Sky RC MC3000 - Buidling Powerwalls is dangerous!

cadric

cadric

Member
Joined
May 3, 2018
Messages
110
Hi Guys,

I'm new to this business, but understood that handling of used 18650 Lio cells can be dangerous, I didn't really believe it though, until yesterday.

To be as save as possible I used 2x Sky RC MC3000 chargers for charging, discharging my used laptop cells.
As these devices are 3 time the price of the Opus or comparable, it has one big advantage: a tempcut function, so when the cell gets to hot( say 45C) the charging process is terminated by the charger. It already happened around 10 times, everything as expected.
This thought in mind gave me enough security to let the chargers run day and night since march.

But yesterday evening I was taught better:

Shortly after I went to bed I heard a loud blast as if a big metal plate had fallen to the ground in my house.
I went down to look into all rooms, didn't expect to see smoke in my cellar.

As I switched on the light there was a big smoke area underneath the ceiling.
I directly turned to my two chargers and saw the misery:


image_sidxlf.jpg

image_iyvkbz.jpg

image_hspyys.jpg


one cell had blasted in the latest bought charger, everything around 2m was covert in some kind of black dust.
I disconnected both chargers directly, opened the windows of the room and placed the damaged charger outside.
I'm not sure what the issue was, in general I make sure, that the cell have good contact to the temperature sensor underneath.

The bad thing was the smoke detector also didn't act.
I worst case, this could have caused serious damage to my house or much worse to us living in, sleeping.

I contacted the reseller today, curious what they say to this.

For future I will do further charging outside in an old metal cupboard under my pergola.
But I''m not sure how I create my Powerwall from security view, although I already planned to build a shed outside for all the electricity.

Keep it save, guys.

And I will start cleaning the room today........


regards


cadric
 
Generally speaking it is not terribly dangerous. But yes, as with most activities, a small risk remains. However this is not just an inherent risk and that's it, there is a reason why this happened. I don't know the reason but there is one and it probably could have been avoided.

The automated cutoff of the MC3000 works reliably. Because of the way it is build there is an offset between the set temperature and the actual temperature. When set to 45C the actual cell temperature is about 55C to 60C when the cutoff happens. At least that's what I observed on several occasions. And that is fine, 60C is not critical.
But sure, it may very well be that the charger has failed. In this case you can't do anything about it, devices can fail at any time.
 
mike said:
Do you know what brand/model those cells were? They appear unmarked like generic rewraps, unless the writing is just downward on all of them.

This is why you should never charge or test these cells unattended :)
Click to expand...

Hi Mike,

can't recall it atm exactly, but if I remember correctly it is Samsung XX18650-22F, but I will check again.
Ihave charged roundabout 50 of them, none did behave like that.

regards

cadric
 
Interesting ... I notice what looks like some aluminium foil near the terminal of the second cell ...

I will hazard a guess of what might have happened .... Sometimes , at the positive end of cells , the insulation become removed , so there is exposed metal negative terminal , a mm away from the positive terminal ...if this is shorted by a badly designed connector from the charger, or a sliver from spot welded nickel strip , of aluminum foil this will cause cell to short ,and no safety feature in the charger can stop this ...

I don't like these type of chargers they are designed for many different cell sizes and so don't hold 18650s firmly and reliably ...

But anyway , this shows how safe these cells are ...NO FIRE WAS INITIATED .... no catastrophe ....not enough smoke to trigger the smoke detector ( these have to be very reliable and it probably functioned as it should) ...you say a "loud blast" ...really ?? no exageration ??? hard to see what could cause such an explosion , the charger still looks intact , may still work .

It doesn't appear the cell case was breached ... heat build up appears to be around positive terminal which seems to confirm my diagnosis of a short there .... do the cells still work? does the charger still work??

This is all part of the fun and excitement of our game ... at 15 years old I was making nitroglycerine in the kitchen at home ! I kid you not ! so I see no threat from these cells ....

