Studio 1745 - CMOS Battery to blame? - The ac power adapter wattage and type cannot be determined

Hello,

I'm currently running a dell studio 1745 without a battery as as I previously had the "plugged in but not charging" nonsense. Back then I didn't have the initial error message pop up at startup. It was fine for a while. My laptop seemed to running at full speed without the battery slowing it down. 

Eventually I noticed that it was still dreadfully slow so I have spent hours upon hours trying to get it back up to speed. The CPU just wasn't cutting it. Long story short I have upgraded the RAM, done various malware scans, changed antivirus from Norton to AVG Free, messed around with all the services,changed thermal paste and cleaned out insides(ruling out overheating) and just recently I have purchased a new charger.

What seems to be the problem is the "Core Voltage(VID)" identified by CPU-Z keeps jumping around. These ranges are ~0.8V - 1V - 1.13V and when these change, my CPU multiplier ranges from x2.5 - x3.5 - x4.5 respectively. Currently its a hit or a miss as to what I get with the new charger but I changed a few of the services so sometimes I can get a higher multiplier.

During my research I have came across the fact that processors have the ability to limit their speed to save energy when they aren't being used. Its definitely not that because when using my intensive programs(autodesk, photoshop etc) the processor just wont speed up. 

Like I stated new charger so its not that charger that's to fault.

Recently I have came across the possibility that it might be CMOS Battery. If i for example disconnect the battery for a while (also another option which I found out might work) and then plug it back in, when I turn my laptop on I get 5 beeps which I understand as "Five beeps — Real Time Clock failure - Replace the battery" taken from the manual. So the only thing I have left to do is replace the CMOS Battery? Where would I buy one?

Thanks for reading, really like to get this fixed asap so I can get back to work.

Darren