Thread: Solar controllers

Originally Posted by Floydo

Do you need to fuse between your solar panel and your MPPT controller? What size fuse

I can't see the point of adding a fuse between the panel and the MPPT controller, As long as your MPPT controller is rated at more amps than your panel/panels are capable of producing there shouldn't be any problems.

Have a look on the back of you solar panel/panels to see the max ampage they produce and get an MPPT controller that can accomodate this amount of ampage

The panels on my 79 Series produce 15a MAX and the MPPT contoller is rated at 40a and I have never had a problem in the last 6 years.

Originally Posted by trout1105

I can't see the point of adding a fuse between the panel and the MPPT controller, As long as your MPPT controller is rated at more amps than your panel/panels are capable of producing there shouldn't be any problems.

Have a look on the back of you solar panel/panels to see the max ampage they produce and get an MPPT controller that can accomodate this amount of ampage

The panels on my 79 Series produce 15a MAX and the MPPT contoller is rated at 40a and I have never had a problem in the last 6 years.

And if that wire chafes through between roof and vehicle in a panel cavity pre-MPPT - what do you think those amps are going to do?

Prevention is better than cure.

Originally Posted by Tombie

And if that wire chafes through between roof and vehicle in a panel cavity pre-MPPT - what do you think those amps are going to do?

Prevention is better than cure.

This is why you always use a rubber grommets/cable glands when you run the wires through metal and the panel cables are always double insulated.
IF there is an issue with "Chaffing" the usual culprit is a poorly exicuted installation eg. cables not secured, poor crimps/joins and of course not using grommets/cable glands/shielding where they are required.
Ading fuses from/at the panel is just over complicating a very simple installation and IF the panels/wireing are fitted correctly there is absolutely no need for fuses at this point.

cable gland.jpg

Happy to add a relay to a 800mA circuit, not happy to add a fuse to a 10+ amp solar panel, that will not stop burning if under short circuit fault until out of the sunlight.

Originally Posted by trout1105

This is why you always use a rubber grommets/cable glands when you run the wires through metal and the panel cables are always double insulated.
IF there is an issue with "Chaffing" the usual culprit is a poorly exicuted installation eg. cables not secured, poor crimps/joins and of course not using grommets/cable glands/shielding where they are required.
Ading fuses from/at the panel is just over complicating a very simple installation and IF the panels/wireing are fitted correctly there is absolutely no need for fuses at this point.

cable gland.jpg

If my double insulated house wiring is installed correctly then why do they need to install fuses?
And RCDs etc?

Because things happen.

Copper fatigues, insulation breaks down, vibration loosens connections and joints.

This can cause arcs, shorts and hot joints.

Btw, your curve radius on that cable is too tight into that cable gland

If my double insulated house wiring is installed correctly then why do they need to install fuses?
And RCDs etc?

For the same reasons why these items are used in a 12/24v system between the battery/batteries and whatever they are powering up.
You won't find a fuse from your power line to your house, The power goes into your fuse box and is distributed through the house via fuses from there So why would you need a fuse from your solar panel to your battery?

A solar panel can only produce its max rated current as per its design /cell limits, so a short doesn't increase its output or damage it.

Put a panel in the sun and short the leads together, it (current) just goes round and round all day no damage as it is working at its ratings. An individual fuse per panel above the max panel current is a waste and will never blow.

Panels in series increase the voltage not the current output.

Panels in parallel increase the current output but not the voltage.

You only use a fuse where the source (panel/array of panels) is capable of supplying more current than the load (pwm/mppt regulator) normally requires and if the load itself faults then the fuse will blow as the panel/array will then put max current into the load.

Example - 2 x 24 volt 5 amp panels in parallel = 24 volts 10 amps output (ignore light conditions)

You have an MPPT regulator charger that is 8-36 volts input but only draws max of 5 amps input to do its job. So within its operating parameters, which exceed the voltage of the panels comfortably, it will draw only what it is designed for by varying its internal resistance.

Should said regulator develop an internal fault it may draw up to the 10 amp self limit of the array, this wont harm the panels but will be burning up the regulator, however your 6 amp fuse placed inline AFTER the panels have been paralleled will blow and stop the current flow.

I can try and clarify if I haven't explained properly.

Originally Posted by trout1105

For the same reasons why these items are used in a 12/24v system between the battery/batteries and whatever they are powering up.
You won't find a fuse from your power line to your house, The power goes into your fuse box and is distributed through the house via fuses from there So why would you need a fuse from your solar panel to your battery?

Not sure where u live but here in QLD I can say with 100% that the Power Service cable coming into your house from the street IS fused. It is HIGHLY dangerous not to have it Fused. It's usually located on the Pole or the Underground Pillar box on the footpath for those in underground powered estates.