Max array size & few other qustions

[Gros21]

Let say I choose a 5kw 48v all in one unit.

Now I prefer to run a heap of pannels to make sure even on adverage days I'm making power.

If I want to run 10kw panels am I right to do that with a single 5kw inverter?

I understand it will produce a max of 5kw and that's fine but will it produce 5kw power and also charge my batterys?

Also if I run a few in parrall and want to run 3 indentical battery banks is there a way I can cycle them so they all don't sit at 100% full 90% of the time.

If it helps it will be a fully off grid property and as I work away there is a good chance noone will use power for 10-12 days at a time then on weekend I will use it as i please.

Im looking at 3 banks of 16s 280ah lifepo4 batts. With a smaller SOD range 30kwh~ but I'll also add 3 x 5kw mpp solar pip 5048 inverters. So they should also produce 75kwh but even on adverage days 20kw+.

We also have darn good rebates based on panel array size not inverter or battery's.

System may be overkill but rather size it up to allow full time living there while on holidays ect ect.

Plus I like my ac and hotwater will likely be via heat pumps.

 

[labeeman]

I think you are putting the cart before the horse you need to define what your needs are first then size the system to your needs and a 5kw inverter sounds a little short of your needs.

 

[Hedges]

Most charge controllers don't have a problem with extra PV wattage available. They just have a limit on maximum Voc (which increases on a cold day.) Some list a maximum short-circuit current; I think that is due to their using a diode to short out the input if wired backwards.

About 6 kW (STC) of PV panels will fully load a 5 kW charge controller.

With two strings of PV panels oriented at the sun two different times of day 6 hours (90 degrees) apart, like 10:00 AM and 4:00 PM, peak will be about 0.7 times as high.

9 kW consisting of 4.5 kW oriented 10:00 AM and 4.5 kW 4:00 PM should fully load the controller.

Somewhat larger array would help with other seasons and partial overcast.

An inverter like SolArk accepts 12 kW PV input, makes up to 9 kW AC while charging batteries as well.

Rebates on panels? Sure, stock up!

 

[Gros21]

I will be running 3-4 x 5kw inverters. 20kw of panels will not provide enough during adverage days. I'd much rather 30kw+

5kw is 20A (240v) could prolly get with 7.5kw/30A will be all gas cooking and led lights through out. Just the AC unit is the only real power draw.

 

[Hedges]

Using two orientations of PV strings, 35 kW (STC) for 30 kW (PTC) of panels could be a good fit for 20 kW of MPPT.

Running strictly off-grid (never backfeeds), a system with two SMA SI-6048 and four 6 kW Sunny Boy would process up to 24 kW from PV to AC, and continuous 11.5 kW from battery to AC (22 kW surge). That would be good for higher daytime usage, lower nighttime, but while clouds passed over its power would be reduced.
If you want more wattage from battery, four SI-6048.

Your loads ought to be enabled/disabled based on battery state of charge and other signals. Otherwise, you have to overbuild the system or it will shut down at times.

I run A/C during the day if there is grid failure, but not after sun goes down.

 

[Gros21]

I do want to over build it diy batts are cheap. Property is 100m (300ft) off the road where power is there is no SWER on the frontage.

Basicly power company gave me a rough price of 20kaud (17kusd) for new tx and 2 power poles I still would need at least 1 property pole (5kaud/4kusd) plus run beefy cables underground to house to eliminate voltage drop.

Place is 12m x 20m (36ft x 60ft) roof space which I will max out with pannels at approx $100aud ($70usd) installed each. Prolly 80 pannels of et solar/trina or similar which will well over 20kw but may also do a small string on a 12v inverter house has a a large 4 bay 12m x 6m of vechicle/toy storage but its 8kaud (6.5kusd) pannels, inverters will likely be mpp 5048 max inverters $1kaud each.

Battery's will be 280ah 16s packs with ideally 64 batts total. To make 4 total packs but I'm worried about leaving packs sitting at 100% for weeks on end and alot of the time when I go there there won't be much load. But spend a week or 2 in summer I'll be wanting to run the ac 24/7

I will set up esstional/non esstional loads.

Hell I'm even thinking of running a large heater to heat the spare water tank (5000gal) (which must be kept full for firefighting) just to keep a load on there then remote in a few days before and turn it off let batts get back to 100%

Will be running a lower DOD though

 

[Hedges]

Can you get a power drop to a pole at the edge of your property for cheaper?
Utility power is pretty reliable, and they fix it. It would be good to have that available, could bury smaller wires to have a feed during overcast/winter to recharge your system.

For now I just have one load-shed relay of the entire house at 70% DoD. That leaves just Sunny Boys connected. I manually turn off things like A/C in the evening if grid is down. Eventually I'll have a second load-shed around 20% DoD for A/C, laundry, etc.

Make sure your BMS prevents charging below freezing. Depending on the charge rate available from PV, a higher cutout temperature than 0 degrees C might be indicated. Insulation/heating can probably let you charge in all weather, but the disconnect needs to be there for backup protection.

$850 USD for 5kW hybrid? Certainly cheap enough at $0.17/W. With 3 or 4 of them working together, should handle moderate motor loads.
My Sunny Island and Sunny Boy have much higher MSRP, but cost me $0.25 and $0.10/W respectively.

 

[Gros21]

It's a swer based system (single wire earth return) so not that flash.

I by all means could but should be similar cost plus voltage drop would kill me I don't think 25mm conducters would even do it.

If 1 fails I still have redunacy so I don't care so much.

Im a lecky by trade (I work for the power company) but solar is well above my head. I rather play with 256kv transformers than a 48v battery string.

On a better note work does upgrade there 12v 120ah battery's every 2 years so I have about 8 of those. A couple running some trail cameras and some just sitting in the current 12x6m shed till I finish building there. I run a 24vdc xantrex 1800w inverter while Im there that get trickle charged by 2 x 120w panels for the weeks I'm not there. There is a Honda clone 1kva genny there but only use it if I have to.

I cashed in some btc so trying to use all cash.

And not spend a dime other than my "play money" ideally transitioning there semi permently to become a redneck. Its 50acres 200m x 1000m (600x3000ft) with larger property's either side, 1 guy runs his cattle on it but he has a dozer so has cleared the housepad and helped moved the rainwater tanks and dug my septic hole/trench.