I see you have a Mugen's back cover which came with a bigger capacity battery. How did you get that, or do you also have the Mugen 2400 mAh battery?

Did you just connect two BL-5J batteries parallel on their pins 1 and 2 (+ and -)? How did you manage to do that? Soldered cables tolerable to 1A to the battery contacts, or did you break the cover of the batteries to solder cables inside? More accurate photo of the connection of the two batteries in parallel would be nice.