For how long does the battery that comes with the HV20 run?

Ron, the answer to this question really depends on several variables. To get a complete picture of the battery endurance, you need to refer to a chart located on page 19 of the operator's manual. You can download the manual in .PDF format for free, see http://www.dvinfo.net/conf/showthread.php?t=75445 -- hope this helps,

Thanks, that makes sense.