what busbar needed/ tabbing wire needed

[rainworm]

What kind of busbar and tabwire sizes would be needed to build a 300W panel that can be put in a system for 48V 2500W?
buswire thickness 1.jpg
busbar thickness 2.jpg

[Mike90250]

Bussbar is not used inside the solar panel, tabwire is. Wire cells in series to get about 80V and then use a MPPT charge controller to down convert it.

But before you sink a lot of $ and time into this large project, try making a 100w panel and stick it outside for a year first.

[inetdog]

Bussbar is not used inside the solar panel, tabwire is.

Some people call the thin foil which is either thicker or wider than the tab wire (or both) that is used to connect the two or three tabs at the end of a string of cells and run to the location of the jbox buss wire, or less commonly bussbar wire. That is what the tables are describing.
The buss wire needs to be lower resistance than the tab wire because it carries at least 2 or 3 times the current of the tab wire, more if two or more strings of cells are paralleled within the panel.

To know what size buss wire to use, you need to know what current it will be carrying!

[rainworm]

300w

It will be a 300W panel to be standing on its own first for this year and then if it is still working a second panel etc. but in the end it will hopefully become a 2500W 48V system.
The plates to buy for this would be 0.5W and would be for instance:
Type:2 busbar
Rated power: 3.6w-3.9w Thickness:200um
Vm(V): 0.513V IM (A): 7.45A
VOC (V): 0.618V ISC (V):7.91V
or similar.
But I do not want to overload the first panel by the time it goes into the system. I want to use this first panel as the last in line carrying the most because it will be the most on the edge of the roof where I can most easily replace it.
Yes there is only a small chance that there will be more than one panel build and most likely it will last 3 months or so and then we cry.
But just for the fun of it, could you tell me how big the wires should be between the cells and how big between the string of cells?

[Mike90250]

you need to draw up a schematic of your panel, BEFORE you start building it.

How many cells in series string (in one panel)

How many strings paralleled?

It looks like each cell will produce about 7.5 amps. So all the wires in the panel, will need to be rated for at least 10 amps, and if you parallel strings in one panel, you are up to 20 amps. Any bypass diodes need to be able to handle the amps being sent through them as well as being properly heat sunk.

The trade offs are, the thicker the buss wire, the "more lumps" will be in the finished panel, and possibility for cell breakage at the lumps.

[Naptown]

you need to draw up a schematic of your panel, BEFORE you start building it.

How many cells in series string (in one panel)

How many strings paralleled?

It looks like each cell will produce about 7.5 amps. So all the wires in the panel, will need to be rated for at least 10 amps, and if you parallel strings in one panel, you are up to 20 amps. Any bypass diodes need to be able to handle the amps being sent through them as well as being properly heat sunk.

The trade offs are, the thicker the buss wire, the "more lumps" will be in the finished panel, and possibility for cell breakage at the lumps.

At least 11.7 or 156% of the ISC of the cells whatever that is.

[rainworm]

2

So 2 mm wide and 5 mm wide is standard for small use but how much would it be then for bigger panels? I read up that the pure copper ones are better than the ones containing tin also.
I dont know what is best for such a large amount of watts. 24V or 48V system?
Some people told me 48 is better for some reason.

[rainworm]

isc

what does 165% of Isc mean?
Has anyone got experience with a bigger system and knows how big the wires inside the panels should be?
I was thinking of building following. It would be average 3.8W I think per plate? (see specifications above)
So 78 plates for the panel? So all in series? 13 by 6 and all in one big string?
I have no clue to be honest.
Just do not want to blow up the panel with too small wiring.
Might go for a smaller total system or other voltage depending on what I can find.
But it would be great to have an average guide to how big the wires should be for systems up to a certain size.
I cannot find this guide on the net yet.

[Naptown]

what does 165% of Isc mean?

It is 156% of the short circuit current the panel could produce.
So if the panel has a short circuit current of say 10A then the buss wires should be capable of 15.6A

[rainworm]

After being hit with the import tax I still went ahead and ordered 5 by 0.2 busbar wire 40% lead pre solder.
Now I look at tabbing wire. should that then also be 0.2 thick? it is 2 wide.
Thank you for looking it up. so 7 A per cell makes for 10.5 A wires.
Please do not read the next line.

calculating, I feel more like having a banana in my hand than a calculator when I look at these difficult calculations you looked up for me.
But the busbar looked nice and shiny so I bought it.

Now shop for the tabbing wire.

[Guest]

hrm..