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Old Nov 20, 2014, 11:34 PM
Heli's rule!
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Midvale, Utah, USA
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Quote:
Originally Posted by hardrive View Post
Just when I had the courage to plunged in to lipo I end up reading here
Crap now im kind of worried again
Don't be worried. Just a few commons sense rules will keep you safe. Always be in the room with them when charging, and glance at them every few min, and if you crash one, leave it outside for a few hours. There are few to no fires without cause... The most common is wrong charger setting, next is crash damage.
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Old Nov 21, 2014, 01:26 PM
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So most of the mishaps of lipo are from human errors?
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Old Nov 21, 2014, 01:43 PM
Space Coast USA
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Why batteries fail? Some % is due to manufacturing defects.
See HERE and HERE.
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Old Nov 21, 2014, 03:37 PM
Heli's rule!
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Midvale, Utah, USA
Joined Mar 2005
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yes the vast majority are human error. After wrong charger settings, physical damage accounts for most of the rest. lipos are dangerous after a crash, and even dropping them can cause an internal short, which can result in anything from a dead cell to a fire.
Most "unexplained" lipo fires (not wrong charger settings and no damage (that you know of)) are on new batteries, either before or during the first charge.... Likely they were dropped a few too many times during shipping, or left in a hot truck too long....
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Old Nov 21, 2014, 06:09 PM
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My mistake was to not balance charge, and in parallel
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Old Nov 21, 2014, 08:44 PM
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United States, WA, Woodinville
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Quote:
Originally Posted by dacaur View Post
yes the vast majority are human error. After wrong charger settings, physical damage accounts for most of the rest. lipos are dangerous after a crash, and even dropping them can cause an internal short, which can result in anything from a dead cell to a fire.
Most "unexplained" lipo fires (not wrong charger settings and no damage (that you know of)) are on new batteries, either before or during the first charge.... Likely they were dropped a few too many times during shipping, or left in a hot truck too long....
Or just manufactured improperly. If you take apart a dead LiPo and look at the internal construction you can see it wouldn't take much of a defect or stray flake of metal to punch through the dielectric and cause a short.
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Old Nov 22, 2014, 12:12 AM
Boffin
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Victoria, BC, Canada
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Quote:
Originally Posted by dacaur View Post
yes the vast majority are human error.
There are no statistics on failure rates of hobby lipos so that statement is nothing more than a personal belief. Statistics are meaningless if one of your batteries fails and burns down your house -- even though you did nothing wrong.
The important thing is that any battery you have may fail and you should treat it accordingly.
Putting a smoke alarm in your charging/storage container can be the earliest warning.
A temperature probe will stop the charging but won't stop a thermal runaway. A temperature probe with an alarm is the best of both worlds.

Rick.
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Old Nov 22, 2014, 12:21 AM
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And so you know that's not just my personal opinion.
"Exact failure rates of lithium-ion cells and battery packs in the field are not published. Due to confidentiality
requirements, the CPSC publishes very limited information regarding the circumstances of failures that have
triggered lithium-ion cell recall actions. Failure rates are not published, nor are specific details regarding
individual battery failures. Occasionally battery failures are reported in news stories. However, these reports
generally do not contain details sufficient to make a determination regarding the cause of failure, or the rate of
failure or the products described. In addition, some incidents reported in the news have later been found to
have been the result of user abuse rather than a defect in the battery. OEM investigations of failed product are
generally kept confidential. Therefore, it is very difficult to determine the rate of failure of cells in the field."

http://www.prba.org/wp-content/uploa...PA_-_20111.pdf
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Old Nov 22, 2014, 08:23 AM
Space Coast USA
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[QUOTE=dacaur;30000116]Don't be worried. Just a few commons sense rules will keep you safe. Always be in the room with them when charging, and glance at them every few min, and if you crash one, leave it outside for a few hours. There are few to no fires without cause... The most common is wrong charger setting, next is crash damage.

"The most common is wrong charger setting,"
That might have been true 10 years ago but todays chargers are very good at not starting a charge if the settings do not match the battery attached to the charger. Charging at too high a charge rate would be the exception.
What type of wrong charger settings were you thinking about?

