Battery Disconnect - Latching Relays

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Mikethezipper

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Was wondering if there was a general consensus on what to use for a battery disconnect (OV & UV protection)

Latching relays in the 200A range aren't exactly common - so I was wondering what others recommended.
 
A disconnect is a disconnect and for that I would not use relays. I would use a breaker of some kind. In my case i use Breakers with trip function like an ABB S5N or S3 series

Just make sure you get one rated for the voltage you need at DC and not just AC!
 
Thanks for getting back to me! I guess I'm a little confused as to why - If a latching relay/contactor is rated for continuous duty at 200A DC, why would I use a breaker and then have to trip it via microcontroller for an undervoltage condition?
I don't know enough about the difference to understand why one would be chosen over the other.
 
Mikethezipper said:
Thanks for getting back to me! I guess I'm a little confused as to why - If a latching relay/contactor is rated for continuous duty at 200A DC, why would I use a breaker and then have to trip it via microcontroller for an undervoltage condition?
I don't know enough about the difference to understand why one would be chosen over the other.
Click to expand...

You would need to control the latching relay somehow as well.....
A breaker would also be an over current protection device.
A breaker would need to be manually reset, ie you could not get a switch on/off cycle going.
 
The reason for a breaker is as redpacket said. Its one way kind of so you know its off when its off. Thats the main reason you do shut it off right? last protection if neededn.

Using relays that you do when you should via a system switch somtehing on again but I do not see the use in a powerwall for that. The software on the gear should act as the on off instead.
 
I was thinking it might be needed if a single with a lower capacity was rising in voltage faster than the others - you would turn off current into the system until equalization was done - then allow current back into the battery pack to finish charging. I'm realizing at this point, that was a probably insane thought - balancing shouldn't work like what I was originally thinking.

Is there a breaker with external tripping functionality that doesn't cost so darn much? Even used ABB breakers are nearly $200
 
Does not have to be ABB only, any top brand manufacturer will do the job as long as it is rated for DC and the needed A. For instance the NS250N from Schneider can be found at very reasonable prices and it is rated up to 250 VDC and 250A. Just do not rush it and wait for the right deal.
 
Ahh, I see now. Thanks for the heads up, yeah looks like I can probably get one around the $60 range.

Just wondering - Since I'm also working on a BMS - are most of these tripped by 24VDC? Is that a standard trip voltage for these breakers?
 
The Schneider I mentioned avobe uses a 220 V coil for tripping, at least the one I got in EU
 
Mikethezipper said:
Ahh, I see now. Thanks for the heads up, yeah looks like I can probably get one around the $60 range.

Just wondering - Since I'm also working on a BMS - are most of these tripped by 24VDC? Is that a standard trip voltage for these breakers?
Click to expand...

The ABB I bought has a 24v trip coil. There are a few different voltages available for the trip coil, 24v is a standard one. Make sure you check the trip voltage before you buy to make sure it has the coil you want.
 
There are some BMS systems out there that can control or feed data to a charger to make sure it ramps down when needed like when a cell gets full. batrium can do that towards some systems.
 
I'm looking for remotely controlled cell-level (1S) cutoff relays / contactors, 3-4V range (LFP)

NO, ideally very unlikely to fail closed, easily withstand continuous 6-10A at a minimum.

Later on will need higher ampacities, even 100+A.

Does the lower Voltage make them cheaper than cutting off at the bank / pack level?

Don't think I can use CBs, will need to flip open / closed by a central controller, Arduino, rPi driven maybe PLC?

Any suggestions welcome, TIA
 
No they wont be cheaper at 4V compare to 24 or 48 in my world. No matter if you break in middle of pack or jus tbefore the inverter you will have the same voltage.
 
I'm asking for links to recommended relays given the specs above, will need many dozens, perhaps to be controlled by Arduino and/ rPi?

Don't mind cheap Chinese, long as I know the relationship between the published contactor-current rating and what they can **actually** handle safely.

But obviously known-good brands with accurate and detaile spec sheets would be better, long as they don't cost 10x the above?
 
Disconnect ones Schneider or ABB ones. They can do many 100s of A. Cheap? Hell no...

Up to 25A you can get normal contactors from almost anywhere i would say. Dont have many links at hand since im not sure what exactly you look for. Its a rather wide range you look for....
 
daromer said:
Dont have many links at hand since im not sure what exactly you look for. Its a rather wide range you look for....
Click to expand...
Problem is I don't know enough myself to give any more requirements. What sort of questions would help narrow things down?

And of course, looking for suggestions from anyone reading the thread.
 
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