Fuses, kill switches, and more

[robbob2112]

OH,
one other thing on bending - if you are having trouble even after practicing your bends and the tubing kinks or collapses you can fill it totally full with sand and tape the ends shut. Then when you bend it the tube can't collapse. This also works with large gentle bends as well.

I've used the method without a bender in a pinch you just can't go as tight a radius as with a bender.

 

[robbob2112]

negative, All batteries are 48v

Hrm,

all 48 - I would torn - maybe get a series of small bus bars - put two batteries to each, then a class T up to the main one. This prevents a bunch from dumping into one and cuts the number of class T in half.

 

[ScrotpusGobbleBottom]

Hrm,

all 48 - I would torn - maybe get a series of small bus bars - put two batteries to each, then a class T up to the main one. This prevents a bunch from dumping into one and cuts the number of class T in half.

I think I saw you dish out some good links for 50ah class ts and mounts.
I think I remember us talking about it anyway.

Any chance you have a quick link?
I do not want bare wire connections on fine stranded wire and I have not had much luck with ferrules. I would need lugs preferably. Everything I've seen so far has been a lot. 350 dollar 3 port fuse blocks are not going to work

 

[robbob2112]

There are some midget mount class T fuses. But, due to the small size the AIC isn't much different than a MRBF. I did find a few other small sizes that were as fast as a class T and 100ka AIC, but the cost was insane...like $200each fuse plus mounts.

I can poke around more for similar and see if I can find a reasonable cost. Reasonable cost to me means $100ish for a triple mount and $20 a fuse.


How many amps do each of your batteries put out?


Here is an interesting one, just have to go back and find the holder.

Mersen UL Class Fuse, T Class, A3T Series, Very Fast Acting, 50A, 300V AC, Non-Indicating A3T50 | Zoro

Order Mersen UL Class Fuse, T Class, A3T Series, Very Fast Acting, 50A, 300V AC, Non-Indicating, A3T50 at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

 

[ScrotpusGobbleBottom]

How many amps do each of your batteries put out?

They are good for 1c so 50 amps each. How many amps get drawn? I have a smart shunt on both sets, the 280ks and then the 8 renogys. I have never seen more than 70 coming from the renogys while connected to the 2, 280ks but I plan on a second 6000xp so that will for sure double at least. I would guess that I wouldnt need more than a 25-30 amp fuse per battery so if we wire them with the MRBFs individualy and then wire in pairs like I already have going on, We could do 4 strings of 2 50ah batteries with a 75 amp class t on each string. 4 total.

expected draw on all 8 should typically never exceed 150 amps so that leaves 18.75 amps per battery X 2 per string =37.5 amps per pair. I could certainly do a 50 amp class T there but that would be 200 amps total and the 2 XPs could use over 250 not including peaks. So 4, 75 amp fuses would make 300 amps and cover all of 2 XPs and more peaks than I would need.

Sound about right? I would be leaving it open to run the 2 XPs on just the 8 renogys. Just because I think that would be a good idea.

Reasonable cost to me means $100ish for a triple mount and $20 a fuse.

Yes, that seems reasonable to me as well.

Thanks again for your help!

 

[robbob2112]

Here is a prospect -JLLN fuse - in this small size is 20k instead of 50k AIC.

Mersen Open Fuse Block, T UL Class, 2 Poles, 60A Amp Range, 300V AC/DC Volt Rating 30607T | Zoro

Order Mersen Open Fuse Block, T UL Class, 2 Poles, 60A Amp Range, 300V AC/DC Volt Rating, 30607T at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

https://www.digikey.com/en/products/detail/littelfuse-inc./JLLN060.T/2517729

Can go up to 90amps.

And more interesting - with an open holder you could do 10 of these

Littelfuse UL Class Fuse, T Class, JLLN Series, Fast-Acting, 100A, 300V AC, Non-Indicating JLLN100 | Zoro

Order Littelfuse UL Class Fuse, T Class, JLLN Series, Fast-Acting, 100A, 300V AC, Non-Indicating, JLLN100 at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

 

[ScrotpusGobbleBottom]

Here is a prospect

So I recently put together a Luyuan 48v battery box for my second set of 280ks. It came with a breaker. I couldnt for the life of me get the wire in there tight enough. Tiny screw head..... I tried the supplied ferrules and I could just yank the wires with the ferrule out. I ended up not using a breaker on the box.

My point is that Id like lug connections. I imagine I would be fine with the prospect #1 if the screws were good enough.

 

[robbob2112]

Will poke around more.

 

[HRTKD]

I tried the supplied ferrules and I could just yank the wires with the ferrule out. I ended up not using a breaker on the box.

This was discussed on another thread I believe. My approach with that same box will be to crimp the ferrule and see how that works. Plan B is to use my own cable and ends. I will be putting my own Class T fuse in the box even though the box has a breaker on it.

My opinion is that the (breaker?) terminal should not be responsible for crimping the ferrule.

