Charge Controller Low Amp From Panels

[dick_slade]

Just got done installing my solar set up:

- 3x Renogy 100W Panels wired in parallel
- 3x 15amp fuses at each panel
- Renogy Rover 40amp Charge Controller
- 1x 40amp ANL fuse from controller to batteries
- 2x 6v 230ah Golf Cart Batteries in series

Right now in direct sunlight in Alaska the charge controller is only showing 2amps in (also showing 20 volts in). This seems low to me as the panels should pull around 5.75amps each and wired in parallel I should be seeing around 17amps in. I did some googling and read that the since my batteries are fully charged this is normal to have a low reading in to the charge controller and that it is working properly. Does this sound correct? I had though the amps in reading from the panel should still be what amps are coming in from the panels and not just what the batteries need.


Thank you!

[DavidM]

If the batteries are fully charged and there are no loads on them, what you are seeing is exactly what should happen in that case.

Unplug from shore power, and put some load like all fans running. The output of the charge controller should jump up after a few minutes.

Btw, the only fuse you really need is the 40 amp one and it should be located very near the batteries not the controller.

David

[dick_slade]

Perfect thank you! Just wanted to confirm what the google machine gave me.

As far as the fuses, I’m safe to not have any from the panels to the controller? Just the 40amp from the controller to the battery closest to the battery?

[DavidM]

Originally Posted by dick_slade

Perfect thank you! Just wanted to confirm what the google machine gave me.

As far as the fuses, I’m safe to not have any from the panels to the controller? Just the 40amp from the controller to the battery closest to the battery?

Fuses are used to protect the wire from an over current fault that could fry it. The panels are absolutely limited to their Isc value which is usually about 7 amps for 100 watt panels. Since you should have at least 14 gauge wire from each panel, that wire can easily handle the current. From the other direction, the charge controller blocks any current coming from the batteries.

The only way you could have an over current situation in a solar installation is originating at the battery. That is why your fuse should be near it.

What is the wire size from the controller to the battery? You want to keep that voltage drop as low as possible- about 0.2V. That will take 10 gauge wire if the controller is within 5' of the battery, bigger if further.

David

[creativepart]

As previously stated this is normal. The same will happen when your battery bank is being charged by any other source. Because the other charger’s voltage will show up on the batteries and your solar controller will see it as battery voltage.

This is what a solar charge controller does.

[Morich]

Looking at definition of voltage may help. It a difference of potential that makes current flow.
Thinking of water may help as we know and can see how water flows. If we have a tall tank of 15 feet high and a pipe going to a tank with 12 feet of water and connected together, the water from the tall tank will flow quite fast at first but as the two levels come closer together, the water flow slows down as there is not so much difference in "potential".
Battery power works the same way. When both are at the same level, there is no current flow but if we take some out of the battery, that causes a difference in potential and current begins to flow again if nothing else has changed.

[dick_slade]

Originally Posted by DavidM

Fuses are used to protect the wire from an over current fault that could fry it. The panels are absolutely limited to their Isc value which is usually about 7 amps for 100 watt panels. Since you should have at least 14 gauge wire from each panel, that wire can easily handle the current. From the other direction, the charge controller blocks any current coming from the batteries.

The only way you could have an over current situation in a solar installation is originating at the battery. That is why your fuse should be near it.

What is the wire size from the controller to the battery? You want to keep that voltage drop as low as possible- about 0.2V. That will take 10 gauge wire if the controller is within 5' of the battery, bigger if further.

David

That makes sense. The wiring is 10awg so it should be able to handle that current with no issue.

Thank you!

[JoeC]

Remember Thanksgiving dinner when you thought you were going to explode after the meal and Aunt Edna stops by with her super double chocolate and whipped heavy cream truffle? If it doesn't fit, it doesn't fit. The truffle is still there but it isn't going anywhere. Not much difference between you and your batteries. No more room, no more food.

[Pianotuna]

Originally Posted by dick_slade

Perfect thank you! Just wanted to confirm what the google machine gave me.

As far as the fuses, I’m safe to not have any from the panels to the controller? Just the 40amp from the controller to the battery closest to the battery?

I would replace the 3 15 amp fuses with a switch just before the controller. Many controllers may let out the magic blue smoke if they are not connected to the battery before being connect to the panels.