House burned down

Jejochen said:

Batrium bms i thought and still think is a great bms. I have no idea why 1 central bms for 112 cells is "bad". If something is wrong with the system design, thats possible, but thats not the bms to blame, it did always a great job.

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If you had a watchmon and a relay/disconnect per string, you have more fine grained control of things and potentially wouldn't have this potential series to series cascade failure.

In the design you had there is no way for the Batrium to clamp down/disconnect a problematic string. All of that energy is free to do what it wants because it is all behind the single watchmon contactor. I would say the warnings that are provided in the Orion BMS documentation about parallel string without ability to disconnect individual sytings would also apply to your Batrium watchmon design but they only have a small section about system qualifications and not using breakers ambetween the multiple banks

kolek said:

So according to the OP, a grade A cell from Luyuan that had been treated exactly according to guidelines, spontaneously expands and vents for no reason.

I'd be very curious to hear expert opinions on this.

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I'm not an expert, but I sure do have an opinion

kolek said:

Can this actually happen, and if so, what is the rough probability of it happening? I would have assumed it's practically impossible, or maybe 1 chance in 10,000. I thought these cells are extremely stable, especially the "real" grade A ones from Luyuan, and if they do expand and vent, you must have done something to provoke them.

Not blaming the OP of course, just curious because many of us on the forum have grade A cells from Luyuan and if they are spontaneously failing, that is a major concern.

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IMO, this is electrochemistry with huge amounts of energy stored separated by very little material. There is always a possibility of material failure, or process failure at the plant. Separator weak spot, bad mixing of solids that happened in one particular spot etc. No doubt a huge percentage of such issues cause cells to fail QA tests, but things do slip. Although rare, we do have EV car fires now and then and they have always had the best quality cells. Personally I think a chance a cell fails like this based on a manufacturing issue is much lower than 1 in 10000. But probability exists.

And if large number of people use these cells... sadly some houses will burn. There is a reason why there is regulation in my country that there has to be smoke detection in the same room as domestic batteries(also some silly regulation, like if tyhe battery is installed underground it needs to be elevated by 30cm - I never heard flooding is generally limited to 30cm...why not 10cm, or 1m?). Earlier in this thread someone posted a link to show a small CO2 air displacement fire extinguising system. If I had a large lifepo battery in my house I'd definitely install this in a room where it's at. Or consider the battery enclosure a furnace. Make it from heavy gauge steel and vent it outside. Lifepo is probably the safest lithium chemistry there is, but still it contains flammable liquid under pressure (in case of failure and subsequent heat buildup). It just takes a spark to ignite it. A spark, like from a blowing melt fuse.

Personally I don't have more trust in ready made batteries. Some are equipped with fire supression, but what kind? Is it going to displace oxygen in the entire room? If yes, it can be potentially as deadly as a fire itself if the user is unaware, if not, I'm not sure how it can work.

Brucey said:

If you had a watchmon and a relay/disconnect per string, you have more fine grained control of things and potentially wouldn't have this potential series to series cascade failure.

In the design you had there is no way for the Batrium to clamp down/disconnect a problematic string. All of that energy is free to do what it wants because it is all behind the single watchmon contactor. I would say the warnings that are provided in the Orion BMS documentation about parallel string without ability to disconnect individual sytings would also apply to your Batrium watchmon design but they only have a small section about system qualifications and not using breakers ambetween the multiple banks

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Note the section at the bottom, if there is a breaker (or in your case fuses) between each bank, that's not what Batrium considers multi string and you need a watchmon per string.

Supervstech said:

What voltage is the system?
Just under 3kW on a single phase.
Is that the last info the bms recorded? Last info of the solar assistant?

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Not off Batrium, appears to be Victron, look at the icon on the upper left.

Supervstech said:

The reason WHY a single bms is bad for several strings of cells is, you have no data for issues causing the bad cell.

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Not true.

Supervstech said:

You have no data for issues discharging each string.

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I'll give you this one, but when using a BMS for each 48V battery, can one view all the batteries and cells at the same time on one screen?

Rhetorical.

Supervstech said:

Same reason why a single fuse is bad for three sets of batteries.

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OP had a fuse for each 16S 48V set.

Supervstech said:

Zero protection for the other strings, if one goes bad...

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Batrium has plenty of data, way more than the standard BMS. Also has way more settings and adaptability.

Brucey said:

Note the section at the bottom, if there is a breaker (or in your case fuses) between each bank, that's not what Batrium considers multi string and you need a watchmon per string.

View attachment 212777

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If you add a Class T fuse for each 16S string, there won't be a problem. No contactor needed.

As for multi bank, of course you would need another Watchmon CORE. And another shunt trip.

upnorthandpersonal said:

I probably read your post as this cell doing that now in this event, not three years ago.

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It is an interesting observation. Might not be relevant to the event we are discussing. But what caused a luyuan grade A cell to vent to begin with

G00SE said:

It is an interesting observation. Might not be relevant to the event we are discussing. But what caused a luyuan grade A cell to vent to begin with

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My thought is that the reason we don't see this in manufactured batteries is that they don't put the cells we can purchase in them. Chances are that even though the numbers look good on the cells we can buy, something probably shows up in testing that they don't like. These cells are "Grade A" as far as capacity goes, but not necessarily in quality. We are literally buying batteries at the bargain outlet/Mr. Seconds.

crossy said:

This post is nothing without a suitably explosive video!!! Where are The Mythbusters when you need them?

Enjoy!

