Just an idea

Has anyone used a battery in conjuntion with a servomotor power
supply?

Reason for the question:

Brush DC servomotors have peak torque values that are up to 10 times
their rated continuous torque, thus peak current draw can be up to 10
times the continuous draw. This peak current event can last from 10
millisec to 1 second and the duty cycle must be under 10% to stay
within the motor's dissipation rating.

Unfortunately the power supply has to be sized to this peak power,
when on average a supply 1/10 the size would do.

My idea would be to use a small NiCad or NiH battery connected to the
power supply output bus via a diode. During a high current pulse the
power supply voltage would sag, the diode would forward bias and pick
up the load for the duration. A quick-charge IC would handle the
charge restoration to the NiCad between the pulses.

Even little AA .5 AH NiCad cells would do; a 25 Amp, 1 second load
would discharge only .007 AH (25Amp / 3600 sec). The internal
resistance of a Nicad cell is on the order of .02 ohms, so they are
quite capable of supplying this level of current.

It seems a 100 watt supply / battery combo could replace a 1kW
supply. Has this been done before?

Mariss