Makita pack exploded - was connected incorrectly

[crashalot]

I thought these were safer ? I found out that while they take lots of abuse ( I use this for my radio controlled lawnmower), they do explode and catch fire.

I mistakenly connected ground and power reversed to Sabretooth 2x32 and it short circuited the pack for about 3 seconds, it started smoking and I disconnected the pack. The pack continued to smoke/burn and then couple of minutes later exploded with loud noise like a firecracker.

Good news is, I removed damaged cells, cleaned the pack as good as I could, soldered two good cells and the pack is working just like before.

 

[kfong]

I don't think you would of had any good news if it was RC lipos. All batteries require some caution, some more than others.

 

[alexis57]

I thought these were safer ? I found out that while they take lots of abuse ( I use this for my radio controlled lawnmower), they do explode and catch fire.

I mistakenly connected ground and power reversed to Sabretooth 2x32 and it short circuited the pack for about 3 seconds, it started smoking and I disconnected the pack. The pack continued to smoke/burn and then couple of minutes later exploded with loud noise like a firecracker.

Good news is, I removed damaged cells, cleaned the pack as good as I could, soldered two good cells and the pack is working just like before.

That's why. It's safe as soon as people use correctly and safely. But I see the connector, how could you connected ground and power reversed ?!

 

[amberwolf]

You need to edit your first post so the Subject reads

"I connected my Makita pack backwards, left it that way until it started smoking, and then it exploded"

because that kind of abuse is the kind of thing that blows up or burns most batteries.

 

[mistercrash]

Totally speculating here, it looks like your cells are stuck together without spacers. I'm thinking that when you made the wrong connection, the cells heated very quickly and the shrinks started to melt. The cells shorted between themselves at the cans and bus bars which is why it continued shorting even after you disconnected.

 

[speedmd]

You need to edit your first post so the Subject reads

"I connected my Makita pack backwards, left it that way until it started smoking, and then it exploded"

because that kind of abuse is the kind of thing that blows up or burns most batteries.

LOL, yes one can also write a warning label; "Improper connection may result in meltdown, fire or death". It looks to have popped apart when the other obvious warnings (smoke/ sparks /arcing/ welding of leads) were ignored just to get your attention. Looks to have worked as designed. You can make stuff idiot proof, but not often, "dam idiot proof". 3 seconds is a bit of a long time to ignore things like this. Something is going to get red hot somewhere for certain.

 

[spinningmagnets]

thanks for posting this. there is a natural desire to avoid embarrassment, but that would mean incidents like this would go un-noticed, and...we couldn't learn from them.

 

[docnjoj]

Is that connector a Deans style one. They are supposed to be polarized, with the blades at 90 degrees from each other?
otherDoc

 

[crashalot]

Hey Guys,

My goal for posting this was to remind myself and others that dbl check your connections. Also, do your experiments outside and charge batteries in fire proof box ( I use clay flower pot)/ cinder block.

To answer few questions, I used the Makita pack spacers (plastic) and yes deans are polarized but the connections were made incorrectly at screw terminals on brushed speed controller side. It was late at night and I was high from solder smoke

I use RC lipo for RC Airplanes for long time now without any incidents so I was overconfident and relaxed the precautions and that's when it happened, so never let your guard down with high power batteries.

thx
crash.

 

[999zip999]

I was buying used makita battery packs 35 or 350 cells. He only had 22 then a few days later found the rest of the order. I had carefully open up and on a few fire shot out of the top of the cell on four different packs. Some packs arrived at 8 volts not 12volt as advertised. I think these returned defected packs may have been dropped in water or something. Getting and using defected cells can be a time bomb. I believe the packs where able to be charged to 12v and stuck in the box. With some of the rejects in a pile open, but not taken apart or charged. Caught on fire in the garage and burned half of my garage. Someone getting Free packs figurine a way to force a charge of 12volt so to stick in a box for profit. Remember these are defected returned packs. PROFIT equals FIRE. As he just happen to find 12 more 12v good packs ??? For Profit.

 

[Hillhater]

I thought these were safer ? ....
...I found out that while they take lots of abuse , they do explode and catch fire.
e.

Excellent photo and a timely warning to anyone who thought 18650 were a guarantee against lithium fire or explosion !

 

[Punx0r]

It sounds like there was some sort of runaway thermal effect started by the brief short-circuit?

 

[alexis57]

It sounds like there was some sort of runaway thermal effect started by the brief short-circuit?

Brief ? mmmh 3sec, when you know the shortcut current of 18650 is at least 100-150A. You can calculate for the whole pack... The metal inside the battery is really thin...
Like for everything, never shortcut ...

 

[Alan B]

Thanks for sharing your experience here. It is good to be reminded of how easily a problem can occur with high energy batteries.

A few things I try to remember:

1) Don't work on wiring when tired. It requires good attention and careful checking.

2) Use safe polarized connectors and double check all screw terminal wiring before plugging in. Don't change the screw terminal wiring often, only plugs or switches are used for frequent events such as charging.

3) Include a circuit breaker or fuse very close to the power source.

It looks like the original short caused heating inside the pack and subsequent internal shorting in the pack, if there had been a fuse or circuit breaker the initial event would have been shortened to a fraction of a second and the internal failure in the pack probably prevented.

Thanks again for reminding us what can happen.