Marc,
That's a simple yet elegant idea. Incandescent lamps also work well for charging or discharging capacitors, or discharging nicd batteries prior to recharging.
A little refinement would be to charge the battery up to 29.5V with the lightbulb in series with the battery, detect this and switch to a 26.7 Volt regulated source putting out about 100ma or so in order to 'float' charge.
In my prior life I was a fire alarm tech, and you can maintain 100AmpHour SLA's with just a few 10's of ma.
Of course this scheme requires the comparator circuit to have some hystereses, and have a stable voltage reference. (The 'equalzation' charge should cut out at 29.5 Volts and switch to the 'float' charge voltage (26.7V).
This would work well with a 'standard' 24VAC transformer with a filtered full wave bridge.
Incandescent lamps also work well for charging or discharging capacitors, or discharging nicd batteries prior to recharging.
