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diy solar

diy solar

I had a meltdown and could have burned my building down.

...

I think this is the breaker that's in the box right now but I can't remember for sure :


It's been in place for a year now with no issues. The wires may of just gotten loose but if that is the problem then that is another reason to go with the midnite solar breakers lug connector design.
I used those DC breakers at first but notice a distressing tendency for the wires to become loose. It was a reason why I switched to the much larger MCCB style DC breakers with Allen head bolts to connect with crimped on ring terminals.
 
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what were you doing when all the breakers failed?

How are you wiring that you are using multiple breakers? Using 2 or more in place of 1 is generally not ideal ... according to what I've read on the internet, there's no guarantee each will share an equal portion the load.

Blue Sea Systems is a popular T-class fuse brand.
I had 1 inline breaker per battery that feeds buss bars. Everything was going great until mt temperature at home hit 107 and.my AC was running non-stop.
 
I used those DC breakers at first but notice a distressing tendency for the wires to become loose. It was a reason why I switched to the much larger MCCB style DC breakers with hex head bolts to connect with crimped on
 
what were you doing when all the breakers failed?

I think deleting those breakers from each battery, using a fuse to the busbar then a t-class fuse from the busbar to inverter is a safer practice.

I size to inverter shut down voltage which is 42v in my case (48v system).

Blue Sea Systems is a popular T-class fuse brand.
So would you say Blue Sea 125 amp fuse with rated Blue Sea base per battery I would be good?
 
I haven't seen Ampere Interrupting Capacity (AIC) mentioned.

Fuses/breakers need to have an AIC rating greater than the short circuit potential.

As an example, a 12.8V LFP battery with 4mΩ resistance has a short circuit potential of 12.8/.004 = 3200A, so any fuse/breaker used must have an AIC rating this high or better.

A 16S DIY LFP battery will have a cell series resistance of 2.56mΩ. That's capable of 51.2V/.00256 = 20,000A - hence why Class T fuses are preferred.
I looked up the Blue Sea t rated fuse and it did say 20000A. I will go with that one.
 
Thanks everyone for all the response so quickly. I love this solar stuff. Everything went really well until I got to the batteries and cheaped out on those inline breakers. Wish I would have asked this forum before I went that direction. I learned my lesson, and Thank God it wasn't too late!
 
Those breakers are gash.
Use something like these https://www.amazon.com/dp/B0B1WBT8YK
Or these https://www.amazon.com/dp/B0CFQCLS3X
Find the 100a versions.

I am not sure these breakers are a ton better than the ones listed - Well, they probably are - but the reason I say that is they are built to a particular standard but haven't actually been through certification for UL, CEC, or any of the other world respected labs. So They may be good quality and they may be junk and we don't know which is true.

I would use an imo disconnect versus that for disconnect. Or something like this if you need over current protection and 15 or 20A per string is enough:


Just remember - it is allover all of the IMO website - these are intended to be used in a zero current situtation. This means the panels have already been switched off through other means. Other means would be a quality DC rated breaker that is listed with some agency.


See the later post - they can and do work under load - just 1500cycles verse 8500cycles with no load.

The fuses in a combiner box are not intended to be used to switch stuff off from the PV either. The arc can damage them.

A listed breaker will cost you a bit more to use it as a switch than the cheaper ones that look the same, but at least you know for sure what you are dealing with.

And, in case you are tempted by the plastic enclosures - IMO uses a self-extenguishing plastic, so it might catch if it overheats but it won't sustain a fire. I wouldn't be at all surprised if the cheap plastic enclosures that come with the cheaper breakers are just generic plastic.

I happen to have one I got before I knew better and I am tempted to put a blow torch to it and see how it holds up.
 
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I am not sure these breakers are a ton better than the ones listed - Well, they probably are - but the reason I say that is they are built to a particular standard but haven't actually been through certification for UL, CEC, or any of the other world respected labs. So They may be good quality and they may be junk and we don't know which is true.



Just remember - it is allover all of the IMO website - these are intended to be used in a zero current situtation. This means the panels have already been switched off through other means. Other means would be a quality DC rated breaker that is listed with some agency.

The fuses in a combiner box are not intended to be used to switch stuff off from the PV either. The arc can damage them.

A listed breaker will cost you a bit more to use it as a switch than the cheaper ones that look the same, but at least you know for sure what you are dealing with.
I thought the main selling point of the imo disconnects was the cam loaded disconnect action that handles/extinguishes the resulting arc?
 
I used those DC breakers at first but notice a distressing tendency for the wires to become loose. It was a reason why I switched to the much larger MCCB style DC breakers with Allen head bolts to connect with crimped on ring terminals.
100% true dat
 
I would use an imo disconnect versus that for disconnect. Or something like this if you need over current protection and 15 or 20A per string is enough:

I'm not sure if you understood what I was posting. It was my battery breaker that went nuclear. I just happened to of notice it because I was flipping the breaker back on for my solar panels and my hand brushed up against the battery wires and noticed that the battery wires/breaker was very hot.
 
