Lossless dynamic battery equalizer system and method
A system and method dynamically equalizes battery voltages with low inherent power losses in a string of series connected electrochemical batteries. The method includes charging/discharging a group of batteries using magnetic storage in a transformer with bipolar magnetic excursion, individually isolated circuits and pulsed energy transfer. A method also exchanges current between batteries using direct current transfer between them and limiting inductance. Using this method, battery voltage may be measured from an isolated circuit, thus enabling information transfer to a central monitoring system. The method also has the benefit of providing an estimation of battery internal resistance from isolated circuits in the series of batteries.
1. A method of equalizing a plurality of batteries, the method comprising the steps of:
providing a first set of interconnected inductive windings wherein a first subset of such windings are wound in a first polarity configuration and a second subset of such windings are wound in a second polarity configuration;
providing a plurality of controllable switches each directly connected in series with an associated winding of the first set of inductive windings to form a plurality of series-connected components each connected directly to one of the batteries;
providing a second plurality of interconnected inductive windings each of which is connected in series with a battery and a series-connected component; and
selectively operating the controllable switches to transfer power through inductive windings of the first set between selected one or more first batteries coupled to the windings of the first subset and selected one or more second batteries coupled to the windings of the second subset and wherein the inductive windings of the second set limit currents flowing between the batteries.
2. The method of claim 1 , further including the step of detecting a parameter of a battery associated with the operated switch.
3. The method of claim 2 , further including the step of detecting a resistance of a battery associated with the operated switch.
4. A battery equalization circuit, comprising:
a plurality of batteries each directly connected to an associated one of a first plurality of subcircuits, wherein each subcircuit includes a single transistor and an associated one of a second plurality of magnetically linked inductive windings connected between the single transistor and to the associated battery and wherein at least some of the subcircuits further include an associated one of a third plurality of magnetically linked inductive windings;
wherein a first subset of windings of the second plurality of magnetically linked inductive windings are wound in a first polarity configuration and a second subset of windings of the second plurality of magnetically linked inductive windings are wound in a second polarity configuration; and
a control for selectively operating the transistors to transfer power between one or more first batteries and one or more second batteries through inductive windings of the second plurality of magnetically linked inductive windings and wherein the inductive windings of the third plurality of magnetically linked inductive windings limit currents flowing between batteries when transistors connected to inductive windings of the first subset of windings are simultaneously operated.
5. The battery equalization circuit of claim 4 , further including a monitoring circuit operable when a transistor is operated for detecting a parameter of a battery associated with the operated transistor.
6. The battery equalization circuit of claim 5 , further including an estimation circuit operable when a transistor is operated for detecting a resistance of a battery associated with the operated transistor.
7. A battery equalization circuit, comprising:
a plurality of batteries each directly connected to an associated one of a first plurality of subcircuits, wherein each subcircuit includes a single transistor, an associated one of a second plurality of magnetically linked inductive windings, and an associated one of a third plurality of magnetically linked inductive windings and wherein the single transistor, the associated one of the second plurality of magnetically linked inductive windings, and the associated one of a third plurality of magnetically linked inductive windings are connected in series with the associated battery;
wherein a first subset of windings of the second plurality of magnetically linked inductive windings are wound in a first polarity configuration and a second subset of windings of the second plurality of magnetically linked inductive windings are wound in a second polarity configuration; and
a control for selectively operating the transistors to transfer power without diode drops or substantial resistive losses between one or more first batteries and one or more second batteries through inductive windings of the second plurality of magnetically linked inductive windings and wherein the inductive windings of the third plurality of magnetically linked inductive windings limit currents flowing between batteries when transistors connected to inductive windings of the first subset of windings are simultaneously operated.
8. The battery equalization circuit of claim 7 , further including a monitoring circuit operable when a transistor is operated for detecting a parameter of a battery associated with the operated transistor.
9. The battery equalization circuit of claim 8 , further including an estimation circuit including the inductive windings of the third plurality of magnetically linked inductive windings and means operable when a transistor is operated for detecting a resistance of a battery associated with the operated transistor.