MPP LV6548 restarting when there is a small load and only solar

Man

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Jul 26, 2021
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I am brand new to solar and electricity, but have done a lot of research, design, planning, and want to be as safe as possible. Have been lurking the forum for a while but this is my first post. Any insight will help me out tremendously.😊

Setup:
Solar Array - 6 panels in 3 series 2 parallel 1500W total
Inverter - MPP Solar LV6548
No batteries yet

I don't have my battery cells yet, so just testing out the solar panels and inverter for now. Inverter is powered by 120VAC utility and solar array. I have the AC input plugged into a standard US wall outlet, and AC output on an extension cable. Wiring diagram and pictures below:
Inverter wiring.jpgLoads.jpg

Some Inverter Settings:
  • Output Source Priority: Tried 'Solar Utility Battery' and 'Utility Solar Battery'
  • AC Input Range: Tried both 'Appliance' and 'UPS'
  • Bypass Function: Tried 'Disabled' and 'Enabled'
  • Over Temperature Auto Restart: Disabled
  • Overload Auto Restart: Disabled
Problem:
The inverter restarts with small loads when the AC power is disconnected. I have seen it work with up to 400W, and stop working at as little as 100W. The inverter alone runs fine on just solar with no load. Have been testing this 12 pm - 3pm with full sun on the panels. I have utility power connected, and the solar array outputting 100V, confirmed with multimeter. I tried both yanking the AC power with load connected, and also connecting load with AC already disconnected. Once AC power is removed, the AC output is disabled and the inverter restarts. The issue seems to be with the inverter? Did I fry my inverter somehow? Am I expecting too much from the panels, and the occasional cloud is reducing output to less than 100W?

Things I tried:
  • Confirmed polarity is correct on all panel wires, and double-checked they are hooked up properly per my diagram.
  • At first I was confused my clamp meter was showing low amps on the solar panel wires. I realized that is normal when no load is connected, because the amps and watts only go when the loads are connected and current is able to flow. The clamp meter shows roughly 5 amps on the panels when I had around 500W load connected to utility through the inverter. With the array showing 100V, that math checks out to me. The inverter confirms this with the panels outputting roughly 500W. I presume if I connected more loads I would see nearly the 1500W max of the array. I should probably check that next.
  • None of the wires feel hot.
  • Inverter alarm sometimes not always shows LINE_FAIL when the AC gets pulled. Also shows 'Battery Under Shutdown' and 'Eeprom Fault' at seemingly random times.
 

lekeola

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Sep 5, 2021
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Just add more panels but make sure you don't exceed the Maximum open voltage
 
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Man

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Just add more panels but make sure you don't exceed the Maximum open voltage
That's unfortunate to hear. I would have to get all new panels since I was going to install this in an rv. Can you explain a bit more?
 

jasonhc73

Cat herder, and dog toy tosser.
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Location
Wichita, Kansas
Using SolarAssistant there is a way to force Utility First, not just 'Solar Utility Battery' or 'Utility Solar Battery'

Every since I started using Solar Assistant, I have completely forgotten how to use the panel or watchtower.


1632866558824.png

1632866660205.png
 
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Man

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I learned a few things after some troubleshooting:
I’m just not getting the wattage I expected from the solar array. I don't think it's the inverter. The max I have seen is less than half the 1500W. Is there a calculator somewhere to estimate what output to expect from the panels in full sunlight based on coordinates, tilt, etc.?
  • I shorted each of the panels and they all get about half their rated 8 amps in full sun.
  • The full array gets about half the rated 16 amps as well.
  • I eliminated the MC4 combiners and fuses as factors and they are fine.
  • The inverter does not detect any wattage from an array below 80V, which is expected per the manual (Start-up voltage). I guess this means I would need at least 3 panels in series to run any loads or charge batteries.
Moral of the story so far: The panels are used and were the cheapest on SanTan's site, so maybe they drastically lost their efficiency. But all the panels test similarly. I might ask SanTan. I don't expect to use the system without batteries, just wanted to test it out. Maybe the array will be enough to charge the batteries and run the system as designed. Will's batteryless video kind of indicates to me these inverters may not be optimal for batteryless. I thought I was oversizing the system enough, since I wanted at least 1000W solar.
 

jasonhc73

Cat herder, and dog toy tosser.
Joined
Oct 1, 2019
Messages
1,640
Location
Wichita, Kansas
I learned a few things after some troubleshooting:
I’m just not getting the wattage I expected from the solar array. I don't think it's the inverter. The max I have seen is less than half the 1500W. Is there a calculator somewhere to estimate what output to expect from the panels in full sunlight based on coordinates, tilt, etc.?
  • I shorted each of the panels and they all get about half their rated 8 amps in full sun.
  • The full array gets about half the rated 16 amps as well.
  • I eliminated the MC4 combiners and fuses as factors and they are fine.
  • The inverter does not detect any wattage from an array below 80V, which is expected per the manual (Start-up voltage). I guess this means I would need at least 3 panels in series to run any loads or charge batteries.
Moral of the story so far: The panels are used and were the cheapest on SanTan's site, so maybe they drastically lost their efficiency. But all the panels test similarly. I might ask SanTan. I don't expect to use the system without batteries, just wanted to test it out. Maybe the array will be enough to charge the batteries and run the system as designed. Will's batteryless video kind of indicates to me these inverters may not be optimal for batteryless. I thought I was oversizing the system enough, since I wanted at least 1000W solar.
I'm using 12 panels used from Santan and 10 new ones. :)

Your low amp output explains it all, they are just not getting enough juice to work your load. 😲👍
 
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Man

New Member
Joined
Jul 26, 2021
Messages
6
Using SolarAssistant there is a way to force Utility First, not just 'Solar Utility Battery' or 'Utility Solar Battery'

Every since I started using Solar Assistant, I have completely forgotten how to use the panel or watchtower.


View attachment 66766

View attachment 66767
Not sure if I would want to run Utility First? I would prefer it to use solar first for an RV scenario. Looks nice but Watchpower and the panel have been ok so far.
 

Man

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Joined
Jul 26, 2021
Messages
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I'm using 12 panels used from Santan and 10 new ones. :)

Your low amp output explains it all, they are just not getting enough juice to work your load. 😲👍
I'm going to spray them off and reposition them a little better then see how they do tomorrow.
 

jasonhc73

Cat herder, and dog toy tosser.
Joined
Oct 1, 2019
Messages
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Location
Wichita, Kansas
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