Explosion! Fire!

[vertman]

Did you balance charge your packs?
I don't think 4mm bullets or traxxas connectors caused your problem. Likely just a parts failure.
How old were the packs? Were they puffy at all before you ran?

packs had maybe 20-30 runs in them - always balance charged and not puffy

[vertman]

I guess I was under the false impression that the LVC would kick in and protect the packs from draining too low.

so far the opinions appear to be

1) cheap packs
2) capacitor in ESC blew
3) bad connectors (4mm bullets and traxxas) too much heat and impedance
4) too long run time
5) packs shouldn't explode if they were discharged
6) 4000 mah too small

[Doby]

LVC is a bit of a joke and should not be used as the be all and end all to keeping LiPos safe.

Remaining capacity is whats important. Timing runs is the main way to keep the batteries happy

Where in Ontario are you?

[Make-a-Wake]

I guess I was under the false impression that the LVC would kick in and protect the packs from draining too low.

so far the opinions appear to be

1) cheap packs - POSSIBLY
2) capacitor in ESC blew - DONT THINK SO
3) bad connectors (4mm bullets and traxxas) too much heat and impedance - YES
4) too long run time YES
5) packs shouldn't explode if they were discharged - ??
6) 4000 mah too small - YES, IN MAH AND IN C RATING(30C)

[Fella1340]

I can understand all the prop, voltage and low mah batteries being contributing factors to the explosion but for two batteries to go at the same time there must have been some kind of epic dead short. I would be curious to see the inside of the esc and where the damage occured. The packs aren't that poor of quality. Lots of people run them without issue and the op says they were still balancing nicely and never puffed. The motor didn't have any real bad burned out spots, i wonder if it's still a runner or not. If it is, the esc may have simply dead shorter across one or all the phases. That would make some crazy stuff happen. Just my guess, it would be good to hear back on the motor.

[Peter A]

Is it possible that being over discharged the batteries created an explosive gas that was ignited by a short? It would explain the result.

[kevinpratt823]

I don't think it's that strange to see both packs go together when in series. If it was a single 6s we probably wouldn't be thinking nearly as much of it, and essentially that is what it is, just separated by a bit of space. It may not have been so much an "explosion", as just so much pressure built up in the puffing cells that when the foil finally let go it was enough to blow the hatch off, then the exposure to the elements just continued the process of destruction......just another theory though.

[Brushless55]

interesting

[Brushless55]

I guess I was under the false impression that the LVC would kick in and protect the packs from draining too low.

so far the opinions appear to be

1) cheap packs
2) capacitor in ESC blew
3) bad connectors (4mm bullets and traxxas) too much heat and impedance
4) too long run time
5) packs shouldn't explode if they were discharged
6) 4000 mah too small

When we race in NAMBA20 our races last less than 2min and we run 5000mah and bigger packs, some races last just over 1min
and we come back with 20-35% left in our packs
for what its worth....

[kevinpratt823]

FWIW, people run lipos down to 3.2v in cars all the time with few problems. I have set my cutoffs up to 3.3-3.4v in my cars over the past few years after I learned my lesson with boats, but it obviously has more to do with the kind of constant draw we pull from them when they get lower. The same 5000 mah that gives me probably 15 minutes runtime in my 1/10 2wd buggy has no problem running right down to lvc of 3.2 v because the draw is nowhere near as high or continuous at the end of the charge, same pack in a boat, pulling a steady 100+ amps, will likely puff if I continue to run it down past 3.6v