[Elecraft] A simple solar charger for the K2

[Martin Kohler]

A simple solar charger for the K2
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Here's what you need:

- Solar panel (e.g. SP10 from Siemens, 10W, 17.4 V at 0.60 A) 17.24" x 12.2"
- Voltage regulator uA7815
- Diode 1N4001

Using a uA 7815 voltage regulator, followed by a 1N4001 diode, a constant
voltage of 14.3V is obtained at the DC power plug of the K2, when connected
to the internal battery (K2 turned off, current 20 mA). When the K2 is
turned on (current 180 mA), tapping DISPLAY reads a voltage of 13.8 V.

The panel can be left plugged in all the time. Since the voltage is limited
by the uA7815 and the diode, the battery will not be overcharged. One day
of full sunlight (8 hours x 0.6 A = 4.8 Ah) is enough to get the battery
(2.9 Ah) fully charged.

73!
-- Martin (HB9DOZ)

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Martin Kohler                              phone: +41 1 430 47 70
Grimselstrasse 43                            fax: +41 1 430 47 71
CH 8048 Zurich                  e-mail: martin.kohler@freesurf.ch
SWITZERLAND                 position: N 47 23'05.7" E 08 29'16.1"
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