Solar panel terminals

Jul 16, 2018
I am fitting a solar panel to charge a lesiure battery, I have a 30w solar panel, when I came to fixing the wire into the back of the panel, i noticed that there was three terminals, one doesnt seem to be for use as its not solderd to anything,... that left me with two, but they are not marked Poss or Neg, would i be correct in assuming that it doesnt matter which wire goes to which terminal, bearing in mind that it does matter where each wire goes to at the controler end

I did put a meter onto the terminals and got a reading both ways round

The wires are a red one, and a red/black one as normal
Mar 14, 2005
Solar panels usually produce DC which means one will be positive and the the other negative, so choosing which way to connect is vitally important. The same applies to the controller also.

You should be able to check the panels polarity with a multi-meter, just make sure that light is able to reach the working surface, and the polarity will become evident using a multi-meter.

If in doubt, check the manufacturers information sheet, or refer the job to a competent person.
Jul 16, 2018
Thank you...I wish I could send a photo,... I was wrong, there are a poss and neg sybols where the cables go into the box [ just found them not easy to see]..... but there are still three terminals and I can get a positive reading on the muti meter from two different selections,... so I am still unsure

I would take it to someone who could help, but I am in the Scottish Highland 50 miles from Fort William, so I have to try and work it out myself

I have no problem with the controler, thats clearly marked
Oct 12, 2013
There's a bit too much pictures on one of them!! try scolling down to the 7th option copy it then go back to this form and paste it . the picture should come up on the screen rather than going through your link.
Apr 19, 2017
The LH and center terminals are the connections directly to the panel. There is a bypass diode between them (as is common to most panels). This diode is useful if there multiple panels in series.
The RH terminal has a forward-conducting diodefrom the panel +ve. This diode prevents current flowing backwards into the panel when it is dark (although most controllers will do this anyway).. Use the RH terminal.


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