Fuses

[Revid]

Iam in process of upgrading my 12v system to 24. It was a bare bones setup but would like to have better. So got 1 405w panel but will have two later. 6 125 ah 12v agm batteries in series, 60 a controller and a 3000 w inverter. 10 gauge wires from panels ,#2 wires between batteries Can someone tell me what size fuses/ breakers I need and where to put them. I think I have 10 gauge from batteries to controller and inverter, maybe I need heavier? Thanks guys

[organic farmer]

Everyone who is off-grid looks around at everyone else' systems. I greatly admire the 12vdc systems for their simplicity.

I have a 48vdc system. Often I have wished that mine was 12vdc instead.

But you have one photovoltaic panel while I have 20 of them.

If I were you, I would add your second PV panel in parallel to the first and keep it all 12vdc.

[Revid]

Thanks for your input but everyone I talk to tells me to go 24 v. I can use more panels per inverter and overall more efficient. Dont knock me, Iam only repeating from other forums and Iam very new to this, hence why Iam looking for some guidance on fuses.

[SunEagle]

The size of a fuse is determined by either the wire size rating or the "input/output" rating of the panel, charger or other equipment. Just remember a fuse that is rated too low may "blow" or open to soon. If it is rated to high then you run the risk of possibly causing a fire or equipment failure.

[littleharbor2]

Revid, welcome to the forum,

Details matter when describing your system.
Your 6 12 volt batteries all in series will give you a 72 volt system. You need to series/parallel wire your batteries 2s 3p for a 24 volt system.
Going 24 volts will allow you to use more panels into your Charge Controller. Your inverter really doesn't care how many panels you use.

When asking questions on the forum, you really need to include all details about your system for the best chances of getting a meaningful answer.

[Revid]

Thanks and I apologize but very new to the solar scene. Trying to get the best info before I buy. So batteries will go in series like you mentioned. I will have 2awg wire from cc to batteries and inverter to batteries cause I’ve been told that’s what I should use. Will be hooking up 1200 watts of panels. 3000 w inverter and a 60 a controller. Hope that’s enough info

[SunEagle]

Well the wire from the 60Amp charge controller needs to have about a 60amp fuse which will easily protect the 2 awg wire. You can probably go with smaller wire that is closer to 60amp but in case you have a high inrush amp the larger wire will easily handle it.

If you plan on using the 2 awg wire between the batteries and inverter you should go with a fuse size that the inverter is rated for based on the battery voltage you plan to use. A 3000 watt inverter at 24V can see 125amps (3000w / 24V = 125 amps) but most inverters can provide higher outputs for a brief time and that will increase the amp draw. So a fuse less then 125amps may blow depending on what is being turned on at the inverter. Again the fuse is there to protect the wire or equipment.

The wire size and fusing between the panes and charge controller depends on how the panels are wired and what it can generate. So I can't really help you there..

[Revid]

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

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

[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

[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]

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]

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 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!