DC Volt reading from 6 panels, is it accurate?

[sabo]

I am testing 6 panels. I tool the Open Circuit Voltage reading with my AMES CM 1000A
Panel1 32.26
Panel2 32.13
Panel3 31.77
Panel4 31.67
Panel5 31.69
Panel6 31.76

When i put in serial and take the combined panel reading i get 95.7. Does that make sense?

 

[BentleyJ]

I am testing 6 panels. I tool the Open Circuit Voltage reading with my AMES CM 1000A
Panel1 32.26
Panel2 32.13
Panel3 31.77
Panel4 31.67
Panel5 31.69
Panel6 31.76

When i put in serial and take the combined panel reading i get 95.7. Does that make sense?

Must be a bad connection somewhere. If all the panels are connected in series (+ to - daisy chain configuration) the voltage should be the sum of all 6. Approx. 190V. That's a significant DC voltage, please take necessary precautions and wear PPE.

 

[Hedges]

95V looks like exactly 3 in series.

"series" is supposed to still be open circuit. Hope you didn't connect all 6 in a ring. If you did, do NOT unplug with sun on the panels, cover or wait for dark first!

(Not that I would expect 95V if you did that.)

 

[sabo]

95V looks like exactly 3 in series.

"series" is supposed to still be open circuit. Hope you didn't connect all 6 in a ring. If you did, do NOT unplug with sun on the panels, cover or wait for dark first!

(Not that I would expect 95V if you did that.)

I am duplicating this diagram but with 6 panels. on both ends i am using a 4 in to 1 out cable to connect the end panels. But I am using only 2 of the four connectors

 

[TacomaJoe]

The upper ring is series, the lower ring is series. The two rings are in parallel. As noted, your 95V is correct for the 3 in series.

 

[sabo]

The upper ring is series, the lower ring is series. The two rings are in parallel. As noted, your 95V is correct for the 3 in series.

Now i see i should have done followed the right diagram and not the left.

 

[Hedges]

Now i see i should have done followed the right diagram and not the left.

6 panels connected like diagram on right would be 190V.
At the illumination and temperature conditions you had.

"MPP 6548", I think there may be multiple models.
LV6548 I read "High PV Input 250V (Voc) Open circuit)"
If that's your model, 190Voc nominal from array is good, more than 15% voltage margin works for just about any panel at ambient temperature.

Always good to check voltage and polarity as you go.

 

[sabo]

6 panels connected like diagram on right would be 190V.
At the illumination and temperature conditions you had.

"MPP 6548", I think there may be multiple models.
LV6548 I read "High PV Input 250V (Voc) Open circuit)"
If that's your model, 190Voc nominal from array is good, more than 15% voltage margin works for just about any panel at ambient temperature.

Always good to check voltage and polarity as you go.

Mine is 6548V 390Voc. I have 12 total panels on the array and was planning on 9 or 10 for this string because of the 390Voc. My 6 string test was a panel output test because my multimeter leads are too short to test all 9ish

 

[Hedges]

If 3s was 95V, 9s will be 285Voc

390Voc (max allowed) / 285Voc (nominal) = 1.37, which is enough margin I won't both considering cold temperatures and temperature coefficient of Voc.

12s would be 380Voc (nominal), which is too close.
For 12 panels, 6s2p and 190Voc (nominal) fits the inverter voltage. That would have to be on separate MPPT from 9s.

Two MPPT, 18A each

https://www.mppsolar.com/v3/catalogs/LV6548_V.pdf

"Current Solar Power System20 250w San Tan used panels"

I think Santan/Trina panels are "Short Circuit Current (ISC): 8.85A"

So 9s into one MPPT, 6s2p into other MPPT should work. But that's 21 panels. 8s into one MPPT, 6s2p into other.

 

[sabo]

95V looks like exactly 3 in series.

"series" is supposed to still be open circuit. Hope you didn't connect all 6 in a ring. If you did, do NOT unplug with sun on the panels, cover or wait for dark first!

(Not that I would expect 95V if you did that.)

I was under the impression under load was when I was pulling power from the power source. Like a motor running on AC power. Ex: when the motor is running its under load. So does this mean that a solar power in the sun is considered under load? I know there is power is available when the sun is out shining on the panel. I was wearing protective rubber coated gloves to keep from getting a jolt. I have seen video of a person holding bare wires about 1/2 an inch apart and seeing the arc.

 

[Hedges]

Since your panels were wired 3s2p, so long as not feeding current into something else, OK to unplug in the sun.
I though for a moment you had wired 6s and then shorted output + to output -, in which case current flowing and you wouldn't want to unplug with sun on them.

If pulling power from PV to let inverter run a load, or simply to charge battery, current would be flowing. You should always interrupt current with switch or breaker before unplugging MC connector or removing a fuse. I check voltage at terminals before/after opening switch, to confirm I've interrupted current on the correct string (I have several GT PV inverters and open AC breaker to interrupt DC current flow.)

An open circuit series string of panels in the sun, OK to unplug. Only a current and arcing problem if current flowing.

Non-electrical rubber gloves might provide protection, or they might not.
We were given cut-resistant gloves at work for mechanical assembly. Fibers include steel 15% !
For electrical, we are given rubber gloves, tested and rated for electricity. Lowest category good for 500Vrms.
Electrical gloves are to be used with leather protectors on the outside. (no jewelry inside which could damage them.) If used without leather outer gloves, only considered good for one day's use, then must be retested.

