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Solar panels in series/parallel


jenevers

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Parallel is usually best, especially if any have a chance of being in the shade.    Check how many panels can be added in series with the seller/manufacturer if deciding to go in series.     

Edited by Robbo
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10 minutes ago, Robbo said:

Parallel is usually best, especially if any have a chance of being in the shade.    Check how many panels can be added in series with the seller/manufacturer if deciding to go in series.     

Parallel is the way I’m thinking. Just need to see a diagram cos I think I’ll need a couple of 4 into 1 connectors, if there are such things?

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21 minutes ago, jenevers said:

Or is it best to wire them in parallel.

pros and cons?

 

The voltage &/or current rating of your controller may well determine how you wire them up, or you will need to buy a suitable controller for your preferred method of connection.

 

What voltage panels are they ?

Example mine are 110 volts, - so I get (say) 103 volts at 0.8 amp going in and 5.9 amps at 14.7v coming out.

 

 

05-06-16.jpg

Edited by Alan de Enfield
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Parallel has the advantage that if one panel is partially shaded it won’t affect the output of the other. Series has the advantage that in low light you’ll still have enough voltage for an MPPT controller to track. On balance on UK canals parallel will probably give the best overall results. 

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Mine are in series, but that was more down to being able to connect a higher wattage of panels to my controller than if they are in parallel. Check the controllers max voltage, current and power specifications. Series allows thinner connection wires to be used between the panels and controller without getting voltage drop issues. Be aware that the DC voltages that can be reached in a solar installation are high enough to be dangerous. Particularly for series installations.Cover the panels over with thick blankets, or similar when working on the wiring and treat it as you would working on mains.

 

Jenny

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1 hour ago, jenevers said:

I suppose I’ll need “Y” connectors.

Here are some 4 way ones if you want to keep to MC4, https://amzn.to/2Cr1Ovb      A built in diode and pref a fuse would be handy.

6 minutes ago, Jen-in-Wellies said:

Be aware that the DC voltages that can be reached in a solar installation are high enough to be dangerous.

Not with 4 100w panels it won't be, probably about 100v which you would feel but not dangerous  (although you'll get some nice arcing at that voltage!).

Edited by Robbo
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3 minutes ago, Robbo said:

Not with 4 100w panels it won't be, probably about 100v which you would feel but not dangerous.

Wouldn't that depend on the voltage of the individual panels ?

Mine are 110v EACH - connect in series and its 440 volts DC

 

Apparently Higher DC voltages(over 200V) make blood electrolysis...then very small bubbles of gas come into brain...this effect is lethal...human body can feel fine and then after 1 or 2 min. : bang !!!

 

Best to treat all voltages as dangerous and isolate.

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6 minutes ago, Alan de Enfield said:

Wouldn't that depend on the voltage of the individual panels ?

Mine are 110v EACH - connect in series and its 440 volts DC

 

Apparently Higher DC voltages(over 200V) make blood electrolysis...then very small bubbles of gas come into brain...this effect is lethal...human body can feel fine and then after 1 or 2 min. : bang !!!

 

Best to treat all voltages as dangerous and isolate.

What wattage are your panels tho?   The 100watt ones I've seen are roughly 20v (open circuit).

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12 minutes ago, Robbo said:

Not with 4 100w panels it won't be, probably about 100v which you would feel but not dangerous 

Completely untrue. For a start, 4 panels in series can be much higher than 100V as Alan has pointed out.  It’s current that kills, not voltage and thanks to that nice Mr Ohm we can see that the higher the voltage the higher the current into a fixed load. 100mA will probably kill you and being DC you won’t be able to let go. The resistance of the human body varies between 1kr and 100kr dependant on which parts of the body and how wet they are. Taking the lower figure and a voltage of 100V we get: 100/1000, which happens to be exactly 100mA. Certainly enough to kill. 

9 minutes ago, Alan de Enfield said:

Best to treat all voltages as dangerous and isolate

Always. :)

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I have had a shock off 100V DC and it can be felt as @Robbo says. I was working on a live circuit in an industrial laser, right next to a very large capacitor, normally charged to 40kV that I had discharged and shorted out before doing this procedure. My first thought was "Didn't safe the capacitor properly. I'm dead." ?. Second thought was "Still thinking, therefore not dead and the capacitor is safe.". ?

 

I had a look at the specs for some of the smaller Victron controllers they are selling now and the max open input voltages are around 100V, so OK. Their largest ones are maximum 150V.

 

Jen

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2 minutes ago, Jen-in-Wellies said:

I have had a shock off 100V DC and it can be felt as @Robbo says. I was working on a live circuit in an industrial laser, right next to a very large capacitor, normally charged to 40kV that I had discharged and shorted out before doing this procedure. My first thought was "Didn't safe the capacitor properly. I'm dead." ?. Second thought was "Still thinking, therefore not dead and the capacitor is safe.". ?

