contactor vs. shunt trip breaker

[100FUEGOS]

If you turn off your Batrium if / when the MCCB trips due to a critical fault then it does not really matter which option to choose. I choose to turn off everything except the Batrium hence the right function selected for the shunt trip coil, and I do not say this, Batrium says. They designed it this way.

But hey I am not saying you are doing it wrong on your setup it is that Batrium designed the whole Shunt trip mechanism with a different option than you chose for your use case scenario.

 

[OffGridInTheCity]

If you turn off your Batrium if / when the MCCB trips due to a critical fault then it does not really matter which option to choose. I choose to turn off everything except the Batrium hence the right function selected for the shunt trip coil, and I do not say this, Batrium says. They designed it this way.

Batrium is "designed" to provide a wide range of options - not just one.

For example, leaving Batrium running off your battery could be argued as defeating the purpose of a shunt-trip. In fact, my personal recommendation is not only to disconnect ALL load but also all PV (charging) input as well. Complete isolation from all charge/discharge, till the battery situation can be manually reviewed / corrected.

It's an interesting topic with several layers and this is why I come back to - it's a DIY decision, customized for the local situation. All I can really do is share as solid info as I can, what I did, and why... .

 

[jtvt]

For example, leaving Batrium running off your battery could be argued as defeating the purpose of a shunt-trip.

That's what I do. However, my trip points for temps and shunt volts are within a range so I'd would have a usable battery for a while. If I have a cell go bad, not sure it would really matter if the batrium was still powered up. I use a DC-DC converter to run my batrium at 24v and it has a fairly wide input voltage spec. If the breaker trips, everything but the batrium gets disconnected.

I have been pondering putting a UPS on the laptop that I keep usb connected to the batrium. I have two power sources connected to the batrium: usb and direct power. Then another UPS on my network hardware.

I'm not sure "Critical Pulse Off (CB Trip)" option has been around that long. Could be people are using generic "critical fault" as more of a legacy thing.

 

[OffGridInTheCity]

I'm not sure "Critical Pulse Off (CB Trip)" option has been around that long. Could be people are using generic "critical fault" as more of a legacy thing.

Agree with this. I'm closing in on 4 years of operation, and in the beginning I got lambasted for not using "Critical Fault". I run a Watchmon 4 core + expansion.

So let me apologize for sounding defensive and let's continue a bit as it's interesting

That's what I do. However, my trip points for temps and shunt volts are within a range so I'd would have a usable battery for a while. If I have a cell go bad, not sure it would really matter if the batrium was still powered up. I use a DC-DC converter to run my batrium at 24v and it has a fairly wide input voltage spec. If the breaker trips, everything but the batrium gets disconnected.

If one were remote, the batrium load would continue to draw down the battery - and in theory it could make the battery problem worse. Over-discharge is not as serious (in my view) as over-charge in terms of fire, but after enough time it could actually draw down a pack enough to do damage.

One could do layers - e.g. use batrium to disconnect PV(Charging) on a pack too hi and/or temp too low but leave discharge in place. One could do multiple levels of disconnect - perhaps an initial disconnect and then later a total disconnect depending on different metrics.

The initial folks I followed to setup my system were strong proponents of *all* shut-down. And I accept that as one reasonable view - but I've never hand anything close to any critical issue so it's been theoretical for me. What's more likely is the house will burn down from a forrest fire and all of this will be mute.

I have been pondering putting a UPS on the laptop that I keep usb connected to the batrium. I have two power sources connected to the batrium: usb and direct power. Then another UPS on my network hardware.

You can power Batrium thru non-powerwall USB only and leave Batrium running with total battery shutdown. You can also simultaneously leave the USB plugged in (and providing power) AND have battery power routed but it's possible the USB will take preference. This page https://wiki.batrium.com/en/faq/power-the-watchmon warns about USB power.

But if you're doing you're own power thru the expansion relays such as a 48vdc -> 24vdc tap directly from the battery - I don't see where USB lower power is an issue. They say batrium may not run but I have powered my Batriums (Watchmon 4 + Watchmon Core ) thru USB for long periods (months at a time) and it worked for me. Doesn't mean it's a good idea.

I'm not sure "Critical Pulse Off (CB Trip)" option has been around that long. Could be people are using generic "critical fault" as more of a legacy thing.

Agree with this. I'm closing in on 4 years of operation, and in the beginning I got lambasted for not using "Critical Fault".


Earlier you said "Batrium recommends / designed for...". Is this what you're referring to? From: https://wiki.batrium.com/en/wiring/circuit-breaker-remote-trip



I could make the case (for the sake of discussion) that this 2sec pulse is long enough to create same scenario as the constant current worry that started this section of the discussion. The shunt-trip coil should trip <1sec. The remaining 1+ sec = constant current if the shunt-trip doesn't disconnect the flow of current as designed. So a 2 sec pulse may not be any better for a malfunctioning shunt-trip coil than constant current.