I discovered rubber hose isn't always an electrical insulator.

Using non-UL insulation

A while back I bragged about creative use of heater hose as tough, large size insulation for electrical terminals: https://diysolarforum.com/threads/fire-never-cover-lifepo4-with-wood.19373/page-12#post-238207 It seemed like a good idea at the time. More recently, I was wiring up...

diysolarforum.com

 

[sabo]

Since your panels were wired 3s2p, so long as not feeding current into something else, OK to unplug in the sun.
I though for a moment you had wired 6s and then shorted output + to output -, in which case current flowing and you wouldn't want to unplug with sun on them.

I was also worried I had shorted something or that the connectors were faulty /bad. good to know it was just that I dont know how to read a solar panel power diagram

If pulling power from PV to let inverter run a load, or simply to charge battery, current would be flowing. You should always interrupt current with switch or breaker before unplugging MC connector or removing a fuse. I check voltage at terminals before/after opening switch, to confirm I've interrupted current on the correct string (I have several GT PV inverters and open AC breaker to interrupt DC current flow.)

An open circuit series string of panels in the sun, OK to unplug. Only a current and arcing problem if current flowing.

Non-electrical rubber gloves might provide protection, or they might not.
We were given cut-resistant gloves at work for mechanical assembly. Fibers include steel 15% !
For electrical, we are given rubber gloves, tested and rated for electricity. Lowest category good for 500Vrms.
Electrical gloves are to be used with leather protectors on the outside. (no jewelry inside which could damage them.) If used without leather outer gloves, only considered good for one day's use, then must be retested.

Good to know. I try to not ever work on live wires but was wearing gloves with an abundance of paranoia.

I discovered rubber hose isn't always an electrical insulator.

Using non-UL insulation

A while back I bragged about creative use of heater hose as tough, large size insulation for electrical terminals: https://diysolarforum.com/threads/fire-never-cover-lifepo4-with-wood.19373/page-12#post-238207 It seemed like a good idea at the time. More recently, I was wiring up...

diysolarforum.com

 

[sabo]

Since your panels were wired 3s2p, so long as not feeding current into something else, OK to unplug in the sun.
I though for a moment you had wired 6s and then shorted output + to output -, in which case current flowing and you wouldn't want to unplug with sun on them.

If pulling power from PV to let inverter run a load, or simply to charge battery, current would be flowing. You should always interrupt current with switch or breaker before unplugging MC connector or removing a fuse. I check voltage at terminals before/after opening switch, to confirm I've interrupted current on the correct string (I have several GT PV inverters and open AC breaker to interrupt DC current flow.)

An open circuit series string of panels in the sun, OK to unplug. Only a current and arcing problem if current flowing.

Non-electrical rubber gloves might provide protection, or they might not.
We were given cut-resistant gloves at work for mechanical assembly. Fibers include steel 15% !
For electrical, we are given rubber gloves, tested and rated for electricity. Lowest category good for 500Vrms.
Electrical gloves are to be used with leather protectors on the outside. (no jewelry inside which could damage them.) If used without leather outer gloves, only considered good for one day's use, then must be retested.

I discovered rubber hose isn't always an electrical insulator.

Using non-UL insulation

A while back I bragged about creative use of heater hose as tough, large size insulation for electrical terminals: https://diysolarforum.com/threads/fire-never-cover-lifepo4-with-wood.19373/page-12#post-238207 It seemed like a good idea at the time. More recently, I was wiring up...

diysolarforum.com

Are you familiar with this brand? I am thinking about upgrading

Ultimate Nitrile Grip Work Gloves

What do you think?

 

[Hedges]

I rarely use gloves because I like to feel what I'm doing and handle small parts.
Exception being yard work, welding, chemicals, skiing.

Those work gloves of course are not meant for electrical safety

For electrical work, "Hot work" is something that should essentially never be done.
Exception is lineman connecting wires for a house, or plutonium facility keeping negative-pressure fans operating.
Lock-out, Tag-out, Test-out. Do all work cold. Then you can wear work gloves instead of voltage rated gloves.

Where you can't make it cold will be battery terminals and PV panels, and MC4 connectors make those touch safe. So 48V battery is the only thing you might come in contact with hot. Use insulated tools and covers to make sure nothing gets shorted. You may be able to isolate the battery from everything else and attach a ground wire to the terminal you're working on so it is zero volts, no shock hazard.

As a youth I used to rewire my parents house with the power on. Do as I say, not as I do.

 

[Hedges]

Good to know. I try to not ever work on live wires but was wearing gloves with an abundance of paranoia.

Wrong gloves might test open circuit with low-voltage DMM, but break down at 240VAC or 400VDC.
I measured my body hand to hand as 300k ohm DC, 150k ohm at 60 Hz. That would give 1 mA, wouldn't explain the bad shock I got at 200Vrms.
Then I read that skin breaks down under high voltage and the body is 500 to 1000 ohms, so I may have had a fraction of an amp through my chest.

Electrical gloves are tested with margin, like 1000V above rating. They are also tested by the user rolling or blowing up to check for leaks, which you can't do with cloth lined gloves. They may in fact protect against shocks but you can't be certain, or know if they are intact.