Initially to test of unloading to the battery, if it fulfills this requirement to continue with the following step. In case that the battery does not respond positively, to change of battery and to continue with the following step.

Electrical system, the flight of allowed energy is up to 25 mA (due to a clock or another accessory), when the automobile is without contact. If it fulfills this requirement to continue to the following step. If the flight exceeds the mentioned value to look for where this the cut, verifying with the fuses (when one of them becomes disconnected and the flight diminishes to track that streamline).

The total consumption of current (of all the accessories in operation: High light, halogenous, radio with average, guiñador sound, air, etc), does not have to exceed the 54,25% of the capacity (in amperes) of the alternator. If this happens to suggest the change of the alternator and not of battery (redimensionamiento).

During the starting, the current tip (I specify of each automobile), does not have to exceed the capacity of current of cold start or cold craking (I specify of the battery). If this happens to verify the tip that would have to consume the starting with the specified one and to review Earth return and/or bushings of starting.
One assumes that the battery well is determine the proportions (to verify by means of catalogues the necessity of battery for the model of the automobile).