System input requested

[Bluedog225]

Good afternoon,

I appreciate all the help over the last year or two. I’ve tried to put pen to paper and start listing out my actual components. Install would realistically begin in September, once it cools down.

I don’t have any graphic design skills but I will try to make this clear with words.

Any input appreciated before I get too deep down this rabbit hole.

The strings are convenient given the layout of the roof, and that they work with the charge controller. But not set in stone.

Off-grid. Generator on site (7500W).
Power audit max consumption at 110F=approx 1500W/hour continuous with air condition mini-split load. We have had 100 days over 100F. I am assuming a high duty cycle on the air conditioning. Also, there is a strong correlation between the high temps and full sun and cloudless skies.

46 panels (purchased used).
Roof mount.
(295W, Voc 40.1A; Pmax V 32.7; short-circuit current 9.52A; current at Pmax 9.03; max system voltage 1000V) (Spec sheet attached. The numbers below are from actual panels)

2 strings of 9 panels (9*40.1=360.9V per string)
4 strings of 7 panels (7*40.1=280.7V per string)
6 strings total
Short-circuit current 9.52A
Combined (2x) 9-panel strings=9.52A*2=19.04A (feeding 1 mppt input)
Combined (4x) 7-panel strings=9.52A*4=38.08A (feeding 2 mppt inputs/19A each)

Midnite MNPV6 Disconnect with breaker
Victron Smart Solar RS 450/200 (4 mppt trackers)
Victron Multiplus 3000/48/35
48V/100Ah SOK batteries (starting with 4)-ordered.
Various Victron bits and pieces (Cerbo GX, Lynx, etc).

I think the panel array matches nicely with the Victron RS 450/200. Slightly over-paneled. Max DC output is 11,520W. Theoretical max of array is 13,570W)

Any input or thoughts much appreciated.

Thanks!

 

[rmaddy]

So you are planning 9S2P to one tracker, 7S2P to a second tracker, and 7S2P to a third tracker? Did I read that right? If so, that works.

Since Texas rarely gets as low as -62ºF you won't have to worry about exceed the 450Voc max

 

[Bluedog225]

Yes. And it leaves one tracker open for a pole mount, East or west depending on need.

 

[chrisski]

You have a lot of panels and seem to have a pretty good plan for the power production. The comments I will make is

-What is your power requirement in kWh? You mention a 1500 watt AC, but other than that not my much. I am able to run a 1700 watt AC for 6 hours a day with 2.5 kw of panels and my total use for the RV for that day will be about 15 kwh, with as much produced. 11+kw of panels seems like some serious power being produced and I'm sure you have that in accounted for in an energy audit.

-For 48 volt batteries in ideal conditions you have the potential to charge slightly over 200 amps once charging voltage is figured in, which would rarely happen, but seems to be a good pair for the 450/200. I would just ensure that the batteries can handle a 200 amp charge. My guess is 400 ah of batteries will handle that, but I don't know the SOK specs.

-I find the specs kind of confusing on the MNPV6. I have one and I see this listed for Over Current Circuit Protection, so it seems like you may need to install fuses for over 150 volts and not use breakers. With the fuses appears you are limited to 4 strings, so you could add one more down the road. You mention breakers, but as I read the spec sheet, the enclose won't handle breakers designed for the voltage you're planning.

 

[Bluedog225]

Very helpful.

The 1500 watts/hour covers air conditioning, basic lights, tv, fridge, freezer. Some of these in a timer to run at only at peak production.

I’m assuming a 100% duty cycle on the mini split at times when the temp stays up. But it’s a guess. The house is still under construction. So I’d estimate 36,000 kWh/day (seems high).

Covering the flat roof with panels will add needed shading.

Good point on the battery charge capacity. I was assuming I could match the charging rate to the batteries. I’ll look into this. Or get more batteries sooner than later.

Edit-I also had trouble with the Midnite specs. But I an pretty confident they can cover my need one way or another.

Thanks!

 

[rmaddy]

Good point on the battery charge capacity.

The SCC you are planning is 200A max charge current.

With 4 batteries in parallel you will be fine as long as each of the SOK batteries can handle 50A of charge current or more. The spec sheet for the SOK 48V 100Ah server rack battery can be seen on the Current Connected website. The recommend charge current is up to 63A with a max of 100A. No problem.

 

[Bluedog225]

Great. Thanks for checking.