[Elecraft] Adjusting Samlex PS for proper battery charge voltage

[Don Brown]

Hi

The battery blocking diodes voltage drop does not come into play in this =
circuit only D10 in the K2. When charging the internal battery the =
battery blocking diode is reversed biased so does not conduct. The =
charge current is limited by the 6.2 ohm resistor across the diode. The =
blocking diode in the K2 (D10) is in series with the power supply and =
the battery so the drop across it will show up on the display. The =
battery will charge up to the applied voltage less the diode drop in =
D10. The early <3000 s/n K2's had a standard diode in D10 so the drop is =
.6-.7 volts. The newer >3000 K2's have a low drop diode with a .2-.3 =
volt drop so the power supply will need to be adjusted slightly =
different for the older or the newer radios. The A to B mod kit also =
changes out D10 to the low drop diode. The easiest way to set the power =
supply to the correct charging voltage is to measure the voltage at the =
aux 12 volt connector. So you don't short anything out connect the =
negative lead to one of the RF board grounds and carefully touch the =
positive probe to the back of the red wire crimp terminal on the battery =
plug connected to the AUX 12 volt connector. Adjust the power supply for =
a reading of 13.8 volts. At this point you will read the charging =
voltage including the drop of D10 but not the drop across the limit =
resistor because of any current into the battery. If you don't want to =
go to all this trouble then just adjust the power supply to 14.4 volts =
for the older K2's or 14.0 for the newer measured at the power connector =
for the K2. Then tap display and read the voltage on the K2 display. =
Make note of the read voltage and always set the power supply to that =
voltage.

Don Brown
KD5NDB=20


----- Original Message -----=20
  From: Don Wilhelm=20
  To: Gil Stacy ; elecraft@mailman.qth.net=20
  Sent: Friday, August 01, 2003 10:58 PM
  Subject: Re: [Elecraft] Adjusting Samlex PS for proper battery charge =
voltage


  Gil,
  Probably not a lot to be concerned with though - both the K2 and the
  internal battery have a protection diode in the path from the point =
where
  the power splits.  So the voltage measured at the battery terminals =
should
  be very close to the voltage in the K2 that is seen by the internal =
meter.
  It is just that measuring at the battery terminals is a bit more =
correct.


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