the battery is located in a bad spot, you have to dismantle the system to get to it..

I have similar case, my I8100 has been using for almost 7 years, all hardware are running properly instead of the CMOS battery issue... Actually, I found that the CMOS battery itself doesn't have any problem (Dell support ask me to replace the whole motherboard...) and it is not related to recharagable issue. Remember to "unplug" from your notebook from power socket everytime after you shut down the computer, you will find that the battery issue disappear... very straight...

By following your process does that maintain the date and time.  Seems odd that by shutting off power to the computer when not in use that the cmos battery stays charged.  I was under the impression that the cmos battery does not recharge but once depleated the only fix is to change battery.  OR are you just ignoring the date and time issue that is the main purpose of the cmos battery, as I understand its purpose. 

Yes, it is very odd to unplug the power. But it solved the problem, and I find that the date and time can be maintained for a long period of time without the AC power (Well, CMOS just needs small amount of power to maintain the clock, right? Even it needs power, it can be recharged by notebook battery instead of AC...) I guess, the rechargable CMOS battery is okay, there may be some problems in the power source... try and see whether it fix the problem. Good luck!