Is solar panel high voltage anything to worry about?

[ice2484]

Solar panels wired in series for high voltage can they shock you?

How many dc volts do you need to start to worry?

[Mike90250]

At about 12V, you can start arc welding with just a couple panels. 24V, and above, you could get a shock, 48V is the "low voltage system" upper limit.
With care, you are going to be OK. Just don't get a wrench or screwdriver across the battery terminals, or the explosion will make your eyeballs hurt real bad.

[SunEagle]

OSHA states that anything above 50 volts should not be touched by anyone without the proper training and Personal Protection Equipment (PPE) due to the possibility of being hurt or worse.

Although as Mike states, 48v is the upper limit but you can get burned pretty badly by a 12volt battery. It comes down to the amount of amperage the battery can deliver regardless of the voltage.

So when you wire those pv panels in series the potential of going over 48vdc is pretty good. You can get yourself a pair of insulated Class 00 electrical gloves (good for 500v) or make sure the wires are not energized when you can come in contact with them.

[Sunking]

or make sure the wires are not energized when you can come in contact with them.

Kind of hard to do in daylight if not impossible. That is why fireman carry a solar panel off switch with them when they respond to house fires with solar panels. They take their off switch (fire ax) on the roof, insert the switch right in the middle of the panel and turn it off.

[SunEagle]

Kind of hard to do in daylight if not impossible. That is why fireman carry a solar panel off switch with them when they respond to house fires with solar panels. They take their off switch (fire ax) on the roof, insert the switch right in the middle of the panel and turn it off.

I guess that beats dragging a large tarp onto the roof.

[inetdog]

I guess that beats dragging a large tarp onto the roof.

Especially when the tarp also has to be non-combustible.
Fiberglass is too itchy and Nomex is too expensive.

[ice2484]

So with this charge controller how many volts in series should solar panels be wired at.

Solar panels are 265 watt 31.2 volts each
24 volt battery bank

http://www.midnitesolar.com/pdfs/classicManual.pdf

mid night Classic 150 model

[SunEagle]

So with this charge controller how many volts in series should solar panels be wired at.

Solar panels are 265 watt 31.2 volts each
24 volt battery bank

http://www.midnitesolar.com/pdfs/classicManual.pdf

mid night Classic 150 model

The mid night classic 150 will accepts up to 150VDC input.

If 31.2v is the Voc of that panel then I would say a max of 4 in series. If 31.2v is the Vmp of the panel then maybe 3 in series.

[Sunking]

So with this charge controller how many volts in series should solar panels be wired at.

Solar panels are 265 watt 31.2 volts each
24 volt battery bank

http://www.midnitesolar.com/pdfs/classicManual.pdf

mid night Classic 150 model

As high as possible without going over the input Voc limit. 3 in series with your panels.

[ice2484]

Why go so high of volts besides smaller wire and less wire?

[inetdog]

Why go so high of volts besides smaller wire and less wire?

That it basically it.
For a given size of wire, you lose a smaller percentage of the total panel energy with a higher voltage.

[SunEagle]

Why go so high of volts besides smaller wire and less wire?

Yes higher voltage means lower amps and smaller wire. Also with a higher voltage between the panels and CC you can see a little higher voltage drop without any consequences.

[Mike90250]

Why go so high of volts besides smaller wire and less wire?

Well, there is a bit of a trade off showing up now. Seems like Vpmax = 2x-3x battery bank is a sweet spot for the MPPT controllers, get too high of a voltage differential between the PV array and the batteries, the controller has to dissipate more heat, doing more work to down-convert the array voltage to the battery. I'm finding this out, on a controller that should handle almost twice the wattage, it's just cooking itself because I went to the high voltage array to get long distance and wire size issue balanced. But I discovered the thermal part of the matter.

[Sunking]

Well, there is a bit of a trade off showing up now. Seems like Vpmax = 2x-3x battery bank is a sweet spot for the MPPT controllers, get too high of a voltage differential between the PV array and the batteries, the controller has to dissipate more heat, doing more work to down-convert the array voltage to the battery. I'm finding this out, on a controller that should handle almost twice the wattage, it's just cooking itself because I went to the high voltage array to get long distance and wire size issue balanced. But I discovered the thermal part of the matter.

What controller Mike? Did you use the Efficiency Curves to hit the sweet spot?

[Mike90250]

What controller Mike? Did you use the Efficiency Curves to hit the sweet spot?

I've got a classic 200, fed by a 2Kw array @ 160VOC Got about 100+ feet to the battery shed from this new array, and was adding wires to the existing 2" conduit, and could not get too large of wire. And i was unable to find any published curves from Midnight Solar, that had VOC vs efficiency, but have discovered that much more than 2x battery voltage will be less than optimal.