 

[Brucey]

its a cool site...thanks for sharing.
their enclosures are ABS plastic. Think metal required in california? Not certain.
The ones you linked - how and where do they mount? only in their ABS plastic boxes? Love a photo of one mounted.
I have no idea if I have magnetic or thermal, but they are in a box, and likely chinese, and was a will recommended one somewhere like his mobile solar site. I think i got from amazon...looking for it now...

I found the battery switch:

https://www.amazon.com/dp/B07413JWLD?psc=1&ref=product_details

and the disconnect which came in a box:

https://www.amazon.com/dp/B0CFCZX9N4?psc=1&ref=product_details

spec sheet under product details below reads:

Breaker Type

Thermal-magnetic

and it is the 30 amp one with 2 wires/disconnects (red / black).

Very unlikely that switch is rated for 48V nominal operation, would recommend the Victron 275A one which is rated for up to 60V.

https://www.amazon.com/Victron-Energy-VIC-VBS127010010-Battery-Switch44/dp/B095X94JXF/

 

[Brucey]

would love to see a link to a disconnect in a metal box that can handle 2 pairs of cables. Only have one string now, but potentially two in future. Not even sure what brand to buy or who makes them.

Same with T-class fuses. Everyone talks about them - not seen a link to buy them. Don't see them at signature solar or rich solar or any others will recommends like current connected.

I saw where someone said that if battery has a built-in circuit breaker, as many do right on the front of the larger 48 volt ones along with a power switch and big lugs for heavy gauge conductors, then you do not need another breaker or t-class fuse. Is that accurate? I looked for the post in my history but could not find. Just want to do things right.

Take a Midnite mnpv6 combiner box. Split the positive bus bar in two (this will allow you to have two strings to two sccs in the future). I was just using some splitters here for quick test normally you'd have one string per breaker.

For each string you would have an mnepv DC breaker, either 15 or 20A usually. So in this configuration you could have three parallel strings to each SCC.

 

[robbob2112]

This was discussed on another thread I believe. My approach with that same box will be to crimp the ferrule and see how that works. Plan B is to use my own cable and ends. I will be putting my own Class T fuse in the box even though the box has a breaker on it.

My opinion is that the (breaker?) terminal should not be responsible for crimping the ferrule.

This is my take on ferrules

Robbob2112 Answer thread

Just putting this thread together as a place for me to post answers to common questions I see over and over. Whatever you read below is my opinion - read at your own risk - I found them all in the cellar at the end of the hall in the bottom of a locked filing cabinet stuck in a disused...

diysolarforum.com

And you are right, the ferrule should be crimped prior to use. Right ferrules, crimper, method.

 

[robbob2112]

Take a Midnite mnpv6 combiner box. Split the positive bus bar in two (this will allow you to have two strings to two sccs in the future). I was just using some splitters here for quick test normally you'd have one string per breaker.

For each string you would have an mnepv DC breaker, either 15 or 20A usually. So in this configuration you could have three parallel strings to each SCC.

View attachment 232661

I am curious why you are only doing the breaker on the positive verse both. I have seen it both ways so am interested in the logic of why?

 

[Brucey]

I am curious why you are only doing the breaker on the positive verse both. I have seen it both ways so am interested in the logic of why?

At the time I was planning on using 150/35s, so using the 150V breakers. Just a matter of not enough breaker spaces in the combiner. For code as a disconnect you'd want to have both positive and negative on a breaker.

I've since switched to a 450/100 and I'm using 600V (300V tandem) breakers so I will be connecting the positive and negative of each string (two strings, one to each tracker). The leftmost breaker is an MNEAC 60A AC breaker for the output of a Rosie.

 

[Jonathan86]

Fuse if you have more than 2 parallel strings. Fuse both positive and negative. You can use a 2 pole DC breaker instead of. You don't need multiples.
If you want to disconnect PV under load your need a PV disconnect isolator, this is required if it is on a residencefor fire fighter use. Fuses and breakers should not be removed/flipped with current coming from the panels. You can do fuses or breakers, no need for both.

I didn't know this. I have done this many times on my system. What is the issue with doing this?

 

[ScrotpusGobbleBottom]

What is the issue with doing this?

I am assuming you are referring to disconnecting under load?

Breakers can erupt in flames in less than 2 seconds. That is why.
This happens because of arcs.

 

[Brucey]

I didn't know this. I have done this many times on my system. What is the issue with doing this?

Some specific DC breakers like Midnite/carling tech can be operated under load as they have a robust arc shute to dissipate the arc. In general though for most DC breakers, it's best to not operate them under load.

 

[HRTKD]

On those rare times when I need to work on the system or just the solar charge controller, I do flip the breaker to cut off power from the PV. I run a dual pole DC breaker (positive on one pole, negative on the other) rated well above what the PV can produce. But I try to make sure there are no loads on the system beyond any battery charging that may be taking place. No sense temping fate.