In-line fuses for off grid solar

[CraigOwl]

Hi there. Im a newby to the group and have just built a small off grid cabin in the Scottish Highlands with my husband. I have the task of setting up the small solar panel system and have a wee question about inline fuses if I may?

I’m trying to figure out If it is possible to purchase an inline fuse (30amp) and holder that would attach directly to my 4mm cable? The fuse will sit between the charge controller and the battery. Ive seen a few pics online but they seem to come with a thin wire build in which Im not clear would be any good.

Thanks in advance

[SunEagle]

Hello CraigOwl and welcome to Solar Panel Talk

You should be able to find in line fuse and holders for solar circuits. Some actually come with the MC4 connectors already in place which allows you to connect it directly to the panel wire. If you don't have the MC4 connectors then you may have to install a junction box to keep the connection out of the rain.

[CraigOwl]

Hello CraigOwl and welcome to Solar Panel Talk

You should be able to find in line fuse and holders for solar circuits. Some actually come with the MC4 connectors already in place which allows you to connect it directly to the panel wire. If you don't have the MC4 connectors then you may have to install a junction box to keep the connection out of the rain.

Thanks for this. This particular part of the system will be indoors so Im not concerned about water/rain but I will have a look and see what I can see re ones specifically for solar systems

[foo1bar]

Hi there. Im a newby to the group and have just built a small off grid cabin in the Scottish Highlands with my husband. I have the task of setting up the small solar panel system and have a wee question about inline fuses if I may?

I’m trying to figure out If it is possible to purchase an inline fuse (30amp) and holder that would attach directly to my 4mm cable? The fuse will sit between the charge controller and the battery. Ive seen a few pics online but they seem to come with a thin wire build in which Im not clear would be any good.

Thanks in advance

I'm in the US - so I'm not sure how big "4mm cable" is (is that diameter of the conductor? Or radius? Or something else?)

But I would generally expect a 10AWG wire will support 30A current.
10AWG isn't very big - especially compared to the large battery cables that you probably are using.
But it is sufficient for 30A.
If this is going to be indoors, I'd probably look at having the fuse holders mounted to something, not just supported by wires. If I search "ANL fuse holder" or "30A ANL fuse" I see some holders that might work for you. They generally don't have wires, but rather terminals you'd attach your wire to, some have a screw-down terminal block, most have a stud that you could put a ring terminal on.

There's also DIN mounted fuse holders.

And there is probably 30A fuse panels/disconnects for regular AC work that you can check if they're rated for DC (and if so, for how much DC)

[CraigOwl]

I'm in the US - so I'm not sure how big "4mm cable" is (is that diameter of the conductor? Or radius? Or something else?)

But I would generally expect a 10AWG wire will support 30A current.
10AWG isn't very big - especially compared to the large battery cables that you probably are using.
But it is sufficient for 30A.
If this is going to be indoors, I'd probably look at having the fuse holders mounted to something, not just supported by wires. If I search "ANL fuse holder" or "30A ANL fuse" I see some holders that might work for you. They generally don't have wires, but rather terminals you'd attach your wire to, some have a screw-down terminal block, most have a stud that you could put a ring terminal on.

There's also DIN mounted fuse holders.

And there is probably 30A fuse panels/disconnects for regular AC work that you can check if they're rated for DC (and if so, for how much DC)

Thanks for that. I think 4 mm is equivalent to 12 AWG.Ive been looking online and have sourced a circuit breaker that looks like it will do the job and will mount on the wall. Top tip about not allowing it to be supported by wires so cheers

[Mike90250]

Might I suggest spending a bit more money, and getting a circuit breaker for this ? If at any time, you need to reboot or test the Charge Controller, the solar PV must be disconnected so that the Controller does not fry.
Most fuse holders are not rated to disconnect / reconnect a live circuit, and are likely to arc with higher DC voltages !!

Turning on: power up the Controller first, after it boots, then connect the PV
Turning off: disconnect the PV first, then shut down the controller

With clever wiring - you can fit both Controller Disconnects in the same breaker box

MidnightSolar box & DC rated breakers

http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=9&productCatName=Combiners

http://www.midnitesolar.com/productPhoto.php?product_ID=183&productCatName=Breakers&productCat_ID=16&sortOrder=18&act=p

My install:

20160821_132247.jpg

[CraigOwl]

Mike90250 Thanks for that. Your system looks good but much more complex that mone. I have indeed gone for a couple of circuit breakers tho as advised

[CraigOwl]

Another question: Solar panel obvs outside but I was told battery needs ventilation coz of hydrogen gas emissions which would mean that charge controller would need to be outside too, with inverter inside. Any views on best solution. Mice may be a problem

[chrisski]

