Battery charger and method utilizing alternating DC charging current
View Patent ↗A battery charger is disclosed for use with various batteries, such as automotive- and marine-type batteries. In accordance with an aspect of the invention, the charging current is alternated between non-zero DC charging current levels. By alternating the charging current between non-zero DC charging levels, the battery can be charged to a higher capacity (i.e., ampere hours) faster, thus reducing the charging time and at the same time allow the rating of the battery charger to be increased. In accordance with another important aspect of the invention, the technique for alternating the charging current can be implemented in both linear- and switched-mode battery chargers.
1. A battery charger comprising:
a pair of battery charger terminals; and
a microprocessor controlled battery charging circuit to supply a battery charging current to a battery connected across the pair of battery charger terminals,
wherein said microprocessor controlled battery charging circuit periodically measures a voltage across the pair of battery charger terminals, defining a measured voltage,
wherein said microprocessor controlled battery charging circuit does not supply the battery charging current when the measured voltage is less than a first predetermined voltage,
wherein said microprocessor controlled battery charging circuit operates in (1) a first charging cycle mode while the measured voltage is greater than said first predetermined voltage and less than a second predetermined voltage, and (2) a second charging cycle mode while the measured voltage is greater than or equal to said second predetermined voltage,
wherein said first charging cycle mode comprises two DC charging values, each having a non-zero average DC value defining a maximum charging current value and a minimum charging current value, said microprocessor controlled battery charging circuit alternating the battery charging current between said maximum charging current value and said minimum charging current value until said battery voltage reaches said second predetermined voltage,
wherein said maximum charging current value (1) ramps up from said minimum charging current value to said maximum level charging current or (2) ramps down from said maximum charging current value to said minimum charging current value.
2. The battery charger of claim 1 , wherein said maximum charging current value (1) ramps up from said minimum charging current value to said maximum level charging current and (2) ramps down from said maximum charging current value to said minimum charging current value.
3. The battery charger of claim 1 , wherein the first predetermined voltage is about 0.1 volts DC.
4. The battery charger of claim 1 , wherein the second predetermined voltage is a maximum recommended charging voltage by the battery's manufacturer plus a third predetermined voltage.
5. The battery charger of claim 4 , wherein the third predetermined voltage is between 0 volts and 0.02% of the maximum recommended charging voltage.
6. The battery charger as recited in claim 1 , wherein said maximum charging current value and said minimum charging current values are not constant over a charging cycle.
7. The battery charger as recited in claim 1 , wherein the duty cycle of said maximum charging current varies as a function of the battery's state of charge.
8. The battery charger as recited in claim 1 , wherein said battery charger is configured with a plurality of selectable charge rates.
9. The battery charger as recited in claim 8 , wherein said battery charger is configured so that said maximum charging current value is automatically generated when one or more of said plurality of selectable charge rates are selected.
10. The battery charger as recited in claim 1 , wherein said maximum charging current value and said minimum charging current value are constant over a charging cycle.
11. The battery charger as recited in claim 8 , wherein said plurality of selectable charge rates includes a slow charging mode, a medium charging mode, and a fast charging mode.
12. The battery charger as recited in claim 1 , wherein said plurality of selectable charge rates includes a slow charging mode, a medium charging mode, and a fast charging mode.
13. The battery charger as recited in claim 1 , wherein said battery charger is configured to be placed in a test mode.
14. The battery charger as recited in claim 1 , wherein said battery charger is configured to determine whether a predetermined time period has passed since the battery charger provided amperes of current, to start an automobile engine.
15. A method for charging a battery, the method comprising the steps of:
periodically measuring a voltage across a pair of battery charger terminals, defining a measured voltage;
supplying the battery charging current across the pair of battery charger terminals when the measured voltage is greater than a first predetermined voltage;
operating in a first charging cycle mode while the measured voltage is greater than said first predetermined voltage and less than a second predetermined voltage; and
operating in a second charging cycle mode while the measured voltage is greater than or equal to said second predetermined voltage,
wherein said first charging cycle mode comprises two DC charging values, each having a non-zero average DC value defining a maximum charging current value and a minimum charging current value, said microprocessor controlled battery charging circuit alternating the battery charging current between said maximum charging current value and said minimum charging current value until said battery voltage reaches said second predetermined voltage,
wherein said maximum charging current value (1) ramps up from said minimum charging current value to said maximum level charging current or (2) ramps down from said maximum charging current value to said minimum charging current value.
16. The method of claim 15 , further comprising the step of determining whether a predetermined time period has passed since the battery charger provided amperes of current to start an automobile engine.
17. A battery charger comprising:
a pair of battery charger terminals; and
a microprocessor controlled battery charging circuit to provides a plurality of selectable charging modes, at least one of said plurality of selectable charging modes being a fast charge mode,
wherein said microprocessor controlled battery charging circuit periodically measures a voltage across the pair of battery charger terminals, defining a measured voltage,
wherein said microprocessor controlled battery charging circuit does not supply the battery charging current when the measured voltage is less than a first predetermined voltage,
wherein, in said fast charge mode, the battery charger alternates between two different DC charging currents,
wherein said DC charging currents have a non-zero average value and define a maximum charging current value and a minimum charging current value, said microprocessor controlled battery charging circuit alternating the battery charging current between said maximum charging current value and said minimum charging current value until said battery's battery voltage exceeds a second predetermined voltage, and charges said battery at a constant current thereafter, said DC charging currents selected to cause said battery to be at least partially charged during said fast charging cycle at a voltage greater than said second predetermined voltage,
wherein said maximum charging current value (1) ramps up from said minimum charging current value to said maximum level charging current or (2) ramps down from said maximum charging current value to said minimum charging current value.
18. The battery charger of claim 17 , wherein the first predetermined voltage is about 0.1 volts DC.
19. The battery charger of claim 17 , wherein the second predetermined voltage is a maximum recommended charging voltage by the battery's manufacturer plus a third predetermined voltage.
20. The battery charger of claim 19 , wherein the third predetermined voltage is between 0 volts and 0.02% of the maximum recommended charging voltage.