Last night I had a terrible scare trying to run my 680 with the Tekkeon MP3300. Perhaps there was some user error in that it it occurred in a last minute rush to get up and running, but I DO NOT recommend taking chances with this battery!
As I prepare for my first multi-stage 3 day festival of the season, I wanted to test run time and reliability (I bought 3 of these batteries.) I used it the previous night without issue to power a 680 (4 channels line in, 2 channels p48, digi in from UA5.)
Last night I had 4 channels running p48 and 2 line-in. I had the battery voltage set at 12v. Weird responses and levels, then no levels, unit went dead, what was going on?! Re-powered unit, found that settings had I think changed back to those from previous night. This was a harried moment so I don't recall exactly, but I reset everything and still couldn't get any signal on any channel and noticed bad smell (like I imagine those fires in china where they burn off stuff from electric components to reclaim the metals)
The unit went dead again. I unplugged the from the battery, but the unit wouldn't start up on the internals.
Boys done with sound check and about to start, (I was set up at the side of the stage with 4 mics at stage lip and board feed) so with a sinking feeling in my heart I ran to start my other aud set up (CA-14 into DR-2d)
Returning to the 680, I connected a PB15000, held my breath, and the unit started up and ran fine the rest of the night. Whew!
Reflecting back on this today, wondering what I could have done differently. I had the battery connected (and locked at 12v) before turning on the 680. Perhaps I should have set the MP3300 at 9v. I don't know what combination of circumstances actually took place to have this weird experience, but these Tekkeon will probably not be going back into my gear bag. (Ordered another PB15000 this morning)
YMMV