[Elecraft] KX1 LiPo Batteries

[Bob Follett]

To further Phil's comments about substituting LiPo's for internal KX1 use, I
studied the specs found at FMA Direct on their various Kokam LiPo offerings.

My conclusion is that the 1200mAh High Discharge (5C) cells would barely fit
assuming you removed the existing battery holders and attendent bulk.  One
battery is 51.5mm X 37.5mm X 5.6mm high.  Stacking 3 batteries in series
would make a package that should be about the same thickness as a std. AA
plus the holder thickness....

Two stacks, in parallel, would yield 2400mAh of steady voltage with a very
large current tolerance.  The plus, of course, is that you now have 11V
instead of 9V -- A substantial power out difference in Wayne's scheme of
things. (Just make sure the 'Batt Lo" setting is sightly above 9V).

Considering the life of the batteries -- up to 300 charges, the price is
much better than one-use lithiums -- The downside, of course, is that most
of us don't own a LiPo battery charger.  There are several on the market,
from small current capacity up to Astroflight's 'biggie' that will handle up
to 9 cells in series with adjustable current from 50ma to 8 Amps!  If you
ask, you can't afford it :-)  $130us....  As an aside, if you need a new
charger/discharger anyway, there are a few multipurpose chargers now
available that provide delta voltage charge along with regulated current
discharge that support everything you could own.  That is, NiCad, NiMH,
LiPo, and Lead acid/SLA.  They don't have quite the current capacity as the
Astroflight specialty, but are much easier to use than anything you could
currently own if it's older than a few years.... Fully automatic on
charging, including sensing the number of cells in series....  You still
have to be very careful running discharge cycles on any charger of
course.... as you set the current and the shutdown voltage.  I have
personally used the Greatplanes charger -- very nice, but still over $100!
MRC now offers one that will handle dual outputs up to 4.5amps assuming you
have a large, 12V power supply.

I know some of you are thinking -- "great for the star-wars types out
there", but think about it:  The price of LiPo technology is falling, and
they have up to  5X power density over NiCad, lower weight, and much, much
better current handling than NiMH.  I predict NiMH will disappear from the
the horizon in the next few years -- you heard it here first....

-- Bob, AB7ST