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Author Topic: Adding batteries to a grid tied system  (Read 904 times)
wehey
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« on: June 02, 2018, 05:18:42 PM »

Hi all,
I'm new to all this so treat me gently.  Smiley
I have just DIY installed 1.5Kwh of panels on my shed roof along with a Sunny Boy SB1200 inverter, which simply plugs into the mains.
The background draw of the house is about 150-200 watts and on days like today I am sending 90% of it back to the grid.
I do have an electric car that I use to soak up some of the surplus but am still losing quite a lot of my production.

I have been looking at the Powerflow Sundial 2Kwh battery system. Basically you just attach a clamp to the mains cables as the enter the building. It senses whether you are importing or exporting. If exporting it begins to charge the battery from the mains, and when it senses your importing the battery begins to discharge to balance.
You can also program it to charge on E7 over night and discharge in the daytime, which will be perfect in winter when the panels won't be producing any excess.

The problem is that is costs about 2.5K and although i love the idea of it, it would take a lifetime to pay for itself.

So my question is whether there is an alternative out there, maybe something I can DIY together that will work with my current setup?
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nowty
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« Reply #1 on: June 02, 2018, 07:07:17 PM »

I have just DIY installed 1.5Kwh of panels on my shed roof along with a Sunny Boy SB1200 inverter, which simply plugs into the mains.

Not strictly legal. whistlie Should be wired into the consumer unit with an AC isolator on its own dedicated circuit.

I have been looking at the Powerflow Sundial 2Kwh battery system. Basically you just attach a clamp to the mains cables as the enter the building. It senses whether you are importing or exporting. If exporting it begins to charge the battery from the mains, and when it senses your importing the battery begins to discharge to balance.
You can also program it to charge on E7 over night and discharge in the daytime, which will be perfect in winter when the panels won't be producing any excess.

The problem is that is costs about 2.5K and although i love the idea of it, it would take a lifetime to pay for itself.

So my question is whether there is an alternative out there, maybe something I can DIY together that will work with my current setup?

A cheaper alternative is either a second hand DC coupled Growatt SP2000, sometimes they come up on fleebay for under 1k with a 4.8kWh (4kWh usable) lithium battery.

Or even better a new AC coupled Sofar Solar me3000sp with 1 or 2 pylontech 2.4kWh lithium batteries, 1.5k and much better spec than the Powerflow Sundial system.

Example,

The Powerflow Sundial with 2Kwh battery.
Usable battery only 1.6kWh
Max power output 500w (and only steps in 4 x 125w increments)
Min import for it to work 200w (thats a bit high).
Cost 2.5k

Compare with a Sofar Solar system with a single 2.4kWh battery.
Usable battery 2kWh
Max Power output 1,250w (2,500w with two batteries and is completely variable to match load)
Min import for it to work 100w (much better)
Cost 1.5k
Add a second battery for 800 more and its still cheaper.
And ability to add more batteries if you expand your PV, i've got 8.  wackoold
« Last Edit: June 03, 2018, 08:46:19 AM by nowty » Logged

10kW of PV installed and 40+ MWh generated.
Usable battery storage of 50+ kWh.
Heat storage of 20+ kWh.
6kW Ground Source Heatpump.
190,000+ litres of water harvested from underground river.
A few cold frames and raised beds.
wehey
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« Reply #2 on: June 02, 2018, 07:41:46 PM »

Thanks Nowty, that Sofar system looks just the ticket, and at a good price too.

I have had a quick read through the installation diagrams. I can see one possible problem though. It uses 2 current sensors. My inverter is way down the garden in the shed and the consumer unit is 50ft away by the front door.

Coild this be an issue as I presume they both have to send data to a central control box?
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nowty
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« Reply #3 on: June 02, 2018, 08:07:52 PM »

I have had a quick read through the installation diagrams. I can see one possible problem though. It uses 2 current sensors. My inverter is way down the garden in the shed and the consumer unit is 50ft away by the front door.

Coild this be an issue as I presume they both have to send data to a central control box?

The manual says you can extend the current sensors with CAT5 cable and you parallel up 4 wires of the CAT5 cable for each single cable from the current sensor. The manual does not give a max cable run length but a 20m run should be ok. Alternatively, if you ran a dedicated mains cable from your consumer unit down to the shed inverter, that would correctly connect the inverter to the house wiring too. fingers crossed!
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10kW of PV installed and 40+ MWh generated.
Usable battery storage of 50+ kWh.
Heat storage of 20+ kWh.
6kW Ground Source Heatpump.
190,000+ litres of water harvested from underground river.
A few cold frames and raised beds.
M
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« Reply #4 on: June 03, 2018, 08:02:10 AM »

Hi all,
I'm new to all this so treat me gently.  Smiley
I have just DIY installed 1.5Kwh of panels on my shed roof along with a Sunny Boy SB1200 inverter, which simply plugs into the mains.

Hiya.

Sorry to be a downer, but that sentence scared me. Have you notified the DNO, and do you really mean it just plugs into the mains, as that's illegal in the UK, and has to be hardwired into the CU and on a circuit with no other items or sockets. I think plug n play is legal in some EU countries, but not so in the UK.

Sorry to be a pain, but i do worry about any PV that might draw negative attention. Also I believe (but may be wrong) that you might have voided your home insurance.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
oliver90owner
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« Reply #5 on: June 03, 2018, 10:16:37 AM »

Hi all,
I'm new to all this so treat me gently.  Smiley
I have just DIY installed 1.5Kwh of panels on my shed roof along with a Sunny Boy SB1200 inverter, which simply plugs into the mains.

Hiya.

Sorry to be a downer, but that sentence scared me. Have you notified the DNO, and do you really mean it just plugs into the mains, as that's illegal in the UK, and has to be hardwired into the CU and on a circuit with no other items or sockets. I think plug n play is legal in some EU countries, but not so in the UK.

Sorry to be a pain, but i do worry about any PV that might draw negative attention. Also I believe (but may be wrong) that you might have voided your home insurance.

M is correct.  You may be subjecting your supply wiring (likely a ring circuit) to an excess of six amps - that means that wiring is not being protected by its supply fuse....

A 4kW system could be overloading a 30A ring main by over 50%.
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billi
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WWW
« Reply #6 on: June 03, 2018, 01:02:35 PM »

Just get a battery  and an AC couppling able battery inverter and do what you want
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
Sprinter
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« Reply #7 on: June 04, 2018, 09:39:36 AM »

Ignoring the other bits, and focusing on the batter clamp run length, I think 25M is the maximum, and of course that is "cable length" not as the "crow flies" length.

However you do not have to have the batteries in the same place as the inverter if you are drawing the power that would generally be exported, it can be installed in a place much closer, though to be honest my batteries are in the garage which is just a bit less than 20M as i still think that if they went bang i would rather have then in a separate building.

Not that i think there is much change of them going bang.
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