Greetings all

I have an existing Solar PV system, 10Kw of panels, 8kw Hybrid inverter and 5Kw battery. The Main house DB is split for essential and non-essential loads. All running like a dream and i'm very happy.

My in laws - in my granny flat are not so happy, as when the blackouts hit, they in the dark, and i'm in the light! The granny flat has its own Sub DB run from the main house DB on the non-essential load side.

I'm looking at ways to get the granny flat onto battery backup, but at the same time, I want to expand my PV array by about 3kw. Thought about 2 options:

1. Run the granny flat essentials off a new breaker on the essential DB fed from the main house. Probably add a battery to cope with the extra load. The load on the inverter should be fine. If i want to expand the PV array with this option, it forces me to get another 8kw inverter to expand the system - which is quite expensive and overkill. At least this is what i understand, you can't mix and match inverter sizes when expanding in parallel?

2.  Get a complete standalone system (3kw PV+Inverter+battery - flat is tiny and has minimal power draw) for the granny flat. Question is here, can excess power produced by this system feed back into the grid alongside the main house system? How would that be wired?

 

Appreciate any thoughts on the matter. Thanks

27 minutes ago, boatmaker said:

Greetings all

I have an existing Solar PV system, 10Kw of panels, 8kw Hybrid inverter and 5Kw battery. The Main house DB is split for essential and non-essential loads. All running like a dream and i'm very happy.

My in laws - in my granny flat are not so happy, as when the blackouts hit, they in the dark, and i'm in the light! The granny flat has its own Sub DB run from the main house DB on the non-essential load side.

I'm looking at ways to get the granny flat onto battery backup, but at the same time, I want to expand my PV array by about 3kw. Thought about 2 options:

1. Run the granny flat essentials off a new breaker on the essential DB fed from the main house. Probably add a battery to cope with the extra load. The load on the inverter should be fine. If i want to expand the PV array with this option, it forces me to get another 8kw inverter to expand the system - which is quite expensive and overkill. At least this is what i understand, you can't mix and match inverter sizes when expanding in parallel?

2.  Get a complete standalone system (3kw PV+Inverter+battery - flat is tiny and has minimal power draw) for the granny flat. Question is here, can excess power produced by this system feed back into the grid alongside the main house system? How would that be wired?

 

Appreciate any thoughts on the matter. Thanks

Without knowing if the current 10kW of panels generating up to 50kWh a day is enough for your needs and you really need to add a 2nd 8kW on your side? 

If present system with 5kWh battery is fine as said I would just add that 2nd battery and feed from the main house essentials to their plugs and lights. See how it goes as far as not using high power items during LS. 

28 minutes ago, boatmaker said:

Appreciate any thoughts on the matter. Thanks

If your 8kW is enough for both dwellings then stick to this, another 3kW inverter would not likely be able to feed back and now you're looking at an inverter + battery + possible panels... I'd say add battery capacity to your 8kW and depending on your consumption you may not need more panels... but only you, having some consumption graphs for recent times would be able to know this for sure... if you do need more panels, then you could consider a separate MPPT that, in parallel with you inverter feeds power to the batteries...

I have a similar setup, I run my granny flat from my inverter.

I have a smart switch on the 40A connection to my cottage so I can check how much power is going there. 

I also have a smart switch on the geyser so that 

I also have a smart globe in the cottage that changes colour to red so that my tenant knows when there is load shedding. 

What 5kw battery do you have? I assume that you are limited on power from battery of 5kw, maybe good idea to get another battery.

Actually I did suggest the 2nd battery option. But here is also a plan B. 

3kVA 24V inverter R6000

8 x 190Ah lithium incl BMS R10000 DIY

2 x 455W panels R6500. 

Wire this inverter to low power plugs for essentials and lights. The UPS side can be used for always on power. 

This leaves R8000 for installation and comes to a bit cheaper than a 2nd battery. For the balance left take them out for supper and celebrate. 😀😀

The 2nd battery does provide more security due to more storage for the main system. 

 

3 hours ago, Scorp007 said:

Actually I did suggest the 2nd battery option. But here is also a plan B. 

3kVA 24V inverter R6000

8 x 190Ah lithium incl BMS R10000 DIY

2 x 455W panels R6500. 

Wire this inverter to low power plugs for essentials and lights. The UPS side can be used for always on power. 

This leaves R8000 for installation and comes to a bit cheaper than a 2nd battery. For the balance left take them out for supper and celebrate. 😀😀

The 2nd battery does provide more security due to more storage for the main system. 

 

8 x 190Ah lithium incl BMS R10000 DIY

Where can one get these batteries at that price?

 

Just now, Thunderdolt said:

8 x 190Ah lithium incl BMS R10000 DIY

Where can one get these batteries at that price?

 

Electromann have 4 x 190-200Ah at R3995. You just need to see if they have a BMS as well. This is R2000/kWh without a BMS. 

2 hours ago, Scorp007 said:

Electromann have 4 x 190-200Ah at R3995. You just need to see if they have a BMS as well. This is R2000/kWh without a BMS. 

go to the page and it seems they want 3995 per cell, not for 4 of them...

 

10 minutes ago, Kalahari Meerkat said:

go to the page and it seems they want 3995 per cell, not for 4 of them...

 

Slaan my met 'n plank.  The Google picture showed 4 and I did not read further. Thanks for it. Hopefully I'm awake now. 

Edited February 5, 20233 yr by Scorp007

Maybe some micro-inverters or a small grid-tied inverter (eg. Solis 2.0kW) added into the system? Just using 2kW of panels from the existing 10kW array that's on the 8kW inverter? Should increase the export capability to 10kW. Depends on your usage, but a 5kWh battery should be charged easily either way. Not saying it's the right choice, just a thought I'd be curious to explore.

