[Elecraft] Internal Battery Charging Question

Thu Jan 23 13:52:01 2003

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

Andreas, KU7T

-----Original Message-----
From: Steve Holton [mailto:[email protected]]=20
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=20
tenths of a volt from the actual voltage presented to it - over and=20
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=20
several years ago) to supply K2 #2846 and charge the KBT2. The Power
supply=20
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=20
low drop D10 and 13.62 volts at the voltage divider for the voltmeter.
The=20
low reading of about 0.3V ( about 2.2% ) comes from two sources. The R9
in=20
the voltage divider is 3 ohms off and that'll make an error of about
1/4%=20
low. Second the A/D in the micro-controller doesn't measure absolute=20
voltages, but relative a reference which is the uC "5V" Vdd which was=20
measured on this machine to be 5.11 volts contributing about 2% too low
a=20
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=20
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 =3D
voltmeter
----snip

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