I have had this product for about one year now but I haven’t fully tested it except anecdotally.  During this one year time I have kept the device plugged into its ac charger (this is the manufacturers recommendation).   So for my first test I took my Mac Book with 2.4 Ghz Intel Core 2 Duo and 4gb of memory with a 100% charged battery and plugged it into the Duracell Powerpack 600 using the Apple AC Adapter.  The begin time was 10.08.00 and the Unrelenting alarm started at 18:39:00.  This was a total run time of 8 hours and 31 minutes.  Not too bad.  I left the Powerpack 600 on my Pulsetech Xtreme charger overnight and it was completely charged by the next morning.  Started at 23:31 and finished at 08:29 the next morning.   So basically had it charging for 8 hours.  Not sure when it was completely charged though.  I will continue doing more tests with the lap top and various other loads to see how well this device works.  Stay tuned…..