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Old Apr 26, 2004, 01:05 PM
Registered User
FREDERICK, MD
Joined Jul 2003
197 Posts
Help!
My first Lipo pack death!

I finally killed my first Lipo pack (only had a half dozen or so flights on it ). I'm not quite sure what happened, but this is the story......My son was flying my Dandy Sport with a Kokam 1500 2s pack when he hit a lightpole head-on during a landing approach, totally demolishing the nose of the plane. I carefully examined the pack for damage, but could find no signs. I put the pack on my Scott Henion designed DIY charger, turned it on, and read the normal as designed 950mA current on my always connected ammeter. The charge current dropped down to 650mA after about 45 minutes which seemed normal, so I decided to remove that pack, with the intent of finshing one pack, and at least starting the other,and fully charge my other pack that I also used that evening. After the charge LED went off on that pack (at 10mA), I reconnected the first pack to finish it off. No problems so far. Two days later, I went to top off the packs to fly that evening (they usually only draw about 15mA at this point), but when I connected the "crashed" pack, it briefly drew an amp, then settled in at 950mA. Now I was confused;did I actually charge this pack two days ago or not?? I decided to allow it to charge, maybe I did forget! An hour and a half later, I went back and was shocked to see 950mA still on the ammeter. When I looked at the pack, I saw that it had inflated. I carefully removed it from the charger, took it outside, and measured 0 Volts at the terminals. Stone dead! After flying my remaining pack, I re-charged it while constantly monitoring both the current and voltage; both dead on. My assumption is that the battery was internally damaged upon impact; no holes or dentsto be seen. The pack had not been run down either before the crash, plenty of charge should have been left. I guess the lesson here is to suspect a problem in a hard crash; if none occurrs, feel lucky!
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Old Apr 26, 2004, 02:59 PM
A Clinger
rclark's Avatar
Butte, MT
Joined Sep 2001
7,073 Posts
Hmmm, so even if a pack doesn't seem externally damaged after a crash, you still need to be very careful with it, as internally it could very well be damaged . Something to keep in mind .
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Old Apr 26, 2004, 03:58 PM
Aerobatic Extremist
SharksTooth's Avatar
United States of America For Which We Stand!
Joined Jan 2004
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It's possible that the pack could'v been damaged by the sudden g forces without damaging the outside...kinda like an individual in an automobile accident that has had 'cavitation' injuries to the brain from the sudden jolt. The brain will be injured when it literally collides with the inside of the scull, but there is no external injury to the scull. That's just a theory though...it would have to backed up with some sort of evidence to prove it. The odds are it was damaged in the crash though, becasue it was working fine, but after the crash it failed.
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Old Apr 28, 2004, 02:04 PM
Eat, sleep and FLY
BigDave's Avatar
Conway, Arkansas
Joined Dec 2002
436 Posts
Interesting.

My Asto 109 Li charger insructions state very clearly that a Li pack is not to be reconnected to the charger and "topped off" after it has been charged.

Hmmmm. Astro knows something about this little issue don't they.

By the way, be glad the pack did not rupture. What happens after that is not pretty. I know, I have the shirt to prove it.

BigDave
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Old Apr 28, 2004, 05:25 PM
The Airplane Gremlin
Seared Ice's Avatar
United States, PA, Pittsburgh
Joined Jun 2003
388 Posts
lets see a picture of that shirt of yours!!!

I can't see what what would be wrong with topping off a lipo...unless it's been 100% charged, in which case the charger (if automatic) might assume its a discharged 3-cell pack (if you're using a 2-cell pack)...

charging a 1000mah pack at 1A for 1 Hour only charges to aprox. 90%...two hours for true 100% charge. Hooking up a pack that's at that 90% mark should top off fine...the charger will recognize that its in the new charge phase that slowly drops off to almost 0mah charge rate from whatever you are charging at.

strange occurance eabiker...
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Old Apr 29, 2004, 07:56 AM
Eat, sleep and FLY
BigDave's Avatar
Conway, Arkansas
Joined Dec 2002
436 Posts
Quote:
Originally Posted by Seared Ice
lets see a picture of that shirt of yours!!!

I can't see what what would be wrong with topping off a lipo...unless it's been 100% charged, in which case the charger (if automatic) might assume its a discharged 3-cell pack (if you're using a 2-cell pack)...

strange occurance eabiker...
Not sure why Astro mentions not "topping off" packs. Just an interesting statement in their manual. I thought it might apply to this posting.

I am going to try to attach the photo of my burned out pack to this post.

It was an ugly scene. (By the way, it was NOT the batteries fault, I set the wrong jumper on the charger for a two cell pack, Duhhhh).
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Old Apr 29, 2004, 12:10 PM
Registered User
Arnold , Maryland, United States
Joined Nov 2002
897 Posts
Biker, thanks for the input. I have no doubt that a lipo cell CAN be internally damaged in a crash, and yet show no external marks.
The only way to tell, is to monitor your cells for changes in performance, after a crash.

I had a cell puff up a little for no obvious reason. I had about 10 cycles on it with no problems. It was not abused at all. Honest. but after it puffed up, it would not charge, or discharge, at the same rate as its mates. I can't use it in any of the packs made up from its group that I bought at the same time, because something has changed inside of it.

I sometimes wonder if an irregular cell in an un-noticed pack might be causing some of the incidents we read about ?
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Old Apr 29, 2004, 01:26 PM
Aerobatic Extremist
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United States of America For Which We Stand!
Joined Jan 2004
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It is doing exactly that, that is why people who don't watch their chargers have no buisness running these packs. If you are not going to monitor these packs while they are charging like the directions tell you, then you'll get exactly what you deserve when you get something burned up! It's that simple. Just about everything in this hobby is for people who can follow directions...if you can't do that, or are incapable of doing that please don't use these batteries! The people that don't follow directions are the cause of every single one f the problems associated with them...including the latest AMA scare tactic. Wanna pay GOLD for these batteries? Keep using them without following directions, and you'll do just that, and you may need to get a waiver to do it even then. If you're gonna give the AMA a good reason to cause the rest of us to have to get waivers to use these things, then do us all a favor and DON'T use them at all!
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