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Author Topic: Solar Inverter Auto Switch Between Grid & Battery  (Read 3438 times)
antsals
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« on: January 29, 2020, 09:56:07 AM »

Morning all,
I'm after a bit of advice before purchasing a new solar array. I've been looking at battery systems for a while but find that many of the hybrid inverters look at the battery unit as back up. Does anyone know or can advise is there such an inverter in the UK that can charge / feed the house during the day and then auto swap over to battery at night; if battery is depleted; could swap back to grid etc.

There seems to be a sol-ark in the US that does this but can't find much info in the uk on this type of principle.

Any help would be appreciated.

Regards,
Ant
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RIT
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« Reply #1 on: January 29, 2020, 10:58:23 AM »

For a grid-connected solution, this can be done with solutions from a number of vendors that provide a solution that monitors the home's import/export via current sensors and then varies the output of the inverter to just cover the current demand.

The most comprehensive solution (and most costly) is from SMA where their PV inverters and battery charger/inverter can be combined with their monitoring and management solutions to dynamically vary the output of the PV inverters and charger inverter to meet any imposed export limits and the household usage.

Other posters will be able to describe the solutions they have, which may meet your needs and will normally be far cheaper.


If you are looking for a solution that can handle off-grid situations this gets more complicated due to the system needing to isolate itself from the grid in a way that conforms to the UK regs. If this is your direction you may want to just give Navitron a call as this is an area they have a focus on. Navitron provides this forum as a free and open service but does ask it's users to reference them rather than competing third parties where it makes sense.
« Last Edit: January 29, 2020, 11:10:10 AM by RIT » Logged

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antsals
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« Reply #2 on: January 29, 2020, 01:51:18 PM »

Thanks for your reply;
I have been following DIY Solar Power with Will Prowse on YouTube....I can recommend if anyone is interested. Problem is it is US based and not all the kit is available here in the UK.

What I wanted to sort out was if I buy a grid tie inverter now say a SOLIS 4G Mini inverter now; monitor how much of my baseline power usage is removed from the grid during the day, then I wanted to increase...add new inverter to the system and battery unit.

My optimum would be all baseline power covered by solar (while everyone is at work) then at evenings auto switch / pull from battery and if I'm short flip back to the grid......is it possible with the available kit?

I can see some of the hybrid inverters allow a tie to the grid; but what is not clear is if the inverter can cope / control the feed from battery / grid automatically. MPP Solar seem to have one but I'm just not sure.

Going totally off-grid setup makes sense....its this backup grid tie.....

Cheers,
Ant
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Joereynolds89
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« Reply #3 on: January 29, 2020, 06:14:00 PM »

Maybe I am miss understanding, but what you are asking sounds like the basic functionality of all Hybrid and AC Charge Controllers?

Each one may have slightly different features sets and configuration options but most will charge when excess solar and discharge when insufficient solar.

If you went AC connected charge controller rather than hybrid then I know for sure that both the Sofar and AC Lux are programmable to discharge only at required times, but also have the ability to AC charge from the grid on TOU/E7 type energy tariffs.

In fact, the AC Lux in particular also has the ability to combine units and run between the grid connection and CU (therefore effectively as a microgrid) if required.
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woodi
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« Reply #4 on: January 29, 2020, 06:30:17 PM »

A Victron Multiplus or Multiplus II would do this.  So typically if there's a power requirement it'd prioritise battery, and then if more than the battery can provide, it'd supplement with some grid power. If the batteries get too low, and solar isn't providing enough charge, it'll likewise use grid power to charge the batteries sufficiently.  Look at ESS (Energy Storage Systems) on Victron. Very configurable.
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9.4kw PV -  Victron 150/70, 100/50, 150/60, 150/35 MPPT; 3x Victron Multiplus 24/3000/70; Color Control GX Monitoring; 1800ah@24v traction batteries - 50 tube solar thermal - 3kw Bornay Inclin grid tie/ac coupled wind turbine - wood cooking & heating. 28kw Ponast pellet boiler.
antsals
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« Reply #5 on: January 30, 2020, 08:45:21 AM »

Joereynolds89 & woodi,
This was exactly what I was looking for......I've looked at the Victron units already but it wasn't that version.

