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Extremely overheated BMS, fused Breaker and dead Inverter. What could be the root cause?

Hope no one was hurt.

The thing hate about breakers “if” trip ppl reset them right away… giving it a second or finite number of chances to cause problems. VS inspecting everything like would usually be done with fuse replacement. Breakers will fail if recycled over and over. Thermal protection helps solve some of that…breaker won’t reset until cooled off.

Ppl if you read it the OP says breaker tripped. Tripped again. Then smell from battery pack. Then read the breaker was fused melted inside when he tried it. Effective reading is critical. So no telling what really happened.

Everyone is blaming the daly bms which might not of been the problem. Lightening does weird stuff.

IMG_6324.jpeg

The temptation to just reset breakers is strong. Don’t do it without looking and smelling for smoke.

I have a fuse and breaker on my battery ….. the breaker is 120amp the fuse is 125amp. Breaker close to battery and fuse close to inverter. I am still waiting on my t class fuse to replace anl. I think the anl would work but it would depend on load when system fails.

I suspect mosfet in inverter…damaged during reported storm. ppl cycling tripped breakers over and over never leads to good things. Always inspect.

I’d remove all power - cables … remove cover and look around inside the inverter. Was inverter unit hooked to grid or generator or anything? Just battery? Sometimes you can remove from mount and shake stuff to hear pieces rattling around in the case. Good indication pieces went to something Like doing old light bulb rattle. 🤣

“1hp aircom” Assume air conditioner. Did you check out the air conditioner? Does it look good … any weird burned smells from it? Sometimes when inverters go take out appliances. Sometimes appliances feed back when hit by lightening.

Edit add: This might be better breaker. Those mini might not be so good… arc travel.

www.nsbjd.com

DHM1B-2P Molded Case Circuit Breaker DC MCCB

www.nsbjd.com www.nsbjd.com
 
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I have a mechanic that I trust with my cars. It wasn’t an advertisement in a slick add that took me to his shop. It started with a face to face conversation. And then a successful repair followed by countless successful repairs over the years.

The BMS I chose is similar. I have read posts from those whose entire household depends upon their equipment, not a shop or a garage. I currently have two Overkill and two JK Active BMS in operation.

There are those who are very happy with their Overkill units. Having run them side by side for my build the JK is heads and tails above the other.

Brand loyalty is a trust relationship. Even at three years my learning process has never stopped. My post is not intended to pass judgment on one brand over another. Only to suggest to keep an open mind during the journey.

I have found my multimeter to be a good friend. At times I have been surprised to note that something as simple as a loose connection can be a factor.

Power surges of any type can be tough on electronics regardless of brand. Sometimes rotating units or plugging in a new unit can get things running again.

Having said that sometimes a thorough inspection can be beneficial to reduce the risk of a repeat performance.
 
robbob2112 said:
5. And, realize the BMS is not a fuse and can't act as a fuse since if it fails most of the time it will fail as a short. If there is sufficent current the short will get all explodey and become an open.
Click to expand...
Explodey, Funny word. Must be a technical term.

Anyway, as to BMS's, My main house battery runs a daly 250 amp, "dumb" version. It seems to be working fine as I haven't had any issues so far 2 1/2 years in service now. We do get a lot of lightning down here in the summer and so far, so good.
I've built many batteries for others since and have gotten my best results from the JK BMS's
 
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I just wanted to share a lightning story, it will really show just how odd lightning is.

Years ago, like 30 I had setup a computer network at a John Deere dealership. Most of the computers had modems so they could fax out quotes and such as well as access Deere home office for parts and all that jazz. It was a different time.

A thunderstorm came along and lightning hit NEXT to the building. By next I mean about 30 feet away, it hit a tractor. The entire network went down.

Long story short, and after a lot of figuring it turned out that every single modem got smoked. The rest of the computer was fine. Take the modem card out of the PC and it would be fine, put it back in and it would not boot. Oddest thing I have ever seen.

When thunderstorms are around and you think it might have done something expect anything. Nothing will make sense. Those blown modems also stopped the server from booting. This is in the old days of Novell 2.2.
 
JJJJ said:
Having said that sometimes a thorough inspection can be beneficial to reduce the risk of a repeat performance.
Click to expand...
This is exactly what I am trying to figure out. I do not wish to have another similar incident. But the Inverter must've been the main culprit. (16 FETS blown and got replaced.)
The resetting of tripped breaker by the user must be the next step in overheating the BMS.
The BMS still works after I tested it with a temporary battery pack. Can connect with PC. Or Bluetooth. But I have not tried charging or discharging. And maybe i'll just put it on display.
I cannot read the Alarm History using either PC software or Bluetooth.
It also stuck on "Reading Alarm History" when i tried to read it on another exact same model in use. So it is probably a software problem.

Like others have mentioned I am thinking of switching to JK at this point.
 
zedconnor said:
Yes I have put a layer of double-sided tape (about 3mm thickness) as well as a PP-board between the bms and the cells. (The PP Board was able to withstand the heat)


I have attached the re-packed pictures. This time I screwed down the bms above the cells.
There will be no more foams.



They only have a single 1HP Aircon and lighting to use. The normal usage may not be the problem.
I am guessing it's the Inverter
Click to expand...
Sorry, just figured out this was just a temp install on the rebuild?

One minor comment that has no impact on function.

Neatness counts when it comes to wire. Make a neat bundle of the balance wires like a tree trunk and pull putbranchess to the battery posts/bus bars.

Just my opinion, take or leave it.
 
