Adding battery storage to your existing solar array

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jonescg
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Adding battery storage to your existing solar array

Post by jonescg » Mon, 10 Sep 2018, 16:35

Of the 95 people who bought the AVASS battery cells, there's probably a good ten who are wondering whether or not they're bitten off more than they can chew. Chances are, they already have a solar system which is grid connected, and the batteries were an affordable way of capturing some of that energy. But it is a DIY project and there are lots of things to do before the 16 cells sitting in your garage will be working for you.

But it's not too difficult - hang in there! This thread is about adding a 48 volt battery to an existing grid-tied solar array.

Most homes with PV installed are simply exporting to the grid while the sun shines, and you're getting paid 7 to 13 cents for every kWh exported. Any electricity consumption during the day is a dollar not spent, so that's good. The reality is, very few grid-tied solar inverters will have provision for adding a 48 volt battery. So what do you do?

There are two options. A quick and inexpensive yet slightly less efficient one, and a more expensive complicated one which DC couples the battery.

The quick and easy one is to buy an AC coupled, grid-tied battery inverter. There are a few options out there - Goodwe SBP, Selectronic SP Pro, SMA, Victron and Enphase spring to mind, but there are others. Expect to pay between $1100 and $2000 for such an inverter, plus installation.

Most solar homes have something like this:
Grid tied PV house.png
Grid tied PV house.png (12.24 KiB) Viewed 1736 times
Adding a battery isn't practical using the existing inverter, but you can add an AC coupled inverter like this:
AC Coupled home with battery.png
AC Coupled home with battery.png (15.77 KiB) Viewed 1736 times
It measures the AC from the grid and the AC from the solar inverter and decides where to send the energy - if it's sunny and the household loads are low, charge the battery. If the sun has set, the battery provides the energy to run the home via the battery inverter. If the loads exceed what the inverter is capable of, the grid can step in to make up the shortfall. Finally, when the battery is fully discharged, the grid takes over completely until sunrise.

The more expensive and complicated option is to replace your grid-tie inverter with a hybrid inverter with DC coupling. The Goodwe ES series, Victron, SMA and BYD hybrid inverters are all viable options. Expect to pay between $2000 and $3000 for the inverter, plus installation. There may be some roof time too.

Some of these inverters will operate on a specific PV input voltage, meaning the solar panels on the roof might need to be re-configured into a new series-parallel arrangement - MPP Solar have a range of inverters that have a MPPT voltage of 150 V max, so the panels would need to be configured into multiples of 3 in series.
DC Coupled home with battery.png
DC Coupled home with battery.png (15.42 KiB) Viewed 1736 times
But the first thing anyone must do is get their battery build into a nice cabinet close to the inverter(s) and set up with a contactor, current sensor, isolation breaker and fuse. And a good BMS! We have plenty of experience to share details on that front.
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Gobopolice
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Re: Adding battery storage to your existing solar array

Post by Gobopolice » Tue, 11 Sep 2018, 13:24

great to see this thread started, I am 1 of those 95 people and I am a Noob to all of this.
I have 32 of the 220amp hour Brighsun batterys. Going to wire them up as 16S2P 48v.
Bought a nice hydraulic crimper and serious wire cutters, Lugs are on order , any day now to arrive.
I have just collected my Goodwe 5000SBP and have ordered the Zeva BMS with 200amp shunt and LCD screen.
I have started welding together my Battery Dolly yesterday. Putting it on 4 x 200kg rated wheels !

Just waiting on Richard to start setting his system up which is the same as what I have :lol:
As Im not sure how the Goodwe will comunicate to the Zeva BMS, cross that bridge later.

I have an existing solar setup of 22 x Jinko panels 265w in 2 strings of 11 each paralell into 1 mppt input in a Fronius 5kw inverter.

Exciting times :shock:

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Re: Adding battery storage to your existing solar array

Post by Gobopolice » Tue, 04 Dec 2018, 22:25

Had my system live now for just over 2 months.....
Im basically 99% off grid..
Couldnt be happier.

