Many installations already have them in /var/log/asterisk/cdr-csv/Master.csv* (installing asterisk will do that by default)
If the are not there then perhaps add
[csv]
usegmtime=yes ; log date/time in GMT. Default is "no"
loguniqueid=yes ; log uniqueid. Default is "no"
loguserfield=yes ; log user field. Default is "no"
in /etc/asterisk/cdr.conf and customize it in cdr_custom.conf if you want/need to.