going down the track of the Sofar ME 3000SP.
Going through discussions with Aus agent at the moment around not wanting to buy a battery etc.
Hopefully Ill have something to share over the next few months.
This and a batrium, and collect a couple more cells, think Im up to about 500 USABLE cells so far.
 
Just an update on this as Ive recieved a couple of PM queries.
Sofar products got delisted in Aus due to a failing in anti idlanding protection settings.

Im now working on a Victron - Batrium solution.

Thanks
jon
 
Very cool... I find microinverters very interesting.

With the performance and shading control in the forefront it reminds of me of the marine industry where many people use a dedicated MPPT charge controller per panel. The Genasun controllers are generally very popular for that application as each panel is now independent and has better tolerance to shading.

So if I understand this correctly OP, is the problem that this system is more of a grid tie type setup where you are exporting AC, and instead of doing that you want to capture your over-production into batteries?
 
Jon said:
Just an update on this as Ive recieved a couple of PM queries.
Sofar products got delisted in Aus due to a failing in anti idlanding protection settings.

Im now working on a Victron - Batrium solution.

Thanks
jon
Click to expand...

Dang, where did you see that? I guess this will be EU-wide? But none-the-less I don't want to have a dead linesman on my conscience so they need to fix that!

I haven't bought mine yet...
 
You could just install a contractor that is powered by the grid only. When the grid goes down, the contactor will turn off the switch so there'd be no back-feeding into the grid.

Daromer has several videos showing how to wire up a single contactor, or multiple contactors to autoswitch sources.
 
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