Dual HRM Strap not working with Edge 830

I've been having problems lately using the Garmin dual HRM strap with my Edge 830.  I'm on my third HR strap and still no go.  the last two worked first time out of the box but after the ride I remove the sensor from the strap to dry it then the next ride it doesn't work.  On my second strap after this happened, I checked the battery and it was very low (<2.3 volts).  I assumed it developed a short internally but I checked the battery contact resistance and it was very high (>>1Mohm) so that doesn't appear to be the problem but I can't check current draw while the battery is in the unit and the back plate installed.  I only use it with ANT+ and I removed and re-added the HRM sensor on my 830 several times and power cycled by Edge 830 several times.  I'm all out of troubleshooting ideas. Any help would be appreciated!