[Elecraft] Battery vs Ultracapacitor

[Jim Harris]

Kevin,

The first thing that jumps out at me is that
capacitors voltage drops at what I remember is a log
rate when discharging.  A capacitor would still have
something like half the coulombs of electrons left
inside when the voltage would have dropped too low for
the average rig to work correctly.  Especially newer
batteries hold their voltage much longer and then drop
nearly abruptly when discharged.   Maybe external
components could somehow control the voltage level. 
Then, that takes away from the simplicity.

Good Luck

Jim, AB0UK
K2/100  S/N 4787

<<<I've been reading the technical literature lately
and have been 
following 
an interesting development: ultracapacitors.  These
components are on 
the 
order of 5K to 20K Farads.  So I did a little
calculating.

1F = 1V * 1 Coulomb.
1 Coulomb = 1 Ampere Second
Thus 1F = 1V * 1 Amp Second.

5000 F / 12 V = 416 2/3 Amp Seconds.
416 2/3 Amp Seconds / 0.5 A = 833 seconds or 13.8
minutes.

If I have done this correctly you should be able to
run a QRP rig key 
down 
for approximately 14 minutes with a fully charged 5K
Farad 
ultracapacitor.  From what I have been reading these
are getting 
cheaper 
via economies of scale and from engineering
breakthroughs in dielectric 
and storage plate materials.  The storage plates are
activated charcoal 
plated on aluminum strips and wound into a can filled
with electrolyte.  
The electrolyte material, acetonitrile, is the rub
however.  If it 
burns 
cyanide gas is produced in dangerous quantities. 
Nanotube technology 
and 
more recent electrolyte chemisty advances are offering
even greater 
capacitance in smaller packages.

One day we may be running our rigs from
ultracapacitors instead of 
batteries.  They recharge extremely rapidly.  They
store charge for a 
long 
period of time.  And they discharge at rates that put
the best 
batteries 
to shame.  If you need high amperage devices (think
your 100 watt rig 
on 
transmit) these will fill the bill.

Since electrochemical devices are reaching their
limits this may be the 
next mobile power storage device.
    Kevin.  KD5ONS>>>>>


		
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