[Elecraft] Solar Charger

[Mike B]

David N. wrote:
> Hello all. I just installed the KBT2 battery kit in my
> K2. I have a 5 watt unisolar flex panel

Same setup here.

The design of the KBT2 does not regulate voltage - it just regulates a 
small current to float charge the battery.  It's specifically designed 
for an external, approximately 14 volt supply.

If you want to charge the 2.9 AH battery up fast, by all means you can 
connect it directly to the PV panel, but you must monitor the battery 
voltage as it will try to climb very high.  The voltage must be 
regulated - a common method is to use a small charge controller such as 
the Micro M+ from SunLogic (owned by a ham) 
(http://www.seslogic.com/microm+.html) or Don Brown (I think that's the 
fellow - he offered it here again just in the last day or two).

My older Micro M is external - I used one of the transverter holes to 
add a coaxial jack, clearly separated from the main power, that runs 
direct to the battery.  The charge controller has to bypass the resistor 
and diode included in the KBT2 kit and see the battery directly.  I've 
heard that others have added the Micro M internally to the K2 lid, but I 
haven't seen one.

Some hams also have used a zener diode to clamp the voltage down.  This 
means, however, that the zener must dissipate the excess power, and may 
get warm.  I've never tried this method.

Hope this helps.

-- 
73,
Mike Boice, KW1ND
Karns, TN
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