[Elecraft] KX3 and Solar Panel

[Bob]

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