Wire and fuse suggestions for your 12v DIY solar power system

This guide is not meant to be comprehensive by any means. It’s meant to be simple for beginners to help get them started with their own DIY solar power systems. I am not a professional of any kind, I’m not a contractor, an electrician, licensed solar technician or anything like that. I’m not a doctor, lawyer, psychiatrist or building inspector. I’m just a hobbyist, so take that for what it’s worth. Everything I do or suggest is for entertain purposes only and you should seek the advice of a professional before doing anything in life, no matter how easy or mundane it may seem. 😂

Battery Disconnects and/or breakers

Best Options:

There are a couple of ways to add an extra layer of protection to your system and making it easier and safer to work on by being able to disconnect your battery bank from your entire system. You can use a battery disconnect switch, or you can use a large DC circuit breaker switch. The circuit breaker switch is my preferred method because it offers an additional layer of protection should something go terribly wrong.For a 12v system, I use a breaker switch between the battery and the bus bars that is rated for the amperage of your entire system. See the chart below for the recommended fuse size for your inverter. Because I have every connection in my system protected by a fuse or a breaker along the line, I’m personally more concerned here with just using this as a disconnect switch more than anything. I can assure you the solar guru purists and electrical engineers will breathe a little hate my way for this, but i personally just use a 300a breaker even though my max draw is much less than this, but that is partially because I am constantly testing inverters of various different sizes for my system and I dont want to have to change my breaker all the time. So, I do recommend you figure out your max system draw and size your main breaker/disconnect switch accordingly.

Main DC Breaker

OR

Battery Disconnect Switch

12v INVERTER WIRE & FUSE SIZING

Suggested WIRE Sizes for Common 12v Inverters:

These suggestions are for PURE COPPER WIRE ONLY. The best copper wire is often called “Welding Wire” because it is rated for high amperage usage as well as high heat tolerances. I DO NOT recommend using copper clad aluminum wire for anything. It’s dangerous and you risk causing a fire. It can be tempting to use the minimum you can get away with because the price of copper wire is rather expensive, but my best advice is to think of wire as an investment for the long term in your solar system, this is not the place to skimp. With that in mind, I recommend getting even thicker wire than recommended if you plan on upgrading later because you can always use bigger wire that is over rated even on smaller inverters. So, say you plan to start with a 1000w inverter, but you have plans to upgrade to a 2000w inverter later, it would be a good cost saving measure in the long run to go ahead and buy 1/0 wire now and use that for your 1000w inverter, and when it’s time to upgrade to 2000w you don’t need to replace the 2 awg you already paid for, and then buy 1/0 later. Copper wire goes up year after year, and it lasts for ages, so get the biggest wire you can and save yourself money in the long run.

If you intend to use your inverter for a sustained period of time you definitely want to go with the “Recommended” size or larger rather than the Minimum wire size. The minimum size is ok if you only really plan to use your inverter at around 50% of it’s rated power most of the time, and an occasional max usage for less than 30 minutes or so at a time.

Note: These suggestions are for wire runs of LESS THAN 10 feet. If your wire lengths NEED to be longer than 10 feet, you should reconsider your options on the placement of your battery and inverter to bring them closer, otherwise you are going to need thicker wire… the longer the wire run the thicker the wire needs to be and for this I recommend doing more research before using these suggestions.

Inverter WattageMinimum Wire SizeRecommended Wire Size
500w8 awg10 awg
1000w4 awg2 awg
1500w2 awg2 awg
2000w2 awg1/0 awg
2500w1/0 awg1/0 awg
3000w2/0 awg2/0 awg

I highly recommend WINDYNATION brand cables for their extreme durability and higher amperage and temperature rating than most other brands.

Shop for These Cables On Amazon 

Suggested FUSE Sizes for Common 12v Inverters:

The important thing to understand about fuses is that their purpose is to protect your WIRE. Because of this, its important to know that, unlike wire size, bigger is NOT better. At the same time however, too small of a fuse and you will be blowing fuses all the time and you don’t want that either. A fuse is designed to melt before the wire if there is too many amps going through the wire and disconnecting the circuit to prevent a fire or damage to equipment. Remembering that the main purpose of the fuse is to protect your wire, if you use higher gauge wire than was recommended above, you CAN also use a higher amperage fuse, but that would make things more complicated and I would just stick to the recommended fuse size anyway. For a 12v system you can use either an ANL or AMG/MEGA type fuse. There are other options but I’m trying to keep this simple.

suggestions.

