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 microprocessor controlled battery charging circuit, said microprocessor controlled battery charging circuit being configured to provide a battery charging current for charging a battery,
wherein said microprocessor controlled battery charging circuit (a) repeatedly measures a battery voltage of said battery while said battery is being charged by an AC input source that defines an AC zero crossing, and (b) provides (i) a first charging cycle while the battery voltage is less than a predetermined voltage, and (ii) a second charging cycle while the battery voltage is greater than or equal to said predetermined voltage,
wherein said first charging cycle 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 predetermined voltage, said maximum charging current value and said minimum charging current value being selected to cause said battery to be at least partially charged during said first charging cycle,
wherein said predetermined voltage is a function of V Max , where V MaX is a maximum recommended charging voltage by the battery's manufacturer plus a predetermined value, wherein said predetermined value is greater than 0.0 volts, and less than or equal to 0.2 volts.
2. The battery charger as recited in claim 1 , wherein said battery charging circuit is a linear battery charger.
3. The battery charger as recited in claim 1 , wherein said battery charging circuit is a switched-mode battery charger.
4. The battery charger as recited in claim 1 , wherein said first charging cycle's waveform is a square wave.
5. The battery charger as recited in claim 1 , wherein said maximum charging current value ramps up from said minimum charging current value to said maximum level charging current.
6. The battery charger as recited in claim 1 , wherein said maximum charging current value ramps down from said maximum charging current value to said minimum charging current value.
7. The battery charger as recited in claim 1 , wherein (a) said maximum charging current value ramps up from said minimum charging current value to said maximum charging current value, (b) and said maximum charging current value ramps down from said maximum charging current value to said minimum charging current value.
8. 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.
9. The battery charger as recited in claim 1 , wherein said battery charger is configured with a plurality selectable charge rates.
10. The battery charger as recited in claim 9 , wherein said battery charger is configured so that said maximum charging current value is automatically generated when one or more of said selectable charge rates are selected.
11. 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.
12. 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.
13. A method for charging a battery during a fast charge mode comprising the steps of:
(a) repeatedly measuring a battery voltage of a battery to be charged;
(b) charging said battery with alternating non-zero DC current values during said fast charging cycle until said battery voltage exceeds a predetermined voltage, wherein said DC current values have a non-zero average value defining a maximum charging current value and a minimum charging current value, said DC current values alternating between said maximum charging current value and said minimum charging current value until said battery voltage reaches said predetermined voltage, said charging current values being selected to cause said battery to be at least partially charged during said fast charging cycle at a voltage greater than said predetermined voltage, wherein said predetermined voltage is a function of V MAX , and V MAX is a maximum recommended charging voltage by the battery's manufacturer plus a predetermined value, wherein said predetermined value is greater than 0.0 volts, and less than and or equal to 0.2 volts; and
(c) subsequently charging said battery at a constant voltage.
14. The method as recited in claim 13 , further including the step (d) selecting a selectable charge rate.
15. A battery charger for charging a battery, said battery charger comprising:
a microprocessor controlled battery charging circuit, said microprocessor controlled battery charging circuit being configured to provides a plurality of selectable charging levels, at least one of said plurality of selectable charging levels being a fast charge mode,
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 predetermined voltage, and charges said battery at a constant voltage 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 predetermined voltage, wherein said predetermined voltage is a function of V MAX and V MAX is a maximum recommended charging voltage by the battery's manufacture plus a predetermined value, wherein said predetermined value is greater than 0.0 volts, and less than and or equal to 0.2 volts.
16. The battery charger as recited in claim 15 , wherein said battery charging circuit is a linear battery charger.
17. The battery charger as recited in claim 15 , wherein said battery charging circuit is a switched-mode battery charger.
18. The battery charger as recited in claim 1 , wherein said predetermined value is equal to 0.2 volts.
19. The method as recited in claim 13 , wherein said predetermined value is equal to 0.2 volts.
20. The method as recited in claim 15 , wherein said predetermined value is equal to 0.2 volts.