How to tell if batteries are bad

Our less than 2 year old batteries seem to lose their charge rapidly. Is there a way to tell if they are bad? Is there a way to fix the sluggish ones? Thanks for any suggestions!

How long is rapidly? We get about 25-30 mins of drive time with 2 drive motors. If you are running 6 motors and they are running alot, your times will be much less.

Does the battery pack get hot when it’s charging?

Have the code display the pack voltage to the screen.

IIRC, it’s a 6 cell nimh pack. Nimh is fully dead at .9 volts per cell, so anything below 5.4v is ‘time to recharge’.

Those batteries do not like discharging too far and it will kill them in short order. I would really stop at 6 volts, or 1.0 volts per cell.

There are ways to analyze the discharge curve of the pack. It takes voltmeters, a fixed load bank, alligator clips, and lots of time. If the pack seems bad/flaky it probably is.

Occasionally the batteries get hot when charging, but not on the regular. They have a bot with 6 motors (one is a conveyer, and one is a stick that dumps 6 rings, 2 drive motors, an H drive, and a pick them off the wall motor) It is a heavy bot. They can run about 4-5 runs before they see the robot slowing and need to change the battery. So maybe that is usual.
Thanks for the input!