I'll have my midnite solar 250 amp breaker in place by tonight which was kind of planned anyways but it WILL happen tonight because the breaker I had inline with the batteries almost went into melt down last night. By PURE luck I had gone out to the workshop to flip the solar panel breaker back on after a bad lightning storm yesterday and brushed up against the inverters battery wires while reaching for the solar breaker and noticed they were hot. Sure enough the wires going in and out of the mini plastic box with the din rail breaker were headed for nuclear melt down. Pure freaking luck saved me on this one. I will take pics tonight or tomorrow at the latest to see if there is any visual damage to the breaker. Its inside that aforementioned box so I don't know if there will be any visual signs from it.

I think this is the breaker that's in the box right now but I can't remember for sure :


It's been in place for a year now with no issues. The wires may of just gotten loose but if that is the problem then that is another reason to go with the midnite solar breakers lug connector design.
I hate to be that guy but even a cheap thermal camera can catch a lot of that stuff.

I still look at mine every month and occasionally find loose nuts.
I’m the only loose nut allowed in the shed🫣
 
I haven't seen Ampere Interrupting Capacity (AIC) mentioned.

Fuses/breakers need to have an AIC rating greater than the short circuit potential.

As an example, a 12.8V LFP battery with 4mΩ resistance has a short circuit potential of 12.8/.004 = 3200A, so any fuse/breaker used must have an AIC rating this high or better.

A 16S DIY LFP battery will have a cell series resistance of 2.56mΩ. That's capable of 51.2V/.00256 = 20,000A - hence why Class T fuses are preferred.
I think you should bring this up here as some people seem to think a high voltage lithium battery bank isn't more dangerous than similar voltage PV...... :fp2 For some reason the whole short circuit potential thing doesn't seem to ring any kind of alarm bells for some people over there.....

Just a note for anyone following OP's issue here on this thread though... When/if you use DC breakers, be sure to also observe polarity of the breaker! The source being interrupted needs to feed to the + side of the breaker! (In other words, with the breaker off, the terminal still having voltage should be on the side labeled +.) The reason being that there is an arc arrestor on the one side of the breaker, but not on the other. Opening a reverse connected DC breaker under load has a high potential for meltdown, as the arc will/may not be extinguished!

MNEPV15-300V breaker pic for reference:

1722450923933.png

And by the way, 34A of PV arc fault (*edit*) short circuit fault current can do this!!!

1722451079779.png1722451109113.png1722451147254.png

It is worth doing it right the first time! Proper wire junctions, proper breakering, proper fusing, etc.....

P.S. No, we did not do this. But yes, I took the service call and found this in a hot attic on a nearly 100°F day! The positive wire was literally burned through! This was 4 strings of PV, paralleled in this J-box with wire nuts.... When I went to remove the cover and arc started and didn't stop until I knocked the cover off using my wire stripper!

Do it right folks! Whether it is battery breakers/fuses, PV breakers/fuses, or 120/240V AC.... don't take risks, be sure to look at voltage, amperage and short circuit ratings!
 
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240v not 120v = 50A.
That's not a math error. And I was taking a guess at how OP had arrived at his incorrect estimation of 100A.
Then I laid out some better estimations of the current requirements to operate the system:
Your inverter has a maximum output of 12000 Watts, that's 100 amps AC if it's all at 120V. But if your batteries are at 50V, you need 240 amps! Voltage matters. Also, your 9.4kW of solar panels could charge at nearly 200 amps.

But hey, this was super helpful comment.
Math is wrong
So, thanks.
 
The IMO are DC disconnects for high voltage PV not battery voltage/current.
Yes I had replied to crowz regarding PV disconnects and this got lost in translation. For me, MNEDC250 fully rated DC breakers are the way to go but around $90 when not on clearance, not a lot more than a class t fuse and holder, however you have to figure out an enclosure for them.

20240624_092130.jpg20240624_092231.jpg
 
OK - correction to what I said earlier - the type typically used on the side of a house or on a roof is listed as A in the docs. So, switching with current the life is signifigantly shorter than switching without current. BUT - this isn't something of real concern unless you do it everyday. Artifiacts below.


1722452379940.png

1722452840995.png
 
For my DIY batteries I use a Victron Lynx Power In converted to a Distributor with Mega Fuses for a 48v system. I assume this is an OK system/fuse for my EVE 105 100amp (surge) packs. One mega fuse per pack.
1722453310809.png
 
For my DIY batteries I use a Victron Lynx Power In converted to a Distributor with Mega Fuses for a 48v system. I assume this is an OK system/fuse for my EVE 105 100amp (surge) packs. One mega fuse per pack.
View attachment 232893
There is a new 80V rated "'ceramic" megafuse 5 pack soon to be available from Victron. Which potentially may have higher AIC rating? But I use those 58V in my distributor for inverter, 300A, and SCC, 125A.
 

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