 

When I used to fix stuff the first thing I’d do prior to nosing around inside was to put my screwdriver across the mains switch L&N to cause the psu caps to discharge. Usually a small spark and I’d then feel safer. I did this once on a small oscilloscope and got a really big spark coupled with a bang and a small chunk missing from my screwdriver. Then I remembered to unplug it...

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3 minutes ago, WotEver said:

Completely untrue. For a start, 4 panels in series can be much higher than 100V as Alan has pointed out.  It’s current that kills, not voltage and thanks to that nice Mr Ohm we can see that the higher the voltage the higher the current into a fixed load. 100mA will probably kill you and being DC you won’t be able to let go. The resistance of the human body varies between 1kr and 100kr dependant on which parts of the body and how wet they are. Taking the lower figure and a voltage of 100V we get: 100/1000, which happens to be exactly 100mA. Certainly enough to kill. 

Always. :)

We are talking DC here tho, as we are like a capacitor the DC doesn't pass through us like AC (easily) does. 

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7 minutes ago, Alan de Enfield said:

170 watt (Low light) 110 Volt

Fair enuf.   Not seen anything that high for the panels I've looked at tho.

2 minutes ago, Alan de Enfield said:

Try putting your tongue on the terminals of a PP9 (9v DC) battery.

Now try it with 9v AC and let me know :D    -   It will hurt alot more BTW, start at a low voltage and work ya way up.  

Edited by Robbo
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3 hours ago, WotEver said:

Completely untrue. For a start, 4 panels in series can be much higher than 100V as Alan has pointed out.  It’s current that kills, not voltage and thanks to that nice Mr Ohm we can see that the higher the voltage the higher the current into a fixed load. 100mA will probably kill you and being DC you won’t be able to let go. The resistance of the human body varies between 1kr and 100kr dependant on which parts of the body and how wet they are. Taking the lower figure and a voltage of 100V we get: 100/1000, which happens to be exactly 100mA. Certainly enough to kill. 

Always. :)

Within an AC circuit with the voltage at 230 volts, 20 mA is enough to upset your heart. 

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6 minutes ago, Keith M said:

Within an AC circuit with the voltage at 230 volts, 20 mA is enough to upset your heart. 

With AC (the actual voltage is irrelevant other than to push the current) up to 40mA is unlikely to result in death. 100mA will probably result in death. But any current is unpleasant and should be avoided. At least with AC you might have a chance to let go. 

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4 hours ago, WotEver said:

Completely untrue. For a start, 4 panels in series can be much higher than 100V as Alan has pointed out.  It’s current that kills, not voltage and thanks to that nice Mr Ohm we can see that the higher the voltage the higher the current into a fixed load. 100mA will probably kill you and being DC you won’t be able to let go. The resistance of the human body varies between 1kr and 100kr dependant on which parts of the body and how wet they are. Taking the lower figure and a voltage of 100V we get: 100/1000, which happens to be exactly 100mA. Certainly enough to kill. 

Always. :)

 

Indeed.

 

All of the commercial DC installations that I have seen or worked on that are rated above a nominal 50 volts have isolators in the bstteries to split the batteries into sections of not more than 50 volts.

 

This is done purely to limit current flow in the event of accidental human contact.

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19 minutes ago, WotEver said:

With AC (the actual voltage is irrelevant other than to push the current) up to 40mA is unlikely to result in death. 100mA will probably result in death. But any current is unpleasant and should be avoided. At least with AC you might have a chance to let go. 

I am sorry but I have to disagree 

During all of my AC training which is still ongoing, I have always been told 20 mA has and can be fatal, this is why certain installation requires the use of a 10 mA RCD and normal domestic installation  have 30 mA

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17 minutes ago, Keith M said:

I am sorry but I have to disagree 

During all of my AC training which is still ongoing, I have always been told 20 mA has and can be fatal, this is why certain installation requires the use of a 10 mA RCD and normal domestic installation  have 30 mA

We’re not disagreeing. I said 40mA is unlikely to cause death. You said it can be fatal. They’re both the same thing. It’s unlikely but it could happen, particularly if the shock was from hand to hand. 

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  • 1 year later...
34 minutes ago, solarenergy5 said:

You normally have to do some calculations in order to verify the best connection for your solar panels.

Why?

 

It depends on a few factors - your controller’s maximum panel voltage, how good it is at tracking in low light, and how likely you are to have at least one panel in partial shade, which may be quite often on British inland waterways. 
 

No need for a Python script to consider any of that. 

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