Can a battery, which is running on its last strength, still display the correct weight in a scale?

Answer

A battery supplies a certain voltage, for a certain time depending on the load.

This is because the battery contains an amount of substance that can react with the electrodes. This represents a certain charge (expressed in Coulomb). That charge is the product of a current with a time. Written in an equation:

Q = ixt

Q is charge (in Coulomb), i is current (in Amps), t is time (in seconds). The greater the current, the faster the battery is depleted.

As long as the reactions can continue, the battery supplies a voltage that is determined by the potentials at which the reactions take place. Good batteries provide an almost constant voltage over time. When the substances are almost exhausted, the tension begins to decrease drastically. As soon as the supplied voltage is insufficient to make the application work (in this case a scale), the application stops working. With the scales, this will manifest itself in no reading. An erroneous reading is more likely to point to a poorly calibrated scale.

A battery can be used optimally as long as it generates a constant voltage.