Push onwards , our ancestors were hunting wild animals for food on a daily basis , they laughed at danger ...we should too.
 
ozz93666 said:
Interesting ... I notice what looks like some aluminium foil near the terminal of the second cell ...

I will hazard a guess of what might have happened .... Sometimes , at the positive end of cells , the insulation become removed , so there is exposed metal negative terminal , a mm away from the positive terminal ...if this is shorted by a badly designed connector from the charger, or a sliver from spot welded nickel strip , of aluminum foil this will cause cell to short ,and no safety feature in the charger can stop this ...

I don't like these type of chargers they are designed for many different cell sizes and so don't hold 18650s firmly and reliably ...

But anyway , this shows how safe these cells are ...NO FIRE WAS INITIATED .... no catastrophe ....not enough smoke to trigger the smoke detector ( these have to be very reliable and it probably functioned as it should) ...you say a "loud blast" ...really ?? no exageration ??? hard to see what could cause such an explosion , the charger still looks intact , may still work .

It doesn't appear the cell case was breached ... heat build up appears to be around positive terminal which seems to confirm my diagnosis of a short there .... do the cells still work? does the charger still work??

This is all part of the fun and excitement of our game ... at 15 years old I was making nitroglycerine in the kitchen at home ! I kid you not ! so I see no threat from these cells ....
Click to expand...

Hi Ozz,

No, the cells were in perfect shape, no harm to the insulation. The Aluminium looks for me as a part of the Cellcase. Blastet away under the pressure.
And the new Version of the charger have dot's to get better contact to the plus side.

Believe me, they hold them pervectly, like I said I'm working with this device since beginning of March nearly 24/7.

Sorry, but you're wrong, there was a lot of smoke, but the detector did not work correct, I think.
I'm not sure if there was no fire, because I was not in the room as it happened,
at least there was a lot of smoke, and where does smoke come from?

I didn't check further more, I'm waiting for a response of the dealer. I don't see a thread from the cells either, but savety first is recommended.
I personally think the device hade some kind of an error or something, because it worked before.

Jeah, but if it is dangerous for my Family and my House, the fun stops emidiatly. At least for me.

regards

cadric

DarkRaven said:
Generally speaking it is not terribly dangerous. But yes, as with most activities, a small risk remains. However this is not just an inherent risk and that's it, there is a reason why this happened. I don't know the reason but there is one and it probably could have been avoided.

The automated cutoff of the MC3000 works reliably. Because of the way it is build there is an offset between the set temperature and the actual temperature. When set to 45C the actual cell temperature is about 55C to 60C when the cutoff happens. At least that's what I observed on several occasions. And that is fine, 60C is not critical.
But sure, it may very well be that the charger has failed. In this case you can't do anything about it, devices can fail at any time.
Click to expand...

Hi,

yes, that's what I hade to learn the hard way again. A good friend allways tells me: Don't trust technical Items to much.
I should have been more carefull, like charge them outside the house, which is what I will defenetly do from now on, I don't want them inside the house anymore, but the shed I planned to install everything in is not even planned, just where I want to place it is clear.
I have to find an intermediate solution for charging the cells until then.
And if again want's to burn or explode, nothing else should be harmed.

regards

cadric
 
From your picture the cell appears to be unbroken .... but we cannot see the underside , is the metal case torn , is there a hole in the cell ???

If so then this would explain the black 'smoke' .... the electrodes inside the cell are covered with a black powder a mixture of carbon and Li CoO2 this would be the black dust everywhere ... it's not deadly poisonous but should be cleaned up carefully ...

In this scenario pressure build up in the cell caused rupture of the metal case ejecting a mixture of liquid electrolyte and the black dust , the electrolyte would instantly evaporate leaving a cloud of black particles. If a flame had been present it would have ignited the electrolyte , but there was none . you may have noticed a smell of this electrolyte as you entered the room.
 
This would be my conclusion :

image_qckyng.jpg
 
Wow! That's a bad burst right there. Answering before reading the rest of the comments, make sure to toss those other 3 away. I wouldn't trust them with a bomb having gone off so close to them. No telling what the blast could of done to them internally.
 
