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GooneyBird

With all the LiPo horror stories abound, you'd never expect NiMH-packs to go sour on you!

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But still they did!

So I charged up two packs for the Pajero today, thinking I'd go for a nice stroll in the woods nearby and put some miles on the little CC01. All went well, the charger went *beep* and both packs finished charging within a reasonable time. I tossed one in a cinch bag I have, and stuffed the other one in the car, ready to go. I walked upstairs to grab my phone, radio, wallet, and gave my wife a quick kiss goodbye (I need to build her a trailer too, but that's a different story. :P

When I came downstairs again I smelt something horrid. I thought the neighborhood kids were blasting off the last of their fireworks, but then I saw smoke billowing out from under the Pajero's body. :O 

I pulled the body off, opened up the front door and chucked the whole thing outside in a sandy area of our front yard. It sat there for a good couple of minutes smoking and sputtering god-knows-what out the battery. That's why I left the pack in there. I unplugged it, took the battery retainer off, and felt the heat coming off the pack. As the CC01 has a bit of a fiddly battery removal procedure (the pack is a snug fit, and needs a bit of poking before it'll come out)  I decided that I'd rather throw the whole thing outside. I'd rather lose the chassis than my hand! 

After about 15 minutes it had cooled down enough for me to be able to touch the thing again, and this is what I found:IMG-20200101-134754647.jpg

As you can see, the pack split open and a few cells exploded/went critical. The whole thing heated up to such an extend...

IMG-20200101-134802283.jpg

... that it actually melted through the chassis! Normally the battery pack fits the whole quite snuggly. Now though...

IMG-20200101-134810669.jpg

You can see where it actually tried to melt through the chassis! The metal parts surrounding it seem fine, thankfully.

IMG-20200101-134830794.jpg

This is the other side of the battery compartiment. You can see where the plastic buckled. 

IMG-20200101-134859939.jpg

IMG-20200101-134912097.jpg

Much to my surprise the wiring surrrounding the pack is fine. most of the heat seemed to have been absorbed by the plastic chassis. 

So my plan is to rebuild, obviously. The battery is completely fused with the chassis, and no amount of poking will make it budge. I've put the car back inside, the smell has disappeared mostly, and the whole thing has cooled down. Just to be safe I've connected an H7 bulb to the battery, and when no current came through that thing anymore I dead-shorted it. I'll take the whole car apart, and throw away the bathtub along with the battery. Hopefully everything else is undamaged. I haven't had a chance to test the electronics yet, but the ESC and receiver are far away that I don't think anything happened to them, the motor can take a bit of heat, but the servo is the questionable factor here. 

 

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Looks like 1 cell overcharged enough to burst thru it's wrapping, then shorted out against its neighbour...?

NiMH have been known to explode too.

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Indeed - back in the days when NiCads were common and NiMH was new, people told the same sort of scary stories about them as people tell of LiPos today.

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Wow!

Not seen one split that much.

Only battery I've had blow, so far, is a nimh. Last time it blew the bottom cap off and thought it had put through the kitchen window! 

(Edit, had a nicad go pop too, but that just split a cell open, nothing major)

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The dangers with cell style batterys are mainly shrapnel if they do go pop. A battery with a defective venting assembly at the top can build up pressure and explode. Lipos  dont have this problem, they can explode but the soft casing cant do much damage. The main dangers from Lipos are the flames that shoot out and immense heat which can set other nearby objects on fire. 

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1 hour ago, guggles said:

The main dangers from Lipos are the flames that shoot out and immense heat

That sounds pretty dangerous :o

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That's terrifying, I'm glad the car is in fixable condition. Another reason for me to stick to rope.

2136459112_Screenshot_2020-01-02toycarrope-GoogleSearch.png.02c363876931b2d89d32ce50274ec972.png

 

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I've only really had NIMH and Nicad packs pop/melt on me, never had a lipo pop so far, but I've binned quite a few that got too puffy and stopped taking full charge in one cell.

I think Lipo's if used correctly, with the right charger and discharger equiptment, a bit of knowlege, a touch of common sense, are actually very safe, maybe even safer than NIMH, as NiMH Chargers don't always know if one cell is not behaving. 

NiMH where known to fail/melt/pop if you charged them with a Nicad Charger,

Both Nicad and NiMH charge on a "peak voltage" based system, meaning that the charger detects that the battery is full when the battery begins to reverse its polarity (drops voltage) due to over charge. 

Nicad's more quickly dropped voltage when fully charged, and could handle a bit more abuse than NiMH, so the peak detection on a NiMH battery had to be at a lower voltage loss than Nicad, this ment if you charged a NiMH on a Nicad peak charger that the NiMH would start to reverse it's polarity too far when the charger kept pushing power in when capacity was maxed out, leading to failure. 

When we raced, many will remember the side by side cell packs, there was many reasons to do this, including increased power handling through beefier bars joining the cells together, but also it ment that the battery could be cell equalized on a special discharger that discharged all the cells separately, this was essentially balance discharging for NiMH, it paid dividends in a better overall charge/power output, because the cells are more equally discharged, they charged a little more equally too then. The packs not only performed better but lasted longer. NiMH actually where pretty fragile, just like lipos you couldn't store them charged as they seemed to forget how much capacity they had, and worse still you could not leave them discharged, NiMH had a natural tendency to Discharge themselves, so if you left them flat for a long period, they basically run themselves totally dead, reversing there polarity and basically stuffing up. You needed to store NiMH with a base charge to get the best life, just like a Lipo. Thing is these days its way easier to do it with Lipos as we have all the tools in one device and actually there is no guesswork involved anymore. 

