120V on the PV line?? Discussion of Will's video

[Will Prowse]

There have been a few posts of prior incidents:

Growatt 5000es AC voltage detected on PV input!

Hi. I have two growatt 5000es hybrid inverters connected in parallel. All connections are correct as per instructions: For each inverter: AC input: 230v L and N and ground Ac output: 230 v L and N and ground So ground of input and output are connected to same ground wire. PV input: 300V...

diysolarforum.com

Dc mini breaker confusion

The thing you should have done was check polarity on PV side prior to closing switch. If inverter side is concealed, then after confirming zero volts on that side see if you can verify connections (desired polarity at breaker) with ohm meter. You can connect PV panels and wires in series...

diysolarforum.com

AC voltage from lvx 6048 to a wire not connected to anything? 83V

I'm assuming I have a short somewhere but I'm also a little stumped. My solar arrays are 400ft from the house. I ran 5 wires through plastic conduit, 2 hot, 2 neutral and 1 ground. I'm getting 120 AC voltage on every wire even though they're not connected to the LVX 6048. I get voltage from L1...

diysolarforum.com

Safety tips for all-in-one inverters

Hi All, Are there any safety methods that you know for the longer life of all-in-one inverters? For example, one method I heard was, "Don't cut the battery power while the inverter is powering the loads". Likewise are there any other small tips that you know? Thank you.

diysolarforum.com

The "Meg" Build

Alright, im doing testing. Here's what I've found so far. The negative from my 48v battery is grounded to RV chassis. Im assuming this is happening through the 48v to 12v converter, because the output of the 12v side is grounded to a common ground screw on the frame. The inverters do have...

diysolarforum.com

This forum format works for conversations, but difficult to look up topics.
Think we can get ChatGPT to index it and provide natural language query?
Searchable VAERS database?

Wild that I missed every single one of these posts. And yes that would be nice. That is a downside of discussion forums.

 

[EastTexCowboy]

Can you connect the battery again and turn on the inverter? Why did you disconnect the battery? I do not understand the point of your test. Connect the battery, and turn on the inverter. Or charge from grid and tell us what your results are.

I tested it that way and got 102v AC on the PV input, both positive and negative - post #30 here but I may not have been clear.

I tested it with only the AC input connected based on your video. At about 52 seconds you say that if someone had either the battery and/or the AC input connected you could have a shock hazard. I tested it with only the battery turned on then with only the AC input turned on (the "or" part of the and/or). It was only with the inverters turned on that I see the voltage. Then after watching your video again at about the 3 minute mark you do state that this situation occurs when the inverter is on and there is a battery or AC input connection. So I misconstrued the test configuration and tested with the inverter turned off the first time.

The whole thing is a little confusing what with different models having different results based on what is connected or not connected. But the bottom line is that yes, I do see voltage on those connectors under that situation.

Thanks for all the time you've put into this and for watching out for us!

 

[Gavin Stone]

I tested it that way and got 102v AC on the PV input, both positive and negative - post #30 here but I may not have been clear.

I tested it with only the AC input connected based on your video. At about 52 seconds you say that if someone had either the battery and/or the AC input connected you could have a shock hazard. I tested it with only the battery turned on then with only the AC input turned on (the "or" part of the and/or). It was only with the inverters turned on that I see the voltage. Then after watching your video again at about the 3 minute mark you do state that this situation occurs when the inverter is on and there is a battery or AC input connection. So I misconstrued the test configuration and tested with the inverter turned off the first time.

The whole thing is a little confusing what with different models having different results based on what is connected or not connected. But the bottom line is that yes, I do see voltage on those connectors under that situation.

Thanks for all the time you've put into this and for watching out for us!

Definitely voltage on the lv6548 inputs. I’ll see if I can check mine this week also. I expect similar results.

 

[EastTexCowboy]

Wild that I missed every single one of these posts. And yes that would be nice. That is a downside of discussion forums.

