Restoring dead Ni-MH batteries

It wasn't neglect, I swear!

So, I'm on holidays. An excellent opportunity to get back into robotics, I thought, whilst I eyed my dust entrenched Lego NXT prototype SumoBot built several months prior. It was a uni project at the time, and ever since, I've been busy with other studies. So I quickly brushed off the dust and hit the on button, only to find that the batteries were dead. "That's OK" I thought, "I'll just charge them up again." I was wrong. You see, when you don't charge batteries for a long period of time, they tend to over-discharge. I proceeded to place the batteries in their designated charger, switched it on, and noticed that the status bars for each battery were not changing. In fact, the charger didn't realise there were batteries inserted! Why was this so? Could the issue be resolved? I investigated further...