please review my planned system!

[emily_in_hawaii]

Hi everyone!

Off-grid solar newbie here, trying to cobble together a system out of components I have lying around. Will this work?

-One 25.6 volt, 200ah LifePo Victron battery
-MidNite Solar Kid 30 Amp MPPT charge controller
-800 watt pure since wave inverter 24vdc to 120vac
-Two, 415-watt BSM415M10-54HPH solar panels, operating voltage 37.41 [I want to wire them in parallel, as they will be partially shaded sometimes. Is this an OK idea?]
-10 AWG wire

Thank you in advance for your suggestions and critiques!


Em

 

[Rocketman]

Yes it will work, but an equipment list is not a plan.

I would recommend drawing up your equipment into a diagram - showing all the equipment, wires & fuses &bus bars.

Hint:you will need thicker cable than 10awg, for the main cable going between the battery bus bars and inverter.
Also, I HIGHLY recommend a shunt based battery monitor- like a Victron Smartshunt or BMV712. The voltage curve is so flat on lithium batteries you cannot know if you are almost full or almost empty. The shunt gives you all the needed info.

Don’t forget fuses - the fuses job is to protect the wire - not the equipment.

 

[emily_in_hawaii]

Yes it will work, but an equipment list is not a plan.

I would recommend drawing up your equipment into a diagram - showing all the equipment, wires & fuses &bus bars.

Hint:you will need thicker cable than 10awg, for the main cable going between the battery bus bars and inverter.
Also, I HIGHLY recommend a shunt based battery monitor- like a Victron Smartshunt or BMV712. The voltage curve is so flat on lithium batteries you cannot know if you are almost full or almost empty. The shunt gives you all the needed info.

Don’t forget fuses - the fuses job is to protect the wire - not the equipment.

Thank you so much, Rocketman!! I have a BMV712, will definitely install that. And yes, I have thicker cable going from the battery to the inverter. Right now, I have the whole system set up with two Renogy 100 watt panels. Obviously I'm not getting much power from that, so the only change I'm planning is the bigger panels.

I have 250 fuses between the charge controller, inverter, and battery.

Again, thank you!!

 

[MichaelK]

Rocketman is very much correct. Plan first, assemble later. You haven't mentioned at all what you want to accomplish? What is the goal here? Is this supposed to power a TV and some lights, or whole-home backup in case of power outages? What you need it for is more important than knowing what you have.

For a 24V system, I'd say the 800W of panels is about rock bottom for what is practical. If possible, I'd recommend at least doubling the number of those panels. For my own 24V system, I have 2000W of panels online, as of today, but will eventually upgrade that even higher. That 800W inverter most likely can not power anything as large as a standard refrigerator/freezer. I'd recommend an inverter twice that size for a frig.

How far would you have to go to get clear, unobstructed sunlight? How far can you go? Wired in series, I am sending 8A of 120VDC power ~125' from an array to the controller without any measureable voltage drop. I do however have the 200V Classic, not a 150V Kid.

 

[emily_in_hawaii]

Rocketman is very much correct. Plan first, assemble later. You haven't mentioned at all what you want to accomplish? What is the goal here? Is this supposed to power a TV and some lights, or whole-home backup in case of power outages? What you need it for is more important than knowing what you have.

For a 24V system, I'd say the 800W of panels is about rock bottom for what is practical. If possible, I'd recommend at least doubling the number of those panels. For my own 24V system, I have 2000W of panels online, as of today, but will eventually upgrade that even higher. That 800W inverter most likely can not power anything as large as a standard refrigerator/freezer. I'd recommend an inverter twice that size for a frig.

How far would you have to go to get clear, unobstructed sunlight? How far can you go? Wired in series, I am sending 8A of 120VDC power ~125' from an array to the controller without any measureable voltage drop. I do however have the 200V Classic, not a 150V Kid.

Thank you! Here is some more information.

I live off-grid in a very remote location in Hawaii. I do not have a big house with the typical appliances; I really just need enough power for a couple laptops and low-wattage monitors, Starlink, some light in the evenings, and recharging tool batteries.

I am trying to use the components I already have--mostly consisting of old parts handed down to me from other people ugrading their own systems. If I was designing the system from scratch with a decent budget, I would of course do it much differently! I'm hoping to get away with JUST buying new panels, and using the rest of what I already have.

I'm thinking 800 watts, because the Midnite Solar Kid calculator told me that was the max panels I could be running in parallel. (Parallel to get around voltage drop when not in full sun.) Wouldn't more panels overcharge the Kid?

Thanks!

 

[MichaelK]

Wouldn't more panels overcharge the Kid?

Thanks!

You can use a trick called "virtual tracking". That is pointing multiple solar arrays in different directions. I've been doing it for years now.

You need to make sure that each array produces the same voltage, but you could keep your 800W array pointed South, but add other arrays pointed East or West, or East and West.

At 8am, the East-facing array will be at full power, but the South and West arrays producing almost nothing. At ~10am, the East array will be at ~ 1/2 power, the South array ~1/2, and the West array nothing. At noon, the South array will be at full power, but the East and West little or nothing. By 2pm, the West array is picking up, the South is dropping down, and the East more or less nothing.

So, that means the controller can feed the batteries at 30A or so for a whole 8 hours or more. Not more amps, but the same amps for more time.