You're falling down on the job, Will! You're supposed to monitor and respond to every post no matter what the day or time, and know the answer to every question. You should also know from memory the specs on every piece of solar equipment that's ever been built for the last 20 years and any related known issues.

There's only so many hours in the day. Plus you're dealing with the fact that your forum has set the bar for anything DIY solar so you're paying the price for being so successful. So don't feel bad about missing a few posts. We all appreciate what you've given us!

Ugh. That sure sounded like sucking up to the forum owner. I'm sure I'll catch some flack over that!

 

[Gavin Stone]

You're falling down on the job, Will! You're supposed to monitor and respond to every post no matter what the day or time, and know the answer to every question. You should also know from memory the specs on every piece of solar equipment that's ever been built for the last 20 years and any related known issues.

There's only so many hours in the day. Plus you're dealing with the fact that your forum has set the bar for anything DIY solar so you're paying the price for being so successful. So don't feel bad about missing a few posts. We all appreciate what you've given us!

Ugh. That sure sounded like sucking up to the forum owner. I'm sure I'll catch some flack over that!

Stop sucking up to the forum owner.

 

[timselectric]

Suck
Up

 

[EastTexCowboy]

Suck
Up

Nag

 

[OffGridForGood]

These measurements were done while the inverter is running from the batteries, utility available but not charging. Sun is down so no incoming PV.
I will measure again when the SCC is running on incoming PV to see if that changes things.

It does change things:
With incoming solar on PV:
MPP Pos or Neg to EG Measures zero in Volts AC,
But MPP Pos to EG in Volts DC measures 75-82 volts (which is about the PV voltage).
MPP NEG to EG measures 20-60milli-volts DC
Incoming Utility available or not, makes no change to above.
It seems to me the MPP 6048 is pulling the PV-Neg to EG internally, unless I am missing something.

 

[timselectric]

I think that there's some internal bleed through between DC and AC output. On the inverter/charger boards. And this is what's being measured.
Not uncommon for high frequency stuff.

 

[OffGridForGood]

I think that there's some internal bleed through between DC and AC output. On the inverter/charger boards. And this is what's being measured.
Not uncommon for high frequency stuff.

I have to ask, what is going on though, that different results seem to happen to people with the same model inverter?
I mean Will noted this in the Vid, but these AIO's are being built on assembly-lines cookie cutter identical, should we not see similar results for each interverter model? Are there installation differences that are affecting what we are seeing and measuring?

 

[ko6kL]

First version eg4 6500ex has 20VDC and nearly 0VAC on input when inverter is on. I did not test with AC input connected to grid.
View attachment 135555View attachment 135556

The eg4 6K has 60V .16A on PV input when shorted to ground with 10K resistor. Also makes a buzzing noise when you short the terminals to ground. And arcing.

Original MPP lv6548 has varying voltage but it gets pretty high when it does.

I tested another model which is a prototype that has solid 120VAC at PV terminals. This one was dangerous and blew my meter.

Growatts seem to have same issue and multiple people in my videos comment section reported getting shocked by those units.

you should not be seeing 120 AC on the PV lines... that's going to be a problem at the combiner box. ( somebody skiped a bypass capacitor or something inside to save a buck )
you could be seeing some DC from the SCC towards the PV inputs , i think it squirts a little DC towards the panels every so often looking for current coming back and it controls this voltage up and down to regulate the flow ( just my observations ) I see my SCC send 40v back at the panels when its reached 100% SOC in the afternoon and that shuts her down max power for me is ~36v.
also complex waveforms could look like AC on the meter but its DC-PCM etc....
if you think its really hot remove the PV's and put a light bulb on it... under load you can read the real power remaining.

 

[timselectric]

I have to ask, what is going on though, that different results seem to happen to people with the same model inverter?
I mean Will noted this in the Vid, but these AIO's are being built on assembly-lines cookie cutter identical, should we not see similar results for each interverter model? Are there installation differences that are affecting what we are seeing and measuring?

Bleed through will vary depending on temperature, humidity, and other things I can't remember at the moment. So, I'm not surprised if different voltages are being measured on different units at different times.

