Question about Voltage from Solar Panels

[B and C]

How often have you needed 50ft?  I'm adding a portable panel and trying to figure how long a cord I'll need.

I already have a 12ga. cord but it's only 10'.

Actually, I carry a 50 footer and a 25 footer.  I bought them at Harbor Fright (freight).  I use the 25 footer most for when I hang my panels from the awning and the 50 footer when the van is in the shade.  Twice I have had to put them together for a 75 footer.  My panels are wired in series and I have an MPPT controller.  I figure any charging is better than none.  I have never done the math on how much the voltage drops over that distance but the batteries are getting a charge.

My panels are the flexible kind and have no metal frame.  I wouldn't even know how to ground the panels.  I haven't done the doubling up on connectors either as that would render the extension cords useless for a regular 120V AC extension cord.  More than one use that way.  The more uses something has, the less you have to carry.

 

[wayne49]

Grounding metal framed panels on a roof top may be for protection from lightning.
Grounding a panel to a non grounded vehicle chassis would do what?

 

[user 423]

A chassis ground is fine, which is connecting the frame of the panel to the ground. So no, you don't need to run three wires to the charge controller, nor should you. If the panel is placed on the ground, it's grounded. That's what a ground is, a connection to the earth.

What I've done is built a frame around the panel with 1x2's and 3/8"plywood strips to protect it during travel, sort of like a suitcase. So the aluminum frame wouldn't come into contact with the ground.

 

[highdesertranger]

as far as I know all vehicle chassis are grounded. do you know of one that isn't? highdesertranger

oops, well fiberglass or plastic wouldn't be so a Casita or a Corvette body wouldn't be grounded. but the frame part is still grounded.

 

[user 423]

"If using a standard 3 conductor extension cord you can jumper two of the conductors together cutting the resistance in half for the paired conductors"

that would be nice but it doesn't work that way.

Is that because you would only be lowering the resistance for half the circuit?  I.e: positive side but not negative.

 

[user 423]

I haven't done the doubling up on connectors either as that would render the extension cords useless for a regular 120V AC extension cord.  More than one use that way. 

That's a good point but I already have a 50'-14awg and a 25' -16awg plus a 10'-12awg for general use.

My friend has 50' of 12/2 landscape wire he'll sell me cheap and since I only need 2 conductors, I may go that route.

Cut it into 20' and 30' lengths and experiment maybe.

 

[highdesertranger]

"Is that because you would only be lowering the resistance for half the circuit? I.e: positive side but not negative."

that is correct sir.

highdesertranger

 

[Tom_M]

"If using a standard 3 conductor extension cord you can jumper two of the conductors together cutting the resistance in half for the paired conductors"

that would be nice but it doesn't work that way.

highdesertranger

Paired probably wasn't the correct term. Paralleled would be more appropriate. Parallel the green and white and that would cut the resistance in half for that leg. If each wire is one ohm you would now have .5 ohm of resistance. Add in the black wire and you have a total of 1.5 ohms. If you used just the white and black wires you would have a total resistance of two ohms.

 

[Tom_M]

I haven't done the doubling up on connectors either as that would render the extension cords useless for a regular 120V AC extension cord.  More than one use that way.  The more uses something has, the less you have to carry.

You would not do anything to the extension cord. You would jumper the wires at the connector that the extension cord plugs into.