logistics of the solar upgrade

I met the Craigslist gentleman, who had what appeared to be at least 100 Trinasolar panels (SS250P-60) pulled from a solar farm. There’s not a lot you can do to test panels, so I did a visual inspection, label check, and Voc tests with the multimeter. There is weathering but no snail trails, not that I’m convinced they’d be a performance problem.

I can’t do the actual install for the next couple of days because of wind, but I needed to lay them out to make sure my imagined geometry matches actual geometry. I wouldn’t have any flat surfaces on BLM land so I did it in a city park parking lot before leaving ELP:

The steel runners are 12’ long and 65” apart. The panels are 39” wide so three in a row is 117”. The open area near the camera is spacing for the Maxxfan. Here’s a pic of the existing setup from the side:

the new panels are wider (65” vs 62”) and will sit slightly farther forward and extend over a foot further back

My original plan was to mount the panels between the runners but my rack crossbars are 65” wide; this means these particular panels will need to mount on top of the runners. This will make for much simpler installation (the panels will lie there on the runners while I work on them), but has two minor side effects:

  1. the new array will sit ~3.5” higher than the old array (2” runners + ~1.5” panel height). Not a big deal, it’s still lower than the Maxxfan when extended.
  2. the array will no longer be hidden/protected between the runners. I will have to be a bit more careful when bushwhacking around low branches.

The top-mount means the panels will have to be bolted through their bottom frame edge. Since I won’t have enough clearance to do this after the panels are on the rack I took the ground layout opportunity above to clamp the panels to the runners and drill the mounting holes. I already had one “homer bucket” for water decanting so I picked up 3 more to make poor man’s horses.

Drilling upward toward the underside of the panels was a bit scary; I used a metal spoon as a backing to keep from overpenetrating. I ran the bolts through with all the washers and nuts to ensure it worked; it did. An unexpected win after a hard month.

After that I put the panels back in the van and strapped the runners back onto the roof. Hopefully I can do the install later this week so I can get these ginormous things out of the the van’s living area.

another El Paso moment

I know you’re tired of hearing about the fine people of ELP, but this was illustrative.

The seller was building out a little 5th-wheel Scamp trailer and was eager to give me a little tour. He was using a Big Battery 12v pack, which I didn’t know existed – I thought they were all 24v+.

I paid up and he helped me move the panels. I got $3 back in change and wondered aloud what I’d do with it; he suggested buying a beer and I agreed. Since I was in ELP I mentioned getting Carta Blanca, which is like Modelo Especial but less expensive.

It took me a few minutes to tetris the panels into the van and he came back around. At first I thought he was curious why it was taking me so long to leave, but instead he was bringing me a cold quart of Carta Blanca from his refrigerator. :-) I stored it in the fridge and had it last night with dinner.


I forgot to mention a couple things. arm still sore from the first covid shot (Moderna, according to the paperwork) but nothing special

Doing housework today and got to watch the remaining mounted 380w in action. Solar noon isn’t until 1:09p local, but at 12:21p I observed 304.74w just before the system hit Vabs (12:26p). That’s 80.2% of the rated power, very close to the 83% I use for MPPT max harvest as a general rule of thumb.

The current injured setup is 380w:220Ah, or 1.7-to-1. With the old 2.59-to-1 I would rarely see over 50% of rated during charging because the panels harvest more amps earlier in the day. So why have more panel?

  • run bigger/more loads
  • share power with neighboring campers who might lack it
  • get into Absorption faster (not important with Lithium), minimizing the effects of cycling deeply
  • better harvest in marginal conditions

Longer bulk duration suggests Abs duration will be shorter. I’m guess maybe 3-3.5 hours instead of the usual 4-4.5. So maybe by 3:30p? I’ll set an alarm to remind me to check.