What happens to excess solar panel current when the batteries are full?

[JumbleDuck]

Thank you olewill, this is the most sensible reply in the whole thread. I did not know about the existence of solar panel regulators with the dump resistor because they do not make much sense but... never mind.

In principle, dump resistors are needed only with permanent magnet alternators; in all other cases there are better ways to solve the problem of controlling the charge.

Dump resistors are not required for solar panels, and the "load" connection on some regulators is widely misunderstood, as this thread shows. The point is not to dump power; it's to divert available power to something useful when the batteries don't need any more. You might, for example, use it to warm and ventilate somewhere you'd like to dry out a bit.

 

[30boat]

Is a dump resistor the same as a Zener diode?

 

[JumbleDuck]

Is a dump resistor the same as a Zener diode?

No. A normal diode works like a one way valve, allowing current to flow in one direction and blocking it in the other. A zener diode stops blocking reverse flow abruptly at a certain voltage and when suitably connected will maintain that voltage across itself, so it acts as a voltage regulator. Normal diodes also breakdown in reverse, but less predictably and abruptly.

 

[30boat]

No. A normal diode works like a one way valve, allowing current to flow in one direction and blocking it in the other. A zener diode stops blocking reverse flow abruptly at a certain voltage and when suitably connected will maintain that voltage across itself, so it acts as a voltage regulator. Normal diodes also breakdown in reverse, but less predictably and abruptly.

You're right,now I remember.We used to have them on English bikes.

 

[Heckler]

Thank you olewill, this is the most sensible reply in the whole thread. I did not know about the existence of solar panel regulators with the dump resistor because they do not make much sense but... never mind.

In principle, dump resistors are needed only with permanent magnet alternators; in all other cases there are better ways to solve the problem of controlling the charge.

Daniel

Dont forget he is in Orstraalia. More sun there. I have a simple controller, when the batteries are fully charged it just switches the output to another set of terminals marked load. If I wanted to I could put a dump resistor on that set or let it go to another set of batteries or a water heater terminal or whatever.
In reality I leave those terminals unconnected, then the controller is just switching to open set of terminals so that the panels are open circuit.
S

 

[William_H]

Dont forget he is in Orstraalia. More sun there. I have a simple controller, when the batteries are fully charged it just switches the output to another set of terminals marked load. If I wanted to I could put a dump resistor on that set or let it go to another set of batteries or a water heater terminal or whatever.
In reality I leave those terminals unconnected, then the controller is just switching to open set of terminals so that the panels are open circuit.
S

I think in many cases cheap regulators are made for street lamps. The "load" is not for using excess power but rather the output to the intended load on the battery. ie the light itself. It may be switched on after dark by the solar panel but also possibly on all the time unless the battery voltage falls when it turns off.
So most important read the instructions before assuming what "load " means. good luck olewill
Yes I think we have Scotland's share of sunshine. We would trade it for some rain.