These Pictures are for reference purposes only, so you don’t have to void your warranty.
Please don’t try this at home as I have already done this for you. 🙂
I originally posted this for a few friends inquiring about the RTC Clock on the controller losing its time. Well, the solution is to replace the battery. Here is a snippet of my post
“2504 does contain a battery CR2032. Here is a fresh shot of a controller naked. Good thing I opened up mine as the RAM was partially ejected on one side.
Use a proper CR2032 Energizer / Duracell. Not your dollar store variety. ”
@WirelessStew 
Holy cow, I was actually, honestly looking to see if there was a battery inside a 2504 since I had a customer today with a 2504 that had magically gone back to the year 2000. Thanks!
The pleasure is all mine 🙂
It help me a lot. Thanks,
The normal CIsco factory warranty is 90 days. If a battery goes bad in that period of time, I’d be really worried about the quality of design.
The typical coin style battery usually lasts 4 years. Really its not a big deal in my mind to change out a simple battery. Your should also have a NTP server setup for the WLC to maintian correct time.