 

[rhino]

Not sure if that is a typo or what since another page indicates the pulse is 200ms which is also the pulse a Midnite RT expects. Longer may burn out the RT mechanism.

taken from here: https://wiki.batrium.com/toolkit/hardware/expansion

 

[rhino]

I sent them a support request asking which one is correct.

 

[Goboatingnow]

Personally I would never use shunt trip as it’s not fail safe. Powered contactors with optional economisers built in are fail safe. The bms goes out to lunch and the contactor opens

 

[100FUEGOS]

Batrium is "designed" to provide a wide range of options - not just one.

For example, leaving Batrium running off your battery could be argued as defeating the purpose of a shunt-trip. In fact, my personal recommendation is not only to disconnect ALL load but also all PV (charging) input as well. Complete isolation from all charge/discharge, till the battery situation can be manually reviewed / corrected.

It's an interesting topic with several layers and this is why I come back to - it's a DIY decision, customized for the local situation. All I can really do is share as solid info as I can, what I did, and why... .

I completely agree with you in everything you say here. Isolating the battery in an emergency is the only way I see it also. In my case, I choose to leave the Batrium itself on, so that it can generate the so-called snapshot report. I know it is almost useless but oh well, better to have it at hand in case it provides any useful info.

 

[Ohms_Cousin]

Personally I would never use shunt trip as it’s not fail safe. Powered contactors with optional economisers built in are fail safe. The bms goes out to lunch and the contactor opens

Thats an interesting point of view. Do you have any particular contactor that you prefer ?

 

[Goboatingnow]

Thats an interesting point of view. Do you have any particular contactor that you prefer ?

The TE unit with built in economiser

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Available through Digikey and Mouser too

 

[hwy17]

When I setup my Nuvation BMS in 2019 I couldn’t find any of those ABB 400A breakers for less than $500, so I went with tyco contactors and a 400A fuse, it does have contactors on the negative and positive facing the same direction so it can open or close the contactor with the forward polarity first. I did all sorts of hammering on it testing it out.

I'm digging up this thread because I came across this and want to understand. Is there a better side of a DC circuit to break under load? And it changes sides for charging vs discharging load?

 

[hwy17]

And I would like to hear how Nuvation turned out for you, are you still running it?

 

[hwy17]

I think this video helps me get it:

Contactors are directional because of the direction of the magnets that break the arc. So I imagine two contactors could be placed on positive and negative facing the same direction, or two contactors on the same side facing opposite directions.

I am still confused about directionality, like when the contactor is marked +/- and is in the middle of the positive connection line, which side of the polarity faces the load.

 

[toms]

I prefer to put separate contactors on the load and charge circuits. The charge circuit is usually lower current (hence cheaper/smaller contactor), in an over voltage condition only the charge contactor is opened. In an under voltage condition only the load contactor is opened.

 

[hwy17]

Yeah I've looked at configs like that and it's a nice concept, but I am using a charger/inverter and will be using grid charging so can't really seperate them.

 

[Rocketman]

I used the Tyco EV200AAANA on my RV Batrium build. It has been working great for 2-1/2 years.

I just saw a vendor (Battery Hookup) had these same used contractors (pulled from EV vehicles) for like$25.

They also had a video showing the current they pull at different voltages- if I remember correctly my 12v ones pull like 2watts.

For my Batrium setting I use Critical Battery OK. As long as the battery is OK power flows to keep the Contactor running. When the battery is not ok - no power.

 

[Warpspeed]

These high voltage vacuum relays are also made by Gigavac and, as above ^^ sometimes show up on e-bay at a small fraction of the cost brand new. No really cheap ones there right now, but I bought three used HX241 Gigavacs for $40 each about a year ago.

These have either a 12v or 24v coil, the normally open main contact, and an auxiliary contact that can be used with an external resistor to provide a low holding current. One of these, plus a T rated fuse will end up being much more reliable than a shunt trip circuit breaker of similar cost.

 

[hwy17]

I think I'm going to use the AEV-250GN, 48-72v coil and nonpolar for charging and discharging breaking. The nonpolar model has a lower lifetime rating but I don't think I'll really run into those limits.

 

[Warpspeed]

An alternative way to do this would be to use a T rated fuse and a large SCR as a crowbar to blow the fuse.
Definitely not the most elegant or convenient arrangement, but it would be simple, low cost, and reliable.
This could be used as (a delayed) last resort backup, if your relay/circuit breaker welded together or otherwise failed to open for some reason.

Just an odd off the wall suggestion.
A very slowly rising voltage on the SCR gate might be all you need if the primary under or over voltage protection fails to open the battery circuit within a few seconds.

 

[toms]

Yeah I've looked at configs like that and it's a nice concept, but I am using a charger/inverter and will be using grid charging so can't really seperate them.

You can. An AC contactor on the grid feed to hybrid circuit, and a DC contactor on the PV to inverter charger circuit. Connect the trigger circuit of the contactors in parallel.