As silentmark said, your MT has to have a FULL charge to begin with... I made a bunch of AA chargers and never had luck with them keep up with the MT...
I ended up buying a Digital Concepts PP99 for under $20...
http://www.amazon.com/iConcepts-Digi-Power-Pack-PP99/dp/B0009EXVGC/it is also sold under the brand name "Sakar" I think.
I had to make my own cord, the PP99 does not come with one that will fit the MT's USBmini... it is very easy though...Radio Shack sells the power plug, not the univesal adapter ones, and actual solder type... it is in the parts drawers... I will confirm, but I think it is the "M" one... then buy or take a cheap usb cord and cut of the one end... you need to solder the positive out of the PP99 to pin 1 and the ground to pin 4 of the USBmini... see the USB mini pinouts here
http://pinouts.ws/usb-pinout.htmlmake sure to set the PP99 to 5V for the MT
Radio Shack Plug "M"
http://www.radioshack.com/product/index.jsp?productId=2103614&cp=&sr=1&origkw=plug+m&kw=plug+m&parentPage=searchhere is mine...
http://fecundswamp.peanutonastring.com/usb/img005.jpeg.htmlI made a whole bunch of the AA versions you can see here... from lame to nice 12V wooden one...
http://fecundswamp.peanutonastring.com/usb/index.htmlI found the best one is the DC PP99
although, the wooden one looks totally bitchin'.
I bet you will be able to record for the entire day, maybe more, then charge up over night... the PP99 even has a car charger with it... and a AC charger... for $20 it is amazing.
Note... when changing your cards, unplug the charger... it is not and issue with the newer firmware, but to be safe unplug the power then change the card. I use to have trouble with the MT locking if it was on charge while changing cards... the 1.4.6 works fine, but I got in the habit just to be safe.
and I am able to switch it to 3V for the R9 and 5V for my camera... and they both use the same plug that came with the PP99.