I only get short or no charge in batteries

Dan, you can try to reset the charging system. Remove the battery from the Roomba and unplug the charger from the wall and the Roomba. Hold the power button down for 30 seconds. Then try to charge it and see what happens. Of course you should also make sure that the battery is properly seated. Turn Roomba off, empty the Particle Bin, and turn the Roomba over. Remove and re-insert the battery, pressing firmly on both ends of the battery until it clicks into place. The only other way that I know off to charge the batteries by keeping it on the charger for about 72hrs even when the light is green...and if none of this works I would get some new batteries...Hope it helps, good luck to you and your Robot ;-)