this is a question that is debated a little. most people will probably tell you yes, you need to discharge because nickel batteries form a memory. however I've also been told that nimh are different than nicd and aren't as seceptible to the memory type problems of the nicd. My 5400 7 cell nihm battery works really well and I just make sure I run my truck to the point where it won't move any more before I charge the battery (and after proper cool down). Now I wouldn't consider that discharging completely, but I suppose it's more of a discharge than if you charged the battery as soon as you noticed your truck was starting to slow down a little bit.