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Which fuses can be used for protection in the DC area for two directions
"Fuses" are basically just wires (possibly encased in glass/ceramic/plastic) designed to melt long before anything else in the circuit. Only one time use.

"Breakers" are resettable switches with one or more triggers (eg. overcurrent, thermal, under/over voltage)

at least that's my understanding.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
Call to everyone !!!

I would suggest that all of your solutions for securing and wiring the inverters and batteries are presented here.

Happy with pictures and videos. Exclamation


I am currently testing in the workshop.
Have a car battery with 12v and 74A power (cold start power 640A) added and will do a few tests. Cool

It will be fun ... Big Grin
The solution is apparently very simple.
Called Schneider Electric (formerly known as Merlin Gerin) in Germany / Ratingen.
Ratingen is a neighboring town of Solingen and only 30 km away.

I spoke on the phone with specialists for circuit breakers.

For the DC area with two directions, I was advised against using the Schneider C60H-DC.

The following types of emphases: IC60L, IC60H, IC60N for up to 60V (72V) types up to a maximum of 63A
or C120N, C120H for up to 125V and 125A.
With the use of more than 1 pole connection also 2 times volt or more.

Yes. Now people come back who tell me first that the circuit breakers are AC devices.
But please have a look at the catalog and you will see that there is also the approval for DC.

ABB also has circuit breakers for the DC area, for example. ABB S281 UC
stevelectric likes this post
(06-06-2020, 02:29 PM)OffGridInTheCity Wrote:
(06-05-2020, 03:15 PM)Walde Wrote: Which fuses can be used for protection in the DC area for two directions
I do use a 100a Renogy ANL fuse on one of my 48v batteries.  They also make 20, 30, 40, and 60a...  specs:

* Found a couple of posts that say the 'direction' doesn't matter.
* My Renogy ANL does not have an arrow or anything showing a specific direction - and don't see anything in the specs. 
* The examples all show the fuse on the positive wire rather than negative side.

One cool thing about an ANL... is that it can be turned around (in the holder) - so if you find out at some point that it needs to be reversed you won't have to change any wiring.

I was hesitation to add a ANL fuse... but now no... an extra layer of protection will not hurt....
Fuses are not directional. Breakers can be but dont have to be..

Breaker can not be a fuse....

What you look at in fuses is characteristics . Like what current they blow at and at what rate. A fuse is basically just a thread that burn off.
A breaker is resetable due to that they relese the Contact based on current flowing through a Wire. Thus Making some of Them directional.

Breakers basically have the same definition as fuses since you in your house (as an example) can be swapped between fuses and breakers.
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Also breakers can have different characteristics, eg:
- rated for AC only
- rated for AC with limited DC
- rated for DC one way
- rated for DC both ways
- different time vs overload curves.
On the DC side, the ones we need in powerwall systems are best if rated for DC both ways & have a medium curve.
On the inverter output side, eg AC distribution board, they should be "normal" AC ones of course.
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I for one am going with breakers.
I have investigated this pretty heavily and have come up with the ABB S200  series to be my breaker of choice.

They offer all kinds of trip curves and numerous current protection values, 125 VDC bidirectional support, and are reasonably priced esp on eBay.
They also offer a shunt trip attachment, which I will be installing on all my breakers, and putting a RED emergency button in a conspicuous location to do an emergency shutdown tripping all the breakers at once. Anything over 63 Amps will be a ABB Sace S3 also shunt tripped.
A complete system shutdown with fuses ,I feel, is time consuming esp in an emergency.

Correct me if I am reading these ABB specs wrong but I believe they are correct.
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I never realised how confusing a relatively simple device can be made to appear.

AC breakers - they use an inline coil with a bit of metal to effectively create a small electromagnet. The breaker is setup like a mousetrap so that the relatively little force of the magnet cen then trip open a contact. The coil and bit of metal work in both directions and the arc is extinguished by the zero volt crossing of AC.

DC Breakers are the same setup BUT they have a magnet near the contact opening to push or pull the arc to make it longer and therefore extinguish itlef. The polarity of the magnet in relation to the current direction is what it is all about because of where the arc is moved.

Fuses - there are two basic types, filled or not. High voltage fuses are fulled with sand or something similar to melt and or create an insulating vapour poccket to extinguish the arc. Low voltage fuses just rely on the wire melting. FUSES ARE NOT DIRECTIONAL.

DC circuit breakers that are not voltage rated for DC or using an AC breaker that is too low a voltage. The contacts do not create a gap large enough and I have personally stood and watched one of my 10A AC breakers arc and start smoking until I switched it off via a second breaker. That was with just 140V.

High current DC breakers have a totally different issue because the fault current curve when you start looking at 125A breakers and alike, your wiring may end up becoming the fuse wire because with C type curve you could end up with 500A for longer than your wire insulation can avoid smoking before the breaker trips.

Fault current handling is a different issue again because vapourising the internals creates a conductive ionised cloud.

AND just because abreaker costs 10x more than a cheap China knock off it does no mean the cheap option is not as safe or reliable. I use TOMZN breakers for below 40A and trust them after burning a few out with experiments and trips. The higher current breakers scare the s**t out of me because I have not managed to trip a 100A breaker yet and that was with burning 10mm2 wire on a short with over 600A. Your battery lead resistance then becomes critical.

This is all domestic / toy stuff. Airblast breakers and HV stuff is quite different.

Oh, and multipole (more than 2) DC breakers are another one that nobody seems to use, when they maybe should be considering them..

(07-05-2020, 10:59 AM)daromer Wrote: Breaker can not be a fuse....

They are when the fault current is way higher than the rating and the breaker is either blown appart or vapourised completely. Just like a fuse... Tongue

125A Type C breaker fault current of 1000A can take upto 3 seconds to trip the breaker, 1-2 seconds mid time.

The real concern, which nobody really takes note of initially is that an overload of say 200A can take a minute for the breaker to trip. If your battery wiring is near 80% of the rated current relative to the breaker rating then you run the risk of your wiring setting on fire before the breaker trips.

10mm2 wire is rates for 65A. Double up for 130A...... safe for 125A breaker ?

200A fault current for 60 seconds would start to melt the insulation and the real risk is when the insulation gives that this then allows the conductors to short against other conductive parts. Cascade failure by over rating OR more precsely not enough safety margin..
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
Haha yeah thats true completelycharged. Smile
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
The bizare situation that a lot of DC battery packs end up with is that the additional wiring resistance avoids the absolute maximum possible fault current occuring and therefore virtually any breaker would work on LV packs. I have only managed to get upto about 18kW out of my pack when trying to trip breakers and that ended up limited by the wiring and not by the battery capability. The cells and pack setup I have is rated for 360kW (10C cells) and fault current should be > 2x that.

Think about it.... 500kW fault.... what tiny (or not so tiny) wire will hold for how long ? Everything becomes a fuse at some point, even with small packs..
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......

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