Apple Rechargable Batteries not working right

I recently decided to use an Apple Bluetooth Wireless Keyboard to eliminate the chance that my Logitech keyboard was the cause of a problem (it wasn't). I also got the new Magic Trackpad (which I generally love). While at the Apple Store, I decided to get a set of six rechargeable batteries and wall socket charger with the product name Apple Battery Charger and Designed by Apple in California. It came with six double-A batteries.

Know I a technical background to know that rechargeables do not reach the same voltage as Alkali batteries. Nominally a single cell battery is thought of as 1.5 V. However, the actual voltage depends on the chemicals used. I believe the 1.5 V dated back to the Carbon batteries of yesteryear. The Alkali also achieve something like that. But the NiMh and Lion batteries do not. So I was not surprised when putting the fully charged batteries (the charger changed from orange to green after a number of hours) shows in the System Preferences / Keyboard dialog as less than 100%.

My problem is at the other end. For a few weeks now, the battery is showing 18% according to System Preferences. It does work fine. However, I decided I had better replace them. I put in batteries that had undergone the same charging process until the Green light replaced the Orange one. During this process, I noticed that if I removed the charger from the power socket and put it back in, it went back to orange and stayed there a while before turning Green again.

I put these presumably fully charged batteries in my Apple Bluetooth keyboard. The System Prefernces show it at 18%!!!! I tried the other spare set and it reported the same value.

What is going on here. Anyone know what I can do about it.

Thanks,

Bruce