I have a garmin edge 500 and the power meter just quit reading. I charged it up fully and made sure the garmin had no rides in it then tested it again and nothing. Is there something I can do to recalibrate it? Weird thing is the rest of the stuff is working just not the power/watts. I have a powertap hub.

Have you tried the PT with a different head unit, or the 500 with a different PM?

The 357 silver oxide batteries in second generation PowerTaps are officially only good for 300 hours. I replace mine when they hit the lesser of 2500 miles or 3 months so they don't go dead in the middle of a ride. CycleOps says the non-silver oxide battery flavor is very short lived.

Not yet.

Ya it is probably dead then. I bought it used and have put 1500 miles on it but never changed a battery yet. I didnt know there was one really. Is it easy to change?

It's easy to change as long as you have the tool that comes with it. If you bought the hub/wheel used the tool should have been part of the deal, if you didn't get one you can buy one off of eBay. Note that the current version of the PT uses a different tool than previous versions.

Well, i didnt get the tool. so today I took it off and grabbed it very hard with my hand and it came off. So get some batteries tomorrow and see if it fixes it.