Advice on expanding PV system

SD_DRACULA · 01-11-2021 10:59am #1

A question for the veterans on this forum.

I have a 7kwp system split over two strings, front house 3kw and shed roof 4kws, both S facing, coupled with a Solis 5G 6kw hybrid and 5kw battery.

The shed roof is starting to become shaded by the house around this time of the year.

Firstly, I would like to add 1 more kw to the front house, bringing it to 4kw so 8kw in all.

I feel like in summer I would be losing some gen since the inverter caps at 6kws but at the same time in summer I exported between 150-400kws per month so I couldn't use it anyway.

Looking at these options so maybe you guys can keep me straight:

Just expand the front house to 4kws and leave all as is (maybe go for diy batteries next year)
Add another 4kw inverter and split the shed string into 2 x 2kws strings
Add another 4kw inverter and split the shed string into 2 x 2kws strings, move the front house 3kws to the back of the house and add 4kws to the front (11kw total), split the front/back of house into two strings on the 6kw hybrid

reboot · 01-11-2021 5:29pm

I don't get involved in large scale PV projects,but have recently started using lithium modules from EVs.

My projects up to this point involving lipo, involve careful battery balancing bms.

I was wondering if balancing is a consideration for the large scale kwhr folk using lithium batteries,and what does it consist of? Thanks.

unkel · 01-11-2021 5:38pm

You are not allowed to have more than 6kW in total inverter output. Unless you can prove that you can't export more than 6kW. So I would go for option 1. Just expand front.

quentingargan has posted a few times that the losses of having a system bigger than 6kwp with just a 6kW inverter are tiny, a few percent per year. I'm in this situation myself too, I have just under 8kwp all south facing and a 6kW inverter

If I were you, I would put my next money in a battery setup :-)

SD_DRACULA · 01-11-2021 6:24pm

https://www.boards.ie/discussion/comment/118102934#Comment_118102934

Yes leaning towards option 1 myself.

This 8kwh bad boy https://www.deyeinverter.com/product/hybrid-inverter-1/hybrid-inverter-sun5-6ksg01lp1us-sun7-6-8ksg01lp1us-eu.html wouldn't be too bad either but not sure it supports puredrive batteries or the diy ones

unkel · 01-11-2021 7:31pm

You're not allowed to have that unless you have 3ph though...

graememk · 01-11-2021 9:14pm

https://www.boards.ie/discussion/comment/118103493#Comment_118103493

but bbbut.. 190amps on the DC battery Charge/Discharge and its only 2k usd on alibaba

edit 2: 500V is the max PV voltage..

celtic_oz · 07-11-2021 10:36am

https://www.boards.ie/discussion/comment/118102934#Comment_118102934

I have 6KW on the roof and a 6KW inverter with 4Kwh battery .. thinking of over sizing to 8KW on the roof but not sure how big to go on the battery .. I have an EV .. how big did you go on the house battery ?

SD_DRACULA · 08-11-2021 11:07am

Just testing the waters, would anyone be interested in buying 9 x Qcell G9s all black 335w panels from me? Less than 6 months old so basically still new. PM me for details.

Looking to put up 11 x 360w panels in their place.

unkel · 08-11-2021 7:58pm

https://www.boards.ie/discussion/comment/118130586#Comment_118130586

I went 16 cells of 200Ah, so 10kWh usable. But I have ordered double that and sell my current battery, so should have 20kWh

yankinlk · 08-11-2021 8:12pm

https://www.boards.ie/discussion/comment/118137913#Comment_118137913

What is the max about of the batteries all together? Can they handle oven, dishwasher and dryer all at same time for example?

slave1 · 08-11-2021 9:44pm

Depends on inverter, Unkel battery or DrPhil will output 5kW if hooked up to a Solis 4th/5th gen hybrid inverter.

You won’t get any grid tied system outputting more than 6kW from batteries I’d imagine

SD_DRACULA · 08-11-2021 10:25pm

https://www.boards.ie/discussion/comment/118137999#Comment_118137999

Unlikely, my oven can draw up to 3kw, dishwasher 2.5kw, dryer around 800w but also maybe, the over draw less once at temp so it all depends on the gear itself.

yankinlk · 09-11-2021 12:30am

Ok was wondering if each battery would increase the max output. My 4.8 can do about 2.5. So going to 10KW I would still only see 2.5 at any one time? I guess the benefit is to get to 11pm to try and cover all daytime load and still move the heavier stuff to night time (bar cooking)

SD_DRACULA · 09-11-2021 12:58am

All depends on the battery specs and the inverter, I can pull 5kws from my 5kwh battery for example.

unkel · 09-11-2021 2:13am

https://www.boards.ie/discussion/comment/118139119#Comment_118139119

LiFePo4 can easily handle 2-3C, so if you had a 20kWh battery pack, you could draw 40-60kW from it. That is 3 to 4 times the maximum power a house in Ireland draw from the grid. So yeah the battery can easily power not just your own entire house, but your neighbour's too......

.....if only you'd have the inverter to provide that power, most people don't

Advice on expanding PV system

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