 

[timselectric]

The AC voltage is partially being induced onto the nearby DC traces on the boards.

 

[OffGridForGood]

you should not be seeing 120 AC on the PV lines...
if you think its really hot remove the PV's and put a light bulb on it... under load you can read the real power remaining.

Does the type and quality of multi meter also matter? (I used the one recommended by Andy's channel UNI-T UT210D)
Is there posibility how the AIO is grounded or how the Neutral(s) are addressed could be influencing what people are seeing?
I am curious if different results on identical inverters is telling us that connections, looped grounds/neutrals PV-conductors tied to EG are factors that are creating these differences? I mean it seems to me identical inverters should have/show the exact same outcomes - except for the things that are not identical like how each is connected.

 

[timselectric]

Also how many panels are connected. And length of conductors.
Different number of diodes and resistance differences.

 

[Hedges]

Does the type and quality of multi meter also matter? (I used the one recommended by Andy's channel UNI-T UT210D)

If AC is 60 Hz sine wave, they're probably all adjusted to give same reading as RMS.
If waveform is different, non true-RMS will give a different reading. Roll off vs. frequency will differ among brands.

This week at work I was adjusting a filter circuit (actually a DC block and voltage divider), and used a DMM to measure input & output AC voltage, while driving with 20 Hz to 1000 Hz using UPS. I connected two handheld meters so I could take pictures showing input and output voltage simultaneously. Above 180 Hz it rolled off, and had half the ratio at 1 kHz. One clue was the input was cut at half at 1 kHz, but output wasn't. Swapped the meters, and this time output was cut in half. Response was actually flat, as desired.

If the voltage observed is high frequency PWM, each meter will give different reading.

Is there posibility how the AIO is grounded or how the Neutral(s) are addressed could be influencing what people are seeing?
I am curious if different results on identical inverters is telling us that connections, looped grounds/neutrals PV-conductors tied to EG are factors that are creating these differences? I mean it seems to me identical inverters should have/show the exact same outcomes - except for the things that are not identical like how each is connected.

If there is some AC coupled to the PV inputs, amplitude may differ depending on capacitance to ground. But if hard driven in some models, not just coupled, in that case that capacitance won't be able to attenuate it.

 

[OffGridForGood]

1. There could be voltage on the MPP terminals of an AIO
2. This voltage could be AC or DC or signals that appear to a meter like they are AC or DC voltages
3. Using just a multi meter may not identify correctly what is present
So, to know if there is a shock hazard or not, we do what? String a AC load like a 120VAC test lamp and check if there is sufficient voltage and current to light the lamp? Ditto DC load, but what am i going to use for 80VDC as a test load? Will noted his multi meter blew a 10A fuse?
If we can't predict what may be present on the MPP terminals, can we plan a method to test?

 

[EastTexCowboy]

1. There could be voltage on the MPP terminals of an AIO
2. This voltage could be AC or DC or signals that appear to a meter like they are AC or DC voltages
3. Using just a multi meter may not identify correctly what is present
So, to know if there is a shock hazard or not, we do what? String a AC load like a 120VAC test lamp and check if there is sufficient voltage and current to light the lamp? Ditto DC load, but what am i going to use for 80VDC as a test load? Will noted his multi meter blew a 10A fuse?
If we can't predict what may be present on the MPP terminals, can we plan a method to test?

From everything I've read on here and the video, it appears there is no shock hazard unless you open the case with either battery or AC input live at the time. For me, I'm just going to turn everything off before I open the case, which is what I did anyway. If it turns out there is a serious design flaw that could cause a shock hazard during normal operation or that will shorten the life of the equipment, I'm guess we'll all be scrambling for a solution. But that's just me. I also don't have any little kids running around sticking pointy things into anything they can - or big kids for that matter.

 

[timselectric]

So, to know if there is a shock hazard or not, we do what?

Lick it. Duh.

 

[timselectric]

All that I can confirm is in my case it's enough to sting.