[Elecraft] Internal Battery Charging Question

Thu Jan 23 15:09:02 2003

Hi to all and thanks to those who responded to me on this.

  I THINK I finally understand what voltage to look for.

  If you take a look at the K2's schematic you'll see that power supply
voltage enters the rig at J3 and then goes through D10.  From there it goes
to the battery.

The instruction manual for the battery says that the voltage at J3 should be
between 13.8 volts and 14.2 volts.  It also says that at the cathode side
(banded) of D10 it should be between 13.5 volts and 13.9 volts.  Given a .3
volt drop.

In my humble opinion, seeing as though the battery is connected directly to
D10, it would make more sense to measure at D10 at which point you should be
looking for between 13.5volts and 13.9volts.

So the short answer to Andreas' question is 13.7 volts +/- .2 at the cathode
side of D10.

Again thanks to all that helped with this, particularly Steve N1NB for
explaining why the K2 display voltage is different from the actual readings.

On a related note, the RS PS I am using is putting out .5 volts too much for
the K2.  Any suggestions (real basic stuff here, like maybe add a resistor))
on how I can reduce the output by this much.

Thanks again
Tom McCulloch, WB2QDG
K2 s/n 1103

Friend of Bill W.
   ---  If you are too, drop me a line.
-----Original Message-----
From: Andreas Hofmann <[email protected]>
To: Steve Holton <[email protected]>; [email protected]
<[email protected]>
Date: Thursday, January 23, 2003 1:51 PM
Subject: RE: [Elecraft] Internal Battery Charging Question

So, should it be 13.7 V on D10 or on J3?

Andreas, KU7T

-----Original Message-----
From: Steve Holton [mailto:[email protected]]
Sent: Thursday, January 23, 2003 8:52 AM
To: [email protected]
Subject: RE: [Elecraft] Internal Battery Charging Question

The internal voltmeter shouldn't be used for this. It may be off by
several
tenths of a volt from the actual voltage presented to it - over and
above  0.2-0.6V below the power jack due to the drop across D10.
I looked into this because I was setting up a RS 3 Amp supply (vintage
several years ago) to supply K2 #2846 and charge the KBT2. The Power
supply
indicated 13.8 volts and the internal meter said 13.3. Looking into it I

found 13.8V at the power input J3 and 13.62 volts on the cathode of the
new
low drop D10 and 13.62 volts at the voltage divider for the voltmeter.
The
low reading of about 0.3V ( about 2.2% ) comes from two sources. The R9
in
the voltage divider is 3 ohms off and that'll make an error of about
1/4%
low. Second the A/D in the micro-controller doesn't measure absolute
voltages, but relative a reference which is the uC "5V" Vdd which was
measured on this machine to be 5.11 volts contributing about 2% too low
a
reading. The voltage is best measured at the J3 or the cathode of D10.

The RS 3 Amp supply was adjustable once it was opened up - there was a
pot
that could adjust the voltage which I did.

73
Steve N1NB

Original Message:
---snip
I have a question regarding my K2's internal battery, the KBT2 option.
Tom:
You should adjust the PS to read 13.7 as read by the K2 internal =
voltmeter
----snip

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