Charging concerns/questions with NMP Lithium Ion batteries

[Adam Glatt]

Rcmaster199 at aol.com wrote:

> I have tried to stay out of most of this discussion but something is 
> gnawing at me. I have asked this question before, but don't believe I 
> have gotten an answer. Maybe no one on the list knows
>
> Since Li-ion and Li-poly technology is widely used in cameras and cell 
> phones, and these are recharged all  the time (in the home and without 
> special power supplies like separate 12 volt sources and such) with 
> extremely safe circuitry, why is it that the folks who offer these 
> same battery types to us, use charging circuitry that isn't so bullet 
> proof???
>
> Certainly currents and voltages are different in some applications, 
> but the chemistry is the same. And Lithium metal will burn with 
> ferocious intensity whether 20 grams are exposed or 10 times that 
> amount. The heat is enough to burn your plane or house either way.
>
> Matt K

The way I read it from rcgroups, the protection circuitry used in non-RC 
li-po batteries is limited in output current.  We see this with 
Duralites, which use two cables because the charging protection 
circuitry can't handle the current the battery is capable of putting 
out, as I understand it.
http://www.rcgroups.com/forums/showpost.php?p=2147352&postcount=418
It looks like that manufacturer is ready to release a two-wire 
charging-protection-only (over voltage and current protected) for the 
large batteries that electric pattern planes will be using, and a 
single-wire circuitry that protects during charge and discharge (likely 
cuts it off at 3v/cell, and maybe protects from too high current - 
speculation) on smaller batteries we would use as receiver packs in 
nitro planes.  This is exactly what we need to need to have a completely 
simple, idiot and failure proof li-po battery as a receiver battery.  
Li-pos are damaged, and subsequently can ignite or blow, if they see too 
much current, too low voltage, or too high voltage.  This leaves only 
physical (crash) damage that can cause these batteries to blow or burn.
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