Take a look at DIY SRM Battery Change
. The plastic torque cover has a slight lip which is probably obscured by the inner and/or middle chain rings. Once removed, you should see the lip and using a good source of light and possibly a magnifying glass, you will see there very small indentations around the circumference of the plastic torque ring. The torque ring is press fit onto the inner lip of the powermeter and I have used a very sharp shop knife but you can also use a jewelers screwdriver to carefully - plastic is very thin and easily deforms - pry the cover off.
Thanks! I got the cover off and will replace the battery. BTW, I ended up using a surgical scapel #10 blade b/c the fit was so tight. It's a good design to keep water out. Thanks again for your invaluable help.