[Elecraft] KX1 on AAAs or Lithium Polymer?

[W0rw at aol.com]

i am still using NiCad's...in my KX1.
KX1 - 1/2AA NiCad Battery Modification...Rev. D.

Originally i had 6  'AA' NiCad batteries in the KX1 but i needed more power 
for pedestrian mobile operation.
i removed 4 of the 'AA' NiCad batteries and added 8 - 1/2'AA'-250's (short 
type AA) to boost the voltage to 14 VDC. That raises the output power to 3 Watts.
The operating time is about 3 hours on a full charge (depending on your code 
speed and number of "Q's)..
These batteries are available from Batteries Plus. 
(After these batteries age, they will have slightly lower terminal voltage, 
then you can add 2 additional 1/2 AA batteries; i started with 8 and now i am 
using 10 - 1/2 AA-250's and one full sized AA NiCad, still keeping the voltage 
at or below the KX1 maximum of 14V. So be sure to buy a few extra 1/2 AA's).
The 1/2 AA's have flat contacts so they need to have a little solder blob 
added to the + terminal so they will touch each other when in series in the 
battery holder.
These 1/2 AA 'short' batteries (250 mAH) are 7/8 inch long. (There is a lon
ger 1/2 'AA'  battery that is 1.2 inches long but it won't fit the battery 
holder).
Note: These NiCad batteries weigh 4 oz and the Enegerizer L91's also weigh 4 
oz. The capacity of the Energizer L91 non-rechargeable battery is 2.9 AH (at 
1.0V discharge voltage) and the Rechargeable NiCad gives 0.25 AH, thats only 
about 9% of the L91 capacity, but it's still very practical.
Pictures of the NiCad batteries are on the HFPack2 Yahoogroup web site.

See: http://photos.groups.yahoo.com/group/hfpack2

You will have to log in to see the pictures..

Look in the 'Photos' area, Page 2, and in the 'W0RW-Paul' folder.
ps: If you make any modification to your KX1 it will void the warranty...
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Here is a how you can charge the internal NiCad's without taking the KX1 
cover off.
(This is not suggested if you are going to use only the primary L91 Li 
batteries).

i installed a small 2.5 mm mono phone jack with a NC switch to the lower 
corner of the battery chassis. You have to drill hole in the chassis.
The jack goes right below the auxiliary DC connector J1.

Note: For the J1 power switching modification to work correctly this
jack must be isolated from the chassis. That requires a few mica or thin 
fiber washers and a small piece of tubing, or a flanged insulating washer.
This jack has a NC switch built into it so when you plug in the charging plug 
the internal NiCad batteries are disconnected from the radio and the charging 
voltage is applied to the batteries even if the radio is turned on.
The battery pack wiring connection changes are: black wire to the new 
charging jack ground pin, red wire to the jack center pin and the normally closed 
switch wire goes to the red wire of J5-1.

Now you can operate the KX1 from the auxiliary DC connector while 
simultaneously charging the internal NiCad batteries through the new charging jack.
 
You can also monitor the battery voltage through this connector or
when not charging the battery, The battery voltage can be displayed by 
pressing "RIT" and "Band" simultaneously, Twice.
The charger can be made from any wall transformer that puts out about 18VDC 
open circuit.
The charging current for the 1/2AA NiCad batteries should be set for 50 ma 
for 5  hours. You can add a switch to the charger and add an additional resistor 
to give 10ma for trickle charging. If you leave the KX1 NiCads on trickle 
charge it will always be ready to go.
You will need to insert an appropriate resistor in series with the 
transformer to limit the charging current. (If you change the number of batteries in the 
unit you will have to re-adjust the charging current).
---------
Here is the  KX1 Battery Switching Modification:
The original power distribution design "AND's" the internal battery and 
external battery sources together using 2 diodes.
If your external battery voltage goes below the internal battery 
voltage, the internal batteries will start draining.
i left my KX1 on for a few days and after i ran down the external battery and 
the internal batteries took over and became discharged.
These were the expensive Lithium "AA" Primary batteries (L91's).
i wanted to save the use of these Li batteries for special uses
like Pedestrian Mobiling: See the w0rw/pm KX1 report on the Adventure Radio 
Society web site at:
http://www.arsqrp.com/ars/pages/back_issues/2004_text/0204_text/W0RW.html

Here are the details of the DC J1 switching Modification:
The Elecraft DC Power connector has an unused (normally closed) switch.
This modification will use that switch so that when an external power source 
is connected the internal batteries will be disconnected, and conversely when 
the DC power plug is removed the internal batteries will be reconnected.
Open the unit on an ESD grounded work station.
Separate the battery compartment by pulling the battery connector (J1) out.
Cut the 2 traces that ground P1-2 "-" (getting scary now)...Top Side..
Now add an insulated jumper wire from P1-2  "-" to the side contact of J1 (J1 
is the power connector), The unused switch contact is soldered to an isolated 
pad just the left of the marking 'Z2'...
That's it....
Now you can protect those internal batteries.
One other thing that you can do is to set the LED Display Control to "INF" 
then the LED display will act as a pilot light.
72  de w0rw
Paul w0rw at aol.com



       Paul Signorelli   w0rw at aol.com
       P.O. Box 6069
       Colorado Springs, CO  80934