We're still all fishing in the dark as to what happened because of inadequate pictures and information ...

Are there any holes in any cells which allowed inside material to vent????

Weight of remaining burnt cells????

Detailed damage report on charger ????

What was the voltage of cells before putting in charger ??? do you measure this after breaking cells from laptop scrap???

This charger cannot deliver more than 5A to a cell , so a fuse on the cell would not have prevented this , if it had occurred when cell was in powerwall.

Look at the positioning of the cells in the charger .... this charger is designed to accommodate fatter cells , as a result it's possible for the positive contact terminal on the charger to lodge between the positive terminal of the cell and the lip of the cell which is negative . if there is a small break in the insulation on this lip , or if heat from charging causes the plastic insulation to soften and break , then the cell is shorted ....
 
ozz93666 said:
..

Look at the positioning of the cells in the charger .... this charger is designed to accommodate fatter cells , as a result it's possible for the positive contact terminal on the charger to lodge between the positive terminal of the cell and the lip of the cell which is negative . if there is a small break in the insulation on this lip , or if heat from charging causes the plastic insulation to soften and break , then the cell is shorted ....
Click to expand...

That sounds like the most logical conclusion. Old heatshrink combined with heat from the charger. Even a tiny hole could have slowly opened up. Even if the temperature sensor was functioning, it is possible for the cell to get somewhat hotter.

Perhaps even, the cell moved after you inserted it, so the sensor did not make proper contact. I personally believe that this had to be a result of a short.

Definitely I never leave batteries charging unattended, unless they are in a metal box that cancontain any possible fire.

The fact that the smoke alarm never went off is bizarre. However, it makes me consider putting one in very close proximity to my charging station.
 
I monitor my charging stations and discharging stations constantly. I never allow the charging process to happen over night. Way to dangerous. I don't have an issue allowing a discharge cycle to happen over night though.

Sadly though it normally takes a close call or worse to get people to pay closer attention to protecting not only their families, but their home. Be Smart.
 
ozz93666 said:
From your picture the cell appears to be unbroken .... but we cannot see the underside , is the metal case torn , is there a hole in the cell ???

If so then this would explain the black 'smoke' .... the electrodes inside the cell are covered with a black powder a mixture of carbon and Li CoO2 this would be the black dust everywhere ... it's not deadly poisonous but should be cleaned up carefully ...

In this scenario pressure build up in the cell caused rupture of the metal case ejecting a mixture of liquid electrolyte and the black dust , the electrolyte would instantly evaporate leaving a cloud of black particles. If a flame had been present it would have ignited the electrolyte , but there was none . you may have noticed a smell of this electrolyte as you entered the room.
Click to expand...

Hi Ozz,

I took the cell out yesterday, but forgot to take a picture.
The Positive Top has gone and the Cell has emptied that way.
There was no smell of electrolyte, it smelled like my oil heating, when it does not burn the oil completely at startup.
That is what I initially thought, when I got down into the cellar.

I will try to attache a photo ....

Yeah ,the cleaning is a challange now, because in that room all my Folders and documents and a lot of little things are stored. Big mistake ;-(
I will got through it squaremeter by squaremeter......


cadric

Monsterbeats19 said:
Was the charger still on when you came to check the charger or did it appear to not work
Click to expand...
Hi,

the charger was still running as nothing had happened.

ozz93666 said:
We're still all fishing in the dark as to what happened because of inadequate pictures and information ...

Are there any holes in any cells which allowed inside material to vent????

Weight of remaining burnt cells????

Detailed damage report on charger ????

What was the voltage of cells before putting in charger ??? do you measure this after breaking cells from laptop scrap???

This charger cannot deliver more than 5A to a cell , so a fuse on the cell would not have prevented this , if it had occurred when cell was in powerwall.

