Where do I stick this...

[Weldman]

Your Class T fuses belong on the battery cable, as close as possible to the battery. With class T, you are paying for the ability to interrupt a high amperage plasma that can form as a standard fuse blows. Your PV & Controllers cannot produce enough current to require a class T fuse

"A Class T fuse is a fast acting, current limiting, fuse that is rated to interrupt a minimum of 200,000 amps. .." You can only get that sort of amperage from a battery pack.

And that's where it's at now...

[Weldman]

For future reference as a reference point I figure to share a failure on here so someone else won't repeat it...
In Olympic Peninsula area i.e. near Seattle with lack of light this set up does not work
Classic SL150 paired up to
Renogy 100w 12v panels 6 in series of 2 strings

Optimum Operating Voltage (Vmp): 17.9V	Open-Circuit Voltage (Voc): 21.6V
Optimum Operating Current (Imp): 5.72A	Short-Circuit Current (Isc): 6.24A

This set up will not power up the charge controller to get it out of resting mode on cloudy day in the middle of December. Will have to reconfigure to 3 in series to 4 strings, back to drawing board... BTW I'm at 24v system so I am over 130% the battery max voltage with either set up.

[Bala]

If the system worked on a sunny day it may well just be the lack of sun that is the problem.

Even if it were to power up the controller the amount of generation is likely to be minimal.

[Weldman]

If the system worked on a sunny day it may well just be the lack of sun that is the problem.

Even if it were to power up the controller the amount of generation is likely to be minimal.

It's why I wrote this is cause this set up doesn't work with clouds as I believe the other way will or I will see if it will, though running out of time to hit the road for experimentation. Either way it will be good for charge controller not running so many volts.

[Weldman]

Let's say I decide to go crazy and bump everything up to 48v on the batteries and everything that can run of them on 48v and just step down to 24v on stuff I can't find in 48v and 12v for stuff that can't be had in either voltage, would I lose more in efficiency stepping everything down than it's worth? How does everyone else or why does everyone else off grid run on 48v if there isn't anything that really runs straight off it? Are you guys on 48v just not running much DC and just converting it to AC?
Have hard enough time trying to step up to 24v on stuff in a RV, seems this country is in stone age on solar compared to other countries. Anyone just order stuff from foreign countries to work with 48 plus volts?

[Mike90250]

.... Are you guys on 48v just not running much DC and just converting it to AC?.......

Yep. Running a "regular" house, with plugs, outlets and county approved flush toilets. Fully half of my precious filtered water is used to rinse sewage down the drain.

Unless it's a 1 room hermit cottage, trying to run 12VDC to properly rated switches and power outlets, and having 115VAC for the odd thing that you can't get in 12v, the cable lengths are too long, too much power is lost in the cable runs. Run a 48V bank, no DC appliances at all

[Weldman]

Yep. Running a "regular" house, with plugs, outlets and county approved flush toilets. Fully half of my precious filtered water is used to rinse sewage down the drain.

Unless it's a 1 room hermit cottage, trying to run 12VDC to properly rated switches and power outlets, and having 115VAC for the odd thing that you can't get in 12v, the cable lengths are too long, too much power is lost in the cable runs. Run a 48V bank, no DC appliances at all

Basically if you could do a 60 to 72v DC or more inverter you would, only reason for 48v is, it' max they make?

[bob-n]

Forgive me if you know this already. Switching DC is different from switching AC. When you have long wires and DC, you can have serious arcing problems with mechanical switches. Even switches rated for DC may not last a long time if the power source is a long distance away, because the wire acts like an inductor, and when you try to disconnect continuous current, the inductor spikes the voltage up to try to maintain the current.

A simple RC snubber across the switch contacts will solve the problem. For higher current, you need a larger capacitor and larger resistor to safely dissipate the stored energy in the the long wire. It's easy for a 1A load, but for larger loads, the RC gets proportionately larger.

If this isn't clear or you need help selecting switches or snubbers, please ask more questions.

[Mike90250]

Basically if you could do a 60 to 72v DC or more inverter you would, only reason for 48v is, it' max they make?

Yes, Code spells out systems with nominal voltage over 50V, be treated differently, and with higher DC voltages, arcing really becomes a problem. I have special circuit breakers in some of my higher voltage PV wiring, because the standard DC breakers are inadequate.

[Weldman]

Forgive me if you know this already. Switching DC is different from switching AC. When you have long wires and DC, you can have serious arcing problems with mechanical switches. Even switches rated for DC may not last a long time if the power source is a long distance away, because the wire acts like an inductor, and when you try to disconnect continuous current, the inductor spikes the voltage up to try to maintain the current.

A simple RC snubber across the switch contacts will solve the problem. For higher current, you need a larger capacitor and larger resistor to safely dissipate the stored energy in the the long wire. It's easy for a 1A load, but for larger loads, the RC gets proportionately larger.

If this isn't clear or you need help selecting switches or snubbers, please ask more questions.

At this point now knowing this means when I actually start building my home and installing the electrical when I get to the DC portion I know now to consult here on what capacitors and resistors needed for RC snubbers. Is there a formula to it? My dad worked 38 years as senior electrician at a college repairing everything electrical and might know about this too, he is so damn good he retired and they called him back while still paying his retirement check, just don't think DC is his specialty as it is the people in here helping. More knowledge I thirst for.

[Weldman]

Yes, Code spells out systems with nominal voltage over 50V, be treated differently, and with higher DC voltages, arcing really becomes a problem. I have special circuit breakers in some of my higher voltage PV wiring, because the standard DC breakers are inadequate.

Is that why you have the Midnite ePanel? I've noticed after reading history on the foundation of solar and inverter tech Midnite Solar was there through it all and who I mostly trust with right equipment. Like right now I have there master shutoff switch with their breakers and their charge controller.

[Mike90250]

i have the midnight e panel because it's a better piece of gear and more flexible than the Xantrex/Schneider ePanel. (lots more expansion options) Midnight also has the high voltage DC breakers and lots of the "right"goodies.

[bob-n]

This link is a good engineering article on selecting the resistor and capacitor. If you really want to learn, this is good reading:

https://www.cde.com/resources/catalogs/igbtAPPguide.pdf

Even if you're not very familiar with resistors, capacitors and inductors, (V=IR, dV/dt=I/C, dI/dt=V/L), the artcle will be very helpful.
Disclaimer: This article was written by a capacitor maker to help people pick one of their capacitors. The same article applies even if you use a different brand of capacitor.

[Weldman]

i have the midnight e panel because it's a better piece of gear and more flexible than the Xantrex/Schneider ePanel. (lots more expansion options) Midnight also has the high voltage DC breakers and lots of the "right"goodies.

Yeah I'm running their 150vdc breakers myself.

[Mike90250]

Snubbers for DC need to be designed/calculated for each load. Remember when cars had ignition points for the spark plugs? Those had a "condenser" in them and it was different for each car. Sure there were some "ball park" values, but the labor involved to carefully design a DC system is much more than using a proper inverter and "standard" wiring that all electricians know about.

https://www.autozone.com/ignition-tune-up-and-routine-maintenance/ignition-condenser