USB POWER BANK // PORTABLE POWER SUPPLY

OH btw I get it now, by reading back my post earlier haha about xiomi powerbank, it is actually 2.1A, but when pass through/ charge through is perform, its maximum 2.1A becomes less, which I think that it is safe for my pi2mB. if and IF 2.1A power source for the pi2mB is safe. Waiting on replies lol, hope this doesn't bore u guys haha I myself is waiting patiently hihi

Somehow, the last few years, it has become "acceptable" to advertise with technical specs that the devices advertised cannot achieve. This started about 20 years ago with printers and scanners that claimed 600, 1200 and then 2400 DPI.

So, when the raspberry pi foundation recommends you get a 2A adapter, they mean: one that can actually deliver at least 700mA. This is just avoiding the trouble of having to explain that even though you might have an adapter that claims 1A, and the pi doesn't need more than 0.7A, because of the "inflation" of the specifications, the adapter might not be able to deliver on it's specs. It becomes really confusing for many consumers if said 1A adapter works to charge a phone. The phone can (and will!) just adapt its charging rate, if the adapter can't deliver what it claims to be able to do.

Below officially 4.65V the red light on the pi2 will go out and the screen (if attached) will show a rainbow-square. The 'pi will continue to work reliably down to below 3.3V, but this cannot be said about the peripherals on USB and HDMI. (HDMI has a "5V powerline" just like USB, and it can power things like for example HDMI to VGA converters. My first such converter is a bit picky about the voltage).

Again, charging phones is "easy" because the phone runs off its battery. The pi (the first one, for which I can find the schematics) can tolerate a voltage sag for about a third of a milisecond. So if the adapter would need "a break" for millisecond, the pi crashes. When charging a phone such a millisecond voltage drop would not be noticable.

you say: ".... not efficient". That is not the correct way to say it. "not enough" Ah.. Maybe you meant "not sufficient".

Some powerbanks claim to have a 1A and a 2A port. Internally they are mostly wired together. However, through some tricks the adapter can signal to an attached phone that it can do 1A or even more: 2A. This "signalling" is necessary because standard USB only supports 0.5A. So if they say they have a 1A port and a 2A port, they have one signalling wired up like that, but the power, which is what matters to a pi, is the same. The 'pi is not equipped to monitor that "signalling".

Somehow, the last few years, it has become "acceptable" to advertise with technical specs that the devices advertised cannot achieve. This started about 20 years ago with printers and scanners that claimed 600, 1200 and then 2400 DPI.

So, when the raspberry pi foundation recommends you get a 2A adapter, they mean: one that can actually deliver at least 700mA. This is just avoiding the trouble of having to explain that even though you might have an adapter that claims 1A, and the pi doesn't need more than 0.7A, because of the "inflation" of the specifications, the adapter might not be able to deliver on it's specs. It becomes really confusing for many consumers if said 1A adapter works to charge a phone. The phone can (and will!) just adapt its charging rate, if the adapter can't deliver what it claims to be able to do.

Below officially 4.65V the red light on the pi2 will go out and the screen (if attached) will show a rainbow-square. The 'pi will continue to work reliably down to below 3.3V, but this cannot be said about the peripherals on USB and HDMI. (HDMI has a "5V powerline" just like USB, and it can power things like for example HDMI to VGA converters. My first such converter is a bit picky about the voltage).

Again, charging phones is "easy" because the phone runs off its battery. The pi (the first one, for which I can find the schematics) can tolerate a voltage sag for about a third of a milisecond. So if the adapter would need "a break" for millisecond, the pi crashes. When charging a phone such a millisecond voltage drop would not be noticable.

you say: ".... not efficient". That is not the correct way to say it. "not enough" Ah.. Maybe you meant "not sufficient".

Some powerbanks claim to have a 1A and a 2A port. Internally they are mostly wired together. However, through some tricks the adapter can signal to an attached phone that it can do 1A or even more: 2A. This "signalling" is necessary because standard USB only supports 0.5A. So if they say they have a 1A port and a 2A port, they have one signalling wired up like that, but the power, which is what matters to a pi, is the same. The 'pi is not equipped to monitor that "signalling".