Look at the positioning of the cells in the charger .... this charger is designed to accommodate fatter cells , as a result it's possible for the positive contact terminal on the charger to lodge between the positive terminal of the cell and the lip of the cell which is negative . if there is a small break in the insulation on this lip , or if heat from charging causes the plastic insulation to soften and break , then the cell is shorted ....
Click to expand...

No holes, except the top missing on the blasted cell.

Detaile damage report...mhh.
The plastic around the first cell is burned, the metal strip you see standing up is the kontakt of the temerature sensor underneeth the cell.
The initial voltage was around 2 Volt. I first charged them up to 4.2 Volt, then discharge to 3.0 Volt. All this only for the initial check.
After that I do a charge up to 4,0 Volt and discharge down to 3,5 Volt. This is then the cap I note. And I only charge/discharge with 0.5Ah max.
The blast must have happened in the first discharge process, because half an hour before this I was down to check, and everything was ok, the cells were resting an 4,2 Volt. The charger was the latest version which has dots to get better contact to the positive side of the cell. I think from the dimension it is not possible, that it can have contact to pos and negative on one saide at the same time.

Geek said:
ozz93666 said:
..

Look at the positioning of the cells in the charger .... this charger is designed to accommodate fatter cells , as a result it's possible for the positive contact terminal on the charger to lodge between the positive terminal of the cell and the lip of the cell which is negative . if there is a small break in the insulation on this lip , or if heat from charging causes the plastic insulation to soften and break , then the cell is shorted ....
Click to expand...

That sounds like the most logical conclusion. Old heatshrink combined with heat from the charger. Even a tiny hole could have slowly opened up. Even if the temperature sensor was functioning, it is possible for the cell to get somewhat hotter.

Perhaps even, the cell moved after you inserted it, so the sensor did not make proper contact. I personally believe that this had to be a result of a short.

Definitely I never leave batteries charging unattended, unless they are in a metal box that cancontain any possible fire.

The fact that the smoke alarm never went off is bizarre. However, it makes me consider putting one in very close proximity to my charging station.
Click to expand...

jeah, from now on I will do the charging outside in a metal cupboard and install a smoke sensor also, maybe with 433mhz and integrate it into my homeautomation sytem fhem.
And temperature sensors are also planned to be added somehow, from now on I will keep it save save save.....you never know, what issue appears, and this could have gone very bad. I already found a solution for turning an old unused CO2 bottle from a Water sparkler....who knows......

TerryTexas said:
I monitor my charging stations and discharging stations constantly. I never allow the charging process to happen over night. Way to dangerous. I don't have an issue allowing a discharge cycle to happen over night though.

Sadly though it normally takes a close call or worse to get people to pay closer attention to protecting not only their families, but their home. Be Smart.
Click to expand...

Hi Terry,

as I can recall, it happened in the discharging Process, because I checked before I went to bed, and the cell was charged up to 4.2 v and was resting.....

But you are totally right, bad behavior from my side.....and I said, this will not hapen again in my house. I will change my procedure.

cadric

To everyone,

thanks for trying to solve the issue and help me find out, what could have been the issue.
I got an answer from the dealer, they where shocked and directly offered me a new device or money refund,
I will take a new device and restart my work outside.

And rethink my setup.......


regards


cadric
 
If you were down there 30 mins prior and the cells were at 4.2 volt I wonder if the charger kept charging and had not switched over to discharge mode causing this to happen.
 
Well, since it had already gone through one cycle without issue, I doubt it would of been a short. Otherwise the charger would of either gave an error or some really erroneous readings (like really high initial mAh readings).

Here's a thought. Is it "possible" that something in the charger failed and heated the cell up from underneath and then the cell went afterwards? Like a capacitor failing or something. Or possibly the FETs failed on and dumped massive amps into it. It's like what Completelycharged had from his failed pcb where the FETs failed and he had a fireworks display.
I don't know what those boards look like directly and what parts are where as I don't have one myself.
 
Korishan said:
Well, since it had already gone through one cycle without issue, I doubt it would of been a short. Otherwise the charger would of either gave an error or some really erroneous readings (like really high initial mAh readings).

