Fuses

[chrisski]

It’s presently 10 gauge going to inverter cause that’s what I was told in beginning with a 12 v system. Now Iam upgrading hence the questions so I get it right or better this time. I have 4 405w panels and about to buy inverter and controller. Some people say 60 a is big enough others say I need an 80!!! Iam getting a 3000 w pure sine inverter but now waiting on some advice on the controller.. local solar shop says 80 and after joining panels 2s2p I need to go to #8 wire. So looking around fora Y mc4 connector to go from 10 to 8 gauge on the single strand side.Just looking for advice and guidance. Thanks

I recommend you stop planning and go into a research mode. It sounds like the people you’ve talked to have given some dangerous advice if 8 AWG is the only wire to the inverter.

Dangerous as in, “Oh no my trailer burnt down.”

Go through the stickies and read anything by Sunking and consider it gosphel. He leans on the conservative, safe side of a build.

Based of his advice, I built this 24 VDC build

/diysolarforum. com/ threads/rv-build-2-55-kw-panels-560-ah-24-v-lithium-battery.34020/

[Revid]

It’s presently 10 gauge going to inverter cause that’s what I was told in beginning with a 12 v system. Now Iam upgrading hence the questions so I get it right or better this time. I have 4 405w panels and about to buy inverter and controller. Some people say 60 a is big enough others say I need an 80!!! Iam getting a 3000 w pure sine inverter but now waiting on some advice on the controller.. local solar shop says 80 and after joining panels 2s2p I need to go to #8 wire. So looking around fora Y mc4 connector to go from 10 to 8 gauge on the single strand side.Just looking for advice and guidance. Thanks

[chrisski]

What is your wire size to the inverter?

By reading its either 10 AWG or 8 AWG. I have a 24 volt system and my wiring to the inverter is 4/0.

With a 3000 watt inverter, I think you are wise to go to 24 volts. IMO, 3000 watts constant is too much for a 24 volt system, but can be run at 2000 watts hours on end, but the 3000 watt inverter is sometimes needed to cover surge and get inductive loads like motors moving.

Does one or two panel cover your needs?

For planning without knowing your specific area of the world, I use two times the panel ratign for winter and five times the panel rating for summer, so for each panel 800 watt hours produced in the winter and 4000 watt hours produced in the summer. I also assume the system has 200 watt hours per day idle draw and a 300 watt inverter can use 500 watt hours if left on. Also, 6 of your batteries has 9000 watt hours.

This can cover what you want especially if you have built in extra batteries to get you through 1 or more cloudy days.

[BryceFreeman]

Leave a mark here as this thread is helpful to me. Thank you guys.

[littleharbor2]

Littleharbor2 can you explain?

Because 1620 watts divided by 29 volts (max charging voltage) is just over 55 amps.
The same 1620 watts is over 110 amps at 14.5 volts. Meaning you will actually need TWO 60 amp controllers @ 12 volt system voltage.

On the same note @ 48 volt system voltage you would only need a 30 amp controller with those same panels.

[Revid]

Littleharbor2 can you explain?

[littleharbor2]

If you were going with a 12 volt system, then, yes, 80 amp controller. with 24 volt not necessary

[Revid]

Thanks Suneagle for input and your patience. Looking on line most mc4 connectors are 4mm contact pin and take either 10 or 12 awg wire. So after I “join”the two sets of panels I was advised to run 8 awg wire. I think the wires on the panels are 10 gauge now . So I have to have a “Y” with two ordinary mc4s and other single end with mc4 that takes 8 gauge. I don’t know why they said I should go 80 amp controller !! Iam more confused now!

[SunEagle]

Thanks I have four now instead of three, Was told I need a 80 a controller also cause the 60 wasn’t big enough. What you guys think. They said I would have to up my wire size to 8 awg after the panels are wired together 2s2p So 4x31=124v, 4x37=148Voc . So if I wire 2s2p what does that do to the numbers? Is there a 2-1 mc4 connector that goes from standard 2 10 awg to 1 8awg??

Wiring them in 2S2P should yield twice the voltage or 2 x 31 = 62V and twice the amps or 2 x 13.01 = 26.02amps. I am not sure about what are standard connectors and their wire size but you might be able to get a custom connector.

I also am not sure why they stated for you to go to an 80amp controller

[Revid]

Thanks I have four now instead of three, Was told I need a 80 a controller also cause the 60 wasn’t big enough. What you guys think. They said I would have to up my wire size to 8 awg after the panels are wired together 2s2p So 4x31=124v, 4x37=148Voc . So if I wire 2s2p what does that do to the numbers? Is there a 2-1 mc4 connector that goes from standard 2 10 awg to 1 8awg??

[SunEagle]

Here is a pic from the back of my panel. I have three of them Iam planning on getting a 3000 watt inverter and a 60 a controller

Great. With that info we can calculate your voltage which can be anywhere between 93 and 111 volts (3 x 31Vmp = 93 , 3 x 37Voc = 111) and the maximum amps can be Imp= 13.07A.

[Revid]

Here is a pic from the back of my panel. I have three of them Iam planning on getting a 3000 watt inverter and a 80 a controller

[Revid]

Thanks I’ll get bk to you when Iam in front of the panels.

[SunEagle]

Thanks so much. That was great help. Panels will be in series to give me 24v. Three panels at 405w if that helps

The panels have both a voltage and amp rating. When wired in series the voltage adds up and the amps comes to what a single panel is rated.

My guess is that the panels are rated about 22.5 amps at 18 volts (22.5 A x 18V = 405 watts) . That will get you 3 x 18V = 54V and about 22.5 amps going to the charge controller. But again it is best to read the specifications on the panel and not make an assumption.

[Revid]

Thanks so much. That was great help. Panels will be in series to give me 24v. Four panels at 405w if that helps