[Galaxy S II Accessories] asalah0923:
I'll start with officially mentioned spec.

Item: Samsung Galaxy S II Power Pack

Model: EEB-U20BBU

3.7 Li-ion BATTERY , 4.81Wh

Made In Korea

Input : 5.0V = 700 mA

Output : 4.6V = 650 mA

Battery Capacity (1300mAh)

Charging time : about 4 hours

Stand-by Up to 390h (2G) / Up to 250h (3G)

Talk time Up to 557m (2G) / Up to 222m (3G)

And these are some of the important notes in user guide :

-When you insterts your smartphone which features NFC into the power pack , NFC is unavailable .

-While using the phone with power pack where signal strength is weak , you may experience decline signal strength of your phone .

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My own opinion :

1 - pros :-

--Considerable increase in life time compared to increased size of the phone

and I see it in this way the best solution ,

First, size of phone isn't increased badly , and the shape and the style of the phone still great , perfect to hold and still have the looks ,

Also you don't have to get rid of your original battery as other solutions like ( buying 2400 mAh Battery which you'll have to through away the original battery , and stick to only new plus you have to change the back cover with ugly one except for the original 2000 mAh battery which also will not give you the same increase in battery life )

--adding 1300 mAh to 1650 mAh that is to say 2950 mAh is a grat deal but I don't think it 's calculated this way,

as it increases battery life from 40 to 45 % according to my experience . so lasts over the day with my kind of usage , I think it adds hour and half of ( screen on with highest brightness ) time , i.e heavy usage of hour and half to two ( according to my trials ) .

--it works as cover for your phone so really protects the camera ( I 've got a lot of scratches on the Camera, so I wanted something to cover it )

2 - cons :-

-- no support to Usb OTG , who know the configuration of the cable will know why it doesn't support that , as if it does , it will show a notification label " usb OTG connected all the time "

--no power button to shut it off when don't want to use it , although I see this is a useless feature , why I bought it in the first place to turn it off !

--long charging time , adding 4 hours to the original 4 to the battery that is 8 hours charging time , so be sure before you go to sleep to plug it in , or you will have to charge every piece apart ( to get only 4 hours ) . so as to save some time , although I see it normal , as it is not a single battery , it is two separate ones

so expect to spend long time charging it , but in terms of "worth it" , yeah , it gives you your charging time back

--no power cord included , you have to charge it with the one came with the phone .

3 -Additional '' to know stuff "

--tried it a couple of times , when phone is not fully charged i.e. 20% or more , and put the fully charged power pack it charge it up to 40 % or more . , so don't expect it to last much when phone is not charged , it 'll last the time the phone take it to get charged a hour or more by a little , not more .

--when phone is fully chagred thats when it lasts the most , because you only use it now (no power wasted on charging the original battery ) , so it lasts for me 4 - 8 hours according to my usage , and it is great feeling when you look to the phone after 4 hours of usage and still battery full :D

-- basic thing to get is , some theme or mod to remove the battery full notification , and may be the charging Icon too , I use JKay Deluxe framework for that . because if you going to fully charge it , the annoying battery full notification appears as if you pluggin' it to power cord .

JKay Deluxe framework (ICS)

http://xdaforums.com/showthread.php?t=1667846

--the Pack has got dedicated button beside MicroUsb port to show its battery level with the small LED

Red less 20%

Grean 20 -80 %

Blue over 80 %

this is some Pictures to see what it looks like :)

Just wanted to give you some help guys :)

any Questions are welcomed :)