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# Would this Schematic work? Answered

I am an amateur building a solar powered bilge pump and was wondering if the schematic I made would work. The idea of the schematic is that if switch 1 is open and switch 2 is closed, the 5w solar panel will charge the 12 volt battery. And if switch 1 is closed but switch 2 is open, the 12 volt battery will power the 2A bilge pump. My main question is which way will the current be flowing. I have drawn some arrows to show which way I think current will be flowing. Please correct me if I am wrong. Also tell me if any components need to be flipped around.

Connor

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The forums are retiring in 2021 and are now closed for new topics and comments.

I often read these phrases like, "all answers are appreciated", or "please correct me if I am wrong", and I wonder how to interpret language like that. Do you really want me to tell you about everything you're doing wrong?

The first thing is a semantics problem. A switch is "closed" when its contacts are touching each other, allowing current to flow. A switch is "open" when its contacts are separated, preventing current from flowing. A closed switch has zero resistance. An open switch has infinite resistance. This language is actually the opposite of the language for water valves. An open water valve allows water current to flow through it. A closed switch allows electric current to flow it.

The next thing I should mention is you want a diode in series with your solar panel. The reason why is because it is preferable to only allow current to flow from the solar panel in one direction. The diode will act, essentially, as a switch that conducts, allows forward current, when the panel voltage is greater than the battery voltage plus one diode drop (around 0.6 V for a silicon diode), and does not conduct when the solar panel voltage is less than the battery voltage.

When a cloud moves unpredictably between your panel and the sun, the voltage on the panel will drop to a value less than the battery voltage, and the diode will be reverse-biased, and no current will flow backwards into the solar panel.

The diode is pretty much necessary, unless you can watch the sky all the time for clouds, or other shadows that might fall on your solar panel, and then manually open a switch every time that happens.

Modified your circuit as asked added the necessary diode and you can leave S1 forever closed as it is a dunsle item

If your solar panel has a reverse diode in it you are fine, if not add one between panel and battery so the battery won't destroy the panel if there is no sun.

S1 would not be necessary if you have a connector for the panel instead of direct wiring (comes in handy if you have to work on it), with a diode the panel can stay connected.

Otherwise it is all fine.