Need feedback on component selection for a small but expandable off-grid system

[A.Fenderson]

Noob here. I have been watching tons of Will's videos, and doing some reading here and in his book, but I have little prior experience with solar or electrical in general.

I would like to put together a system that accomplishes each of these goals:
* starts minimally small (due to budget and PV-install space constraints)
* modular and expandable (available PV-install space is anticipated to increase)
* components qualify for the Residential Clean Energy Credit
* interfaces to my home's main panel as a generator would, going through a manual transfer switch with per-circuit switches and breakers for each of my six 20Amp/120V circuits
* to the fullest extent possible, allows me to do the labor myself

Here are the initial components from each category I've researched that top their respective lists:

PV modules:
Eco-Worthy US-L02M195TM-1
key specs:
* 195W
* bifacial
selection rationale:
* I already own one that I purchased this year
* they sell and ship single units
* bifacial is ideal to maximize my current very limited install space

MPPT charge controller:
BougeRV BV4820CUK / ISE244
key specs:
* buck-boost circuitry enabling wide 12V to 145V PV input range
* 20A charging
selection rationale:
* allows maximum flexibility in number and type of panels for small system

Battery:
LiTime 48V (51.2V) 60Ah Lithium Golf Cart Battery, 120A BMS, 3072Wh Energy
key specs:
* the name pretty much covers it
* "BORN FOR GOLF CART"
selection rationale:
* literally the smallest, cheapest (though potentially non-trash) battery with the required capacity to qualify for the Residential Clean Energy Credit

Battery:
EG4 LiFePOWER4 5120Wh server-rack battery
key specs:
* 48V nominal & >3kWh
selection rationale:
* good reputation and bang-to-buck ratio
* easy to add one-at-a-time to a system
* exceeds minimum 3kWh requirement for applicable federal tax credit
cons:
* not born for golf cart

Inverter:
Victron MultiPlus-II 48/3000
key specs:
* 2400W continuous output at 25°C
* AC charging generator/mains input for emergency-charging
selection rationale:
* low power consumption in zero-load (11W) or zero-load/search (4W) modes
* up to 95% efficient
* good brand reputation
* upgrade path: parallel 2 units for 240V split-phase output
* Will said to go big on the inverter so you're not constantly upgrading

Transfer Switch:
Nature's Generator HKNGPTKEL
key specs:
* 6x120V circuits, each with 3-way manual generator/off/line switch
selection rationale:
* 240V compatibility not needed initially
* only 6-circuit, single 120V input full manual switch I could find

Thanks for your time!

 

[DIYrich]

Grow the system to what size?

Design your eventual system, and figure out how to install that in stages. I'm guessing you will want one inverter, and grow the system by adding panels and batteries over time.

Victron makes good equipment, but is not typical for a house in the USA.

Note: stand-by power is material when you get to multiple inverters. Each one will draw a constant 30-60 watts. A single AIO is in the 60-90 watt range.

Also, you may need an electrician to install the first inverter. If you will add more inverters, then you will want combiner panels so you can diy addition inverters. Panel to split the grid to each inverter, and panel to combine the outputs to load. Plus a busbar or another panel for the batteries.

 

[A.Fenderson]

Grow the system to what size?

My home is small (700 square feet), and only has 100 Amp electrical service: at present I never come close to tapping that out, and I seriously doubt I will have any need or desire to go beyond that while I live here. So using 19,200 Watts as a reliable absolute ceiling, and noting that a maximum of 6 of these Victron inverters can be paralleled for a total of 14.4 kW, I'd say that would be (likely beyond) a sufficient level of inverter coverage--though I'm not claiming that having 6 inverters would be the ideal way to go about it. As for PV, charge controllers, and battery capacity, those seemingly can be added ad-hoc and nearly infinitely, even if done piecemeal, to incrementally bring my overall system closer to using near-zero grid power.

Design your eventual system, and figure out how to install that in stages. I'm guessing you will want one inverter, and grow the system by adding panels and batteries over time.

I'm too new to this--and too constrained by budget--to execute exactly as you describe. I know I'll be learning as I go, making mistakes, and probably backtracking some decisions; hopefully most components I end up swapping out can be used in other projects or sold on. But I definitely cannot afford to jump in at the level of a 10kW+, high-quality inverter from the start.

Victron makes good equipment, but is not typical for a house in the USA.

The choice of Victron for the inverter was for purposes of reliability, low idle/self-consumption, and support. I don't plan on going full Victron ecosystem at this point, though. As for why it's not common in the USA, I'm guessing (though don't know) that it has more to do with pricing than anything else. Do you think so, or are there other reasons?

Note: stand-by power is material when you get to multiple inverters. Each one will draw a constant 30-60 watts. A single AIO is in the 60-90 watt range.

Understood. I really want to go the AIO route, but that could mean substantially delaying my timeline for having a working (though minimal) system due to the multiple constraints I'm trying to work within (budget, physical space currently available for PV install, etc).

Having said that, I am still highly attracted to the EG4 6000XP for its bang-to-buck ratio. Split-phase 240V output in one unit would be amazing, and I could probably easily live within the 6000 continuous Watt output envelope. Is that unit one you would recommend and/or is still highly regarded generally? Its self-consumption is rated at a max of around 50 Watts, which seems really great.

Also, you may need an electrician to install the first inverter. If you will add more inverters, then you will want combiner panels so you can diy addition inverters. Panel to split the grid to each inverter, and panel to combine the outputs to load. Plus a busbar or another panel for the batteries.

Yes, I will want help with my first inverter install, whether AIO or component. The added complexity of those combiner panels is yet another reason pushing me towards the 6000XP and finding a way to live with the limitations imposed by having just one of them. I am aware of and seriously considering eventually integrating something like the EG4 AC/DC mini-split heat pumps that have their own PV input to supplement their AC input; this would help take some of the pressure off my inverter.

As regards the batteries, I've already decided that going with "cheapest possible" is not so wise; I'm revising my targeted choice to the entry-level EG4 server-rack batteries, which are actually cheaper on a dollar-per-kWh basis anyway.

Thank you so much for taking the time to read my long post and reply; any further advice or information would be appreciated.

 

[DIYrich]

I belive the reason victron is not more popular is that they are not UL Listed. They have CE for Europe, but not UL for USA.

For the cost of two victrons, you can get the 6000xp, which includes the charge controllers. If you need more power, you can parallel a second.

It would be easy to stay under 12kw with two 6000xp, unless you need it for heating.

I don't recommend direct pv to power ac. 1) what happens when you want ac and not enough pv. 2) wasted pv when sun not shining. I'm not saying avoid eg4 minisplit. I'm saying don't run them direct from pv unless you have a special use case (inverter maxed out)

 

[50ShadesOfDirt]

If you've already made the decision to go with 48v100ah batteries, then you've chosen 48v for system reference voltage ...

From what I see of your requirements, and most specifically the need to start out small and/or inexpensive, I'd put in a 48v AIO, and try to get one that can be paired with one or more of the same model. You can always keep the 48v battery(s) and swap out the 48v AIO, and potentially sell off the older one as you upgrade to a newer one with more power (if ever needed).

While you want to go the "component" route, it seems that the AIO route might serve you better, as the AIO's are really easy to work with, and have excellent "pairing/expansion" features and more.

Get an electrician to wire in the transfer switch, because they'll also review everything you currently have (wiring & such), and do the right thing for you based on what they find existing.

Hope this helps ...