mAh was given by iBasso to me on e-mail - 2400mAh. Note though 8.4V at least to my knowledge, is quite non-standard for the Lipo world. Consumer Lipo cells are in multiples of 3.7V. Having said that, none of my Lipo cells were every accurately in 3.7V multiples. At least in Tokyo most of the RC stuff are Lipos or LifePO4 which puts them into the 3.7V and 3.3V respectively although older NiMH/NiCad 1.2V cell multiples do still exist.
The charged voltage, as measured earlier in this thread was 8.2. NiMH are 1.2 but that is the minimal voltage. They normally charge to 1.42 within a .01 or so. So a 3.7 charged with two in series would be about 8.4V so that is not, nonstandard. I would guess that if someone finds a fit with a higher mA, it should work.
Edited by jamato8 - 9/19/12 at 12:37pm