Inverter WattageSuggested Fuse Size
500w50-60 amp
1000w100-150 amp
1500w150-175 amp
2000w200-225 amp
2500w250-275 amp
3000w300-350 amp

Shop for These Fuses on Amazon

Recommended Fuses for 12v Systems

Charge controller wire & fuse sizing

Suggested WIRE Sizes for Common MPPT Solar Charge Controllers:

It’s very important to always connect your battery to the charge controller before you connect your solar panels because you risk damaging the charge controller. It’s best to look in your manual to determine the correct wire size for your inverter because some brands only support the minimum size wire at the terminal post, so all I can give you here is a rule of thumb, but it may not apply to all charge controllers because the terminal posts are often those slip in type where you either use bare wire or a ferrule end rather than a ring or fork style of terminal. I prefer to use silicone jacketed wire rather then PVC jacketed wire here for its excellent flexibility, but feel free to use PVC. For a 100a charge controller I would probably go with the 4AWG welding cable from WindyNation.ANything under 100a and I’d use the Recommended Silicone Wire below.

No matter what kind of wire you choose, never use any wire labeled as “CCA” or “Copper Clad Aluminum”, only use “Pure Copper” or “OFC” (Oxygen Free Copper) wire for safety sake. CCA wire is pure garbage!

Controller Amp RatingSuggested Wire Size
10a 16-14 awg
20a12 awg
30a10-10 awg
40a10-8 awg
50a8 awg
60a8-6 awg
80a6 awg
100a6-4 awg

Recommended Silicone Wire 
16-6 AWG

Suggested FUSE Sizes for Your Charge Controller:

Again, you will want to confirm that this gauge will fit into your terminals. I always go with the max size wire I can fit. Install an inline fuse or breaker rated for the same rating as the controller or the next size up… so, a 40a controller use a 40-50a fuse/breaker, a 60a controller use a 60-80a etc… 

Charge Controller Amp RatingFuse Suggestion
10a10-15a fuse
20a20-25a fuse
30a30-40a fuse
40a40-50a fuse
50a50-60a fuse
60a60-70a fuse
80a80-100a fuse
100a100-120a fuse

Recommended DC Breakers
For 30-100 amp Controllers

Recommended Inline Fuses
For 10-30 amp Controllers

Solar Panel Wiring

Suggested WIRE & Accessories for Solar Connections

Just Get 10AWG Solar Wire…The point of this page is to try and keep things simple for beginners, and forego a bunch of math to figure things out. However, when it comes to connecting several solar panels together, the math cannot be avoided for long. I can tell you that, any properly designed solar array should work with 10AWG wire, and if it doesn’t, then your system needs to be reconfigured. Unless your planning to connect 5000w of solar, and your charge controller is massive, then for most instances 10AWG wire will do the job and that is what most people use even if you can get by with smaller wire. I have several systems, and let’s put it this way, ALL of my solar wire is 10awg, and my buddy with 3kw of solar panels is also using 10awg because he wired his system in a way that keeps makes the 10awg appropriate, and so should you. This is a more complicated subject, and I will be making a video about it very soon, but I wanted to put something up for those just looking to get started and maybe unsure of what stuff to get to get the ball rolling with their  own DIY solar project. So, in conclusion, just get 10awg wire and figure out your exact diagram for your solar array to make sure you don’t blow it up sending too many amps into it. For solar wire you just want to make sure you get tinned copper wire that is rated and designed for solar wire because it has special UV and abrasion properties to keep it in good condition out in the weather. I get the big roll and use the stuff for everything that calls for 12-10awg wire in my systems because I like the thicker jacket on it than standard wire.

HIGHLY recommend you connect your wires into a solar disconnect switch inside near your charge controller so you can disconnect I the solar array before working on your system.

No matter what kind of wire you choose, never use any wire labeled as “CCA” or “Copper Clad Aluminum”, only use “Pure Copper” or “OFC” (Oxygen Free Copper) wire for safety sake. CCA wire is pure garbage! If the wire seems substantially cheaper than everything else, its likely CCA and should be avoided. In case you haven’t noticed, I feel strongly about this junk CCA wire.

Recommended Solar Panel Wire
WindyNation

Recommended MC4 Crimper Set
With Strippers, Cutters & Spanners

Recommended Solar Disconnect Switch
Pre-Wired w/Box