Battery capacity checker

Perhaps someone out in r.a.s land may be able to point me in the direction
of a commercial piece of equipment which would perform the following task.

I would like to be able to charge up a 12 volt (nominal) gell cell battery
and then plug it into a piece of equipment to check its total AmpHour
capacity during discharge at some constant rate current (say the "10 hour"
rate or the "20 hour" rate). All this towards assessing whether the battery
has proven useful capacity and life left in it, or has it reached its
discard date?

The equipment would show the delivered amp-hours up to the point at which
the voltage has fallen to a nominated end voltage.

I realise that you can do it in a way with a light globe to discharge the
battery and then time the length the light holds up glowing brightly. This
is all too primative for this day and age, and there ought to be some piece
of equipment available for the task.

Or some circuit from an electronics hobby magazine??

Thanks in antcipation.
Roger Druce