KX3 and Solar Panel

[Edward R Cole]

Lee,

Most solar panel mfrs assume you are charging a battery which holds
down the voltage or that you are using a solar charge controller
which regulates the current.

I understand that you wish to leave the "heavy" battery at home.  But
a small 4 AH 12v gell-cell is not that heavy and will regulate the
solar panel to an extent.  Under load of a battery the solar panel
voltage drops.  You do not have a heavy enough load on the solar
panel when in receive mode in your present set up.

Many large solar panels (60w) will provide up to 22v open circuit,
but drop down when under load.  To cause a charging current to flow
into a battery the voltage has to be a few volts higher than the
resting voltage of the battery.

Another solution is to build a voltage regulator that will hold the
voltage at 13.8v.  The regulator has to be rated for at least the
current of your rig in transmit.

73, Ed - KL7UW

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[WB4SON]

Charging a small SLA (sealed lead acid) without a charge controller will
destroy the battery.  This will happen at a voltage of > 2.40 volts per
cell (so 14.4 volts total), and a solar panel is capable of producing much
more than that.  When this happens, the SLA will start to outgass (hiss),
and it will start to heat rapidly.  The problem is actually much worse for
smaller SLAs because they charge quickly and it takes a smaller amount of
charge current to cause the problem.

A charge controller is definitely the way to go.  BuddiPole offers a very
small one that is uses PowerPole connections.
http://www.buddipole.com/sobaco.html

73, Bob, WB4SON
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Matt Zilmer]

There is also the CirKits SCC3 solar charge controller.  It scales
from 20A to 60A pretty easily.  I use one for the shack solar to
charge an Optima AGM battery.

The SCC3 is a kit, quick and fun to build.  You have to supply your
own housing though.

http://www.cirkits.com/scc3/

73,
matt W6NIA


On Tue, 28 May 2013 00:01:26 -0800, you wrote:

>Lee,
>
>Most solar panel mfrs assume you are charging a battery which holds
>down the voltage or that you are using a solar charge controller
>which regulates the current.
>
>I understand that you wish to leave the "heavy" battery at home.  But
>a small 4 AH 12v gell-cell is not that heavy and will regulate the
>solar panel to an extent.  Under load of a battery the solar panel
>voltage drops.  You do not have a heavy enough load on the solar
>panel when in receive mode in your present set up.
>
>Many large solar panels (60w) will provide up to 22v open circuit,
>but drop down when under load.  To cause a charging current to flow
>into a battery the voltage has to be a few volts higher than the
>resting voltage of the battery.
>
>Another solution is to build a voltage regulator that will hold the
>voltage at 13.8v.  The regulator has to be rated for at least the
>current of your rig in transmit.
>
>73, Ed - KL7UW
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Dave B]

On 28 May 2013 at 12:00, [hidden email] wrote:

> From: Greg Troxel <[hidden email]>
> To: [hidden email]
> Subject: Re: [Elecraft] KX3 and Solar Panel
>
> A 20W panel that is labeled as for a "12V" system will typically have
> a Voc (open circuit) of 22ish V, and a Vmp (maximum power voltage) of
> 18V.
>
> Generally, one should not hook up a bare panel to a load, and the
> usual recommendation is charge controller and battery.   I wonder
> about a large cap instead of a battery, enough to make the controller
> stable.
>
> I have a 20W (HQRP) panel and use a Genasun GV-5 MPPT charge
> controller and then charge about 100Ah of batteries.  I have not tried
> the controller with no batteries.
>
> The anyvolt3 is an interesting concept for this application.  MPPT
> controllers try different voltage/current combinations to find the one
> that's in-range for the DC-DC converter and results in maximal power.
> I have found that to be around 17.5-18V whenever I get more than 200
> mA >From the system (sometimes I see 1.6A).  The anyvolt3 is expecting
> a voltage source, it seems, and the datasheet seems to imply that.  A
> panel is not a voltage source.  So I really wonder what would happen.
> Has anyone put a high-speed scope on the input when hooked up to a
> panel?

MPPT controllers are usually switch-mode regulators with special control
algorithms, and are notorious HF noise generators!  Take care, you may
need lots of filtering, on both the "regulated" DC out, *AND* the Solar
DC input.

They are also designed (as you rightly say) to work with a battery bank,
and would almost certainly be "unhappy" with a light to non existent
load, especially one that varies a lot over a short time scale, as a SSB
or CW transmitter does.

For portable HF radio battery-less use, a linear series regulator, or
more likely a parallel shunt regulator would be best.  Inefficient true,
but quiet!.

73.

Dave G0WBX.

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html