How To Battery Back RAM

I would like to know how to connect a batter to my FEZ Spider to backup the 2K RAM and the RTC. Is there a way to do this?

Looking at the schematic for the Spider mainboard I see that pin 5 of socket 2 is labeled “RTC Battery”.

I would use an extender module, and connect the plus side of a 3.3V battery to pin 5, and the minus side to the ground pin of the extender.

Thanks for the info!