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upnorthandpersonal said:
Finding the root cause of this should be a priority. Also, put a fast acting fuse at 125A or so (Class T) at the inverter input.
Click to expand...
Root cause? hate to be the mean guy in the room, but below is my idea of what the issue is. you can only skimp so much when building something, and 687 USD does not buy a whole lot of anything these days.

problem found.png
 
Daddy Tanuki said:
Root cause? hate to be the mean guy in the room, but below is my idea of what the issue is. you can only skimp so much when building something, and 687 USD does not buy a whole lot of anything these days.
Click to expand...

I've been running a 6kW MUST inverter for a long time. Mine was $430 back in 2020; but shipping was high because it's a low frequency inverter and weighs close to 50kg. I also run their charge controllers (PC18-10015F, 100A) without issues.

One of the reasons I went with these is because I wanted something I could fix and get spare parts for, and MUST is popular in certain African countries where they don't have a grid to rely on and things need to be able to be fixed. MUST sent me a spare power and control board when I asked for it for my inverter (spare parts, just in case), and the components (for board level repair) are readily available.
 
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upnorthandpersonal said:
I've been running a 6kW MUST inverter for a long time. Mine was $430 back in 2020; but shipping was high because it's a low frequency inverter and weighs close to 50kg. I also run their charge controllers (PC18-10015F, 100A) without issues.

One of the reasons I went with these is because I wanted something I could fix and get spare parts for, and MUST is popular in certain African countries where they don't have a grid to rely on and things need to be able to be fixed. MUST sent me a spare power and control board when I asked for it for my inverter (spare parts, just in case), and the components (for board level repair) are readily available.
Click to expand...
I stand by my statement, you liking or disliking it does not alter the fact that something this cheap is going to have issues. its really that simple.
 
Reliability and being fixable are not mutually exclusive attributes, its good to have both but given a choice which you choose is up to you and your funds available.
 
I don’t care what you have if it got zapped by lightning then the price doesn’t matter. It goes to smoke.

I hope the OP checked his air conditioner to see if it was struck and feedback. Think he has a mini split.

The breaker was recycled most likely several times which is clearly stated until smoke was seen from battery and breaker fuses. Cycling breakers without determining the reason never ends well. Most ppl look for problem longer if have to replace fuse.

I’ve seen these things catch on fire while other ppl swear by them. Lightning is rough on anything if that is what happened. This is one of those things may never know. Blaming the inverter is like blaming the Daly. Where OP is listed for residence it is probably limited. Again seen these things go up in smoke too. Some ppl swear by surge. The old computer surge power strips might protect 1 time but were suppose to be repaired-replaced. The surge devices are not cheap either. They were all over Nuclear plants…. They made nice fire when popped.

IMG_6399.jpeg

I’ve got MPP Solar 3048 and don’t trust it ….cheaper price than that MUST. The way they relabel stuff who knows who made that inverter. 🤣 Anything can give problems. Anything.

OP mentioned only lights and 1 hp air con. Might of came in on solar array if has one. May of came in on line if hooked to grid. Again probably never be solved.

My theory on some of the inverter failures is just this….I think some get zapped by battery when turning on and the capacitors have bleed down. With 48v you have a mini lightning strike. Capacitors go bad anyway. Most failures for inverters have noticed it is mosfets and capacitors.

On locomotives we used a hypot machine was labeled hypot to clear high voltage grounds. It had breaker on it. The procedure was flip ac hypot breaker until found the light show, hear the crack, and or seen smoke. The ground showed up quickly. There was a burn feature on hypot but an electrician got severe shock bad procedures so it was disabled. Eventually ac hypot was replaced with megger which was not quick to find hv grounds. The hypot machine was mini lightning… if fed back through sensors then burned them up at 1000-2000 volts. Shhhhssss sometimes the hv grounds came from defective high voltage module sensors….sometimes the ground was high and low getting together. Point is we brought the lightning… the armature of traction motors could only take 500 volts from megger. Everything else could handle 1000-2000 volts except some modules… the flipping circuit breaker with hypot would kill them. We called it destructive testing. It was fast and effective if done properly . Locomotives have float grounds tied to ground relays. I can hardly wait until ground faults pop up on ev as they age. 🤣
 
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zedconnor said:
This is exactly what I am trying to figure out. I do not wish to have another similar incident. But the Inverter must've been the main culprit. (16 FETS blown and got replaced.)
The resetting of tripped breaker by the user must be the next step in overheating the BMS.
The BMS still works after I tested it with a temporary battery pack. Can connect with PC. Or Bluetooth. But I have not tried charging or discharging. And maybe i'll just put it on display.
I cannot read the Alarm History using either PC software or Bluetooth.
It also stuck on "Reading Alarm History" when i tried to read it on another exact same model in use. So it is probably a software problem.

Like others have mentioned I am thinking of switching to JK at this point.
Click to expand...

Hybrid Solar Inverter & ESS Manufacturer – Must Energy Storage System

www.mustpower.com www.mustpower.com

Do you know if MUST makes their own inverters or do they relabel?

Who replaced the “ 16Fets?” Were the capacitors blown up? They usually get zapped too.
Any pictures?

Was 1hp Aircon checked out? Split unit?
 
D71 said:

Hybrid Solar Inverter & ESS Manufacturer – Must Energy Storage System

www.mustpower.com www.mustpower.com

Do you know if MUST makes their own inverters or do they relabel?

Who replaced the “ 16Fets?” Were the capacitors blown up? They usually get zapped too.
Any pictures?

Was 1hp Aircon checked out? Split unit?
Click to expand...
As far as I know MUST makes their own inverters. But Chinese got alot of oem factories so they may as well be outsourcing too. Nobody knows.

The FETS are replaced by a local repair shop.

The aircon and everything else on the load side is fine.

I put a new BMS and repacked the cell. The customer is using it without any problems so far.
Same setup same battery and inverter. I replaced the breaker with a Suntree brand.
Ps there is no solar installed.
Inverter is a hybrid inverter so it works with grid at the moment.
 
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