Allen Jackson

This is sorta what I have in mind, but subbing the retractable shade with solar panels and maybe larger...

https://www.youtube.com/watch?v=r5TZx7krOaE&pp=ygUWd29vZCBieSB3cmlnaHQgcGVyZ29sYQ%3D%3D

He lives in the northern Illinois area, and appears to have many of the same local building code restrictions I do.

I've been looking at those for a few years, and the reason I haven't pulled the trigger, is that I saw a YouTube video where someone showed you could be both more flexible with a DIY battery/inverter and an off-the-shelf mini-split AND do it cheaper too.

The most common question I see on those product pages, is whether there's any way to use the solar panels for any other purpose when AC wasn't needed. With a DIY battery/inverter, you can plug in anything that you want, not just the mini-split.  Not to mention that I already have the batteries, inverter, and nearly everything but the solar panels (and a place to put them...)

The EG4 hybrid units will allow it to run from either grid or solar power, but won't allow the solar to power anything else.

I've got intentions to build a large "pergola" I can mount solar panels to, but my wife keeps trying to plant shade trees there ☹️

Recent changes to the NEC require solar panels installed on building roofs have module-level shutdown capabilities, in case a firefighter needed to cut through the roof to save lives during a structure fire, without worry about being shocked/electrocuted. They later ammended the code to exclude "ground-mounted arrays", because no one will ever need to chop through those panels to access & save a life. I believe that a pergola so equipped, without any walls, would qualify as such a ground mounted array, thus saving the considerable extra expense of needing all components to drop down to below 30 Vdc in 15 seconds, or whatever the new ridiculous standard has become.

In the same update, they separated battery energy storage systems, recognizing that it's impossible to get such a system to go down to zero volts in a hurry safely, and the best they can do is require clear hazard labeling and a rapid shutdown switch for the inverter.

A nearly PERFECT day for solar, ruined by having to work (inside)...

More toys came in the mail today - I now have (I think) all the remaining parts I need to complete this build. I can hook up & use all 3 charge controllers with these parts.  Now I just need to get the time to do it!

1 horsepower = 746 watts. DC power (in watts) = volts x amps.

For a 4-cell LiFePO4 battery, the voltage is nominally 12.8 Vdc, so you can multiply each horsepower rating x 746, then divide the result by 12.8 volts to get the ideal current required from the battery with 0 losses.  If you have the wattage already, you can skip that first step and just divide by the voltage.

Divide that by the system efficiency to get the real-world current draw. That should give you a better idea of whether you're really needing to go to a 24 Vdc system, in terms of current requirements, and the duty cycle will determine how many (more?) Ah of capacity you might need.

I've been up to no good again...

Very warm and sunny day, but I chose not to work on the outdoor testing of this, and instead, work on some polish and trim details.

I discovered hot glue - the world may never be the same now! The 50 amp controller is now firmly in place (and I drilled holes in the toolbox, so I can't return it now!). It's mostly wired - still need to terminate the solar end of those wires at a DC disconnect breaker.

I've cut off the 5/16" ring terminals on the 12 Vdc outlets (can't return them now either!) and re-terminated with 10-12 GA 1/4" ring terminals, so I can move them to the smaller (M4) screws on the bus bars and save the 5/16" studs for higher current connections.

I have ran wires to the 30 amp (idle) charge controller, because it will be buried when everything else is in place and there's no way to get tool access to connect to it later without tearing everything apart. Only a few more connections to the negative bus bar, then I can move on to the positive end of the toolbox.

The charge controllers in the lid will have their battery breakers hot-glued inset in the lid, and the negatives will connect directly to the negative bus bar. I've done a test fit with the breakers in the hollow area above the handle in the lid, and I can still close the top.

If my numbers are correct, 1/2" soft copper pipe (type M) has a cross-sectional wall size that's just over that of 2 AWG wire (33.8 sq mm vs 33.6 sq mm), so flattened copper pipe would make a good bus bar, with at least a current capacity of 190 amps (at 105 degrees C). I could use 3/4" copper pipe instead, but that doesn't seem necessary & I haven't run the numbers on anything larger yet.

3/4" type M copper pipe appears to have a cross-sectional area that's just over the size of 1/0 copper wire, and can probably handle equivalent current to that.

1" type M copper appears to have a cross-sectional area that's just over halfway between 2/0 and 3/0 copper cable...

My homework/showing my work, just to allow others to check my figures:

{Nominal outside diameter of the pipe/2 squared x Pi (radius squared x Pi)} - {nominal inside diameter of the pipe/2 squared x Pi} should equal just the area of the wall thickness.

Conversion of square inches to square mm is done by multiplying the sq inches x 25.4 x 25.4 (squared).

Most of the charts showing pipe sizes are listing in SAE/English units, ie. inches, not metric, but the chart I found showing wire gage equivalents was a chart showing everything in metric (mm). Wire sizes larger than 4/0 use the metric system anyway.  The European norm is to use a comma delimited where Americans are accustomed to using a period, so be mindful of that when reading that chart.

https://www.sab-cable.com/cables-wires-harnessing-temperature-measurement/technical-data/cables-and-wires/american-cable-stranding.html

Types K and L are thicker walled pipe, so they could support even higher current than these examples.

https://pexuniverse.com/copper-pipe-dimensions-specs

After finding the next smaller size wire on the chart, one can then cross-reference the ampacity charts for that size wire, using whichever temperature column one is willing to insulate to.  This post is dedicated to my high school math teacher Ms. Klingsic, who insisted that EVERYONE wants to see my work... 😉

John Weiland wrote:

Allen Jackson wrote:Do you have the specs of the pump?

Mine didn't come with any bus bars or terminal screws, or separator sheets, but I'll sort it out. (I think they're M4 holes?)

I will track down pump specs for a next post.

Do your cells look like the ones I recently bought (below).....mine also did not come with bolts or bus-bars or separator sheets, so I purchased those separately.  And yes, M4 bolt size for the terminals.

Mine are apparently sold as "100 Ah" cells, and yours are "105 Ah" cells. I'm a little concerned about the "3C" listing on mine, because I don't want to put 300 amp bus bars on this set... Nice to know the capacity is there, but I don't expect to ever use that unless I were to get a set of 8 for a 4S2P configuration to replace my car battery, with a 600 amp current capacity. If I use the old 40 amp BMS the I won't have to worry about it, & I can just use 6 AWG wire to connect them.

The ones I bought:
https://www.amazon.com/dp/B0GFFSFWWN?

I must add, I'm having trouble reconciling a 300 amp terminal connection that's held together with only an M4 screw... I might need to drill the holes out and tap to at least M6?