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Sorry, I do not intend anything so colorful. Instead I intend to use a clamp meter and victron shunt to watch the current and gradually increase it until past the rated amps and time the blow...not as much fun I know, but safer and more meaningful.

robbob2112 said:

Sorry, I do not intend anything so colorful. Instead I intend to use a clamp meter and victron shunt to watch the current and gradually increase it until past the rated amps and time the blow...not as much fun I know, but safer and more meaningful.

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I want to see dead short results.

upnorthandpersonal said:

You joke, but just look online to find images of melted/burnt fuse holders.

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To be fair almost all melted / burnt fuse holders are caused from poor connections, not from faulty fuses. There's a huge difference.

G00SE said:

It is an interesting observation. Might not be relevant to the event we are discussing. But what caused a luyuan grade A cell to vent to begin with

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Exactly.

Nothing against how the OP handled the situation, and hindsight is always 20/20, but if one of my grade A cells from Luyuan vented and swelled up suddenly, I would first assume there was something wrong with something in my system. Much more likely that I had made a mistake or there was a problem with my system than the Luyuan factory shipped a bad cell. My last thought would be the possibility that this grade A battery was faulty from the factory.

Of course we're just guessing with these estimates, but @Luk88 also just estimated that the chance of a grade A battery from Luyuan expanding and venting for no reason is maybe less than 1 in 10,000.

But the OP says he assumed the battery itself was the problem and didn't investigate:
"Imo the leaking cell was an exception. Sometimes things just break. Thats why i didnt gave it any futher attention."

Anyway, personally I would not be surprised if the two events, the case of the battery venting and the eventual fire which happened a few years later are related.

SparkyJJO said:

I want to see dead short results.

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buy your own... I paid $38 for these, the largest part was for the ceramic holders...... and I don't have the setup to safely do a dead short.

Thinking about this a bit this morning an idea for a safety alarm besides the smoke detectors struck me. Perhaps a thermal detector for rooms that if the ambient temperature rises beyond a reasonable value (85F) the klaxons get set off and the sirens wail. Maybe some spot temperature sensors near equipment.

kolek said:

Exactly.

Nothing against how the OP handled the situation, and hindsight is always 20/20, but if one of my grade A cells from Luyuan vented and swelled up suddenly, I would first assume there was something wrong with something in my system. Much more likely that I had made a mistake or there was a problem with my system than the Luyuan factory shipped a bad cell. My last thought would be the possibility that this grade A battery was faulty from the factory.

Of course we're just guessing with these estimates, but @Luk88 also just estimated that the chance of a grade A battery from Luyuan expanding and venting for no reason is maybe less than 1 in 10,000.

On the other hand, what are the odds that the cell was fine from the factory, and the expanding and venting was caused by something external, maybe a problem with the BMS or whatever? The probability of that would seem to be much higher than 1 in 10,000. A battery is a relatively simple single discrete component, whereas in a system, there's lots of potential problems with lots of different components, and there's lots of external factors which could have caused that event.

But the OP says he assumed the battery itself was the problem and didn't investigate:
"Imo the leaking cell was an exception. Sometimes things just break. Thats why i didnt gave it any futher attention."

Anyway, personally I would not be surprised if the two events, the case of the battery venting and the eventual fire which happened a few years later are related.

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I think you are beating a dead horse.... 3 years later with weekly routine checks and nothing... is it possible other cells were damaged? sure, but I think they would have shown their issues in the intervening 3 years.

Mattb4 said:

Thinking about this a bit this morning an idea for a safety alarm besides the smoke detectors struck me. Perhaps a thermal detector for rooms that if the ambient temperature rises beyond a reasonable value (85F) the klaxons get set off and the sirens wail. Maybe some spot temperature sensors near equipment.

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A raspberry pi with sensors tucked in around the room and in the gear. You can do the 1-wire sensors on it and tack on as many as you like. Each has its own ID so simple enough to label them all.

I used to use one on a wall behind and a few feet in front of a resistive heater to track ambient temp in a small room. But it also told me when the heater was on and off. I've since repurposed it to have a sensor in the aquarium and a sensor outside to tell when the water temp is low and give an alarm.

These sensors + a resistor tied to the pi in series. (I know out of stock, but many look alikes available)

The actual sensor

kolek said:

When you take the safety element and the time investment into account, buying finished batteries is just smarter for most people. Unless you're too cheap or too poor to afford pre-built batteries, or your life is devoid of other more worthwhile pursuits, or you're doing it for the sake of learning, and/or you derive some kind of perverse enjoyment from DIY battery-build projects.

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I probably meet 3, if not all 4, of those criteria

robbob2112 said:

I think you are beating a dead horse.... 3 years later with weekly routine checks and nothing... is it possible other cells were damaged? sure, but I think they would have shown their issues in the intervening 3 years.

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So if it was you, you'd do weekly routine checks when everything appeared to be running fine, but not actively seek out potential causes after a grade A cell suddenly swelled and vented out of the blue?

kolek said:

So if it was you, you'd do weekly routine checks when everything appeared to be running fine, but not actively seek out potential causes after a grade A cell suddenly swelled and vented out of the blue?

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I am saying that a bad cell from the same batch would have shown its colors earlier than now.

Zwy said:

OP had a fuse for each 16S 48V set.

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if I'm interpreting this picture correctly, the 16s strings didn't have separate fuses, as the fuse is after the common bus bar ?

summit said:

if I'm interpreting this picture correctly, the 16s strings didn't have separate fuses, as the fuse is after the common bus bar ?
View attachment 212805

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Read the whole thread the OP started on a power wall. He started with 3 strings and increased to 7 over time and totally reorganized things.