@Estel, How about a Auto-Expanding-Design..

1) it will stay inside normally when there is one Extra battery "Aligned Normally(0˚ with main battery)"(Total 2 Batteries)


2) it will slide out(both sides) a to accommodate Two Extra batteries "Aligned Perpendicularly(90˚ with main battery)"(Total 3 Batteries)

3) And will get back inside when you want to use one extra battery like in #1

4) This Arrangement will also hold the main Battery in place when No Extra Battery is used in Big cover i.e "(Total 1 Batteriy Only)


something like this:





Transparent Render showing Design of Auto-Expanders



Transparent Render showing How Auto-Expanders Accommodate 1 extra Battery in Normal mode(total 1 Batteries)



Transparent Render showing How Auto-Expanders Accommodate 2 Extra Batteries(total 3 Batteries)



Auto-Expander Inside when Normal (1 Extra Battery total 2)



Auto-Expander Out when Extreme-Mode (2 Extra Battery total 3)



Almost flat & Sleek along the Body when Not Used



By IMMI.SHK at 2012-05-09


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P.s. - @Estel, @dr_frost_dk
IMHO to make it possible.. we will be requiring a detachable extra battery circuit.. for comfortable using it in 1-Extra Battery Mode & 2-Extra Battery Mode or even No-Extra Battery Mode
the circuit can be shifted aside camera region leaving just "3 + 3" i.e. 6 Contact pins in Auto-Expanding-Bracket


GODbless

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NOTE - THESE ARE NOT ESTEL'S DESIGN...
IF SOME(I HOPE NOT ALL) OF YOU GUY'S "DONT LIKE IT/FIND IT UGLY/WEIRD/FAT/TANK"... THEN THE CREDIT GOES TO ME

THEY ARE JUST TO EXPLAIN THE CONCEPT "THATS IT"

M SURE ESTEL'S ORIGINAL DESIGN R GOING TO BE MUCH BETTER AND SLEEK

CHEERS