Question about how to interpret our Charge Controller numbers

[Wellbuilt]

That's a very nice place you got there though? Have you thought of wind power?

I’m on top of a Mountain and it’s gets 15/ 20 know winds most days Fall winter spring I would like to try it
But Pretty much everyone agrees it’s not worth the expense the maintenance and the hassle of all the moving parts.
I would need a large unit for it to work . And it’s expensive.
If I was by the equator it could be interesting but with snow and ice not so much .
With 4500 watts of solar I get 2/400watts for most of the day even if it’s cloudy and raining snowing
I’m going to add a second charge controler and a extra 4500 watts of solar and that will give me 4 /800 watts in bad weather so I’ll only have to run the Honda on occasion not every day .
You are lucky with enough solar you won’t need to run a generator .
In my area some one turns off the sun around the 3rd week of November and it dosent pop out much until February .

 

[Cheesemaker]

That's going to get expensive.

At some point, you need to consider if 24V makes more sense. That doubles the wattage the MPPT can deliver...

12V * 30A = 360W
24V * 30A = 720W

At that point, you have to change your inverter, so:

Option 1, stick with 12V:
Need new 30A charge controller with each 330W panel added.
Cost: X ($120 + cost of panel to get to 660W)

Option 2, move to 24V:
No cost to add a 330W panel
Need new 24V inverter
Cost: Y (cost of inverter + cost of panel to get to 660W)
Side benefit: Additional 30A charge controllers allow you to add 2X 330W panels.

Thanks,, if we just get the 30.a controller now , and stick with the 1 panel for now, can we later just switch to 24. V with a new inverter, and then add more panels? Or would we then need a new controller too?

 

[sunshine_eggo]

Thanks,, if we just get the 30.a controller now , and stick with the 1 panel for now, can we later just switch to 24. V with a new inverter, and then add more panels? Or would we then need a new controller too?

30A gets you full power from your panel now.
If you upgrade to 24V, you change to 24V inverter and can add 1 panel for 660W (cost: inverter + panel)

AFTER that, you'll need to add charge controllers/panels accordingly. There are no issues with adding more charge controllers as you need them to expand your array. It comes down to does 1 60A cost 2X as much as 2X 30A? Is it easier financially to add MPPT as needed rather than take big hits at once.

 

[sunshine_eggo]

Note also that your battery capacity will have to change as you expand your solar.

Lead-acid batteries can only accept about 15% of their capacity as charge current, i.e., your 210Ah batteries (2X 105Ah in parallel) can't accept more than about 30A of charging. So a second panel might warrant doubling your battery bank.

Given that you've been struggling with your panel only operating at 1/3 its rated power, getting max power out of the panel may be all you need.

 

[Wellbuilt]

im Not sure what you are trying to accomplish with your system ?
If you are living off grid it will be rough on minimal power .
Your frig really takes you from a small to medium system .
I would get the largest mppt charge controller you can afford / find .
Most will go from 12v up to 48 volt .
It’s a lot easer to just add panels to a controller then keep adding controllers fuses wire runs .
I don’t think your panel will put out full power for more then a hour at noon so more will be better .

 

[Wellbuilt]

If you go with a 30 amp controller I would make sure it can allso charge @24 volts .
This is where I stayed when we built the cabin .
We had 500 watts of solar 40 amp controller 2 215 ah battery’s morning star 300 watt inverter .
The system is going into its 7th year and the battery’s are going to need replacing but I did not baby them and they would get drawn down when they are covered in snow .

 

[Cheesemaker]

im Not sure what you are trying to accomplish with your system ?
If you are living off grid it will be rough on minimal power .
Your frig really takes you from a small to medium system .
I would get the largest mppt charge controller you can afford / find .
Most will go from 12v up to 48 volt .
It’s a lot easer to just add panels to a controller then keep adding controllers fuses wire runs .
I don’t think your panel will put out full power for more then a hour at noon so more will be better .

We are really just starting out and trying to get our electric bills down for now, maybe later we will try to go off grid. For now, we don't need it to cover everything. Slowly slowly catch a monkey

 

[Cheesemaker]

If you go with a 30 amp controller I would make sure it can allso charge @24 volts .
This is where I stayed when we built the cabin .
We had 500 watts of solar 40 amp controller 2 215 ah battery’s morning star 300 watt inverter .
The system is going into its 7th year and the battery’s are going to need replacing but I did not baby them and they would get drawn down when they are covered in snow .
View attachment 74805

yes the new 30a. controller can charge 24V too. Your place looks like somewhere a film should be made. Something starring Billy Bob Thornton and Tommy Lee Jones.

 

[Wellbuilt]

yep, ive been told it looked like the Unabomber shack ?

I really don’t think you will save any measurable amount of money with a few solar panels
Off grid solar cost 10 times the cost of grid power .
It could be good as back up .
I’ve seen some plug and ply systems that you just plug in to a wall outlet and it feed loads in your house
it won’t feed the grid but the do have battery’s for back up but they cost $ .I’ll see it I can post some thing .

 

[Wellbuilt]

This looks cool , you can just use all the power it makes every day all day long ?
Seams like it could work , there are no battery’s so there is no worry of your battery’s getting drawn down
if seen this for less then half the money and more then double .
Look cool ? I’m thinking this will get popular soon .

T

 

[Cheesemaker]

the new 30a. controller

 

[Wellbuilt]

That looks better ?

 

[sunshine_eggo]

I am somewhat concerned by the wiring. The one two the panel is probably okay, but the one to the battery may be undersized.

 

[Wellbuilt]

Yep me to , I like to use the largest gage wire I can fit in the inverter lug . It’s only good practice

 

[Cheesemaker]

I am somewhat concerned by the wiring. The one two the panel is probably okay, but the one to the battery may be undersized.

Thanks again, Sunshine_eggo,
Is it straightforward to replace the wire? Do hardware stores do this kind of wiring in different thicknesses?
If so, what thickness should I ask for? I am electrically illiterate. Cheers again for all your help.

 

[sunshine_eggo]

What is the length of wire needed?

 

[Wellbuilt]

You can probably just Measure the hole in the lug or look in the owners manual .
Battery to inverter wire should be the largest size you can get into the lug , they shouldn’t be to long and won’t cost much .

 

[sunshine_eggo]

You can probably just Measure the hole in the lug or look in the owners manual .
Battery to inverter wire should be the largest size you can get into the lug , they shouldn’t be to long and won’t cost much .

Looking to treat this as a learning exercise starting with voltage, 30A output and distance... if you get my drift.

 

[Cheesemaker]

Looking to treat this as a learning exercise starting with voltage, 30A output and distance... if you get my drift.

It's about 1.5 metres long.

 

[sunshine_eggo]

Using this calculator:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

10awg (5.26mm^2) wire @ 12V, 30A and 1.5m = 2.46% voltage drop. That means you'll lose 2.46% of any power the MPPT can provide. Anything under 3% is considered acceptable.

Not sure what standard metric sizes are, but 10awg/5.26mm^2 is a typical wire size for household 30A AC wiring, and it should work well in this application. Anything larger is fine too.

Moving forward, you can use the voltage drop calculator for wire sizing.

You should also have a 40A fuse/breaker on the (+) wire between the MPPT and battery. If you get a breaker, make sure it's rated for DC.