Juls

 

 

 

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It's worth checking that there's no short somewhere in your electronics.  If the ESC has failed and shorted internally, plugging the battery in would cause the pack to get warm and melt like that.  It's probably not unheard of for a freshly-charged pack to get hot and melt after charging stops, but I would be looking for a short first.

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On 1/1/2020 at 5:27 PM, TurnipJF said:

Indeed - back in the days when NiCads were common and NiMH was new, people told the same sort of scary stories about them as people tell of LiPos today.

I have seen NiCads fail in a fairly spectacular fashion, but almost always because of inexperienced drivers unintentionally shorting them out. That said, I also once saw a very experienced racer accidentally drop a spanner across the terminals of a 12v car battery he was using to charge his race packs, with hugely spectacular results.

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Had the battery on my 2009 MacBook Pro explode while I was using it...

The battery had been dicky for a while, was getting "service battery" in the info box, and it was only good for about 60 minutes use off-power. In retrospect, the touchpad was also not working correctly (not "clicking") due to the battery swelling.

So I was typing away when I heard and felt it go "bang!" under my wrists. Thought it was my imagination for a few minutes then something stirred in my memory about the stuck touchpad so I turned the laptop off and pulled the battery. 

It'd split the case and bowed about a centimeter :lol:

I've seen YouTube of Li batteries failing and was kind of glad mine didn't :blink:

Got a new battery off Amazon and the laptop is still going strong. Well, apart from the things I damaged opening the case for the nth time...

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Yep I recently had to operate on a MacBook Air with a pregnant battery too. Trackpad surface was pushed up above the surrounding case & the spacebar stopped registering too. When the bottom casescrews were released, it popped open 10mm :) 

MBA is one giant battery inside ... only 1 of the 4 pouch cells had bloated. Wasn't that wornout, system stats said only 140ish cycles. 

Luckily the aluminium was elastic enough to snap back into their original shape & it closed up fine with new battery. Keyboard & trackpad fixed themselves too.

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3 hours ago, WillyChang said:

Yep I recently had to operate on a MacBook Air with a pregnant battery too. Trackpad surface was pushed up above the surrounding case & the spacebar stopped registering too. When the bottom casescrews were released, it popped open 10mm :) 

MBA is one giant battery inside ... only 1 of the 4 pouch cells had bloated. Wasn't that wornout, system stats said only 140ish cycles. 

Luckily the aluminium was elastic enough to snap back into their original shape & it closed up fine with new battery. Keyboard & trackpad fixed themselves too.

Funny, in my experience (Ex-Apple CRST, current ChromeOS sysadmin) it's usually the ones with the least cycles on them that go poof. The work horses with 1000+ cycles just sorta lose capacity and go out like a candle in the night, but the ones with maybe 12 cycles and a user that lugs around a charger everywhere (s)he goes are the ones that lose a battery first. It's almost as if.... batteries like to be used! *Gasp!*

With that said, my battery as of right now:

Schermafbeelding-2020-01-04-om-11-18-24. 

 I still regularly get 5+ hours of usage from the battery in this 7 year old Macbook Pro. I'm happy. 

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Not bad, not below 80% yet.

yeah I inherited that MBA some yrs back, probably had around 130 cycles then. It's the very first MBA I think... no backlit kbd, Bluetooth is too antiquated to do anything. Usually sits around gathering dust, every so often I'd plug it in & it'll boot up. Only recently I tried updating OSX and that was a marathon :) when I noticed this one bulged so much its little rubber feet weren't even touching the desk. 

 

Yeah finally getting into rebatt'ing machines with fixed internal batteries. Next got a micro Vaio that's started having batt life issues too (runs an hr 80->60% then dumps shortly after), it'll interesting trying to crack open its slim carbon fibre casing... I don't see any obvious screw holes. :( 

Everything before I'd just buy the new battery and clip it on. 

 

 

Next issue is... nobody wants to collect spent lipo cells! 

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Through a long and convoluted process, I just got a new MBA for some work done, and it's currently on its very first charge :lol: an hour left to go, even. "Cycle charge: 2"

In some ways, the 2009 MBP is a better machine :o Certainly was very good bang for bucks -- got it for $100 from a buddy. Spent maybe $400 on new spares; it's been rocking 16Gb RAM, new speakers, new battery, 850Gb SSD for a few years now...

But it's nice to have everything working now, between my other more modern devices -- got forced into updating my phone too. First English keyboard I've had in years, bit of a struggle to remember where the keys are!

Catalina is a crapfest though, especially Safari. Hoping the older apps I like to use on the MBP still work :angry:

2 hours ago, WillyChang said:

Next issue is... nobody wants to collect spent lipo cells! 

I put my old battery in the burnable trash ... I like to give the poor workers a bit of a thrill sometimes.

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From the LiPo fire video online, the damage done here still seems minimal. At least the end result is not the whole car gone into flame ... 

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