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Under voltage from 12V supply


#1

So here I am on the beautiful island of Sifnos in the Aegean with all my equipment ready to go and activate SV/AG-028 for the first time. Unfortunately, I’ve found that the PSU I brought along is only producing 11.9V DC and the KX3 is unable to charge the internal battery from that PSU voltage.

Currently (!) I’m stuffed unless I can find a way to charge the batteries. Any ideas, given that I’m on a small island with no tools other than my trusty Swiss Army Knife?

I can still operate from the hotel of course, but I’d really like to get out there.

73, Gareth - SV1/M5KVK/P


#2

Must be a local ham that could help out.

Karl


#3

Hello Gareth, why not just buy some AA batteries and my recollection is that the rig takes x8 AA? Good luck.
Mike


#4

Power Supply
For fixed-station use, a low-noise 12-14 VDC
power supply or battery is recommended. (See
linear and switching power supplies in the
Glossary, pg. 49.) For lightweight portable
operation, the KX3’s internal 8-AA-cell battery
pack can be used. See Internal Batteries, pg. 23.

Looks like mike be right on that one

http://www.elecraft.com/manual/E740163%20KX3%20Owner’s%20man%20Rev%20B4.pdf

Recommended Battery Types
Lithium non-rechargeable batteries (e.g., Energizer
L91) are expensive, but their flat discharge curve
and 3 amp-hour rating provides maximum operating
time. In receive, the pack voltage will be about 12
V. In transmit, it will drop to 9-10 V due to the
cells’ high internal series resistance. This voltage is
sufficient for operation at up to 5.0 W.
NiMH (nickel-metal hydride) batteries have a flat
discharge curve, like lithium cells, but a lower pack
voltage (typically 10 V receive, 8.5-9 V transmit).
Power output of 5.0 W is possible. The advantage
of NiMH cells is that they can be recharged
hundreds of times, either externally (in as little as 1
to 2 hours), or internally (typically 8-12 hours,
using the KXBC3 option module).
Alkaline batteries can be used if there’s no other
alternative, but they have several disadvantages.
They should always be used with power output set
to 3.0 W or less to minimize transmit current drain.
They have a steep discharge curve, so the pack will
drop from 12 V to 8 V in about half the time of
Lithium or NiMH cells. They’re also prone to
leakage, and should be removed after use.
Damage caused by battery leakage is not
co

Hope this of help

Karl


#5

…and for next time, get hold of a 14V supply, perhaps? I have a Dell AD-4214N laptop supply, but similar power bricks are (or were) widely used for LCD displays, and it charged my KX3 well enough in Kenya.


#6

As soon as I mentioned this to my ever so practical wife, of course she came up with two strategies:

  1. See if the hotel owner has a charger for AA batteries
  2. Just go out and buy a load of Duracells or similar.

The batteries in the KX3 are Eneloop Pro Ni-MH. I don’t really want to damage them by charging them with a NiCd charger, so I’ll see if I can find a Ni-MH charger in Apollonia - the “capital” of Sifnos.

Thanks all


#7

NiMH are safe to charge with a NiCd charger.

ON/MM0FMF


#8

Yes, I’ve been doing it for years without harm.

Brian


#9

Most modern power supplies will have an adjustable voltage output. If you can open it up there will be a pot to twiddle.


#10

Perhaps there may be a shop that sells some sort of plugpack supply preferably about 3-4A capacity at 14v.

Otherwise just buy a bundle of alkaline cells and run the KX3 at 3 watts. At least this will get you going.

Go into menu and switch off the back light, this will save a bit of current consumption.

With a bit of luck 3 watts will do the job.

Nick


#11
  1. car battery
    or
  2. put another charger, or just one cell, in series with the charger you have.
  3. any desktop PC has a good 12v supply inside it.

Andrew
vk1da