[Elecraft] K1 internal battery bypass

[Mike]

Steve Jackson wrote:
 
> If you have a K1 with the internal battery option, does plugging in an
> external supply bypass the internal source? Or does it parallel it?

Steve,

It NEVER parallels it.  But what really happens depends on the value of
the external voltage applied vs. the KBT1 battery voltage.

The DC from the external connector is applied to the K1 electronics
though a reverse polarity protection diode with about 0.6 vdc drop.  The
DC from the KBT1 is applied to the K1 electronics through a blocking
diode with about a 0.2 vdc drop.

As long as the external DC voltage is about 0.4 to 0.6 vdc higher than
the voltage of the KBT1 battery, then the external DC supply will be
providing ALL the power.  If the external DC voltage less than that,
then the KBT1 will be providing ALL the power.

Since the external DC voltage used by most people will be about 12.6 vdc
or higher, and the KBT1 battery at full charge will usually be about 10
vdc, then the KBT1 battery is effectively blocked from providing ANY
power when the external supply is connected.

Because of the KBT1 blocking diode, external DC power will NEVER flow
into the KBT1 battery.  Similarly, because of the reverse polarity
protection diode in the external DC supply circuit, KBT1 battery current
will NEVER flow into the external DC supply.

Mike / KK5F