[NSRCA-discussion] "Sick" Lipo Packs

[Ron Van Putte]

It's ALIVE!

Ron VP

On Dec 4, 2010, at 6:26 PM, Robert Campbell wrote:

> Ron,
>
> We're going to start calling you Dr. Frankenstine.
>
>
> Rob
>
>
> ----- Original Message ----- From: "Ron Van Putte" <vanputte at cox.net>
> To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
> Sent: Saturday, December 04, 2010 5:45 PM
> Subject: [NSRCA-discussion] "Sick" Lipo Packs
>
>
>> Those of you who use lithium polymer battery packs to power their   
>> competition airplanes are familiar with "puffed" packs.  I  
>> recently  had four elderly 5S packs "puff".  We all know that's  
>> not good, but  what I'd like to know is what's actually happening.
>> I know it's probably not wise for consumers to take lithium  
>> polymer  packs apart, but that's exactly what I did with four  
>> packs.  I  discovered that in three of the "puffed" packs, only a  
>> single cell  was "puffed".  In the last pack, there were two  
>> "puffed cells.  I did  a little arithmetic and quickly discovered  
>> that I could make three  "unpuffed" packs from the good cells I  
>> had.  So, I unsoldered the  "puffed" cells from the four packs and  
>> cannibalized one pack to make  three 5S packs from what I had  
>> left.  This process is obviously not for  the timid or the  
>> careless.  I was careful and had no mishaps.   However, I would  
>> suggest that anyone who says "Oops" a lot should not  attempt  
>> doing this.
>> The three 5S packs I have left are "rock solid".  Experienced   
>> electric-pilots will know just what I mean.
>> I have flown these packs and they seem to perform just as they did  
>> in  their "youth".
>> My questions are:  Why do lithium polymer cells "puff"?  What is  
>> the  likely future of my recovered 5S packs?
>> Ron VP
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>>
>
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