BTW, in regards to "Always be in the room with them when charging, and glance at them every few min", that's about the surest way to prevent a lipo fire. Disconnect at the first sign of any swelling.
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Old Nov 22, 2014, 04:32 PM
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Quote:
Originally Posted by _nicos View Post
My mistake was to not balance charge, and in parallel
What happened?
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Old Nov 22, 2014, 04:40 PM
Heli's rule!
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yea wrong charger settings are less common than they once were, but I am willing to bet there are still a ton of 10 year old chargers out there charging away, one of mine is around 7 years old... also human error includes things like parallel charging in such a way that it allows the charger to pick the wrong settings, even new chargers can be fooled when you parallel charge though the charge leads, or even through the balance leads with a bad cell in the mix....

As for batteries burning your house down when you did nothing wrong and the pack was not damaged, that's not statistically relevant based on all the failure reports recorded in this very forum, supposedly there have been one or two, but who knows what really happened? show me more than a the few there have been reported in a 10+ year period here and I might start to worry.... most likely a bad cell will reveal itself during charge or discharge, not at 3am when everyone is asleep.

And before we get the typical "but not everyone who uses lipos is on this forum", that's also not relevant, because, #1, statistics rarely take into account 100% of the population, they follow a select bunch covering a diverse cross section of the population, such as we have here on RC groups, and #2, we actually get MORE reports than the section of the aforementioned population should account for because there are plenty of reports involving someone's flying buddy who is no on RCgroups...

Im not trying to downplay that there are risks, just trying to bring perspective. Following a couple simple rules would eliminate nearly all lipo fires in homes.
#1, be in the room when charging, and get eyes on the battery every few min. Discounting physical damage, there is ALWAYS plenty of warning before a lipo goes up in flames. Lipos don't combust, they "Vent, with flames", and in order to vent, they have to first burst their foil pouch, which takes time, You will see it swelling long before it becomes a problem.
#2, if a lipo has been physicaly damaged, anything from a crash to a drop, don't bring it back in your house until its been through a few charge discharge cycles.

If you insist on charging unattended, or in a "lipo bunker" where you cannot see the battery, Do it outside away from flammable stuff, problem solved.
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Old Nov 24, 2014, 10:27 AM
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how was the EDF motor?
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Old Nov 24, 2014, 04:14 PM
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Australia, ACT, Canberra
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Quote:
Originally Posted by UlteriorModem View Post
Quote:
Originally Posted by _nicos
My mistake was to not balance charge, and in parallel
What happened?
I was parallel charging (no balancing either) 6x 2s batteries, which were in good shape with correct charger settings. Then thermal runaway started, which triggered other cells/packs to ignite in a chain reaction... it was pretty scary, lost the batteries, charging gear, melted nearby stuff eg. radio and had black soot damage inside from the smoke.

Good thing I noticed and was able to de-energise gear and eject the firey mess safely outside to the driveway. It almost put me off using lipos at all, and life is a bit short to spend my time standing over charing batteries, but I'm happy with the risks given my current regime:

Quote:
Originally Posted by _nicos View Post
Following my scary fire experience (and subsequent fervoured research), this is now my charging method in order of priority...

MUST:
  1. Balance charge each pack separately every time (No parallel charging anymore! I now have an independent 4-channel charger). Your charger should automatically stop if a cell voltage gets out of whack (which seems to be the main issue causing fires in 'undamaged' packs).

  2. Always be within eyeshot and earshot during and >10mins after charging.
  3. Have a fire contingency plan (ie. what to do when there is a fire, eg. you must be able to easily isolate system from mains power, perhaps have some big scissors to cut cables before ejecting the firey mass, and have a good lipo ejection method to a place nearby to then let things burn safely remember that there could be a lot of smoke, heat and flame around).

SHOULD (I do):
  1. Don't charge batteries within 10mins of use.
  2. Don't use batteries within 10mins of charging.
  3. Have a charging bunker (paint-stripped cash box with heat-isolated handle), sitting on fireproof material, located close to an exit.
  4. Have a bucket of sand ready (works much better on lipos than most fire extinguishers on the market, but likely won't stop the exothermic lipo runaway reaction which is already underway).
  5. Have a smoke detector as part of your charging bunker (your house may not burn down if you catch the fire, but that sooty smoke sure does do some damage to the re-sale value of a house!)
  6. Charge at slowish rates where possible/convenient.
  7. Have some fire-resistant containers for storing and travelling with lipos.
  8. Store lipos in a sensible place (eg. not in your car on a hot day)
  9. Properly discharge swollen, old or damaged lipos before disposing... but you already knew that.
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