39 minutes ago, GreenFields said:

Maybe some micro-inverters or a small grid-tied inverter (eg. Solis 2.0kW) added into the system? Just using 2kW of panels from the existing 10kW array that's on the 8kW inverter? Should increase the export capability to 10kW. Depends on your usage, but a 5kWh battery should be charged easily either way. Not saying it's the right choice, just a thought I'd be curious to explore.

To latch on to your idea with a twist. Add the granny flat to the non essentials. Install a Axpert type inverter with battery only which can be charged with excess PV from the 10kW panels. 

A lot of installs with a 5kWh battery would find the PV generated is far more than day time consumption plus the charging of a 5kWh battery. This does away with the cost of a Solis. 

Deleted - solution already proposed.

Edited February 5, 20233 yr by Bobster.

54 minutes ago, GreenFields said:

Maybe some micro-inverters or a small grid-tied inverter (eg. Solis 2.0kW) added into the system? Just using 2kW of panels from the existing 10kW array that's on the 8kW inverter? Should increase the export capability to 10kW. Depends on your usage, but a 5kWh battery should be charged easily either way. Not saying it's the right choice, just a thought I'd be curious to explore.

Thanks for all the advice. To answer some the questions

1. 10kW of panels are producing excess than what i can use in summer - but that is going to the grid. Also, since the Inverter is limited to 8kW, i'm getting  clipped to the tune of 2kW during summer - so i was looking at some way to add an inverter, shift some of panels to another inverter and maximize my export to the grid. This will help bring down my electricity bill to almost zero.

2. Looks like i'll go the simple route and just add the flat to the existing installation and add a battery. See how i go.

3. Question for @GreenFields how do i add a smaller inverter to the system that can also export? Where in the system does it go? Currently the Sunsynk inverter controls the export with thanks to the CT coil.

4. @Sc00bsWhat is a smartglobe?

Sell the 8kva, buy a 12kva

 

add the flat to the house inverter

3 minutes ago, boatmaker said:

3. Question for @GreenFields how do i add a smaller inverter to the system that can also export? Where in the system does it go? Currently the Sunsynk inverter controls the export with thanks to the CT coil

Two options to investigate:

1. Micro-inverters or small grid-tied inverter on the AUX input of the Deye.

2. Grid-tied inverter input on your non-essential side, but between the main switch and the CT coil.

Very important disclaimer: I'm just thinking out loud. By no means definitive, needs expert input.

1 minute ago, Leetpro said:

Sell the 8kva, buy a 12kva

 

add the flat to the house inverter

Interesting idea! Where do you sell 2nd hand Inverters? What you recon i can get for a 3 year old 8kva Sunsynk?

3 minutes ago, boatmaker said:

Interesting idea! Where do you sell 2nd hand Inverters? What you recon i can get for a 3 year old 8kva Sunsynk?

try selling here:

 

https://powerforum.co.za/forum/27-classifieds/

 

3 hours ago, boatmaker said:

4. @Sc00bsWhat is a smartglobe?

Sunsynk have announced an integration of the Sunsynk.net platform with Philips Hue bulbs, allows you to change globe colours etc based on Inverter status. 

Otherwise you could change bulb colours etc using Home Assistant and some Tuya Smart Bulbs, am sure that there are other ways you could do it as well. Maybe using Google Home or something like that. 

 

 

Morning Good People!!!

I am also looking for an advise please for the granny flat. Quick background - I recently installed 5KW solar system (panels, inverter and battery) and one cable runs through Mains from main house to the sub DB in the granny flat. The lights in the granny flat are on essential load and the rest is on non-essential.

So during load shedding, the granny flat lights work as they are on battery backup but the plugs are off. The reason why I never added the plugs on my solar because my system (5KW) is small and I was afraid that I won't be able to control tenant's use of these plugs e.g. if he/she connects motor appliances like hair dryer, microwave, heaters in the winter., it will drain my solar battery out quickly.

I am now thinking of providing power backup for a few additional points such as TV, wifi extender, laptop/cellphone charging plug and the refrigerator in the granny flat for the tenant living in the flat. The option I considered was a GeeWiz inverter (500wh) that can power wifi extender, TV and laptop/cellphone charging.

However I wanted to check with the experts here if there is a better way to handle this requirement?

On 2023/02/05 at 10:20 AM, Sc00bs said:

I have a similar setup, I run my granny flat from my inverter.

I have a smart switch on the 40A connection to my cottage so I can check how much power is going there. 

I also have a smart switch on the geyser so that 

I also have a smart globe in the cottage that changes colour to red so that my tenant knows when there is load shedding. 

What 5kw battery do you have? I assume that you are limited on power from battery of 5kw, maybe good idea to get another battery.

Hi there, can you please explain how does the smart switch work? I have 5KW solar setup installed in the main house and want to share the power during dark hours.

6 hours ago, PB15 said:

Hi there, can you please explain how does the smart switch work? I have 5KW solar setup installed in the main house and want to share the power during dark hours.

You put it in a DB or some box with DIN rail. Pair it to your permanent WiFi via a phone APP. The switch must be in range of the WiFi to work. From the APP you can set times for on and off and at any time just switch it on or off. 

Those in the pic that are light grey are not on line or in this case not connected to 220V AC power. The blue on the right means they are switched on. 

Edited February 6, 20233 yr by Scorp007

Thank you @Scorp007. I will send you PM.