Tulex
Solar Wizard
You are correct, not looking for a fight.Yes, I believe you mean right and not fight.
I don't believe a FET based BMS will help in such a circumstance.
You are correct, not looking for a fight.Yes, I believe you mean right and not fight.
I don't believe a FET based BMS will help in such a circumstance.
That is my understanding of how it works and a possible explanation for the source of the fire in the OP's homeIf if it can arc, it will, because that cell is still wanting to be lit up. Do I have this fight?
In my 18650 powerwall, each cell has fuse wire - which is from Tesla's design for their cars. In my case it's 30awg tinned copper wire - so if an individual cell goes bad -> shorts in a 100p pack the current from the other 99cells burn this this small fuse wire disconnecting that cell from the overall pack so things don't go crazy. As a secondary benefit, if you accidentally short a 100p pack (or overall battery), most of the fuse wires (90%+) will instantly melt pulling the teeth from the pack/battery's destructive potential.That is my understanding of how it works and a possible explanation for the source of the fire in the OP's home
What's running thru my mind these days is...... is secondary damage from flame.We don't know the exact sequence of events in the case of this thread.
I have mine in a box.What's running thru my mind these days is...... is secondary damage from flame.
Obviously one should not put at risk items (batteries for example) near something flammable. But one has to think what 'flammable' means - and I didn't do that to a deep enough extent in my propane fueled event. For example, a fuse can cause flame via arcing... and thus, should be contained so the flame cannot reach other items. Same concept as the shed fire reaching the propane bottles.
One practical takeaway for me is that while I have key breakers and bus in a metal "Control Box" I don't have my ABB SACE S3 400a main battery shunt trip in a metal box... it's just exposed. After all this, I plan to buy a metal box for it.
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Good observation.I have mine in a box.
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Ran across this thread in a boating forum. https://www.cruisersforum.com/forum...o-break-in-a-catastrophic-event-274602-4.html
On the first page of that thread, there was this post by CaptainRivet:
"Yes in a short or anything >25% above (depending o quality of your BMS, some can +25%, some +100% but that is max) your BMS current rating the mosfets in your BMS will fry closed in 95% of the time leaving your plus connected, negative is always connected.your BMS with fried mosfets will most likely still show you the cell voltages...
By the way the same applies to your inverter/charger, eg Multiplus is also only protected via mosfets on plus, the negative is always connected to be able to monitor and eg remote switch on. This a lot sailors connect directly on the terminal of your battery/bank, with an extra fuse to avoid upgrading cabling and main busbars as its the only bigger source added. So this is now your 2nd main battery and main cable fuse combined and must be therefor Class T or NH too!!!
The BMS (and Multiplus) limits the currents to protect lifespan of your battery and switch loads and charge sources off to peotect it from over- or undercharging.
But these protection capabilities cannot withstand the enormous short curcuit or other catastrophic failure currents that a lifepo4 is creating, a rule of thumb is AH capacity multiplied with 20 gives you the roughly the short curcuit current reached by this bank/battery. So a 100Ah can do 2000A, a 500AH bank already 10000A. That is the job of a fuse, see above what and how to implement.
And you just think about your mosfet based BMS. Their are plenty other out there.
Eg My electrodacus BMS has only 2 shunts on the positive busbar of the bank, nothing else that will cut or protect the installation."
Fuses fail too. Even the best. The damage - fire gets started even after fuses blow sometimes. Think ppl are saying add bms as parallel…to batrium. You are saying class t fuses.I see no reason to add a redundant BMS when using a Batrium.
The main takeaway from any of this is fuses for batteries should be Class T or similar construction. Originally when I built my truck camper system, the ANL was popular, over time people tested the ANL and found the Class T was superior when the fuse blew. I had built with ANL back then and it was suggested I switch to Class T which I eventually did.
I do not understand the mindset where the Batrium needs to have a BMS on each 48V battery when a Class T is used on each battery. A mosfet BMS can fail under high current and still allow high current to pass. The only safe system is a Class T type fuse that will blow, not sustain an arc, start/sustain ignition and not blow molten material around.
I buy my Class T fuses from Don Rowe for $60 each and that includes the holder. Protection so cheap it doesn't make any sense to do anything else.
These builders wanted save money. Profit. Csst is cheaper and thin. Deemed safe even though reports and fire inspectors see other wise. It is the world we live in.There is Type K copper with the yellow pvc covering.
How exactly did you mount that in the box?I have mine in a box.
You don't need a separate BMS, but you do need a controlled means of disconnection of an individual string. The fuse only senses current; it cannot address other failure or risk modes.I do not understand the mindset where the Batrium needs to have a BMS on each 48V battery when a Class T is used on each battery. A mosfet BMS can fail under high current and still allow high current to pass. The only safe system is a Class T type fuse that will blow, not sustain an arc, start/sustain ignition and not blow molten material around.
It all comes down to fault impedance. If you have a low enough impedance and the fuse exceeds its interrupting rating then it will arc. With DC it is significantly harder to break that arc, so it will continue until something else manages to break it-- like a significant length of wire melting.Once the fuse blows, that flow stops. If if it can arc, it will, because that cell is still wanting to be lit up. Do I have this right?
