I have a Tekkeon 3450 and a PMD 661. I have only run it with the Tekkeon about 6 times, but I notice that with my AKG's using phantom it would go around 10 hours per charge. We used it at Vibes last year, and it did most of the entire day of recording which is close to 10-12 hours record time. I also found out at Mule Cap Theatre in March that if you don't remember to turn it on, you don't drain any power! (doh) I had internals in and it ran them down then shut off because of my not powering on the Tekkeon.