Suggestions to do a battery mod?

[S4R0M]

I been searching a lot and i want to do this mod:
https://www.acidmods.com/forum/index.php?topic=32190.0

There a guy installed 2 cell phone (i think they are for cell phone because their size) batteries in parallel with the normal psp slim battery; But the first pictures are now missing and i wasn't able to find tutorials for that mod...

I think i know how to do it, for now it doesn't seems too difficult; I've done some psp reparations before, so, at least i know how to replace displays, buttons and add leds...
But i have several questions:

1.- Is really possible to use 2 non-psp batteries along with the normal psp battery?
2.- If is possible, why there's no tutorial for that mod?
3.- If the mod works well, can someone give me suggestions about which battery models are usefull (and can fit in the umd bay) to try that mod?

I really want to try that mod 

[Burning_Battery]

I been searching a lot and i want to do this mod:
https://www.acidmods.com/forum/index.php?topic=32190.0

There a guy installed 2 cell phone (i think they are for cell phone because their size) batteries in parallel with the normal psp slim battery; But the first pictures are now missing and i wasn't able to find tutorials for that mod...

I think i know how to do it, for now it doesn't seems too difficult; I've done some psp reparations before, so, at least i know how to replace displays, buttons and add leds...
But i have several questions:

1.- Is really possible to use 2 non-psp batteries along with the normal psp battery?
2.- If is possible, why there's no tutorial for that mod?
3.- If the mod works well, can someone give me suggestions about which battery models are useful (and can fit in the umd bay) to try that mod?

I really want to try that mod 

Original thread of battery mod here - https://www.acidmods.com/forum/index.php?topic=32190.0

with pictures from first post - http://www.phil.my/blog/2009/09/psp-umd-compartment-battery-mod

And to answer:

1. Yes - it is definitely possible. As long as the Volts add up then it's doable. As in - using 3.7V batteries are fine - 20V is not.

2. I think the creator didn't know how to explain it in English entirely - so he chose not to explain it in case someone blows up a battery... or themselves

3. This battery - http://www.ebay.com.au/itm/Genuine-3-7V-SONY-Lithium-Polymer-Battery-503759-US503759-A7H-1350mAh-SN0023-/130732338509?pt=US_Rechargeable_Batteries&hash=item1e70412d4d

I'm going to attempt this mod as well I've bought the batteries and this protection board - http://dx.com/p/charge-discharge-protective-circuit-board-for-rechargeable-li-ion-batteries-13-4mm-1-7mm-26114    (2x - 1 for each battery since I don't have a multicell protection board like the other two guys in the thread have). - although I'm not sure if this one will work...

What I'm trying to find is a RAZOR X PCB - but since coolmods went out of business its impossible to source the PCBs - so might have to scratch that idea

Although if any other users out there could help me out it would be much appreciated

This mod goes in combination with me restoring a PSP 2K (with hackable motherboard) that I got off ebay

This guy attempted something similar as well - http://www.consolespot.net/forums/general-psp-discussion/12280-make-8-10h-battery-your-psp.html

[Bubsy]

Here's an easy way to go about it, with a video tutorial   

https://www.youtube.com/watch?v=CmcyH8ppxjI