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Tamid 06-26-2007 09:58 PM

My dermatologist is as white as a ghost and when I leave her office she always says "stay pale!" HOWEVER, that is not the topic of this thread. I have two 30 watt, 12 volt solar panels that don't like each other.( Perhaps that is because one is an Eliminator and the other is an ICP). Individually they read 14-15 volts depending on the amount of sun. When I connect them I get really screwy readings of 4-6 volts. What is the problem? I'm thinking perhaps it is because they are running in parallel??

Lee Hillsgrove 06-26-2007 10:10 PM

Stupid question, maybe, but you are connecting the + to + and - to -, right?

Where exactly do you measure the 5-6 volts in the circuit?

Gina D. 06-26-2007 10:42 PM

They are supposed to be in parallel. If you do them in series, the voltage reading would be doubled.

In parallel, the voltage would still be 12v, but the current capability would be doubled. (Or additive, depending on the panels)

I second Lees question.

Tamid 06-27-2007 07:47 AM


Stupid question, maybe, but you are connecting the + to + and - to -, right?

Where exactly do you measure the 5-6 volts in the circuit?
There is only one way to connect them given the ends are molded to fit only one way. Actually I am wrong when saying they run in parallel. When they are connected together they run + to - and + to - so it is actually in series. So this could be the problem however the voltage reading is not doubled but rather reduced. Perhaps the better question is how should panels be wired together given the connections are wired so they fit + to -?

I measure the voltage from the ends of the leads and I took the back plate off the panel and measured it directly as it comes into the lines.

Lee Hillsgrove 06-27-2007 09:53 AM

I'm pretty sure that those should be connected in parallel, NOT in series.

Pictures of the connectors? Are the panels actually designed to be connected together?

I believe that panels wired in parallel should also have blocking diodes to prevent pne panel from back feeding into the other if they are putting out different amounts of power.

Brian B-P 06-27-2007 07:32 PM

Solar panels seem to commonly come with a two-pin version of the type of connector used - with four pins - for simple trailer lights. Now, which pin is which?

Some sets are wired so that each panel as an "in" cable and and "out" cable, so you can string them together. Others, like the Coleman set currently in our local Costco, have an "out" cable from each panel - these cannot be connected to each other, and are intended to connect to an "octopus" type cable to gather them all in parallel. The way those two-pin connectors work, to identically setup panels would connect + to - and - to + if you plugged them directly together... that's not good.

Can you show us the connections of each panel, in a photo, installation guide, website... ? How about the model numbers of each?

I don't know if blocking diodes are really needed; I suppose it depends on how badly they are mismatched in voltage output. A diode will always drop some voltage, so for optimum performance I would not want to add them unnecessarily. Maybe a diode on only the panel most likely to not keep up...

The 30 W Eliminator is a single-crystal type of panel; the ICP product is likely amorphous. That means they're likely not well-matched in characteristics. See Solar Power, ICP Solar website for a previous discussion of this topic.

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