From what I read, you can add the DR100 MKIII into that mid-line list of Iron Film's.
I know about that, but rule it out as it isn't seriously intended for location sound recording.
I'd rather have a Tascam DR70D for about the same price!
Yes the F4 takes redundant battery power, a 3d party external lithium-ion battery pack will automatically roll over to the internal AA's when it runs out of power. Since you can get really large external packs quite cheaply that is a good option.
Yup, I power mine with Sony BP-U60 batteries. Or even a little tiny BP-U30 is plenty!
Also, you can buy extra battery holders which means you can change the internal batteries in less than a
minute.
Have that too, but I've never used mine, as I just go external power.
Actually, I am surprised someone has not come up with an internal LI battery pack for these recorders.
Probably because everyone has their preferences for powering systems. The recorder is not your only thing in your bag needing power!!
However, I have discovered that the F4 eats batteries when it is not being used, plus the RTC is not super accurate, about 5 minutes a month, my 25 year old wrist watch keeps one minute a year.
This is why you should always jam TC at the start of the day, then leave your F4 running non-stop.