[Elecraft] [K3] Solar Power

[W0SD Ed Gray]

Solar power works great and now with the 30% tax incentive you have a 
real decent pay back. However there a some downsides! Remember that PV 
panels have a lot of wind surface and there could be zoning 
considerations and of course you need to face south and being at the 
roof angle you lose a lot of potential production.  At a home 
installation changing the angle about 4 times a year will really 
increase your production if you can find a spot with a clear look to the 
south.  Here in the north country really the crucial time is Dec and Jan 
so I just set them for maximum efficiency for those two months but it 
would be a different story to the south.  I have four 205 watt 24 volt 
panels and eight 150 AH batteries and an Outback Flex 80 MPPT 
controller. I run everything on 12 vdc in the radio room as well as 
emergency lighting.  I plan to add a sine wave inverter to run the 
computer, DSL modem and router and a couple of rotors.

For me the biggest downside to solar power is RFI which is commonly 
generated by the controller and radiated by the wiring from the panels 
and wiring to the batteries.

Another big noise problem with solar power can be the inverter. However 
since the K3 runs on DC and a lot of things in the radio room runs on 12 
vdc you can make a lot of use of the PV system without an inverter.  If 
you need an inverter then you are going to need a true sine wave one and 
even then you might have RFI so be sure and buy one that hams have had 
good success with.  I use a MPPT solar controller, Outback Flex 80, and 
it puts out "birdies" approximately every 24 khz when the controller is 
active. They are loud and can be heard for several 100 feet. Of course 
one can work around these birdies since they are every 24 khz and/or 
shutting off the panels cures the RFI.  One can charge the batteries 
when not operating.  Of course more battery capacity give you more 
flexablilty in this regard.  The birdies are on AM broadcast through two 
meters.  Of course when the controller is "sleeping" there is no 
problem. The birdies do move some in frequency. So far they have not 
ended up on a place I monitor but if they do then the problem is much 
more serious.  An example would be 50.125 or 144.200 or 14.195, etc.  I 
hope to do some more work to try and get rid of the birdies but I 
suspect it is not going to be easy.  So far twisting the wires to the 
batteries and ferrite do nothing so I am going to have to try by passing 
and more shielding.  PV systems and inverters do not seem to be 
regulated by the FCC as to noise generation.

It is possible that the non-MPPT controllers are much cleaner and given 
a couple posts here have not mentioned the RFI problem and they did not 
use MPPT controllers they probably are.  For a PV system you definitely 
do not need a MPPT controller so that is definitely something to check out.

Another important thing is if you are "NOT" using lead acid batteries 
where you can add water be sure and be careful not to run to high a 
float voltage.  These batteries are very easy to ruin by doing this. 
Obviously with the ones you can add water you still have to be sure to 
watch the water level and should run the proper float voltage!

Also do your very best to not discharge your batteries more than 50% and 
better yet as much as possible try not to go below 80% and if you watch 
the water level and float voltage on average batteries will last a long 
time.  I have 16 SAM's Club golf cart 6 vdc batteries that I use for my 
5th wheel and are in a battery box in the box of the F-350 and are 
charged by a second alternator and are now going on 9 years.  I just 
checked them today and the resting voltage was 12.6 volts which is 
excellent for batteries this old. They are equalized twice a year. Your 
pay-back on a solar system will be a lot longer if you end up with a 
short battery life as batteries keep getting more expensive.  They are 
nearly twice what I paid 9 years ago.


Ed W0SD
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