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diy solar

A couple questions to finish our system.

GaryinWV

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Jul 2, 2022
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We have followed Will's 24 volt 2000 watt system to a tee and have purchased most of what we need.

Our remaining purchase is the solar array cable which we need somewhere between 70 and 90 feet. He recommends an 8awg that is prefabricated with ends.

Can we buy the cable and the ends and make our own? Will also recommends a 10 awg cable without ends on another place.

Which to use?

And also need to buy the "splitters" to hook up our four panels.

Can you give links to what we need to purchase?
 
What is your panel Isc value, and how many strings are in parallel?

If < 30, 10awg is fine
If < 40, 8awg is fine
If < 50, 6awg is fine

You can buy pre-made cable or build yourself as needed.
 
Each panel according to the specs has an lsc value of 10.15. We have 4 panels and are planning to follow Will's instructions to do a combination series/parallel hookup.
 
If you fab your own cables, getting an MC4 cable for greater than 10 AWG is challenging.

Probably won’t find a 8AWG or thicker MC4 connector. May find a 8 AWG Amphenol H4 connector which is compatible, each are UL certified, but not certified hooking the connectors together.

It’s hard meeting the no greater than 30 amp limit of the MC4 and no thicker than 10awg. That’s another reason it’s good to make the cables yourself with some sort of combiner instead of a y cable splitter.

I recommend making your cables yourself. You need exact measurements to get them made and a couple of feet off can make it unusable. I estimated my cable run through my roof and through the floor was 60’. It was 90 feet.
 
We're fine with making our own cables but as we are absolute beginners, we get lost a lot on the details.
 
Vmp is 20.3 volts per panel.

20A at 41V (2S2P) is going to have 8.86% loss with 10awg @ 90':


at 8awg, you'd be at 5.57%

at 6awg, you'd be at 3.50%

Those % relate exactly to power loss, i.e., with 10awg, you'll lose nearly 9% of your array power to heating that wire over that distance.

If you have a charge controller capable of 145Voc or higher PV input, 4S would be WAY more desirable.

10awg would only be 2.25%:

 
20A at 41V (2S2P) is going to have 8.86% loss with 10awg @ 90':


at 8awg, you'd be at 5.57%

at 6awg, you'd be at 3.50%

Those % relate exactly to power loss, i.e., with 10awg, you'll lose nearly 9% of your array power to heating that wire over that distance.

If you have a charge controller capable of 145Voc or higher PV input, 4S would be WAY more desirable.

10awg would only be 2.25%:

EPEVER MPPT Solar Charge Controller 40A 150V PV Solar Panel Controller Negative Ground W/ MT50 Remote Meter + Temperature Sensor PC Monitoring Cable[Tracer4215BN]​

Max PV Input Power: 520W (12v battery) / 1040W (24v battery)
 

EPEVER MPPT Solar Charge Controller 40A 150V PV Solar Panel Controller Negative Ground W/ MT50 Remote Meter + Temperature Sensor PC Monitoring Cable[Tracer4215BN]​

Max PV Input Power: 520W (12v battery) / 1040W (24v battery)
Two of these batteries:

Ampere Time LiFePO4 Deep Cycle Battery 12V 100Ah with Built-in 100A BMS​


We have ordered everything on Will's list.
 
YAY!!!! Just wire your panels 4S (assuming Voc < 30V/panel), and run 10awg pre-made or make-your-own, and you'll traverse the 90' with minimal losses.
24.3 voc

4 of these panels:

HQST 190 Watt 12V Monocrystalline Solar Panel 60x26.8x1.4in with Solar Connectors High Efficiency Module PV Power​

 
Two of these batteries:

Ampere Time LiFePO4 Deep Cycle Battery 12V 100Ah with Built-in 100A BMS​


We have ordered everything on Will's list.

Make sure you charge each battery INDIVIDUALLY to full with a 12V charger and then in parallel on a 12V charger BEFORE placing them in series for 24V.

24.3 voc

4 of these panels:

HQST 190 Watt 12V Monocrystalline Solar Panel 60x26.8x1.4in with Solar Connectors High Efficiency Module PV Power​


Yep. 4S of those on the EPEVER will do nicely.
 
Realize we are absolute beginners with Solar...

Our reason for this build was a power out situation. Then we started thinking that we have this free power source so why not use it all the time? Is that doable? What types of appliances?

With power out, we need to rotate power for a fridge, freezer, and second freezer. Two are in the kitchen and one in the basement.

Do we keep the solar panels plugged in at all times or can we unplug them to move the system to each floor of the house to power the appliances?

If we have to keep the panels plugged in, what is the best way to run the extra cable?

Is it possible to use a "y" to have a hookup in the basement and also one near the kitchen so we could alternate between two different places to limit the length of needed cable.

Or use extension cords from the appliance back to the system?

What's better?
 
Realize we are absolute beginners with Solar...

Our reason for this build was a power out situation. Then we started thinking that we have this free power source so why not use it all the time? Is that doable? What types of appliances?

Yes. Whatever can be powered by the amount of available solar.

With power out, we need to rotate power for a fridge, freezer, and second freezer. Two are in the kitchen and one in the basement.

You need to know how much energy they consume on a daily basis with something like a kill-a-watt meter. A typical full size residential fridge consumes 1.5-2kWh daily.

Your 2.56kWh battery is likely going to be the limiting factor.

You can simulate your array performance at https://pvwatts.nrel.gov/. Assuming you're in Charleston, West Virginia, a 760W (0.76kW) array facing due south tilted to 38° from flat will perform as follows:

1666850214469.png

The numbers take average weather into consideration.

You take the # in the Solar Radiation column and multiply it by 0.76 (760W) to get your daily kWh, so in December, you'll get 2.91 * .76 = 2.21kWh. In June, you'll get 5.91 * .76 = 4.49kWh.

Do we keep the solar panels plugged in at all times or can we unplug them to move the system to each floor of the house to power the appliances?

If we have to keep the panels plugged in, what is the best way to run the extra cable?

Is it possible to use a "y" to have a hookup in the basement and also one near the kitchen so we could alternate between two different places to limit the length of needed cable.

Or use extension cords from the appliance back to the system?

The appliances are presumably 120VAC with low current meaning wiring losses will be small. Most practical to leave the system in one place and use extension cords, or break out the desired circuits into an auxiliary AC panel and wire the system to power those circuits with a transfer switch to select power from the inverter or power from mains when your battery gets too low. If you purchased the inverter specified in the system, it doesn't have a charger. Ideally, an inverter/charger could simply be connected to the mains so that the mains recharge the battery automatically when they get low.
 
Figuring on 24v?

Voltage is considered when calculating Wh.

You indicated you had 2X 12V 100ah Ampere time. The calculation clearly shows 2 * 12.8V * 100Ah. It doesn't matter if these batteries are in series for 25.6V or if they're wired in parallel for 12.8V - the total capacity of the two batteries is always 2.56kWh.

Anyway to make it better without breaking the bank?

Buy more batteries.
 
Thanks for your willingness to help.

We're trying to learn and get it figured out.

Would 2 more batteries make a worthwhile difference?
 
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