Here's a thought. Is it "possible" that something in the charger failed and heated the cell up from underneath and then the cell went afterwards? Like a capacitor failing or something. Or possibly the FETs failed on and dumped massive amps into it. It's like what Completelycharged had from his failed pcb where the FETs failed and he had a fireworks display.
I don't know what those boards look like directly and what parts are where as I don't have one myself.
Click to expand...

Hi Korishan,

good point, didn't think about the charger to have been the issue that way, but it could be possible......will take a closer look today....and add some pics.


cadric

Unleashed said:
If you were down there 30 mins prior and the cells were at 4.2 volt I wonder if the charger kept charging and had not switched over to discharge mode causing this to happen.
Click to expand...

Unfortunaltey I can't recall the sign in the display, but I'm sure charging was done and it was in resting state.
Maybe the device still tried to charge.....Thanks for your comment.

cadric
 
Thanks for the detailed report cadric ...

So , it seems , for whatever reason , great heat built up in the lower cell , enough to melt the plastic shrink wrap sleeve ... the safety device in the positive terminal of the cell should have electrically isolated the cell before this happened ,so either

1 ... the safety failed to isolate as the pressure built ... or 2. it did isolate the cell , but internal damage caused heat and pressure to continue to rise ..

Finally blowing the top ....

This must be an extremely rare event ...I should let it force you outside to do charging this seems an overreaction ... even with this freak accident , there was no fire , but some mess to clean up ....

It seems your charging discharging regime is a lot of work , surely all that's needed is to charge up to 4.2 or 4.1 ...leave isolated for 3 days to make sure no self discharge , and then discharge to check capacity...I don't even do that on all cells .. if I extract cells and they have over 4 volts , experience has taught me they're very good , so I put them straight in the wall without further test .

If you can halve your charging regime , you halve the risks ...
 
ozz93666 said:
Thanks for the detailed report cadric ...

So , it seems , for whatever reason , great heat built up in the lower cell , enough to melt the plastic shrink wrap sleeve ... the safety device in the positive terminal of the cell should have electrically isolated the cell before this happened ,so either

1 ... the safety failed to isolate as the pressure built ... or 2. it did isolate the cell , but internal damage caused heat and pressure to continue to rise ..

Finally blowing the top ....

This must be an extremely rare event ...I should let it force you outside to do charging this seems an overreaction ... even with this freak accident , there was no fire , but some mess to clean up ....


It seems your charging discharging regime is a lot of work , surely all that's needed is to charge up to 4.2 or 4.1 ...leave isolated for 3 days to make sure no self discharge , and then discharge to check capacity...I don't even do that on all cells .. if I extract cells and they have over 4 volts , experience has taught me they're very good , so I put them straight in the wall without further test .

If you can halve your charging regime , you halve the risks ...
Click to expand...

I hope that this is extremly seldom, at least I didn't hear about something like this before.
It may be overreacting, but you seldom have twice so much luck.
And I already startet charging outside with a Imax B6 mini and two Powerbanks, so I just have to add my two MC3000 there.

Charging normally takes 1 Day for 8 Cells, I start after work.
First process is: I charge up to 4.2 Volt and discharge down to 3 Volt for the initial check, and like Korishan said: to find the heaters.......;-)
In the morning before work I write down the capacity and start the
second process: charge up to 4 Volt, discharge to 3.5 Volt, after work I write down the cap and take 8 new cells.
I'm only using up to 4.0 and down to 3.5 Volt. I want to have 1Ah as minimum.
8 cells a day isn't that bad, I have to follow up with new cells anyway, which takes also time.
Since I began in March I nearly tested 600 cells, around 150 of them over 1000mAh, so usable for my setup.
Still some way to go, and the only source for me is ebay....and prices ar rising, many people already pay 3 per laptop-battery.
For me this is way to much, I try to stay at around 2, which is still more that enough if you keep in mind that this is rubbish...but still cheaper then buying the cell directly from resellers.

cadric
 
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