Red equates to bought power.
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smithy2167
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Re: Adding battery storage to your existing solar array

Post by smithy2167 » Wed, 19 Dec 2018, 08:44

Great result.

I'm in a similar situation and I'd be interested in hearing more about what you did.

In particular, how did you go about having the Goodwe installed and connected to the home-made battery pack? I'm thinking that most sparkies would take one look and jump back in their van.
(BTW, what state are you in?)

Also, how does the BMS control the Goodwe?

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Re: Adding battery storage to your existing solar array

Post by iamlsd » Mon, 24 Dec 2018, 10:46

Well done Gobopolice - great to see your success with this. I'm also a complete newbie who purchased 16 of the larger batteries. I have an existing solar system, 3 KW with a Growatt inverter. I have got room to add more solar panels later but my household usage averages 12 kw/h per day. All electric house with solar hot water.

It would be great if you were able to post up any pictures of your setup and I echo smith2167 be great to know any configuring tips / gotchas with the BMS and the inverter.

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Re: Adding battery storage to your existing solar array

Post by jonescg » Tue, 05 Feb 2019, 14:18

Hi All,
Goodwe have improved their website and critically, made their datasheets a little easier to follow:
http://www.goodwe.com/

There are really three choices - GW5048ES, GW5048EM, and GW5048SBP. All three of these have a 3.6 kW version too, but for not much extra you can have room to grow.

All of these are best suited to single phase homes. There's nothing stopping you from fitting them to a three-phase home, but you will only be operating on one of the three phases.
This means any loads on the other two phases will be drawing energy from the grid.

The only three-phase option is a high voltage battery which is out of the question with the AVASS cells.
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Re: Adding battery storage to your existing solar array

Post by dgh853 » Tue, 05 Feb 2019, 20:53

jonescg wrote:
Tue, 05 Feb 2019, 14:18
This means any loads on the other two phases will be drawing energy from the grid.
This is not correct for the SBP3600 or SBP5000. The Goodwe SBP's are both single phase battery inverter/chargers (i.e. connected to one phase only) but they use a three phase meter so they can "see" flows on all three phases and adjust the current in the Goodwe accordingly. The grid net meter will net off across all three phases so a Goodwe exporting 2kW on phase 1 will cover 1kW being import on phase 2and another 1kW on phase 3 and the grid net meter will register zero import/export. I have the SBP3600 and three phase home.

To give you an example - in the month of December, I imported just 17kWh from the grid while exporting 678kWh. Importing really only occurs when you exceed the inverter's discharge limit or for the first few seconds of a large load as the Goodwe's don't ramp up instantaneously in response to the net meter seeing draw from the grid.

I've set up my AVASS cells to work with an SBP3600 and it is CAN controlled using Batrium's Watchmon hardware/software. Following a software update about a month ago it has been running solidly using CAN to control the charging and discharging of the battery.

IMO the Goodwe's are an excellent low cost, high power battery inverter/charger (up to 100A charge/discharge) and very stable. Not responsive enough for off grid purposes I suspect but hard to beat for value for money and features for on grid.
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jonescg
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Re: Adding battery storage to your existing solar array

Post by jonescg » Tue, 05 Feb 2019, 21:07

Ah - thanks for clearing that up. So the ES are still single phase only?
I'm thinking of setting one of them up on my house, but its a 3-phase home.
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Re: Adding battery storage to your existing solar array

Post by dgh853 » Tue, 05 Feb 2019, 21:24

jonescg wrote:
Tue, 05 Feb 2019, 21:07
So the ES are still single phase only?
I'm not sure on the ES, quite possibly - check the user/install manual and see whether it lists a three phase EZ meter like the SBP manual does.

If you can't confirm otherwise, I can ask Mike Zhang at Goodwe Australia whether a three phase meter can be used in conjunction with the ES series. I'm actually contemplating adding an ES series invert myself for a second battery pack with some extra panels.
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Re: Adding battery storage to your existing solar array

Post by jonescg » Tue, 05 Feb 2019, 21:43

Hmmm, sure looks that way:
GW5048ES.JPG
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