Out of interest more than anything; If I was only grid tied I assume that generated electricity from PV panels would "automatically" fulfil the power requirement / baseload while no one is in the house.  I assume there is nothing physically stopping the power going out onto the grid?  I assume that generated power will travel through the path of least resistance; therefore staying in the house rather than transferring back onto the grid.

Thanks again,
Anthony
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pantsmachine
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« Reply #6 on: January 30, 2020, 09:32:23 AM »

I have this one which does as you say. The after sales support has been outstanding, can't recommend Goodwe highly enough.

https://www.goodwe.com/energy-storage-inverters/sbp-series-285.asp

Coupled with these batteries

https://zerohomebills.com/product/pylontech-us2000b-plus-2-4-kwh-li-ion-battery-module-48v/
« Last Edit: January 30, 2020, 09:41:43 AM by pantsmachine » Logged

5.12kWh PV system with Solar edge
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antsals
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« Reply #7 on: January 30, 2020, 01:01:15 PM »

pantsmachine,
What is you total setup? Did you orginally just have a grid-tie inverter and added the goodwe inverter and battery units after?  Do you have a charge controller etc. or is that all built into the goodwe kit?  Can you dictate the times at which you pull from battery or is it just when they are charged up?  How many Amps does the inverter allow to switch over too from the grid supply?

Regards,
Anthony
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pantsmachine
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« Reply #8 on: January 30, 2020, 01:51:52 PM »

Hey pal, it all went in together, the unit will do what you want automatically. Can set it to charge at specific times x 4. Will discharge  5kw max draw if you have enough batteries .

Have a look on the Goodwe site and have a read. It is an excellent bit of kit. I have no idea where goodwe is on the perceived high/low scale but it was chosen to be as plug n play no maintenance required as possible. SWMBO  suggested solar, regardless it would have been my fault if anything had to be maintained! Smiley

The solaredge unit (beige box) throws pv power from the roof to the Goodwe charge controller, the Goodwe unit does everything else silently and with no fanfare.


« Last Edit: January 30, 2020, 04:05:27 PM by pantsmachine » Logged

5.12kWh PV system with Solar edge
7.2kWh Pylon tech battery storage
18kWh Heater Storage
Solar I boost charging 12kWh 210 ltr OSO system tank
Deep insulation, air leak controlled home
Zoned & Balanced CH wet system
Hive 2
Low energy bulbs
24 kW Leaf
Masanobu Fukuoka garden & wooden hot tub
billi
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« Reply #9 on: January 30, 2020, 10:42:23 PM »

Quote
Going totally off-grid setup makes sense....its this backup grid tie.....
    Grin

I agree , but for that step , one needs to love it  Smiley
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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
antsals
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« Reply #10 on: January 31, 2020, 10:41:08 AM »

pantsmachine....Thanks for the picture makes much more sense.

How come you went for the solar edge inverter and the SBP Series from Goodwe?  I've noticed you could get a goodwe unit that could do the inverter job also.

On the goodwe website it has diagrams of the load from the batteries going to "on grid loads" and "backup load".  Have you feed directly to your consumer unit from the grid and then one from your goodwe kit to the same breaker?

Have a look at section 1.1 on the website the sketch shows the connectivity.

https://www.goodwe.com/energy-storage.asp

Cheers
Ant

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pantsmachine
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« Reply #11 on: January 31, 2020, 04:13:30 PM »

They do different jobs mate, not to say you couldn't get an all in one package, you'll get there! Gotta go, Its my Birthday!
« Last Edit: January 31, 2020, 04:34:42 PM by pantsmachine » Logged

5.12kWh PV system with Solar edge
7.2kWh Pylon tech battery storage
18kWh Heater Storage
Solar I boost charging 12kWh 210 ltr OSO system tank
Deep insulation, air leak controlled home
Zoned & Balanced CH wet system
Hive 2
Low energy bulbs
24 kW Leaf
Masanobu Fukuoka garden & wooden hot tub
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