Field Day Solar

K2MM at MasPar.COM K2MM at MasPar.COM
Wed Apr 28 21:59:51 EDT 1993

Bruce:  Interesting FD trivia.  I have some observations based on your
reporting of the relevant rules.

The field-day rules about not charging batteries -- even from solar
cells -- while in use do seem a bit foolish.  But the foolish rules can
be sidestepped with a bit of foolish circuitry:

                |\ |
   solar _______| \|____________________________________ radio
   cells    |   | /|                                |    equipment
            |   |/ |                                |
            |                                       |
            |                                       |
            |   |\ |                         |\ |   |
            |___| \|___ battery   battery ___| \|___|
                | /|    being          in    | /|
                |/ |    charged       use    |/ |

This may require periodic swapping of the in-use and being-charged
batteries.  This can be done either manually, or with relays, or with
solid-state switches.  The first case will require shutting down the
equipment for a minute or two.  The last two cases avoid this, provided
that a (big enough) capacitor is put across the load.  But, to toe the
line with the rules, the switches better be break-before-make.

In fact, it looks like solid-state battery switching could be used even
if the batteries are being charged from a generator, or, for that
matter, from commercial mains.  I wonder if the ethics of this parallel
those of using a "spider"?

Bottom line:  compromise.  Solid-state switching of batteries being
charged from commercial mains appears to comply with the letter --
though clearly not the spirit -- of the rules.  So, don't do it.  In
return, lean heavily on the spirit when interpreting the prohibition
against charging in-use batteries.  That is, assume it wasn't meant to
be appled against charging from solar cells.  --John/K2MM

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