Voltage is the amount of "push" that a battery has. A 12 volt battery has more push than a 5 volt one. Amperage or Amps is the amount or rate of flow in an electrical circuit. A milliamp (mA) is one thousandth of an amp.
A milliamp-hour (mAh) is one thousandth of an amp flowing for 1 hour.
A 500 mAh battery could supply 1 mA for 500 hours or 500 mA for 1 hour. (This is theoretical)
If it is a 5 volt battery it would have 5 volts of "push" for the 500 hours or for the 1 hour.
If it is a 12 volt battery, it would have more push so it could run a bigger motor or run a motor faster than the 5 volt battery.

All batteries are made from one or more cells. The amount of voltage of the battery depends on the number of cells and the chemistry of the individual cell. Different types of cell chemistry produce different voltages. (1.1, 1.2, 1.5, 2.0, 3.6). Depending on haw the cells are connected you can get more voltage or more amp hours.

    MissBlossom According to Wikipedia, "the unit of power is the watt (W), which is equal to one joule per second" not Joules x Seconds.

    That's correct. Was a mistake on my side. Should not do physics too early in the morning.

      MissBlossom Does that mean "yes" or "no"?

      In general, if you are powering things with USB, the more mAh, the better.
      What actual problem are you trying to solve? What is you application?

          Tjc What actual problem are you trying to solve? What is you application?

          I just want to know how to compare batteries and power packs.

          You could say I want to be able to figure out which one's bigger without opening the package and testing it out.

          If my summary above is correct, my problem is solved.

          • Tjc replied to this.

              MissBlossom If you are comparing USB batteries and power packs for phone and tablets and things like that (Not starting cars) the more mAh, the better.
              If you are comparing a 12 volt battery and it has USB output, it will turn the 12 volts into 5 volts internally so you don't need to take the 12 volts into account.
              The rest of what you said is correct

                  Tjc

                  If you are comparing USB batteries and power packs for phone and tablets and things like that (Not starting cars) the more mAh, the better.

                  Bingo was his name-o.

                    Unless you are completely repurposing electronic components (in which case you should better know what you are dealing with instead of relying on internet strangers), any product that advertises USB output is going to provide capacity either in Wh or in a mAh figure that works like that of power banks. Else they would be shooting themself in the foot by underreporting their capacity compared to the competition.

                      MissBlossom I agree with @Tjc . If you want to compare it look at the different devices as a black Box. What realy matter is the voltage at the Connection Point and current hours it can Delivery. What realy Happen inside is Not relevant for your comparison

                        4 days later

                        youdontknowme any product that advertises USB output is going to provide capacity either in Wh or in a mAh figure that works like that of power banks. Else they would be shooting themself in the foot by underreporting their capacity compared to the competition.

                        Except when they either intentionally lie or print misleading bullshit because they don't know any better (both situations being unfortunately common). When it comes to characteristics that cannot be easily and independently measured by the end user, anything which does not come from a known, reputable supplier (and is known not to be a forgery) is suspect. And batteries are in exactly the middle of the venne diagram of "extremely common", "surprisingly hard to accurately measure", "sold purely by advertised specifications" that make them ripe for such abuse.

                        I've come across a few power banks which made clearly impossible claims - e.g. a 2-cell pack, containing 2 18650 cells, claiming both a voltage and charge capacity that would require a minimum of 4 cells (7.2v, 5500mAh). Whether that an intentional lie, or simply incompetence at calculating basic specifications, is unknowable.

                            cilarith Sounds consistent with what the TP-Link document says. 2 Lithium-ion cells in series would add up to 7.2 V, and they could contain as much energy as a 5500 mAh LiPo cell.

                            Of course it is rather disingenuous to advertise both in the same figure, since when they are wired in series like that you are going to have the two (I assume) 2750 mAh cells discharged with half as much current draw. But the industry convention appears to be to just add up the charge of each cell, since that is how much phone battery it could top up if you completely ignored inefficiencies. Plus when comparing two power banks, you do not care about the voltages they use internally, you care about what you can get out of the battery at the end of the day, and marketing it as a 2750 mAh power bank would be underselling it compared to a 3.6 V 3000 mAh power bank.

                            Really, they should have just standardized on something more sensible, like Wh or mAh at 5 V, not mAh at 3.6 V. The simple "can top up your phone battery N times" metric does not work anyway because efficiency has not been factored into the mAh figure to begin with.

                              cilarith

                              Except when they either intentionally lie or print misleading bullshit

                              Within a capitalist model, that's a feature, not a bug.

                                a month later

                                MissBlossom
                                The 5 volt charger that plugs into a 110 AC outlet plug- in . Will always have more Juice behind it than on that plugs in basically to a car battery. Why you ask ??? Because car batteries can be run down if it's being used for other things or electrical loads drawn as well. Where a charger being powered and supplied by a charger plug into the wall will not ever be run down .