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Date: Wed, 19 Jan 2011 19:32:23 -0500
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Subject: Re: Lithium Batteries
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Concerning home-packaged lithium batteries, Hamid wrote:

<<You can not just take a bunch of cells and put them in series/parallel=
 to make a pack and put it in your airplane to replace the lead acid batte=
ry. You need to charge balance the pack and pay attention to the charging=
 voltage and over-charge/over-discharge. Better to pay some reliable compa=
ny to do the integration and testing than do it yourself and risk an in-fl=
ight fire. The $100 you saved by doing it yourself will feel the most expe=
nsive $100 in your wallet as you are dealing with an in-flight fire.>>

I have to agree with Hamid here.  I spent a very long two years as a batte=
ry engineer in the mid 1990's and learned a bunch of stuff.  Among these=
 was the requirement to balance the individual cells during the recharging=
 process (which happens at the beginning of every flight, right after you=
 start the engine).  Screwing it up results in overcharging some cells and=
 undercharging others.  Lead acid is rather robust in this regard, as it=
 turns out, but lithium is another story.  In fact, the R/C model guys cha=
rge each cell individually and discharge them in series.  (They also do th=
is in fireproof bags, but that's the more twitchy Li-Po chemistry).  I thi=
nk it's the overcharging of an individual cell that results in fires, but=
 excessively rapid discharge could also do it, I suppose.  (Maybe due to=
 a short in the packaging???)

WARNING! I KNOW NOTHING ABOUT MODERN BATTERIES!  But I do know that lithiu=
m batteries can catch fire and lead acid batteries don't.  So I'd be reluc=
tant to take a chance here -- let the professional research lab do it. =20

I also understand that this technological reticence is why I installed a=
 1940's Lycoming in my 360.  Modern stuff is generally better but we each=
 draw the safety / efficiency / experimental line in different places, I=
 suppose.

- Rob Wolf


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<font color=3D'black' size=3D'2' face=3D'arial'>
<div>Concerning home-packaged lithium batteries, Hamid wrote:</div>


<div>&nbsp;</div>


<div>&lt;&lt;<FONT face=3D"Courier New">You can not just take a bunch of=
 cells and put them in series/parallel to make a pack and put it in your=
 airplane to replace the lead acid battery. You need to charge balance the=
 pack and pay attention to the charging voltage and over-charge/over-disch=
arge. Better to pay some reliable company to do the integration and testin=
g than do it yourself and risk an in-flight fire. The $100 you saved by do=
ing it yourself will feel the most expensive $100 in your wallet as you ar=
e dealing with an in-flight fire.</FONT>&gt;&gt;</div>


<div>&nbsp;</div>


<div>I have to agree with Hamid here.&nbsp; I spent a very long two years=
 as a battery engineer in the mid 1990's and learned a bunch of stuff.&nbs=
p; Among these was the requirement to balance the individual cells during=
 the recharging process (which happens at the beginning of every flight,=
 right after you start the engine).&nbsp; Screwing it up results in overch=
arging some cells and undercharging others.&nbsp; Lead acid is rather robu=
st in this regard, as it turns out, but lithium is another story.&nbsp; In=
 fact, the R/C model guys charge each cell individually and discharge them=
 in series.&nbsp; (They also do this in fireproof bags, but that's the mor=
e twitchy Li-Po chemistry).&nbsp; I think it's the overcharging of an indi=
vidual cell that results in fires, but excessively rapid discharge could=
 also do it, I suppose.&nbsp; (Maybe due to a short in the packaging???)</=
div>


<div>&nbsp;</div>


<div>WARNING! I KNOW NOTHING ABOUT MODERN BATTERIES!&nbsp; But I do know=
 that lithium batteries can catch fire and lead acid batteries don't.&nbsp=
; So I'd be reluctant to take a chance here -- let the professional resear=
ch lab do it.&nbsp;&nbsp;</div>


<div>&nbsp;</div>


<div>I also&nbsp;understand that this technological reticence is why I ins=
talled a 1940's Lycoming in my 360.&nbsp; Modern stuff is generally better=
 but we each draw the safety / efficiency / experimental line in different=
 places, I suppose.</div>


<div>&nbsp;</div>


<div>- Rob Wolf<br>
<br>
</div>


<div style=3D"CLEAR: both"></div>
</font>

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