[Elecraft] K2/100 Power Requirements

[Charles Greene]

Bob,

My experience with a marine battery about that size in my sailboat with a 
solar charger with a regulator was it the battery stayed topped off all 
summer.  TWithout the regulator, it would overcharge.  Also, shop 
around.  I only paid $80 for my 1 amp flexible solar charger a few years 
ago.  BTW, I am using a 45 AH old car battery right now with my K2 and 
K2/100.  A 6 watt wall wart keeps it topped off for the K2 with average use 
but it needs some more for the K2/100.  I use a 6 amp PS which is what I 
have, but a 2  or 4 amp is probably enough for occasional use of the k2/100.

At 06:44 AM 6/3/2005, G3VVT at aol.com wrote:
>
>In a message dated 03/06/05 04:10:11 GMT Daylight Time,
>tbeltran at earthlink.net writes:
>
>Given  the size and weight of batteries, I had hoped to use a 36 Ah battery,
>and  then recharge it with solar power.  But it seems that these  batteries
>charge rather slowly, and that might not be possible.  For  example, I think
>it is powerportstore.com that has a 1.2 amp flexible solar  panel recharger
>that puts out approximately 5.6 - 7 Ah per day.  The  solar panel is about $
>500.00.    The general size/weight and  price is ok, but it doesn't appear
>that such output would be sufficient to  fully recharge a big battery.
>
>
>
>Reply: ------------------------------
>
>The problem of recharging the battery from the 1.2A solar panel (about 16
>-18W capacity) is related to the solar panel being rather lacking in 
>capacity
>and would not do much more than delay the battery being run  down considering
>the drain of a K2/100 on TX. It all depends on the TX to  RX ratio used with
>the K2/100 and the mode of usage to how long the battery  will last. RX is no
>problem with the K2 as that is in the 0.25A range, but the  100W on TX can 
>draw
>something in the region of 20A at full output.
>
>However a 1.2A solar panel would be very usable with a basic K2 which has
>much lower TX current requirements of usually 2.0 to 2.5A at 13.8V. Even 
>with
>this a charging controller would probably not be needed as the battery would
>provide much of the needed voltage regulation. A diode would be needed in
>series with the solar panel to prevent the battery discharging back into the
>panel when the solar insolation is insufficient to provide any 
>charge.  This diode
>is provided internally with most of the larger solar  panels.
>
>For use with a K2/100 a much larger solar charging capacity would be  better,
>probably in the 55W range (4A at 13.8V) or higher together with a  suitable
>charge controller to prevent any possible over charging of the battery  and
>consequent over voltage being applied to the K2/100.
>
>With the solar powered communications systems I was involved with from 1981
>to 2002, these initially used multiple 55W panels (approx 3ft x 1ft) with
>individual controllers on each to provide the charging for the battery 
>plant.
>Later 15kW systems used 200 x 75w panels (approx 4ft x 1.5ft each  panel) and
>switched the solar panels in banks controlled by an intelligent  charger 
>system.
>A matter of balancing the required charging voltage  with the amount of
>panels on line. This was needed to provide for the current  drain of the 
>comms
>systems and allow for days when the sun did not appear,  where the available
>charging current would be insufficient to balance the  24 hr drain. With 
>the latter
>systems running a microwave site it was normal to  see 120A or greater charge
>current at 54 to 58V when the battery  plant was in the morning full charge
>cycle.
>
>Bob, G3VVT
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73,  Chas,  W1CG