Hmmmm

You can do some simple tests - put the robot on the ground, nose aginst a wall; you should be able to spin the wheels easily. Assuming it isnt geared for a high top speed. Now stand on the robot... you should still be able to spin the wheels.

If you cant, measure the battery voltage while youre doing it and see if it drops a lot.

As others have said, cycling the NiCads ocassionally is good practice.

Its also worth pointing out that if you do cycle them it does say in some of the manuals for the charger that it can take about five times for it to have any effect.

Andy