Am I nutz?

[Vern Faulkner]

The Lady and I are aiming to build an off-grid home in the next three-five years. In the interim, we're taking our living area off the grid this autumn.

I have two 6v, 370 Ah  batteries at one  end, and now two 240w solar modules at the other. The second one came yesterday with a MidNite Classic 150.

Previously, I had a single 240W panel leaning against the house, not in an optimal position, but I had a basic POS 15A controller that I didn't wanna blow. It did an OK job of charging the batteries for a month or so, least as I could tell relying on the voltage measurement on the inverter.

Last afternoon, I assembled the controller so it would convert power from the single 240W panel. Occasionally cloudy, some sun. Only pulled 1.2 amps off the panel, which is connected by five feet of #10 wire: shouldn't be any notable loss across that small a run, by my calculations.

This morning, I installed the second module - should be good for near 500W in ideal conditions. It's not ideal, mind you: today is a rainy day, but not gloomy dark. Call it overcast. I've moved both modules slightly, so they are fully exposed to the rainy sky above.

My gut, and a reasonable degree of electronics knowledge, tells me that I should be able to pull a couple of amps, even in a grey-ish day. I'm not getting a thing.

The controller keeps bouncing into "resting" mode (code 15), after the device clicks in - it pulls the input voltage from the 58-60 range, down to 11.9, then the unit shunts into resting mode. It's clicking back and forth, but nary an amp is being put into the battery.

I did a complete reset to factory defaults, followed the wizard through, inserted the various numbers (battery AH, module output, voc, etc.) and still not a thing.

Meanwhile, a cheap-@^# 40W panel feeding into a cheap-o 12v marine deep cycle battery through a cheapo- controller is showing a charge created, though I can't verify current due to the lack of a suitable multimeter.

The only thing I can think of, is that the batteries were drawn down to 12.0 (says the MidNite) or 12.2 (says the inverter) due to about five-six hours of computer/light use last night (90-150 watts over five-six hours- call it 60Ah drawn). (Figured we might as well put some load to take down the charge, since the panels would offer a hefty charge today: part of the test-it-plan I had.)

What gives?

[boB]

That code 15 basically says that it is cloudy and there just isn't much if any there to charge from.

But, you may want to try another MPPT mode just for grins.

Go the the MPPT mode and change it to Legacy P&O.  It should slowly
run the input voltage down towards the battery and find a sweet spot.

Let us know if that works better.   Also watch the power output as it is
bringing the PV voltage down and if there is not any partial shading,
somewhere around 40 volts you should see max power.

boB

[Vern Faulkner]

That code 15 basically says that it is cloudy and there just isn't much if any there to charge from.

But, you may want to try another MPPT mode just for grins.

It's early morning here: 9:22 a.m. Sun is behind the trees in the east, but a nice blue sky.

Tried legacy, it dropped the voltage down to the 40s, as you said, and then clicked out.

I know the modules aren't in an ideal location. Might move 'em (will need to run some long wires) today. Either way, I should get some juice out of the modules today.

[boB]

How many watts did you see when it came down to around 40 volts ??

You also may want to check your connections to make sure there are
no loose connections.   That can cause low power too but would do
that in good sun too.

boB

[Vern Faulkner]

Just wanted a little direct sunlight, I guess: this is the first part of my learning curve ... and the reason I wanted to get things going now, before we build.

[boB]

Just wanted a little direct sunlight, I guess: this is the first part of my learning curve ... and the reason I wanted to get things going now, before we build.

Oooo !  MUCH better I would say !

Thanks, Vern !

boB

[Vern Faulkner]

Continuing a theme ... now I'm worried about the batteries.

We have a generic 12v modified sine wave inverter powering the living room computer and a light. The entire batch, at worst, draws 140 Watts.

The last few days, the controller has pushed 700-900 watts into the system daily. However, the voltage reading on the batteries seems to plummet sharply under minimal use.

For example, I left the house at 6:30 p.m., with the voltage at 12.9. The Lady was watching "Bachelor" for three hours, online. Max draw, call it 140 watt-hours. Voltage was down to 12.5. Now, after about four hours continual use, the voltage is down to 12.1, which by my count is quite discharged.

My math says the wife has really only drawn, at max, 600 watt-hours out of the system - probably closer to 500 watt-hours, or, say, 40 amp-hours.  That should really only represent about 12-15 per cent of the total charge of the 370Ah batteries, but it seems to be representing almost a 75 per cent discharge, if my knowledge of the voltage readings is accurate.

What's worrying me is that the daily input is far exceeding the daily draw, and yet the batteries seem ill-charged. I've set all the voltages on the charge controller accurately, and it is dumping as much as 380 watts - and usually 20-25 amps - into the batteries around noontime.

Thoughts?

[Vern Faulkner]

Ah-hah! Turns out the controller's voltage readout was off by a good 0.3v.... I had assumed it was accurate.

[boB]

Ah-hah! Turns out the controller's voltage readout was off by a good 0.3v.... I had assumed it was accurate.

So, it was more like  12.4V rather than 12.1 ??

boB

[Vern Faulkner]

Ah-hah! Turns out the controller's voltage readout was off by a good 0.3v.... I had assumed it was accurate.

So, it was more like  12.4V rather than 12.1 ??

boB

That's it in a nutshell ...