I hope someone can give me good advice on an upgrade question.

I currently have a 5kw Sunsynk grid tied Inverter with two 5kw sunsynk batteries connected to 8 panels and all is well, this has been running for almost two years and we have realized the limitations this system has on a 3 bedroom home with a garage and outbuilding.

I would like to upgrade the system by at least another 5kw on the battery side and up the inverter to 8kw or even 10kw to handle the additional demand that is required when we have a full house etc.

I have two thoughts of going about this and this is where I require your help please.

Option A:

Sell the 5kw inverter and purchase a new 8kw or 10kw inverter.

Buy one additional 5kw sunsynk battery.

 

Option B:

Buy an additional 5kw Sunsynk Inverter (exact same unit as installed) and install in parallel.

Buy two additional 5kw batteries OR one 5Kw battery and 8 additional panels.

 

Is it a no brainier to go with option B ? Space is not an issue and the cost of the 5kw Sunsynk inverters is currently on sale at most suppliers. The option of another MPPT line is also desirable as I would like to add additional panels at a later stage. We have good sun coverage and the current 10kw system is fully charged before 1pm on most days.

 

Questions:

Has anyone done this system recently and could give me further insight to the pros and cons?

Do I link all the batteries to a common bus and then to both inverters or keep them separate IE basically replicating what I currently have (One inverter inked to two batteries)?

Will it be a problem with only one PV line feeding the system or does the second inverter require the additional panels?

Would I need to upgrade the electrical feed between my existing DB board and the Inverter/s ?

 

Thank you for your help in advance.

 

I might be answering my own question here. I have noticed a lot of issues reported with the parallel inverter setup with multiply batteries.

Maybe the 10kw or 8kw inverter upgrade and single 5kw battery addition is the way to go.

Question on new battery (or batteries)

How are you going to get the new battery cables exactly the same length as existing install?

1 hour ago, Nish4 said:

I have noticed a lot of issues reported with the parallel inverter setup with multiply batteries.

Am running 2x 5kW Sunsynks with 6x Pylontech - and am generally happy with my system.

Yes, I do have a small issue with my system in that my slave has a higher battery draw when the system is connected to the grid. But I would call it more annoyance than issue. I have raised it with Sunsynk and they want me to send in both inverters to be able to replicate the issue - and to me that has not been worth it. The issue only presents when connected to the grid, and I am manually disconnected from the grid 95% of the time - so it is not bothering me really.

Other than than, the system is rock solid and absolutely stable.

I would recommend 2x 5kW over 1x 8kW/10kW to get the additional MPPTs for greater flexibility as well as redundancy in case there is a fault on one inverter.

2 hours ago, Nish4 said:

Do I link all the batteries to a common bus and then to both inverters or keep them separate IE basically replicating what I currently have (One inverter inked to two batteries)?

Batteries and both inverters connected to a common bus bar

2 hours ago, Nish4 said:

Will it be a problem with only one PV line feeding the system or does the second inverter require the additional panels?

From what I understand, it is best to split PV strings across both inverters - e.g., rather have 1 string on each inverter instead of 2 strings on a single inverter and nothing on the other

2 hours ago, Nish4 said:

Buy two additional 5kw batteries OR one 5Kw battery and 8 additional panels.

I would probably go with 1 battery and additional panels. I think you will otherwise struggle to get you batteries charged

2 hours ago, Nish4 said:

Would I need to upgrade the electrical feed between my existing DB board and the Inverter/s ?

Your sparky will need to check. But if you install a 2nd inverter, then your initial inverter connection should be fine

1 hour ago, Virwat said:

Question on new battery (or batteries)

How are you going to get the new battery cables exactly the same length as existing install?

I will redo the cables to ensure all are of equal length.

36 minutes ago, wolfandy said:

Am running 2x 5kW Sunsynks with 6x Pylontech - and am generally happy with my system.

Yes, I do have a small issue with my system in that my slave has a higher battery draw when the system is connected to the grid. But I would call it more annoyance than issue. I have raised it with Sunsynk and they want me to send in both inverters to be able to replicate the issue - and to me that has not been worth it. The issue only presents when connected to the grid, and I am manually disconnected from the grid 95% of the time - so it is not bothering me really.

Other than than, the system is rock solid and absolutely stable.

I would recommend 2x 5kW over 1x 8kW/10kW to get the additional MPPTs for greater flexibility as well as redundancy in case there is a fault on one inverter.

Batteries and both inverters connected to a common bus bar

From what I understand, it is best to split PV strings across both inverters - e.g., rather have 1 string on each inverter instead of 2 strings on a single inverter and nothing on the other

I would probably go with 1 battery and additional panels. I think you will otherwise struggle to get you batteries charged

Your sparky will need to check. But if you install a 2nd inverter, then your initial inverter connection should be fine

Excellent feedback, thank you.

I have 2 x 5kW Sunsynk, initially I had 1 x 15kWh BSL...but that got hit by a lightning strike along with both inverters.
I now have 2 x 5kW Sunsynk inverters, with 2 x 10kWh Dyness batteries.

The system caters for 2 x households, so everything is x2 basically. 2 x geysers (3kw and 4kw), multiple TV's, fridges, washing machines, dishwasher network equipment, borehole pump, booster pump etc. everything except the 2 x ovens are on the system.

Zero issues experienced across both setups, with a single battery or multiple batteries. System just works.

Depending on your budget maybe aim for another 5kW inverter and more panels...

3 minutes ago, Carl Anthony said:

I have 2 x 5kW Sunsynk, initially I had 1 x 15kWh BSL...but that got hit by a lightning strike along with both inverters.
I now have 2 x 5kW Sunsynk inverters, with 2 x 10kWh Dyness batteries.

The system caters for 2 x households, so everything is x2 basically. 2 x geysers (3kw and 4kw), multiple TV's, fridges, washing machines, dishwasher network equipment, borehole pump, booster pump etc. everything except the 2 x ovens are on the system.

Zero issues experienced across both setups, with a single battery or multiple batteries. System just works.

Depending on your budget maybe aim for another 5kW inverter and more panels...

Thank you Carl, Ideally I would like to end up with a system like yours with total 20kWh batteries and additional panels (totally off grid). Looks like the additional 5kW inverter is making more sense. I know I will lose if I try and sell the 5kW inverter as second hand to purchase one single unit.

Forgot to say to aim for another battery as well...so inverter + battery + panels - if budget allows 🙂

At present I am looking at the following estimated costs:

8 x 585w Canadian panels and tiled roof mounting kit - R19000

1 x 5kW Sunsynk inverter - R16000

1 x 5kWh 100Ah Sunsynk wall mounted battery - R20000

Installation estimate - R10000

+-R65000 all in.

Not entirely up to date with costs - but that doesn't seem to bad.
I got my system in 2023 when prices were at their absolute peak 🫣, but the savings and constant power makes up for it...or that's what I tell myself 😆