Solar Voltage

[thinwater]

The disagreement is still alive. My point remains that the controller can output power into a dead short. OCP at the battery is irrelevant, as the controller is the power source.

Consider the picture below. View attachment 226812

Fusing the panels was not the point, although the discussion was interesting. We are in agreement that they do not need to be fused in most circumstances. A disconnect is a good idea though.

Good illustration.

If the controller is rated for 30 A, the panels are 30 A, and the wire is 30 A, and there is a 30 A fuse near the battery (DC bus in the above case--not all controllers wire to the DC bus) what is going to heat until failure? Obviously, everything from the controller to the bus (battery is rated at 30 A). In fact, by fusing at the controller you expose the wire length from the DC bus to the controller fuse to over current. I think what he was suggesting is that it would be best to place the 30 A fuse close to the DC bus (or battery).

Yes, the controller is a power source, but even with the fuse at the battery, the DC bus remains the much, much more powerful energy source.

What we have, I believe, is a failure to communicate.

 

[mermike]

I agree that the DC bus is the more powerful energy source. My thinking is that if properly fused, the OCP on other power sources connected to the bus will open, leaving only the controller putting power into the short.

My assumption, and perhaps this is the error in my thinking, is that the controller or wire will fail with a constant 30A current into a dead short. I supposed if they are all rated for the current, and the controller output doesn't exceed that current, then all will be well.