Looking for a good battery/charging system for K1

[Paul Kirley]

Before you reach a decision on battery packs, be sure to read Wayne's Tech Note at
http://www.elecraft.com/TechNotes/k1_battery_op.htm

Basically, the principle of impedance matching applies to both input and output of a rig.  A DC input mismatch results in waste heat, which is usually not a problem unless the DC is in limited supply, e.g., from a battery.

My particular K1 tends to drift a bit more when its regulators have to dissipate extra DC input voltage as heat.  The second regulators in the K1 put out about 6.3V, so an input of 14.3V results in twice as much wasted voltage in the regulators as an input of 10.3V, i.e., four times as much wasted heat to cause more drift.

For battery supplies, I prefer packs of 8 AA NiMH cells.  Alternatively, I use a variable AC supply which I set to 10V (plus an extra 0.3V that doesn't make it to the K1's voltmeter).  Either of these supplies matches my preferred 4W output setting fairly well, according to Wayne's note.

73, Paul W8TM

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[hf4me]

What about bringing along a couple of diodes to use externally to drop the
excess voltage until your supply batteries have depleated a bit.  Eliminate
them one at a time as the voltage drops.  Same result of having the
longevity of the higher voltage supply and no additional strain on the K1.

JMHO (not a K1 owner),
73, de Jim KG0KP

----- Original Message -----
From: "Paul Kirley" <[hidden email]>
To: <[hidden email]>
Sent: Friday, June 19, 2009 8:37 AM
Subject: [Elecraft] Looking for a good battery/charging system for K1

> Before you reach a decision on battery packs, be sure to read Wayne's Tech
> Note at
> http://www.elecraft.com/TechNotes/k1_battery_op.htm
>
> Basically, the principle of impedance matching applies to both input and
> output of a rig.  A DC input mismatch results in waste heat, which is
> usually not a problem unless the DC is in limited supply, e.g., from a
> battery.
>
> My particular K1 tends to drift a bit more when its regulators have to
> dissipate extra DC input voltage as heat.  The second regulators in the K1
> put out about 6.3V, so an input of 14.3V results in twice as much wasted
> voltage in the regulators as an input of 10.3V, i.e., four times as much
> wasted heat to cause more drift.
>
> For battery supplies, I prefer packs of 8 AA NiMH cells.  Alternatively, I
> use a variable AC supply which I set to 10V (plus an extra 0.3V that
> doesn't make it to the K1's voltmeter).  Either of these supplies matches
> my preferred 4W output setting fairly well, according to Wayne's note.
>
> 73, Paul W8TM
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[P.B. Christensen]

> Before you reach a decision on battery packs, be sure to read Wayne's Tech
> Note at
> http://www.elecraft.com/TechNotes/k1_battery_op.htm

That's a good summary of power supply optimization for the K1.  According to
Wayne's Note, the most efficient use of battery voltage becomes a function
of one's output power target value - ranging from near 14VDC for full-rated
K1 output to a bit less than 10VDC for about 3 watts.

Depending on the discharge characteristics of the battery, I imagine most K1
users would be quite happy starting at a commonly available 12V and allowing
it to drop down to about 9VDC at the end of portable operations or before
connecting a spare battery to continue.

Paul, W9AC

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