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Plain breaker/fusing or Trip Shunt Breaker for Batrium...OR INSTEAD A CONTACTOR??
#21
(06-20-2019, 03:56 AM)Headrc Wrote: Thanks ...so it is a durability issue then when using contactors? Even though they are designed to be used for that continuous current.

It's not about the "continuous" rating that makes the shunt/breaker better. It's the tripping/disconnection. The contactors are usually just 2 pads that come together. When disconnected, DC current will cause an arc that will burn the pads until they are far enough away that the voltage can't sustain the arc.
With the breaker, they are designed differently and have some extra parts inside to draw the arc away from the main contacts. This greatly increases the life of the breaker.

Also, just as the names imply, a contactor just makes contact, that's it. A breaker on the other hand is "also" current sensitive. Just like a breaker in your house panel, if too much current flows for too long, the breaker will flip, disconnecting the load.

This would just be another failsafe in place to keep the lines safe if something goes wrong.

and to add, I'm not sure if there are self-tripping contactors that act like the breaker
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#22
Thanks, that is the kind of feedback I am looking for.  Although I thought that contactors made for the kind of current and voltage we are dealing with here could be as good an approach, I can see the logic in the argument against them.  I just wish I could find a reasonably priced Shunt Trip that would accommodate 48V.  When introducing a resistor in line it could also be a component that could fail.

I also understand your concerns Sean, but really this forum is all about learning ...and although it may seem like some questions posted here are fundamental ... not all of us have done every kind of electrical build there is to be done.  Also, why would the industrial industry for building complex systems using the components discussed here such as contactors use them unless they believed they were a good way to approach a problem.  On this particular topic I have also searched and viewed contactors compared to breakers on some industrial electric sites and they do choose to use contactors instead for some applications.  My question(s) are to see why off grid solar systems folks prefer one approach over another.  Quite often there are different ways to solve a problem and I am always in favor of hearing arguments for those different approaches.  For example, look at how some of the more experienced folks systems have evolved.  Peter's original system is a lot different than he first started out ....no shunt trip breaker back then, no Batrium system etc.   And by the way, on a powerwall build that Jehu did he actually referenced using a contactor.  

The proper approach is to listen, learn and possibly give input ...which I plan to do.  But you also have to ask questions that may seem fundamental to some.  I am not embarrassed to do that.  I appreciate all the input and advice from this great forum.
OffGridInTheCity and Korishan like this post
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#23
I'm following along to see what @Headrc does.

I actually own a Gigivac GV200 48v coil, 400amp contactor that I planed to use with my (780ah @ 48v = 250amp battery) in conjunction with Batrium. But, thanks to this discussion... one of the key differences I see now is that a Shunt-trip such as ABB requires *manual* reset to re-enable the system. A contactor such as the Gigivac being held closed by "Batt OK" function of Batrium would 'open' when Batt OK goes critical.. (like voltage to hi/low, or temp to hi/low) but would automatically resume when the critical value returned OK again (e.g. say temperature went back in range).

I'm gathering that shunt-trip /manual reset is the recommendation? But I must agree with @Headrc - not having an easy time searching for 48v coil shunt-trip that does the 250amps and in general seem quite expensive - so that's pushing me back to the Gigavac / contactor approach ($140). I already have the 250amp circuit breaker in the battery control box.
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#24
A contactor is about to switch things on and off or between stuff. They are not there for safety stuff. Trip shunt breaker also acts as a fuse and therefore have a more general protection usage.

Is it worth skipping this for a few bucks? Isnt safety priority #1 ?

24V contactors is not a problem if you ask me. Its just a reason people find to skip the preffered way. Use a resistor in line or center tap the battery for the trip part with the relay in between to control it. I dont see the problem with it. Also a 24V coil from ABB will easily work on 60VDC system as well. Yes it might not work tripping 1000 times but since when is that the purpose? The purpose is to trip once or twice in event of failure.

Secondly you do not want the system to engage the system again after failure. YOU should be the one engaging the battery again! The breaker is tripped of a reason and that reason is to prevent catastrophic failure. Its a breaker for good damn!

Safety guys... Safety.....

If you want add an contactor too for other things that is fine but do not skip corners on safety.
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#25
Example: I had a failure on the DC side of my inverter. It had melted the mosfets and it was shorted. My breaker did sort this by disengaging. Imagine a system without a breaker or a system that tried to engage the battery every other minute again............
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#26
Very good points Daniel ...TY.
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#27
Im totally fine having a contactor in line.. I have that to some parts Tongue But not for protection Smile
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#28
How about a contactor and a fuse in-line? It's not all-in-one like a shunt-trip, but will still do everything you say, Daromer?
Formerly known as Dallski
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#29
It does everything except you cannot "trip" from the BMS. You can only engage/disengage. If that makes sense?

Potentially the BMS can engage it again after a fault when fault is restored. Ok or not is up do you to decide. If you are after a function like the cheap BMS have where they enable/disable do controll charge then its fine.

Just beware of many charge controlers for solar doesnt even like having the battery disengaged so that function may not be wished for Tongue
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#30
Thanks Daromer! The BMS that I will be using has an integrated solar charge controller, so I believe contactor/fuse is acceptable in that situation. Since this is a Batrium thread, I will just leave it at that.
Formerly known as Dallski
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