Only your volt meter will tell you the truth.
How to tell which wire is positive solar panel.
Connect the negative wires together in the same fashion and the wires off the last panel in the parallel circuit are connected to the battery.
The bare end of the positive extension wire will now be of positive polarity.
Wire solar panels in parallel by connecting the positive wire of the first solar panel to the positive terminal of the second panel and so on.
To measure across the solar panel terminals or wires put the red positive meter lead on one side and the black negative on the other.
Connect this cable to the mc4 male adaptor.
Extend the output wires of the solar panel the positive wire of the solar panel is terminated with an mc4 female connector marked.
A simple voltage reading will show you the polarity of a solar panel even when inside.
Make sure that the locking tabs snap in for a firm connection.
Wiring solar panels in parallel causes the amperage to increase but the voltage remains the same.
Another way to find the polarity of the solar panel is to check with a volt meter.
There is no color code standard for solar pv panels like there is for ac systems.
With parallel solar panels the positive terminal from one panel is connected to the positive terminal of another panel and the negative terminals of the two panels are connected together.
When stringing panels in series each panel additional adds to the total voltage v of the string but the current i in the string remains the same.