Per Ade's request, here are some photos of my DIY single axis tracked arrays.

I have revised all my racks to (3) 2 inch, 0.10 thickness square tube rails for greater stiffness, having retired my original 800W rack and badly snail trailed 175W solar panels.  It was designed for seasonal tilt only with thinwall 1.5 inch rails and wasn't long enough for the 325 to 355 W surplus or used panels I can get locally for very cheap.

This is all part of my custom inverter upgrade, now with sufficient power to run my 1500W home cooler plus have enough power left over for all my other activities. The cooler works by chilling water for my in floor heat system, and that project was previously reported on here.

Under the solar panels you will see two aluminum boxes.  One of these is the Arduino Nano plus Accelerometer board for panel angle sensing, plus real time clock module and H-bridge board for driving the linear actuator.  The second box is unrelated to the tracker, and shorts out one of the 5 panels when there is excess voltage for the current load.  This pre-voltage regulator allows my simple custom linear PV current regulator to handle the new larger capacity input. The linear PV regulator uses 7 IGBT transistors, each with an op amp current sensing driver to evenly share the total current load.  My battery bank is nominal 125VDC, 10 100ah "marine" (lead calcium) batteries in series. 

The entire tracker system is powered by one very small 12V panel and a small AGM battery which is located 1.5 foot below grade in an 8 inch section of round galvanized duct with cap about 12 inches above grade.  The trackers are timed so that they all do their hourly movement staggered in time a couple minutes apart, keeping the max current demand to about 2 amps.  The real time clocks and tracker program of the Nano with specific data table for the individual array orientation are set via laptop and USB cable.  The manual motor drive cable can be used any time by just unplugging the 4 wire auto trailer plug at the Arduino tracker control box, and plugging in the manual cable.  Once the
Arduino is plugged in it checks current position versus table position for month and time of day, and motors the panel to the proper position.  The real time clock has a lithium cell to keep date and time when 12V power is removed.  As you can see in the photo of the tracker box internals, there is zero custom hardware, it is just wiring up of off the shelf components. There is no heat sink required for the H-bridge controller at the puny power levels (2A of 12V) required.  The Nano board provides the 12V to 5V linear regulation.  While the Nano is sleeping, power draw of the whole thing is < 5ma, if the Nano power indicator LEDs are clipped. 

The PV rack mechanicals are pretty simple and derived from older my seasonal tilt rack design.  I'm using 1/2 brass rods with steel split pins as the unlubed pivot points, with stainless steel washers to reduce pivot drag. Many here are very skilled in practical mechanical design  and will come up with there own solutions.  I am pleased with the results here.  It is very solid and does not bounce in the wind, and easily supports my weight and bouncing on the rack with very little movement.  I did all welding myself with my now 3 12V marine battery DC stick welder (with galvanized sheet strip resistor) and 3/32 6013 rods. It was a challenge but I did get the hang of it. MIG would be much better suited to the 0.10 inch wall square tube. 

At present to develop the data table needed for month, hour and position, I used a solar calculator service online to get the plots of sun azimuth and elevation for my location.  I built a scale model with digital inclinometer, and would set up the sun angle and azimuth pointing to the properly oriented scale solar rack, and then eyeball the best tilt angle of the array, reading the angle from the  inclinometer.  A very tedious process.  I then convert via table the angles to accelerometer units. 
A better solution would be to have a program which does this all for you given rack orientation and range of tilt, GPS coordinates and spits out the actual text data table to be inserted in the Arduino Nano program.  I have not done that as my programming skills are now quite diminished.

Having operated this for about a year, (the summer rack for a bit less) I am quite pleased with the cost, performance and reliability.  One design idea I have is to tilt up a version of the summer rack to say 45 degree inclination (I have a south facing hill handy) to do a "winter rack".  This would add to winter day performance but if the drive was changed to +- 90 degrees via gear motor and chain drive, it could also futher increase sunrise/sunset power all year.

I keep watching battery technology and may someday change to LFP or one of it's successors as prices continue to fall and performance continues to improve. 

Best Wishes,
Bruce M


 

Ive been a fan of Bamfords since 38ac first showed one here many years ago.
I ran into this video that others might enjoy.
https://www.youtube.com/watch?v=cbQz5T-VA8s

I've noticed that LiFePO4 cells direct from China have come down quite a bit.  So I've been researching how to best handle cell balancing for a 120VDC battery bank (39 cells in series operated from 119V to 132V. (3.4 to 3.05V)  I've got a few years to get ready for the switch.

I wondered if Starfire or anyone else might chime in on homebrew designs?  I am familiar with the various commercial  balancing products, but they generate a lot more EMI than I'd like.  The modest current, passive balancers are lowest EMI but still it is connecting a microcontroller with SPI interface to all the cells.

