mc4 connector mystery?

schew

Well-known member
so I have a dumb question,
On the roof of my trailer, the cable that has the male connector is labeled "minus". The other cable is not marked.
But on my solar panel, the connector on the negative wire has the same connector. I will not be able to connect the two as the connectors are the same. In order to make a circuit, I would need to connect the positive connector into the wire marked "negative" on my roof cable.*

From what I have read, my solar panel cables are correct, female = positive, male = negative .
What am I missing???
Could the roof cable be mislabeled?
Or could my solar panel cables be mislabeled?
 

schew

Well-known member
I guess as an easy solution, as my trailer came prewired for solar, when I cut the hole in my wall for the controller, I can take the cables coming from my roof and simply wired them backwards into my controller. This way I won't have to cut and crimp new connectors..
 

Big-B

Well-known member
You can put a DC volt meter on your panel and find out if the polarity is correctly marked. If it is wrong it will show minus voltage.

I just finished changing some panels over from mc3 connectors to mc4 and also wiring them into a midnite solar classic 150 mppt charge controller. The connector that you show is what I have on the minus side of the panel so there is the opposite one on the wire that leads to the charge controller. I just went with what I found to be standard on the net.
 

schew

Well-known member
You can put a DC volt meter on your panel and find out if the polarity is correctly marked. If it is wrong it will show minus voltage.

I just finished changing some panels over from mc3 connectors to mc4 and also wiring them into a midnite solar classic 150 mppt charge controller. The connector that you show is what I have on the minus side of the panel so there is the opposite one on the wire that leads to the charge controller. I just went with what I found to be standard on the net.

So if it's labeled backwards, my voltmeter will show -18 volts as opposed to 18v? My panels are 100watt/18v..

I've already checked them with a multimeter, one of them reads consistently in the 19v range, the other one as well but then shows a -1. If I took out the probes and checked it again, it does the same thing, 19v then displays a -1.
Both seemed to push 5+ amps consistently...
Guess I need to find my multimeter manual and see what that -1 means..

It very well may be that heartland labeled the wrong cable...
 
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Big-B

Well-known member
Yes, if the cables on the meter are hooked up backwards on DC voltage it will read minus voltage.
 
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