Question

how do I know how much voltage the "battery" is able to provide me

Answer 1

The total electrostatic potential of a battery is stated in volts. This is one of the most prominent characteristics of a battery, and it has a large bearing on the output power of a battery: generally, the higher the rated voltage, the larger the output power. Also, battery capacity is given in amp hours.

The output voltage of a battery is then either (a) the sum of all the individual cell voltages (if arranged in sequence, ie anode to cathode along the line. It is also known as a “pile” hence the word for “batteries” in places like France and Italy. Or (b) the same as just one of the cells (if arranged in parallel, ie all the anodes connected together and all the cathodes connected together).The advantage of this is you can get a heavier current draw from the latter (b), or a higher voltage from the former (a). For example if you take apart an AA battery you will find it is only one cell of about 1.5 volts. If you take apart a fire alarm battery you will find it is 6 such cells all joined together in series compactly to give 6 x 1.5 volts = the 9 volts needed to activate the smoke detector function.

For cells based on chemical reactions in an aqueous environment the maximum voltage is theoretically restricted to 2 volts because at that point the energy is used up within the cell turning the water into hydrogen and oxygen gas and its shelf life is zero. For practical reasons such commercial cells usually run at 1.5 volts maximum.

Cells based on other non-aqueous environments can have different maximum voltages, but are often restricted by a limit on current density due to the mobility of ions in restrictive media.

Even aqueous based cells reach a current limit due to “polarisation” where the reaction products cannot leave the electrode fast enough to maintain the reaction at the theoretical energy level. This is why a live flashlight might cut out as if the cells were exhausted, but will slowly recover and work again maybe an half hour later.

There are many aspects to the operation of electrical cells (batteries) but fundamentally they are all based on the Free Energy available from some chemical reaction/process or another. The higher the Energy, the Higher the Voltage per cell. The derivation of “half cell” voltages (ie contribution per electrode) has to be based on an arbitrary ZERO voltage., so it has no real independent existence. For most purposes the convenient Zero Marker is the Hydrogen Electrode, the voltage for the interconvertion of standard hydrogen to standard hydrogen ion, and all other ionization (in water) voltages are relative to that. A Table of half cell potentials makes it easier to choose electrodes that might give you the voltage you require, subject to media limitations (vide supra).

You could use any ionization process as the zero and when you added the half cell potentials together you will get the same overall cell voltage, but in a water world the one of the two component atoms of water is an obvious choice.

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