Generally, modern automatic battery chargers employ one of a number of charging methods, such as demand-based automatic boost charging, time-limited demand-based automatic boost charging, fixed extension demand-based automatic boost charging, or the like.
Limitations of standard demand-based boost charging systems and methods include that initiation and reversion thresholds must exceed the DC load on the battery plus the fully charged battery's current at boost charging voltage. Another limitation is that the initiation and reversion thresholds must allow for battery current variations caused by battery manufacturing differences, temperature, and aging. Because the method is not adaptive, another limitation of standard systems is that thresholds must be selected to avoid over-charging for the severe cases. This results in under-charging in most applications.
Limitations of time-limited demand-based boost charging systems and methods include the same general limitations as the standard demand-based boost charging method. The time-limited systems adds a backup means of boost charge termination, limiting the impact of over-charging if the initiation and reversion thresholds are too optimistic for the application. Another limitation is the time limit is not adaptive. It is set to a time that is ideal for only one specific recharge case and non-optimal for all others.
Limitations of fixed-time-extension demand-based boost charging systems and methods have the same general limitations as the standard demand-based boost charging method. It adds a fixed time extension to the boost charge, for the purpose of achieving a more complete charge for conservative reversion transition current settings. The limitation is that time extension is not adaptive. The time extension is the same regardless of battery condition, depth of battery discharge, temperature, etc. The selected value is a compromise between over-charging in some cases and under-charging in others. For example, some existing battery charges have a fixed six-hour extension to a demand-based boost charge. Since this time extension is fixed the battery will be over charged when it is lightly discharged and requires a shorter boost charge, or it will be under-charged when it is deeply discharged and requires a longer boost charge.