This was my solution to four flooded lead acid golf cart batteries that are stored inside my RV. I put them in a battery box with a vent over each box and the hose slopes upwards to outside.
780265DC-4CE0-4584-9591-30AB593AE4C5.jpeg
You mentioned you got circuit breakers. I’m a use the same type circuit breakers that mike mentioned. I do not like audio circuit breakers. Their tripping amperage is not reliable. This is an example of the ones I don’t use for solar builds:
29399771-6A30-47D0-9E69-19214761F188.jpeg

[CraigOwl]

This was my solution to four flooded lead acid golf cart batteries that are stored inside my RV. I put them in a battery box with a vent over each box and the hose slopes upwards to outside.
780265DC-4CE0-4584-9591-30AB593AE4C5.jpeg
You mentioned you got circuit breakers. I’m a use the same type circuit breakers that mike mentioned. I do not like audio circuit breakers. Their tripping amperage is not reliable. This is an example of the ones I don’t use for solar builds:
29399771-6A30-47D0-9E69-19214761F188.jpeg

Just bought 2 of the exact same circuit breakers which have arrived today. I wasnt sure at first but watched some youtube reviews and they seem to rate very well with the experts. Just as a matter of interest did you make or buy the battery boxes with vents? My 100Ah leisure battery will be inside a wooden shed/cabin but I could vent them outside if necessary or I could just mount the battery outside all together.

[Mike90250]

Just bought 2 of the exact same circuit breakers which have arrived today.

The midnight breakers are "switch duty" rated. Many breakers (including the 12v audio breakers) are not rated for turning on and off. When used as a switch, they wear out in a couple dozen cycles.

I wasnt sure at first but watched some youtube reviews and they seem to rate very well with the experts.

There are pod-casters and video-casters, and some are on you tube, but there are few experts there. Chose your advice site well

Just as a matter of interest did you make or buy the battery boxes with vents? My 100Ah leisure battery will be inside a wooden shed/cabin but I could vent them outside if necessary or I could just mount the battery outside all together.

Most DIY wooden shed construction has lots of small air gaps which would be enough to vent a couple of batteries,
You have to get more elaborate with venting if you move batteries into living spaces.

Generally, the charge controller and inverter are mounted close to the battery to reduce cable losses. Once the inverter creates the high voltage, the high voltage is much more practical
to run long distance.

inverters come in 2 major types, Modified Sine wave (which is really a square wave) and Pure sine wave. If you have any appliances with a motor or a transformer, you nee pure sine wave (fridge, fan, electric clock)

I question the effort you are going through here. A 100ah battery is not good for much more than a couple LED lights and charging a phone. And the available sun for recharging, if you drain your battery 40% (leaving 60% in the battery)
( some quick math, 12V 100ah battery holds 1,200 watt hours )
To replace the 480wh you used, with a well aimed 100w panel, would require 6.4 full sun hours.
Panels usually only produce 70-80% of nameplate. How many days of full bright sun do you generally get ? Even in sunny California, 6.4 hours of good recharging sun, is rare

Consuming just 20% of the battery capacity leads to the longest life of the battery, consuming more, shortens the lifetime.

So, please consider your loads and available sun hours ( not 6am - 6pm, only 10am - 3pm counts usually) and how many panels you need to recharge the batteries.

[chrisski]

Just bought 2 of the exact same circuit breakers which have arrived today. I wasn't sure at first but watched some YouTube reviews and they seem to rate very well with the experts. Just as a matter of interest did you make or buy the battery boxes with vents?

I have two of those pictured circuit breakers I got and I never installed. Yes people use them, but that does not make it good.

Those circuit breakers tend to be rated for up to 24 volt systems and I saw a video of someone using this as an easy shutoff for current going into a SCC, but it was certainly not rated for that voltage. You'll notice things from these YouTubers in a little bit.

The mindnite Solar circuit breakers are awesome. They are rated for 150 VDC or 250 VDC. Not using a DC circuit breaker is a fire hazard. There's some good YouTube videos about this. On another forum, I saw someone install AC circuit breakers onto his solar build (Very BAD and DANGEROUS) off a forum member recommendation. You also need to be sure the CB is rated for the correct DC voltage. There's some lower voltage 36 volt breakers that would not cut it for nearly all solar applications. Two panels in series will be more voltage than that.

================================================== ==================

I bought Tall Golf Cart Batteries, Class GC2H, and there were no vented cases available. The batteries I got were 1" taller than a typical golf cart battery which made it too tall for nearly every golf cart case out there. I could only find 2 cases made for these batteries, only one of which would hold four of them. As far as I know, that company from Canada is the only site in the world that makes batteries.

Boy would I have loved to have a pre-made vented case so I would not have to spend two weeks and visit a dozen stores to build what I have in the picture.

I got the case from a company in Canada, the battery vent hose from a local trailer store, and the attachments for the hoses from the plumbing section at the hardware store. A couple of other purchases from Home Depot for things like screws, bolts, nuts and Loctite finished it off.

The batteries sit on a slide out 2' X 2' generator shelf.

My plan from the beginning had been to build a lithium pack from cells, which I am working on now. The FLA I have may have 9 more years left in them.