Plug in chargers vs solar panel polarity

stmar · July 2017

As I stated in a previous post a while ago I ruined a lawn tractor battery by using a plug in charger pig tail with a solar charger. Can anyone explain why they have different polarities for plug in and solar pig tails? Pig tails are opposite polarity, you would think there would be a standard. My Battery Tender model identifies polarity so you can plug any configuration into it but the YUSA model is specific and my two solar chargers are specific but opposite from the YUSA.

BB. · July 2017

Do you have any pictures/links to the problem?

In general, you connect + terminals all together (whether loads, chargers, solar panels, etc.)--Of course with proper fusing/breakers as required. And all - terminals are connected together.

Solar panels are "giant diodes"--And when connecting them, you are really connecting the diodes in "reverse bias" mode. No (or very little current) will flow when connected to the battery. If you connect the solar panel backwards, then the diodes are "forward biased" and will conduct maximum amount of current (near short circuit current). And can/will ruin the panel (fuses/breakers or not).

-Bill

stmar · July 2017

I was wrong about the YUSA model 12V900, it does have polarity protection and will charge no matter what the orientation.
It is not really a problem as such, I am just trying to make heads or tails out of the different orientations from battery tender chargers to solar chargers, they are opposite and I was just wondering why.

littleharbor2 · November 3

Your first two posts, even though they contain some good information are looking more like advertisements to me

Wheelman55 · November 3

From my memory bank, I seem to remember that ZAMP Solar chose to wire their units up in reverse. Some travel trailer brands use ZAMP as there standard for solar connections.

mike_s · November 4

You're apparently asking about the 2 pin "SAE" connectors. There is no standard for wiring them, so you can't really say what's right or wrong or backwards. And if you think about it, there would always be ambiguity, because a battery can be either a source or sink.

The design of the connector allows one contact to always be exposed when disconnected. So it's a matter of choice deciding what wiring method is safest for an application. In general, you want to protect the "hot" side from an accidental short to ground.

Most battery chargers are wired so if used with a battery pigtail, that pigtail uses the shrouded contact for positive so it's better protected from a short. Therefore, the exposed contact on the charger is "hot." Chargers put out less current than batteries can, so I suppose that's the safer option.

For solar connections, it's opposite. On the battery (camper) side, ZAMP connects the "exposed" pin to battery positive. The fact that it's a bulkhead fitting means that pin isn't really exposed like a connector at the end of a cable would be, so it would be hard to short it to something. Therefore, the shrouded pin coming from the solar panels is "hot." The wiring actually makes sense for battery chargers, too, if the battery side has a bulkhead connector and not a pigtail cable.

Use a meter before plugging things together. There are polarity reverse adapters available to adapt, if needed.

manzanita2 · November 5

That would have been surprising to me too. I would have expected the hot / positive lead to be the inner shrouded one.

Thanks for the warning.

Plug in chargers vs solar panel polarity

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