House burned down

[_voltmeter_]

These do draw power all the time when ON.

this make sense for NO contactors
thats why i use fet bms

 

[Ampster]

this make sense for NO contactors

Are there contactors of that capacity which are NC? If so, what is the risk of one of those not getting enough current to open. It is not a fail safe strategy which I would want to employ.

 

[Texas-Mark]

These draw less watts at lower voltages. Coil is 24V, not 48V. This requires a converter. I think the coil will still work at 12V.

I have a few that I am using at 12V. They work fine.

 

[Hedges]

That's voltage of coil for the used ones linked.
Several voltages are available, and Digikey link was for one good at 48V nominal.

With power consumption of 1.3W using economizer, that is insignificant compare to 20 ~ 150W no-load current but 25% to 33% of some inverter idle (no AC output) ratings.

 

[robbob2112]

The ones I linked -

TE Connectivity EV200AAANA 500a 0-900vdc Tyco 12/24v

These were recovered from EV battery modules. These are VERY EXPENSIVE online. If you have any project that needs a high current relay this is your chance to save some money. Make a cheap 30a BMS into a 500a BMS. This will work for batteries in the 9-36v range so perfect for Lifepo4 and Lithium...

batteryhookup.com

 

[Shimmy]

Are there contactors of that capacity which are NC? If so, what is the risk of one of those not getting enough current to open. It is not a fail safe strategy which I would want to employ.

It has to open (and extinguish arc) if it is NO or NC so I don't see a huge problem technically with it. Your coil will likely need to draw more current to open the contact though, and you would need a resettable shutoff if it was just pulsed power so that it didn't re-close. Shunt trip breaker just makes everything easier.

 

[robbob2112]

Are there contactors of that capacity which are NC? If so, what is the risk of one of those not getting enough current to open. It is not a fail safe strategy which I would want to employ.

The idea behind them is if there is a fire and power is lost they open the contact.

 

[Ampster]

The idea behind them is if there is a fire and power is lost they open the contact.

Yes, that is precisely the theory I have assumed with a normally open contact that the power keeps them closed and when the power is lost because of a fire or other reason the fail safe condition is that they open. That is why I would not want to rely on a normally closed contact to require some power or even a trigger voltage to open the contacts.

 

[D71]

This has been an interesting post. May we all learn.

12volt battery mosfets on bms what voltage does a failure occur? What amps? What is the failed state of the 12volt bms when subjected to over voltage? Watch video.
What would could be the conditions of putting over voltage into batteries? Could a failed Victron inverter charger pulling from the grid while charging batteries send more voltage then batteries could handle if equipped with bms? Granted OP was using Batrium system.

Post in thread 'Battleborn caught on fire'…. RCinFLA
https://diysolarforum.com/threads/battleborn-caught-on-fire.58709/post-732414

Electronics - FETs break down due to heat like a lot of things….GIANT HEAT SINKS and fans are often used to protect. BMS is a safety….
Gets hot. So if it was cold and you had low but not dead batteries could they be loaded up heavy in a discharge then charged in below temps due to their own heat generation in a 12volt sok type battery? Hmmm…

Hmmm

I … Think lifepo are still the best pick …

Here is difference between low 12vdc with 100 car batteries in parallel vs ~60vdc series parallel for those batteries. Pay attention.

Again notice difference between low voltage high amps in parallel vs high voltage in series parallel. Look at the amps they are registering. Watch circuit breaker test. Contactor made with log splitter.

Young ppl are not afraid….kid is crazy.

 

[Ampster]

It has to open (and extinguish arc) if it is NO or NC so I don't see a huge problem technically with it

I agree arc suppression is important in either case so that is not the problem I see with normally closed contactors. As you suggest it could be the current reguired to open it in a failure mode or the risk that without that current it would close again and exacerbate the problem. Hopefull by then another form of overcurrent protection like a fuse would solve the problem. There is a reason that most EVs which see currents in excess of what we see in the stationary storage use case that those EVs typically use normally open contactors. Not withstanding the fact that the default is off when the EV is not in use.

 

[Ampster]

12volt battery mosfets on bms what voltage does a failure occur? What amps?

My understanding is that a 12 volt battery is not going to deliver many more volts that the battery's normal voltage but the current could easily exceed many more Amps than one C and that is the risk with any Lithium chemistry. Those are the situations where mosfets fail closed.

 

[Hedges]

Likely normally closed contactors have greater available force to separate them.
Problem of course is they rely on power and control system to keep open.

Remote trip breaker as mentioned sounds good, only needs control working up until tripped.

Another, more robust switch would be pyro fuse.

 

[Ampster]

Another, more robust switch would be pyro fuse.

Of course that is why many EVs also contain a pyro fuse in addition to a normally open contactor. I only mention EVs because they see currents sometimes above 500 Amps in acceleration which is far above what we normally see in staionary applications .

 

[D71]

My understanding is that a 12 volt battery is not going to deliver many more volts that the battery's normal voltage but the current could easily exceed many more Amps than one C and that is the risk with any Lithium chemistry. Those are the situations where mosfets fail closed.

Sorry …. You missed the point and I failed to communicate. I apologize. You are correct about battery voltage is usually not going to exceed but that video is about over voltage applied to the battery and mosfet contained with the SOK battery by external source when charging. Why stated “watch video.”

.

 

[Ampster]

You missed the point and I failed to communicate.

No need to apologize. My post was to clarify the issue for future readers who also might not read the entire thread. Thanks for the clarification.

 

[robbob2112]

Yes, that is precisely the theory I have assumed with a normally open contact that the power keeps them closed and when the power is lost because of a fire or other reason the fail safe condition is that they open. That is why I would not want to rely on a normally closed contact to require some power or even a trigger voltage to open the contacts.

Correct.

I would power them from an independent battery to start them and then from a point beyond the fuse but powered by battery bank after that.

So if the battery fails or the fuse blows the contactor releases.

How I had in mind to install them was

Battery -> fuse -> contactor -> shunt -> busbar -> master shunt-> master contactor -> master breaker -> etc

Repeat up to busbar per string

A RPi wired to temp sensors attached to the battery strings and connected to the shunt detecting the voltage and calibrated to current.

All contactor coils wired through RPi relay board.

If string current varies from other strings by x% and total current And master current less than 80%max drop the string

If string current varies by Y% drop the string and trigger klaxon

If temps are high enough, drop all contactors. Otherwise just drop a string....

That sort of generic logic with more thought put into it.


Attached is the entire datasheet.

 

[_voltmeter_]

What would could be the conditions of putting over voltage into batteries?

if you connect 4x 12v bms in series the fets have to switch 48v
so you have your 50v limit in the video and they fail.

 

[ksmithaz1]

When I hear someone say these batteries are as dangerous as a pile of wood, I think ehhh not quite, wood doesn't contain the capacity to start itself on fire because of something getting dropped on it.

Depends on the something. Buildings with reflective glass melting cars, yea, ...

Don't put a leaky oil can on the shelf above your swimming pool tablets. . .

 

[desjardins]

It seems odd to see the black insulated wires coming from the fuse block. One other oddity I notice is the large washer on the second to bottom left lug. Though the battery failing due to leakage causing a short seems a more likely possibility.

he most likely used a 3/8 ring terminal on a 5/16 bolt.

 

[myles]

glad I stumbled up on this post, I am going to be making plans to move my cells to an exterior storage area ASAP, they are in my garage, protected by JK BMS, class T fuse, TE Contactor from EV, solark inverter, but there is too much riding on the what ifs.