Very low RV solar panel output under clear skies?!?!

[cottersay]

At least you found it. What brand and mode of 120V AC to 12V DC converter? Maybe it was some type of solar ready converter.

It may have been solar ready, but they didn't mention that in the RV's user manual, and I had no extra wires left over when I had to replace it because it couldn't fully charge Li batteries (it was made for lead-acid only).

 

[bobdelso]

Thanks for all the help, guys! I followed the testing procedures as laid out by rickst29, Zwy, and Short_Shot, and discovered that the solar output current didn't change whether there was a single panel connected or all four connected to the solar controller (about 3A). This led me to believe that the RV's solar wiring may be -- for some unknown reason (but knowing RV manufacturer's sloppiness) -- being sent into some input in the RV's 120V-12V converter; so I attached the solar controller's output directly into the Li battery bank and voila; I was now able to get 17A on this hazy day.
Anyone ever heard of this problem before?

Its possible there is a kink in the wire or other damage which is limiting the current

 

[Short_Shot]

Hi Bud. I installed the Renogy solar system, and immediately had this problem. But the RV manufacturer installed the defective internal solar wiring at the factory, which should have been rather idiot proof, as the wiring (of course) need only go from the external bulkhead SAE connector located on the side of the RV, on to the forward battery bank. Yet they somehow screwed it up (it was their first year making "solar ready" trailers, if that's any excuse.)

Edit: I memory bad.

You did say it was "sent" into something else. That's a pretty major problem lol

What specific device was it connected to and which ports?

 

[cottersay]

Hi Short_Shot. Me memory be so bad 2!
I never checked where or even if the built-in solar wire is connected to the new Li converter. And for all I know, they could have also used 20AWG wire. (After all, it would have saved 99 cents on our $30,000 RV!). So I don't know for sure what the problem is, so I just bypassed the whole mess and decided to go directly* to the battery.

*But first through the Victron BMV battery monitor shunt.

 

[Swamplizard]

Glad I found this thread!!!! I have 2S2P flexible 100 watt on an RV. At noon in winter FL I see 2-3 Amps and 75-85 watts according to MPPT. That ain't right! Need to check the wiring and polarity per suggestions above. Should't I see 80% minimum from each panel (somewhere around 80 watts each? Keep in mind this is 2 in series and two banks in parallel .... I'm getting wrapped around the axle a bit here ;-)

 

[Bluedog225]

Yep. Double check ( or abandon) any install done by an RV manufacturer. Glad you figured it out.

 

[Swamplizard]

I only have me to blame - took a Promaster Van and converted it to stealthy RV ... maybe I am expecting too much out of 4 100watt flexible panels

 

[MisterSandals]

At noon in winter FL I see 2-3 Amps and 75-85 watts according to MPPT

Have you checked the actual panel and string (2S) output volts and amps are? Maybe unplug one string and see how it compares to the other?
Looks like something isn't right. Maybe bad or mismatched MC4 connector.

 

[Swamplizard]

I did yesterday as we finally got sunshine…each string is producing the same voltage and wattage….and when I combine them it doubles. Getting 3 amps at 75 watts combined. Battery is 24v lifepo4 and is at 74% charged per the LV2424 all in one. This was at noon, no shade, in Fort Lauderdale area with air temp of 78. Panels are on a flat RV roof.

Are my expectations out of whack…new to solar.?

 

[MisterSandals]

each string is producing the same voltage and wattage

What are the volts and amps for each string?

 

[rickst29]

MisterSandals has given great advice, but your results are already spot-on for your situation. I set the pvwatts cacluator https://pvwatts.nrel.gov/pvwatts.php to match your location, and array size, on a flat roof mount aligned straight South. On THIS January date, the calculator only shows about 213 DC watts from the array at noon. You're claiming "around 225", that's very close.

 

[MisterSandals]

but your results are already spot-on for your situation. I set the pvwatts cacluator...

Where is the fun in taking the guesswork out of it?

(well done!)

 

[Swamplizard]

What are the volts and amps for each string?

31-32volts for combined 2 strings (were identical for each single string) and amps are 2-3.

 

[Swamplizard]

cool?

 

[MisterSandals]

31-32volts for combined 2 strings (were identical for each single string) and amps are 2-3.

Sounds low but you have not provided any info about your panels. 100W panel maybe 19V Vmp so i would think 2 in series would be ~36-40V.

Getting 3 amps at 75 watts combined.

This is 25V.

Your LV2424 is a 24V system right?
I cannot imagine it would charge or even start charging at 25V (which means charge voltage would be ~28V when operating).

Are your "measurements" based on what the LV2424 is displaying or are you measuring with a volt/amp meter? I think you need to see what each panel reads with a meter, then combine into a series of 2 panels and see what they read.

 

[Swamplizard]

Yes 24-volt LIFEPO4 280AH battery.
Saw 130 Watts today at 2 amps today so a bit better than what I have seen in the past. Battery was at about 50% charged.
I see the watts/volts on LV2424 and on the app for the BMS. Volt meter used to confirm each string and combined string and was in sync with LV2424.

 

[Zwy]

Yes 24-volt LIFEPO4 280AH battery.
Saw 130 Watts today at 2 amps today so a bit better than what I have seen in the past. Battery was at about 50% charged.
I see the watts/volts on LV2424 and on the app for the BMS. Volt meter used to confirm each string and combined string and was in sync with LV2424.

You have run into the winter blues when it comes to solar mounted flat on a RV. Many people head for BLM land in AZ or other states for the winter and found that flat mounted panels in winter just will not produce enough output. Part of the reason I made half of my RV array tilt, at least I can tilt those enough to garner some output in winter. If you go on Youtube for people who went to Quartzsite in winter with flat mounted panels on their RV, they learned they needed to tilt panels or have some ground deployed panels tilted perpendicular to the sun which is low on the horizon.

For my house, I spent the extra money on a MT Solar tilting mount with the ability to tilt to 65 degrees in winter. The mount was costly to say the least with current materials' price increases. However, if one runs the numbers thru a calculator that determines solar output on azimuth and tilt at various latitudes, you will find that tilt in the winter months is very important and the return on cost might be worthwhile. What good is a solar array in winter if it doesn't produce? Adding size to arrays might help but still, if fixed angle, at some point you will lose productivity. If tilted to 60 degrees for winter output, then in summer, the output will decline. Maybe the answer for fixed tilt is to make the angle more conducive to winter output as there are more daylight hours during summer. The best solution really is adjustable tilt, although many will argue to simply add more PV but with limited space such as an RV, you can't do that.

 

[Swamplizard]

Thanks Z! Good stuff

 

[Swamplizard]

Quick update: Cleaned up connectors, replaced one that seemed a bit sketchy and am now seeing 110Watts at 4 Amps at noon. Better and considering battery is 90% full I need to do a test with 50% full or under load next. Figured I'd say thanks on connector check suggestions above.

 

[12VoltInstalls]

Quick update: Cleaned up connectors, replaced one that seemed a bit sketchy and am now seeing 110Watts at 4 Amps at noon. Better and considering battery is 90% full I need to do a test with 50% full or under load next. Figured I'd say thanks on connector check suggestions above.

You can test ohms between the contacts in the diode box and the MC4s and make sure they’re all basically the same to seine out any others