What caused this if you dont mind me asking (LEARNING...)?? Wasn't what I expected when you said "butt joint burn-thru". Damage to conductors from stripping cable?? Would this show on a FLIR beforehand??I had a butt-joint burn thru (2 years ago) but it was in a metal connection box and might have saved my house....
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Don't want to derail too much here, it is in my Battery Box Build thread in my signature. Rear bracket came with the ebay sourced breaker, I had to shim it with a couple of nuts to get tight to backside of cover.How exactly did you mount that in the box?
You don't need a separate BMS, but you do need a controlled means of disconnection of an individual string. The fuse only senses current; it cannot address other failure or risk modes.
As I understand it, using a watchmon with an external contactor or shunt-trip breaker on each string does the job.
The purpose of the Class T on my system is overcurrent protection for current either way.The purpose of the class-T fuse is essentially a fail-safe for an unreliable disconnecting means. The only substitute for one is a properly rated DC circuit breaker able to interrupt full bank amps fault current.
You may want to consider a Predator unit for much less unless you really want/need the efi complexity.Inadequate wall thimble for generator exhaust. The idea was to store/run generators from in the shed for shelter and noise abatement. And in fact, I ran the generators every other month for over a year and all seemed OK. The exhaust didn't seem that hot after 5 feet of exhaust pipe - I could pass my hand thru the exhaust.
On the day of the fire, I did a 40min generator run around noon, finished, and visually checked things - all seemed OK. However, it appears a smoldering fire was started and broke out of the wall 12hrs later ~midnight. By 1am the tanks were torching.
There was a formal fire investigation and I learned a few things from the fire folks. For example, did you know that wood can ignite as low as 200F? My research indicated more like 400-500F. Also, wood can slowly char over time from heat and lower the ignition point.
Yikes - DIY has risks and I feel so bad tarnishing DIY'ing with my mistakes.... e.g. inadequate thimble but even more so, not thinking clearly that the outside of a shed wall is *flammable* and propane must not be stored near anything flammable.
And BTW... the Champion 100297 w/74db specs was still causing 70db 5 feet from outside the shed with 2x6 framing, insulation. siding, and double dry-wall! Noise abatement was a failure. Going forward I'm going to spend $ for a Honda eu7000is with 58db and run in the open for emergency power.
The original electrician wired these butt-joints and wrapped them in black electrical tape. I happened to have a pic prior to the burn...What caused this if you dont mind me asking (LEARNING...)?? Wasn't what I expected when you said "butt joint burn-thru". Damage to conductors from stripping cable?? Would this show on a FLIR beforehand??
Maybe - I see this 9500 has 62db at 23feet - https://www.chainsawjournal.com/predator-9500w-inverter-generator-57080/You may want to consider a Predator unit for much less unless you really want/need the efi complexity.
Yes, significantly more powerful, also the Honda is 52dB in Eco mode and is 58dB during normal non eco operation.Maybe - I see this 9500 has 62db at 23feet - https://www.chainsawjournal.com/predator-9500w-inverter-generator-57080/
Still a bit noisier but also a bit more powerful.
Those things are giant pieces of shit. I went through two, both under 75 hours with multiple flushing oil changes. There won’t be a third.Maybe - I see this 9500 has 62db at 23feet - https://www.chainsawjournal.com/predator-9500w-inverter-generator-57080/
Still a bit noisier but also a bit more powerful.
Our primary generator is a 30KW Ingersol Cummins powered unit I picked up used six or seven years ago.Water cooled diesel definately seem like the way to go for long term durability and fuel efficiency.
So far so good with my open frame inverter Predator 8750W, but it’s massively loud and obnoxious.
I wish I could find a more polite way to say this, because you have a lot of great insight and experience... but you are incorrect.High or low voltage cell limit (or any other critical fault you program such as battery temp) is hit, the Batrium shuts down the whole system using the shunt trip ABB breaker. Some might complain, "Well, it shuts down the whole system".
That is what I want, it forces me to go and find the problem. It has happened when I played with charging voltage limits and had a runner. It works exactly as designed
...No need, one shunt trip breaker on the whole battery bank with a Class T fuse on each 16S (or whatever series you are using) battery. Each 16S battery in my case has a K9 that monitors and balances each battery and relays cell, balancing and temp data to the CORE.
...Let's get realistic here. Attempting to find fault with using only a Class T fuse for overcurrent protection is pointless, just like having redundant overcurrent protection in your house electrical panel would be.
I wish I could find a more polite way to say this, because you have a lot of great insight and experience... but you are incorrect.
Once a cell goes out of tolerance tripping the bank will not stop it from charging via the parallel strings. It may not lead to a catastrophic failure, but the BMS is unable to protect the battery from damage.
Your example of fuses in series is poor; if the two fuses provide the same protection then they are very much redundant. Circuit breakers in series with fuses does actually happen in high fault current situations-- the fuse is used for instantaneous protection in the maximum fault current range, but the circuit breaker maintains coordination of the system short of a bolted fault. The difference is those are UL-listed series-rated combinations.
The 3 strings and high current will blow the Class T. My busbars and cable are rated way higher than the Class T. This is on purpose, the Class T is the weak link and will blow before any wire melting. Proper design will mitigate failures.Which can provide more current to a damaged cell, a charge controller or 3+ strings of battery in parallel?