My neighbor with the propane converted DES CS clone just did an old change at 1400 hrs, last one was at 400 and it looked like it just came out of a new oil bottle.  At 1400 hrs today, he said it didn't look quite like new oil but it looked good.

The last 1000 hrs have been utterly problem free until my push rod kludge failed, and with the new welded extension to the push rod, he's back in action with full power again. So the keep to success for a propane CS is a CA110 carburetor, Garrett type regulator, and a hot spark module.  A special thank you to Gary at DES again for his awesome technical support on our conversion project.

I'm surprised there isn't a surge of interest in CS's for conversion. 

I bought a new group 29 "marine deep cycle" battery to give the clean DC, 24V welding thing a go. They are rated 385 cranking amps so a good match for 100+ amp welding current, and they are what I have in my 120V battery bank now.

I made a 600 uH choke from a gapped 1000watt laminated toroid core; 22 turns, 16 feet, of 6 strands of 12 awg. I gapped the core with a 10" abrasive chop saw blade in my table saw. I only lost 1/4" of blade on the job, but it took 4-500 gallon tanks of air to make the cut.  I filled the gap with steel filled epoxy. To save some $ on the trial, I used some heavy jumper cables for welding cables. 

The exciting news for me is that yes, I can do it. While regular welders have me running for the hills from EMI headache, this was doable for me.

Welding on 2-12V batteries does work, and as the article I found by a welding enthusiast stated, the choke makes it possible. When I bypass the choke, it's just not possible to maintain an arc and get the puddle going. Alas, I seem to be a bit lower voltage than I'd like- no such thing as long arcing with this setup!  7018 (3/32) rods were a bust, could not maintain an arc and liked to stick and melt the rod. 6013 (3/32) worked, best with positive on the electrode.  I'll have to set up some meters on volts and amps and get my neighbor to watch them while I do a practice bead.  I'm ordering some 1/8 rods- more current may have better arc length and stability.

I suspect the losses in the jumper cable are not helping, so I will pop for some fat and short welding cables.  I may also reduce the turns on the choke.  No need for that much inductance, but I goofed on calculations when shooting for 250-300uH.  Battery and all cables were cool immediately after a 6 inch test bead. 

I'm very rusty, my last stick welding was in 1974.  I think with some practice and some fine tuning of the setup, I can do my own welding again.

Yippee!

More cloudy and cold stretches this winter than we've had in 20+ years, and last night a forecast 0-3 inch now has turned into 8+ and still snowing this morning.  This just after the last snow finally melted.  I'll be on PV and solar hot water snow removal when/if it stops.  An alarming change after over a decade of milder, warmer winters (and hotter summers).   

Lucky for me a friend brought groceries 2 days ago. There's no county maintenance on our dirt roads here, it's DIY all the way.

11:30
Massive PV to the rescue.  With my additional 1500W, despite heavy overcast (though with snow on the ground assist) I've got plenty of power to charge.  By the time I finished shoveling snow, my main battery bank was up to bulk charge voltage. 

I spent a few hours troubleshooting my remote fiber-cellphone hardware today. My memory is so poor it's a relearning project, though fortunately with pretty good documentation. The fiber-phone was a 2006 project, all hand soldered, no PCB, with a Picaxe M18 controller.  Ended up being one of the few Molex insulation displacement connectors I have left on that...on the 12v power to the solenoid that pushes the button to turn on the cell phone.

I never use Molex IDC connectors anymore, for good cause.  The contact to the wire is just not reliable over time. 

Not much fun working in the cell phone dog house when you're having a bout of Graves and your heart is going 100 BPM and your hands are shaking. 

I'm thinking of leaving my 6/1 on diesel for now instead of doing a propane conversion.  My new SOM wheels are 25  inch diameter so I must increase the ST-3 pulley size.  Since it worked out well for my neighbor's machine, I'm going single B belt.

At the same time, I'm considering a modest increase in RPM- say to 700 (ish) rpm.  This will benefit my air compressor which was being driven well below it's max rated speed. 

Are there any hidden surprises I should be thinking of?  My 6/1 has the iron piston.  Adjusting counterbalance weights on the new SOM wheels for a smooth run isn't be a big deal for me.

The B belt riding flat on the flywheel gives it an effectively large diameter compared to belt on the pulley vee shoulder.  So 1800 rpm at ST3 over the pulley ratio of 25.6"(SOM flywheel effective dia with B v-belt and no grooves)/10 (pulley size at ST3) gives me 1800/2.56 = 703 rpm engine speed.  A 10.25" pulley should give me 720 rpm. Either would be OK for my air compressor speed with existing 19" drive pulley.

Any helpful thoughts or gotchas I'm missing?