Voltage is the overall potential difference that the battery can create. Every battery has a specific voltage that it delivers. One thing to remember is that this voltage will vary slightly based on the charge condition of the battery. That is, when a 12V battery is fully charged, it may be giving an output of 12.6V. However, when it gets fully discharged, it may reach up to 11.4V. So, what battery voltage means is the nominal voltage that the battery would be providing.