I'm building a PS for my shack, and the receive only current draw of
all of my equipment is in the 2A range. QST a few years ago had a
great charger/battery circuit where the PS/charger generated up to
500ma and, depending on the voltage state of the battery (he used a
SLA) would apply the charger voltage, limited to 500 ma (minus anything
used for running equipment, about 220 ma max for him) to the attached
battery in an increasing duty cycle as battery voltage went down. When
he transmitted, his load was about 2A, and it would come out of the
battery.

I'd like to do something similar, but larger. I'd like to build a
charger/PS capable of supplying about 3A max, and use a deep-cycle
marine battery as a reserve supply. Are there any circuits out there
that allow a battery charger to run on a battery that can possibly be
operating?

Thanks.

Marc