Hello!
Let's go back to the basics.
- mA (or mor generally A for Amperes) is a unit for intensity. Intensity is
basically the number of electrons crossing the section of a wire during 1
second, and this is by reference to 1 Coulomb (C). 1 Coulomb is the quantity
of electricity of 1,6 x 10^19 electrons.
So 1 A means that 16,000,000,000,000,000,000 electrons will cross a given
section of the wire every second. Now Coulomb (C) is the unit for quantity
of electricity, which is basically the number of electrons. And if you multiply
Amperes by hours, you get the capacity of the battery. It is expressed in
Ah, and 1 Ah is 3600 coulombs or 5.76 x 10^22 electrons.
What it means is that a battery of 1 Ah can deliver a current of 1 A for 1 hour.
Or 2 A for half an hour. Hint: you multiply the current you need by the time
you want it and it gives you the size of the battery. Exactly like water: if you
need 5 liters of water per day to survive and if you plan to cross a desert for
a week, then you'll need 35 liters.
Second thing, the voltage of a battery has nothing to do with its capacity.
You cannot convert volts into amperes or Ah, neither can you convert volts
into square meters or into seconds or into kilograms.
You may have noticed that there are A, AA, AAA batteries. All of them have
the same voltage, around 1.5V for alkaline, about 1.2V for NiMH, etc.
The difference is the capacity. The bigger the battery, the more electricity
you can store.
Now as MirekCz said, even being only visible means that it may use quite
a lot of current. It depends whether it is a class 1 or 2, but the order of
magnitude is 10 mA (order of magnitude shall mean that the current
is a 2 figures number, it can be 20, it can be 30 or more, but I guess it will
not be 100).
Dora.