What size Solar for 7 Ahr Battery w/K2

[k7nhb]

I've been looking at foldable solar cell supplies. They come in
approximately 10, 15, and 20 watt sizes. The cost difference between
the 10.4 (.75 amps) and 15.6 (1 amp) watt units is $20 and the
difference between the 15 and 20 (1.4 amps) watt units is  $45
respectively)

I can see that getting the most Amps one can afford would be good if
you were going to run your gear (K2) directly off solar - with
(Don's) controller of course. But if you are running off a battery so
you go solar cells to controller to battery to rig then it seems if
you get a solar unit that delivers more amps then you'd want to push
into the battery for charging, that you are spending money for a
"High End" that you would never use.

So if a charging amps of .5 amps is recommended, and given the
variability of solar output, 1 amp would be reliable - then would 1.4
even be recommended?

That is, it is one thing to justify the extra cost vs the extra
performance. But if the extra performance doesn't matter, or many
isn't even desired, then that is an overriding  reason not to buy
more then needed.

Does that make any sense? That is, is the 15.5W array (1 amp) a
better match to the 7 Ahr battery then the 20.8W (1.4 amp) array? Or
should I go for as much solar amps as I can afford that will fit
within the physical contraints of backpacking and kayaking?

73,
Paul
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Thomas Beltran]

That is, is the 15.5W array (1 amp) a much better match to the 7 Ahr battery
then the 20.8W (1.4 amp) array? Or should I go for as much solar amps as I
can afford that will fit within the physical contraints of backpacking and
kayaking?



Paul - I've been using solar power while camping for some time.  The solar
panel ratings are for perfect conditions (which is only a few hours a day at
best).  I use the Connecticut Solar backpacking panels - two 32 Watt panels
and a Morning Star 15 amp controller - very nice equipment, but the panels
are pretty heavy.  With ideal conditions, I get about 5 amps output.
However, typically, the figure is about 2.4 amps.  You might want to factor
that into your calculations.  I'm also curious about the experiences of
other people - perhaps I am doing something wrong.  Tom W6EIJ




_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[aa2vk]

Thomas Beltran wrote:

>Or should I go for as much solar amps as I
>can afford that will fit within the physical contraints of backpacking and
>kayaking?
>

Yes!
But I've used a few and found the 10watt Uniflex panel to be a good size
vs output.  It puts out abt half of rated (500ma) during normal timed use,
but has been enough for the radios  that most backpackers will carry.

Prob the biggest rigs you would want to carry would be a K2, 703, 718
sized  or Smaller like the DSW units...  the larger only need aprox
700-1000ma
per hour during normal 1:4 of TX vs RX(high use) .  Good battery
selection and a small charger will handle the larger rigs.  As to the
smaller like the DSW 's or
AT's or KX1's the power draw is low enough to never run out of power  
with the a small charger and battery pack.

Tom aa2vk
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com