diy solar

diy solar

8% voltage drop and running 80amps in 4 AWG for 300'

The Midnite Classic 250 appears to be limited to 55 amps output to the battery for a 48 volt nominal system, or about 2860 watts (52*55).

That would be about 15 amps input at 200 volts. So good news- your losses aren’t that high.
 
hwy17 said:
You can't have 3 series strings of mixed panel types and run them all over 2 4 awg wires.

My advice is just to scrap your old panels and go all new 8S2P over the existing 4 awg.

Otherwise, easiest to leave your old panels as they are on your old CC then run conduit and new wire to your new array and new CC.
Click to expand...

Curious why you said "you can't have 3 series strings of mixed panel types" from what I've seen I can mix panel types, as long as the resulting voltages are near enough. The voltage will drop to the lower of the strings' voltage though, which I accounted for in my calculations by assuming amps at source is based on the lowest voltage of various strings.

Does that sound correct to you?
 
ddxv said:
Curious why you said "you can't have 3 series strings of mixed panel types" from what I've seen I can mix panel types, as long as the resulting voltages are near enough. The voltage will drop to the lower of the strings' voltage though, which I accounted for in my calculations by assuming amps at source is based on the lowest voltage of various strings.

Does that sound correct to you?
Click to expand...
Oh I assumed they'd be different cell counts, looks like they are actually all 72 cell type panels (144 for bifacial) so nevermind, yeah I guess it could work.
 
s
hwy17 said:
Oh I assumed they'd be different cell counts, looks like they are actually all 72 cell type panels (144 for bifacial) so nevermind, yeah I guess it could work.
Click to expand...
Well then that is just luck, I never knew about that being an issue, I thought the only thing I needed to line up was the total Voltage for each string type.
 
ddxv said:
Well then that is just luck, I never knew about that being an issue, I thought the only thing I needed to line up was the total Voltage for each string type.
Click to expand...
There could be more flexibility than I'm respecting in paralleling like that. For me equal cell count would be the bare minimum.

You got any charge controllers in mind yet?
 
Skypower said:
Your VMPP is important, but also look at your OCV. If you add that value up in series, factor in cold panel voltage increase and if it’s higher than your max of your charge controller OCV rating, it’ll get expensive. The first day that those conditions are exceeded and your battery is fully charged with nothing to hold the voltage down, poof! The charge controller makes magic smoke.
Click to expand...

Thanks, You were correct that 8 in series VOC would go over the max VOC for Midnite Classic 250. Likely will stick with the inefficient 4 panels in series for now until other parts of the setup can be fixed.


1717902459100.png
 
hwy17 said:
There could be more flexibility than I'm respecting in paralleling like that. For me equal cell count would be the bare minimum.

You got any charge controllers in mind yet?
Click to expand...

Just keeping their existing Midnite Classic 250. It's pretty beat up at this point, hums like crazy and the screen craps out all the time, but I think I'd like make that a separate project and avoid upgrading multiple things at once.
 
ddxv said:
Just keeping their existing Midnite Classic 250. It's pretty beat up at this point, hums like crazy and the screen craps out all the time, but I think I'd like make that a separate project and avoid upgrading multiple things at once.
Click to expand...
Oh got it, sticking with 4S strings.

The good thing about voltage drop is it's only that bad at full output, which is when the solar is more plentiful anyway. In winter and on cloudy days when you really need all it can get it'll be pulling less amps and the losses are smaller.
 
I don't know why you want to run higher amperage instead of higher voltage. I'd look for a charge controller that is higher than 250VOC rated and run new wire for it.

I run 16 panels with 8S and 2 strings. The run is 420 feet from array to house. My Vmp is around 350V. I run 10AWG wire. If I had run 8AWG it would have cost $2600, moving to higher voltage allowed 10AWG to be used and cost $600. I don't use a combiner, each string has it's own MPPT and circuits.

Running higher amperage creates power loss which is an exponential as amps go up. The heating of the wire is what causes the loss.

Are the current array wires in conduit or direct burial?
 
You must log in or register to reply here.

Similar threads

ddxv
How to calculate Amps for strings of bifacial panels?
Replies
5
Views
179
ddxv
ddxv
J
AWG WIRE SIZE - 200Ft ? - Voltage Drop
Replies
17
Views
500
JUMPSTART
J
G
Monofacial vs Bifacial - Are they calculated the same and how does the rear ISC impact the total ISC of 2 strings in parallel
Replies
24
Views
2K
garybryan33
G
A
Need batteries in a pinch, or possibly a VFX3648 Outback Inverter 3600W
Replies
7
Views
475
Arlene303
A
W
Add and additional panel
Replies
6
Views
339
sunshine_eggo
sunshine_eggo

diy solar

diy solar
Back
Top