This is my battery:
http://www.amazon.com/MACALLY-External-Battery-all-iPods/dp/B000CGG8LW/ref=pd_sim_e_4
They are out of production and a bit hard to find, but it is the only one that seems to work with the MR-1. The problem is that the MR-1 periodically needs a high current, so you need to find one that has over 1 A. Most have 500 mA or less current. I've tried a few. For the low current ones, I keep having to unplug and replug the battery because the on screen battery indicator will switch from "charging" to not charging.
Nice set of pics, tedyun!
So how much time can you get with that battery?
The problem I have, is that it needs to keep supplying enough power (5v or UP, right?) to convince the MR1 that it is plugged in, and all the stuff I've tried so far, including the Korg's own battery pack will power it, but sometimes its charging and sometimes it isn't.
With the 4 AA pack, I can get a solid 2 hrs. + whatever life is left in the internal. In a decent unit, that's 2 hours already, so there you have 4 hrs, but in order to preserve the internal, you want to keep supplying it power so that it doesn't lose its charge except when absolutely necessary.
I hope this battery information will help you, igene, we'll see:
Check how many tapes were made on the unit. Assume that each one drained a 2.5 hour battery.
The MR1 needs a nice 24hr charge before you take it out in the field, which is a huge problem if you are taping 2 nights in a row.
Sometimes I can't get it to charge up completely before I'm out the door for the next night.
That's why the need for an external. (see above about keeping it charged.)
Right now I have a very nice (and slightly large and heavy) Tekkeon 3450 that I got from Rich in the yard sale.
Tested it last night and got 6+hours and the MR1 shows 3 bars afterwards. So it is good at keeping it think it is "plugged in".
The moment you take it out into the field with the internal, the crappy battery begins its demise!
So you'll have to charge it up good and then run it and see how much juice it has.
I'll have to look for one of those adapters at Walmart.
Haven't seen one anywhere until your picture.