Wanted to thank all the posters for all the tips and info. I took the plunge and swapped out my lead acid for a 20ah prismatic LiFeMnPO4 battery. Should meet my needs. I found the easiest swap was using:
4 gauge battery cables like these:
http://www.canadiantire.ca/en/pdp/motom ... p.html#srp
Battery with case like one of these (option for BMS if you don't want to check it periodically):
http://www.batteryspace.com/lifepo4-pri ... d-dgr.aspx
Water resistant tape to cover any gaps or holes in the case since I'm a little paranoid.
Just screw one end of the cable onto the LiFePO4 battery terminals (a round metal washer helps hold it tight), and screw the other end of the cable between the car's battery post clamps (threaded the screw through the cable terminal end), and done! Took like 10 minutes.
My only difficulty now is how to keep the battery in place since it's so small. For now some foam inserts work, but it's not optimal. Any tips from early adopters would be appreciated!