HP MU09 Long Life Notebook Battery - How does the extra reserve charge function work?

I just received my HP MU09 Long Life Notebook Battery and I am impressed that it actually improved the life of my laptop computer greatly. However, there is a button on this battery that looks to provide an extra reserve charge but I am not exactly sure how it works. I pressed it and some lights turned on but they quickly shut off. I've been looking for any information and have had no luck in finding a manual. I was wondering if anyone has had any experience with this battery or any model similar to it. I hope anyone could tell me how to use it, or provide specs for this device.

Also, I'm going to see if this function only works when the computer is at a low charge. Otherwise I hope anyone can help me figure it out.