[Galaxy Note II Accessories] nerys71:
no. it won't

remember a 20amp hour battery does not equal 20 amp hour into your device !!! For example I have a 9300 mah battery pack. My Note 3 is 3200mah. Can I charge it 3 times? NO. twice? Probably not.

why? 9300/3200 is about 3 ?

its called conversion losses and overhead.

a 5000mah battery SHOULD be enough for "one" full charge of my 3200mah Note 3.

First you converting the power twice. once when you convert the 3.7volt of your battery pack to 5.2v and then again when the charging circuit in your phone converts the 5.2v input back down to 3.7 volts to charge the battery (roughly it could be 3.2 to 4.2 volts)

each of those conversions are VERY inefficient. possibly costing you 10 to 15% of your rated capacity "EACH CONVERSION" so 15 to 30% of your power just went POOF now your 20amp pack is a 14amp pack.

then you have load issues. the more "load" the lower the effective capacity. the higher the load the lower the effective capacity. so you could charge an ipod a lot more than you can charge say a note 3 that sucks down 2 amps charging. this could easily again be 10-20% of your rated capacity!! SO now your 20amp battery is effectively 10amps.

AND THEN you have operating overhead. the lights on the device take power (not much) and the device "ITSELF" consumes power while its operating and that power is coming from your battery pack. so if your phone commands 500mah an hour and takes 2 hours to charge that is another "amp" gone and if you charge it twice thats 2 amps gone.

SO now your 20amp battery is an 8 amp battery. (worst case scenario probably more along 12 amps effective)

this happens with "ALL" if your chargers. you don't notice this because you have an unlimited (effectively) upstream power source. the mains plug in your wall.

but if you have the equipment you can in fact measure this. deplete your battery and charge it up. you can run software to see how much power the battery used (and therefore how much your putting back in) and a watt meter to measure the consumption at the outlet (a typical watts up kind of meter won't work here its not accurate enough by quite a large margin the load is too small)

the difference is all the "losses"

problem is when your using an external battery pack you have a constrained amount of power. what's in that pack and that is it. SO you "MUST" account for all the losses to figure out how much power you need.

even the manufacturers don't fully realizes and can not really estimate how much power your going to lose. there are too many variables.

a good safe bet is 50% assume the battery will "net" you 50% of rated after losses. so if you need a 10 amp battery you want to buy a 20amp battery.

my phone is 3200mah so I need one of those 5600-6000mah batteries to make sure I get one full charge.

ALSO do NOT use the battery pack to charge the phone if you can help it. use it to "RUN" the phone and deplete the external battery "FIRST" leaving your internal battery 100% full.

this will greatly extend the mah usage from the external pack because OPERATING power sans charging consumption is a far lower load (and therefore more efficient) than operating "PLUS" charging since charging circuits are typically VERY inefficient. why? because they just don't NEED to be efficient since most of the time 99.99999% of the time they are plugging into mains power and the loss is irrelevant.

I use a LOT of external batteries I Have over a dozen of them. I use them to rechrage my gizmos in the field when I am out flying planes or rockets. so I have learned a lot about how the little buggers work :)

another good way to estimate power in a battery pack if you suspect the rated power is fiction.

price. how much would a 20amp "cell" cost you to buy? if its cheaper than a same size cell its probably not that size cell.

some tips to maximize your power output? never charge "operating" devices if power levels are a concern. turn it OFF then plug it in. this reduces load and reduces overhead (operating power consumption)

the BEST way to do this is an external charger and a second battery pack. you put the dead battery in the usb charger and plug that into the batter pack while your phone operates on the second battery that is already charged.

for the most part unless explicitly stated otherwise NEVER charge and use at the same time. Most of the time the device won't let you it will switch "modes" but if it does let you it could overload its circuitry and burn out (I have done this till I learned not too!)