portables and a rainy day

vevor panels

I picked up the weirdo panels from Home Depot for use as portables. The box was damaged so I popped the box open in the van; looks good at first glance.

The design is wonky but the build quality of the panels themselves seems fine. No trails, suspicious solder joints, etc. I suspect they are so cheap because the design makes them nearly useless for typical buyers: apparently 15Voc / 12Vmp.

Update: I got a pic of the backside label and it really says 15Voc / 12Vmp.

rain, rain

It’s been raining since I got back so I can’t set them out to take a Voc reading. And since the solar port isn’t installed yet I’d have to run the wires through a cracked window. I’ll just wait

At this moment it’s 100% overcast and raining. The mounted array is pulling 13.6% of rated based on the cosine of solar zenith. Certainly not the “zero watts” often claimed by those who have not actually tested/observed an actual system.

DIY tilt mount

When I had the 2x 100w Grape panels before I just leaned them against a log or whatever. This year I want to tilt/orient them for optimum stationary harvest.

Commercial tilt racks like the Renogy are >$20 and are not well-suited to my purposes:

  • my panels are separate so would require two racks (~$50)
  • the rack brackets are permanently affixed to the panels, which would ~double the thickness of the stored panels in my use case

So I’m going to try to DIY a kind of adjustable support. For $15 I picked up a thrift store camera tripod, a 36” redwood 2x2, and some hardware (including wingnuts) for attaching the 2x2 to the top of the panels.

The idea is to use two bolts to hold the panels to the 2x2, then suspend the 2x2 from the tripod at a height that provides that optimal tilt.

update - rain stopped, set up portables

Rain stopped for a bit so I set the panels out. In present conditions and in series they are 27.43Voc, just right for my intended usage.

first use of ferrule crimper

I ordered a “bootlace” ferrule crimper that came in a case with different sized insulated ferrules. I’d watched a bunch of videos on proper use and finally got to put it to use.

Today I crimped the bare ends of the MC4 plugs that go into the controller’s PV inputs. Worked better than I expected for my first attempt. It’s not perfect, one of the four sides is a little crumpled inwards. Maybe a more $$$ crimper would do it more evenly?

running the extension

I ran the long extension (50ft!) out behind the van and through drivers side window. If the panels behave I’ll install the port to avoid such shenanigans.

When I measured Voc at the end of the extensions it was somewhere in the high 26v range, so I’m losing about a volt on the run. Don’t care, 50ft of positioning freedom covers a multitude of sins.

connecting to the 10A MPPT

By the time I got everything hooked up the system was already well into Absorption. Even so, the portables were making 99w. So they work.

I reconfigged the 10A mppt to mirror the main controller, but +0.5v on all setpoints. I did this for a couple reasons described below.

observations: Float

During Float the portables carry the background loads and the main controller loafs. For example, right now the portables are making 74w and the main controller is making 2w.

With a small load I’ve seen the 10A put out 128w, north of 9A.

observations: Float with heavy load

When a heavy load is applied (making Peruvian beans in the Instant Pot, in this case) the main array carries more than its fair share, The main controller talks to the Smart BatterySense to get actual bank voltage and therefore deliver precise power.

observations: Bulk

[the following morning]

Both the 200w portable and 750w mounted are laying flat. The mounte

  • the portables on a 50ft extension are making 63% of rated
  • the mounted panels are making 69% of rated
  • The cosine of solar zenith angle says the max harvest would be 75.01% of rated (before wiring, temp, and MPPT losses).

At 10:10am I’m seeing net 37A into the battery bank. I can live with that. :-)

tweaking the portable controller setpoints

The portables are running on a spare 10A EpEver MPPT controller that has no way to voltage sense. Other than the BATT terminals on the controller, I mean.

In addition, for convenience and historical reasons the controller’s BATT output goes to the POS/NEG buses instead of directly to the battery.

Both of these mean that the controller cannot accurately assess bank voltage under heavy charge/discharge. This isn’t a problem for my hide-in-the-shade summer use case. The van is positioned where it will receive sun after noon, by which time the bank is already 100%. The portables are intended to support normal background loads by sitting in the afternoon sun.

If this (or 10A clipping) bothers me enough I can break out a spare 50A EpEver MPPT I have as a backup. It can voltage sense with a sense wire and obviously handle more than 10A. :-)

The 1210A and EpEver apps

My 10A is actually the older A (not AN) model, which introduces some software weirdness.

  1. as of this writing the newest EpEver software (Solar Guardian is better than the older app below; it has realtime data, graphing, etc. It is compatible with the AN but not the old A. In my testing it showed data from the A but threw errors on read/write.
  2. the older janky app [Charge Controller (Sealed)][https://www.epever.com/support/softwares/] does read/write correctly but requires constant refreshing to see stats.

The workaround is to configure the A in the old app then do the monitoring in Solar Guardian.


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