there are a total of 6 cells in pn-912.

Hi All,

WTA some clarification with regards to 1st post...  So if I have a 2800 mAh and the handphone battery is 1700 mAh, how do I calculate what the the true charge capacity ? 

Appreciate if could explain also the reason behind the calculation. I would like to learn more about powerbanks : )  Thanks in advance.

Thanks for the reply.

Assuming that the powerbank is made of multiple cylindrical batteries output at 3.7V, the powerbank consolidates the output of each battery into one main output, the USB interface, which discharge at 5V. Hence the formula used above, correct ?

I have a YooBao YB-645 which claims to have the capacity of 8800mAh. The Input was stated as 5V/1500mA and the output was stated as 5V/1000mA.

So based on what I understand so far,

a) 8800mAh * 3.7V = 32,560 then 32,560 / 5V = 6,512 mAh is the ACTUAL capacity (assuming 100%).
Further Questions :

1) Is 100% output capacity a reasonable expectation for NEW powerbanks or is it by nature not possible ?  (Kinda like buying a 1TB HDD is not possible to get *exactly* 1TB space inside)

2) Input basically just tells you at what rate it is charging the power bank, rite? It doesn't in any way change the total capacity of the powerbank since the capacity is already fixed, right ?

yes usb is 5V but it's also charging a lower volatage 3.7V handphone battery.. so means MAh will increase back..
so just compare powerbank capacity with handphone battery since both is 3.7V type , of cos with some conversion losses..

what you toking.. if battery is 3.7V use direct 3.7V charger lor..

if use USB 5V charger, there is already a step down circuit in your phone.. you think plug terus 5V into a 3.7V battery?

and you think 5V from the charger goes directly into the phone battery?

Overcharging Lithium-ion

Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified voltage. Prolonged charging above 4.30V forms plating of metallic lithium on the anode, while the cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO2). The cell pressure rises, and if charging is allowed to continue the current interrupt device (CID) responsible for cell safety disconnects the current at 1,380kPa (200psi).

must be crazy to pump 5V directly into a 3.7V battery..

er.. so you saying 5V with 2000mAH = 3.7V with 2000mAH ? (after 3-5% conversion loss)

2800mah x 3.7V / 5V = 2072mah..
should be able to charge ur phone at least one times with phone off..
if on wifi, play video etc while charging, wont fully charge of course.

powerbank mah times nominal powebank battery output, 3.7V, divide by its output voltage which is 5V..

simply said, the 2800mah is at 3.7V,
if change voltage to 5V, mah will drop..

that;'s why I said from that 5V going into the phone circuit will be reduced back to 4.2-3.7V charging.. the capacity wont be just 2072mah..

think in terms of WH, 2800mah x 3.7 = 10.36WH  at 5V it'll still be 10.36WH

when it goes back into the phone battery of 3.7V it'll still be 10.36WH (less conversion inefficiencies)

Got myself Pineng Powerbank from TaoBao .... Straight from Pineng itself.. definitely original.... No doubt... however , this powerbank is disappointing.... 

Tried to charge my S4 from 40% to 90%.... around 1300mAh... took me 2-3hours to do so ... using 2.1A port ... average charging was 300-500mAh per hour...not as stated of 2A / 1A .... charging history was based on 3rd party android apps...

But to be fair , i got it for RM50+ for a 15,000mAh powerbank . for this price , i didnt expect anything , so long it didnt spoil after using for few times... I still prefer YooBao which can charge much more faster than Pineng ...

The review placed by TaoBao user is simply useless... never ever trust china ppl review ... they have never use high quality product ... LOL

Just need to open from the side written power bank (opposite the usb)
Use as much as energy you can 

rm79

what about this.? should i buy or not.. is it product is good ?
i just try google but not found many information review

Hi all, saw one which might be good, Ramoss sailing, claim to have a 3.1 max output charging and 2.1 input. 10,000mAh Rm150+. If it's true it will charge your gadget super fast since its the only one with the 3.1 output. Anybody have that might want to share your experience here, would appreciated.